Membrane Technology for Waste Water Treatment 4 Preface Membrane technology for the treatment of water and waste water shows impressively how innovative, future-orientated, and economically

Municipal Water and Waste Management

Membrane Technology for Waste Water Treatment

Institut für Siedlungswasserwirtschaft der RWTH Aachen



Edited by:

Univ.-Prof. Dr.-Ing. Johannes Pinnekamp

Institute of Environmental Engineering

of the RWTH Aachen University

Dr. rer. nat. Harald Friedrich

Head of Department

Waste Management, Soil Conservation,

Water Management

Ministry for Environment and Nature Conser-

vation, Agriculture and Consumer Protection

of the federal state North Rhine-Westphalia

Edited by:

Univ.-Prof. Dr.-Ing. Johannes Pinnekamp

Institute of Environmental Engineering

of the RWTH Aachen University


Head of Department

Waste Management, Soil Conservation,

Water Management

Ministry for Environment and Nature Conser-

vation, Agriculture and Consumer Protection



Institut für Siedlungswasserwirtschaft der RWTH Aachen


Volume 2

Preface

4

Preface

Membrane technology for the treatment of water and

waste water shows impressively how innovative, future-

orientated, and economically meaningful environmental

protection technology can be. In the past 100 years of

modern water and waste water treatment for households

and enterprises, no other new technology has been intro-

duced offering so many positive effects like the membrane

technology.

Numerous different problems in water treatment can be

solved, simultaneously resulting in significantly better

cleaning of the waste water.

Membrane technology allows the internal recovery and

reprocessing of solid and dissolved substances.

Due to the wide range of available membranes and

modules, technically suitable systems for nearly every

type of problem in water treatment can be found.

A large number of scientific institutions, industrial enter-

prises, water suppliers and waste water boards have parti-

cipated in the development and application of membrane

technology. The Federal Government as well as the

governments of the federal states support this technical

development.

In Germany, membrane technology today represents a

proven alternative to classical processes of municipal and

industrial waste water treatment. This pays off in terms

of ecology and economy because the usage of membrane

technology denotes fewer costs for water supply and

waste water disposal as well as industrial production, and

also results in significantly less environmental stress.

In municipal waste water treatment, certain types of

membrane installations – the biomembrane filtration

plants (membrane bioreactor process) – haven’t been

used often so far, both for historical and economical

reasons. But the application of membrane processes in

municipal waste water treatment may be proven to be

cost-effective, in particular if the following conditions

occur:

• the space for the new construction or the expansion

for waste water treatment plants is limited,

• the possibilities for subsequent recycling of the treated

waste water are to be used,

• advanced or additional standards for the effluent

quality of the waste water are required,

• toxic substances have to be removed,

• hygienically excellent waste water quality is demanded.

In Germany, the biomembrane filtration process has

become competitive already today in the field of domestic

and small waste water treatment plants as well as in ship

waste water treatment plants, and increasingly in muni-

cipal waste water treatment.

Membrane technology can be applied in diverse fields of

industry, which is proven by a large number of references.

In industrial waste water treatment, membrane technology

is used for production-integrated pollution control.

Preface

5

With the help of membrane technology, water – the sol-

vent most frequently used in industry – can be cleaned

to such an extent that it may be reused. The substances

filtered from the water may also be reused again for

industrial processes. Although it’s impossible to realize a

completely closed water circuit by membrane technology,

the waste water quantity may be significantly reduced by

multiplied usage of the water. Thus the enterprises save

costs.

This publication presents the membrane technology and

its application in municipal and industrial waste water

treatment in Germany according to the state of the art

and science. Examples of installations realized in an in-

dustrial scale in municipalities and industrial enterprises

demonstrate the range of application and the efficiency

of membrane installations – including planning, con-

struction and operation as well as the related costs. Thus

planners, municipalities responsible for waste water

disposal and licensing authorities are provided with a

fundamental basis for the decision whether membrane

technology might be a solution for their specific problem.

Eckhard Uhlenberg

Minister for Environment and

Nature Conservation, Agriculture

and Consumer Protection of the

federal state North Rhine-Westphalia

Sigmar Gabriel

Federal Minister for the Environment,

Nature Conservation and Nuclear

Safety

Prof. Dr. Andreas Troge

President of the Federal

Environmental Agency

imprint

6

This scientific elaboration was supported by

the Ministry for Environment and Nature Conservation,

Agriculture and Consumer Protection

of the federal state North Rhine-Westphalia.

Responsible


Head of Department

Waste Management, Soil Conservation, Water Management

Dr.-Ing. Viktor Mertsch

Waste Water Disposal and Waste Water Technology

Ministry for Environment and Nature Conservation,

Agriculture and Consumer Protection


Revising the contents of this 2nd updated edition

FiW at the RWTH Aachen University

M. Lange, Dr.- Ing. F.-W. Bolle, Dr.-Ing. S. Schilling,

S. Baumgarten (ISA, RWTH Aachen)

Revising the contents of the 1st edition 2003:

FiW and ISA, RWTH Aachen

M. Lange (chairperson), S. Baumgarten, F.-W. Bolle,

Dr.-Ing. T. Buer, J. Schunicht, Dr.-Ing. K. Voßenkaul

Team accompanying the 1st edition 2003:

Dr. V. Mertsch, I. Dierschke, K. Drensla, A. Kaste,

RBD A. Schmidt, Prof. Dr. W. Schmidt, S. Tenkamp,

Dr.-Ing. J. R. Tschesche, C. Wiedenhöft, T. Wozniak,

Dr. K. Zimmermann

Assessment of the 1st edition 2003:

Prof. Dr.-Ing. P. Cornel, Dr.-Ing. W. Firk,

Dr.-Ing. J. Oles, Dr.-Ing. T. A. Peters, U. Voss

Translation:

F. Pohl

German edition

A German edition titled

“Siedlungswasser- und Siedlungsabfallwirtschaft

Nordrhein-Westfalen: Membrantechnik

für die Abwasserreinigung”

is available with the following ISBN:

ISBN 3-939377-00-7

ISBN 978-3-939377-00-9

The translation was supported by:

Umweltbundesamt

Postfach 330022

D-14191 Berlin

FiW Verlag

Mies-van-der-Rohe-Straße 17

D-52074 Aachen

Phone: +49 (0) 241- 80 2 68 25

Fax: +49 (0) 241- 87 09 24

E-Mail: [email protected]

ISBN 3-939377-01-5

ISBN 978-3-939377-01-6

Layout

ID-Kommunikation

S 1, 1

D-68161 Mannheim

Phone: +49 (0) 6 21-10 29 24

Fax: +49 (0) 6 21-10 29 91


Cover photo

Erftverband

Print

Greiserdruck GmbH & Co. KG

Karlsruher Straße 22

D-76437 Rastatt

Phone: +49 (0) 72 22 -105-129

Fax: +49 (0) 72 22 -105-137

www.greiserdruck.de

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List of contents

1 Basics of Membrane Technology 27

1.1 Basics of Material Separation by means of Membrane Technology 28

1.2 Membrane Processes in Waste Water Purification 29

1.2.1 Micro- and Ultrafiltration 32

1.2.2 Nanofiltration 33

1.2.3 Reverse Osmosis 34

1.3 Membrane Materials, Structure and Classification 35

1.3.1 Origin and Materials 35

1.3.2 Morphology, Structure and Manufacturing 36

1.4 Membrane Forms and Modules 38

1.5 Arrangement of Modules 46

1.6 Operating Modes 48

1.7 Formation of Covering Layers 50

1.8 Measures for Maintenance of the Filtration Capacity 52

1.9 Other Aspects Concerning the Use of Membrane Technology in Waste Water Treatment 55

2 Membrane Technology in Municipal Waste Water Treatment 61

2.1 The Membrane Bioreactor Process 66

2.1.1 Description of the Process and Fields of Application 66

2.1.2 Membrane Modules 70

2.1.3 Planning and Operation of Membrane Bioreactors 82

2.1.3.1 Design 82

2.1.3.2 Mechanical Design and Planning 87

2.1.3.3 Operation 89

2.1.4 Investments and Operating Costs 92

2.1.4.1 Investments 92

2.1.4.2 Operating and Maintenance Costs 94

2.2 Concrete Examples of Membrane Bioreactors 95

2.2.1 Waste Water Treatment Plants with Microfiltration Membrane Installations in Germany 98

2.2.1.1 Seelscheid Waste Water Treatment Plant and Training Centre 98

2.2.1.2 Büchel Pilot Plant 101

2.2.1.3 Richtheim Waste Water Treatment Plant 103

2.2.1.4 Eitorf Waste Water Treatment Plant (Commissioning) 104

2.2.1.5 Xanten-Vynen Waste Water Treatment Plant (Commissioning) 106

2.2.1.6 Piene Waste Water Treatment Plant (in Planning Stage) 107

2.2.1.7 Rurberg-Woffelsbach and Konzen Waste Water Treatment Plants (Commissioned) 108

2.2.1.8 Kohlfurth Waste Water Treatment Plant, Process Water Treatment 109

2.2.1.9 Dormagen Waste Water Treatment Plant, Process Water Treatment (Commissioned) 110

2.2.2 Installations Outside of Germany with Microfiltration Membranes 111

2.2.2.1 Glasgow Waste Water Treatment Plant, Scotland 112

2.2.2.2 Ebisu Prime Square Building Waste Water Treatment Plant, Japan 114

2.2.2.3 St. Peter ob Judenburg Waste Water Treatment Plant, Austria 115

2.2.3 Waste Water Treatment Plants in Germany with Ultrafiltration Membranes 116

2.2.3.1 Nordkanal Waste Water Treatment Plant 116

2.2.3.2 Monheim Waste Water Treatment Plant 118

2.2.3.3 Markranstädt Waste Water Treatment Plant 121

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2.2.3.4 Rödingen Waste Water Treatment Plant 123

2.2.3.5 Schramberg-Waldmössingen Waste Water Treatment Plant 125

2.2.3.6 Knautnaundorf Waste Water Treatment Plant 127

2.2.3.7 Simmerath Pilot Plant 128

2.2.3.8 St. Wendel Golf Course 130

2.2.3.9 Glessen Waste Water Treatment Plant (Planning Stage) 132

2.2.4 Installations Outside of Germany with Ultrafiltration Membranes 133

2.2.4.1 Pilot Plants at the Beverwijk Waste Water Treatment Plant, The Netherlands 134

2.2.4.2 Varsseveld Waste Water Treatment Plant, The Netherlands 136

2.2.4.3 Brescia Waste Water Treatment Plant, Italy 137

2.2.4.4 Säntis Waste Water Treatment Plant, Switzerland 139

2.3 Small Waste Water Treatment Plants, Mobile Installations and

Ships Waste Water Treatment with Membrane Technology 140

2.3.1 Busse-MF Installation from the Company Busse 140

2.3.2 UltraSept Installation from the Company Mall 142

2.3.3 Small Waste Water Treatment Plant for 4 PE in North-Rhine Westphalia 143

2.3.4 Kreditanstalt für Wiederaufbau (KfW), Service Water Treatment 143

2.3.5 Small Waste Water Treatment Plant MembraneClearBox™ and Huber HoneyComb™

from the Company Huber AG 144

2.3.6 Mobile Installations for the Use in Military Camps 146

2.3.7 Ships’ Waste Water Treatment Plants with Membrane Technology 147

2.3.8 Cruise Liner Queen Mary 2 148

2.3.9 Grey and Black Water Treatment on Ships 150

2.4 Downstream Membrane Stage for Waste Water Disinfection 152

2.4.1 Process Description and Fields of Application 152

2.4.2 Membrane Modules Used 152

2.4.3 Operating Experience 153

2.4.4 Large-Scale Applications in Germany for Waste Water Disinfection by Ultrafiltration 153

2.4.4.1 Geiselbullach Waste Water Treatment Plant 154

2.4.4.2 Merklingen Waste Water Treatment Plant 155

2.4.4.3 Bondorf-Hailfingen Waste Water Treatment Plant 157

2.4.5 Large-Scale Applications Outside of Germany for Waste Water Disinfection by Ultrafiltration 159

2.4.5.1 Torreele, Belgium 159

2.4.5.2 Katowice Treatment Plant, Poland 161

2.4.5.3 Bedok Waste Water Treatment Plant, Singapore 162

2.5 Example for the Design of a Membrane Bioreactor 163

2.5.1 Design Basis 163

2.5.2 Interpretation of the ARA-BER Calculation According to the Design Recommendations for

Membrane Bioreactors 164

2.5.3 Design of the Membrane Filtration Stage 165

2.5.4 Printout of the Design Results with ARA-BER 166

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3 Membrane Technology in Industrial Waste Water Treatment 167

3.1 Brief Overview 168

3.2 Objectives and Applications in Different Industrial Branches 170

3.3 Decision Criteria 172

3.4 Economic Efficiency of Membrane Installations in Industrial

Waste Water Treatment 174

3.5 Sample Applications of Plants in Germany 177

3.5.1 Food Industry 179

3.5.1.1 Potato Starch Production 180

3.5.1.1.1 Food Industry, Emsland Stärke GmbH 181

3.5.1.2 Malt Houses 182

3.5.1.2.1 Malthouse Durst Malz – H. Durst Malzfabriken GmbH & Co. KG 183

3.5.1.3 Food Industry, BEECK Feinkost GmbH & Co. KG 184

3.5.2 Printing Industry, Peter Leis 185

3.5.3 Paper Mills 186

3.5.3.1 Paper Mill Palm, Works Eltmann 187

3.5.4 Textile Industry 188

3.5.4.1 Textile Industry, Drews Meerane 189

3.5.4.2 Silk Weaving Mill PONGS 191

3.5.4.3 Textile Finishing Works Gerhard van Clewe GmbH & Co. KG 193

3.5.5 Fibre Industry, Vulcanized Fibre 195

3.5.6 Plastics Industry, Troplast 197

3.5.7 Laundries 198

3.5.7.1 Laundry Alsco 198

3.5.7.2 Textile Service Mewa GmbH 201

3.5.8 Metal Processing Industry 203

3.5.8.1 Metal Processing Industry, Rasselstein Hoesch GmbH 204

3.5.8.2 Metal Processing Industry, Faurecia Bertrand Faure Sitztechnik GmbH & Co. KG 205

3.5.8.3 Metal Processing Industry, Electroplating Enterprise Rudolf Jatzke 206

3.5.8.4 Metal Processing Industry, Wieland Werke AG 208

3.5.9 Treatment of Waste Water from Car Painting 210

3.5.9.1 Treatment of Waste Water from Car Painting, DaimlerChrysler AG 210

3.5.9.2 Treatment of Paint Waste Water from the Production of Spare Parts in the Ford Works,

Cologne 211

3.5.10 Pharmaceutical Industry, Schering 213

3.5.11 Miscellaneous 215

3.5.11.1 Landfill Leachate 215

3.5.11.1.1 Alsdorf-Warden Landfill 218

3.5.11.2 Fish Hatchery 220

3.5.11.3 Power Stations, Dresden Gas and Steam Turbine Heating Power Station (GuD) 221

3.5.11.4 De-oiling of Bilge Water 223

3.5.11.5 Swimming Pools 225

3.5.11.5.1 Swimming Pool, Aquana Freizeitbad GmbH & Co. KG 225

3.5.11.5.2 Swimming Pool, Freizeitbad Copa Ca Backum 227

3.6 Sample Applications of Plants Outside of Germany 229

3.6.1 Food Industry 230

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3.6.1.1 Muesli Production at the Kellogg Company, Great Britain 230

3.6.1.2 Primary Starch Production at Raisio Chemicals, Belgium 232

3.6.1.3 Dairygold Food Products, Ireland 233

3.6.1.4 Dairy Crest Limited, Great Britain 235

3.6.1.5 Malthouse Sobelgra n. v., Belgium 236

3.6.2 Laundry Massop, The Netherlands 239

3.6.3 Pharmaceutical Industry, Penicillin Production at the Company Sandoz/Biochemistry, Spain 240

3.6.4 Miscellaneous 242

3.6.4.1 Animal Carcass Disposal Plant of SARIA Bio-Industries, France 242

3.6.4.2 Mechanical-Biological Waste Treatment Plant 244

3.6.4.2.1 Waste Disposal at the Company TIRME, Spain 244

4 Instructions and Standards in Membrane Technology 247

5 Summary and Outlook 251

6 References 253

A Annex 263

A.1 Addresses (mentioned in the concrete examples) 264

A.1.1 Locations of the membrane systems in Germany 264

A.1.2 Planners and manufacturers of installations, membrane manufacturers, Consulting Engineers 268

A.1.3 Scientific assistance for the realization of this publication 272

A.1.4 Other institutions and persons having contributed to the contents 274

A.1.5 Other information sources in the field of membrane technology 275

A.2 Possibilities for promotion 276

A.2.1 Development programs and advisory service of the Federal Government 276

A.2.2 Development programs of the federal states 277

A.2.3 Development programs of the EU in the field of pollution control and water management 282

A.3 Short check lists for Figure 2-1 284

A.4 Short check lists for Figure 3-1 286

A.5 Work report of the ATV-DVWK working group

IG-5.5 “Membrane Technology”: Treatment of industrial waste water and

process water by membrane processes and membrane bioreactor processes 288

Part I Membrane processes 288

A.5.1 Introduction 288

A.5.2 Choice of a membrane process 291

A.5.2.1 Determination of the necessary molecular separation size 291

A.5.2.2 Determination of the membrane material 291

A.5.2.3 Determination of the membrane module 293

A.5.2.4 Determination of the operating mode of membrane installations 295

A.5.3 Examples for the use of membrane processes 296

A.5.4 Planning of membrane installations 296

A.5.4.1 Acquisition of basic data 296

A.5.4.2 Planning and design 296

A.5.4.2.1 Preliminary laboratory tests 296

List of contents 1

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A.5.4.2.2 On-site pilot tests 297

A.5.4.2.3 Planning of the installation 297

A.5.5 Assessment criteria for the choice of a membrane installation 298

A.5.5.1 Technical assessment of a membrane process concerning employment and completeness 298

A.5.5.1.1 Definition of the terms of reference 298

A.5.5.1.2 Material and mass fluxes during operation of a membrane installation 298

A.5.5.1.3 Utilization or discharge of the resulting products 299

A.5.5.1.4 Pretreatment 299

A.5.5.1.5 Technical realization 299

A.5.5.1.6 Redundancies 299

A.5.5.1.7 References/similar applications 299

A.5.5.2 Operating costs 299

A.5.5.2.1 Equipment 299

A.5.5.2.2 Auxiliaries 299

A.5.5.2.4 Service life and replacement of membranes 299

A.5.5.3 Change of the conditions during operation of the installation 300

A.5.5.4 Other items 300

A.5.5.4.1 Failures 300

A.5.5.4.2 Preliminary tests 300

A.5.6 Questionnaire for the acquisition of process data 300

A.5.6.1 Description of the separation problem to be solved with the help of a membrane process 300

A.5.6.2 Concerning the assessment or the integration of a membrane process into an

overall treatment concept 301

A.5.6.3 Sizing of the installation 301

A.5.6.4 Requirements for the construction of the membrane installation 301

Part II Aerobic membrane bioreactor processes 301

A.5.7 General information 301

A.5.8 Construction 302

A.5.8.1 Arrangement 302

A.5.8.1.1 Immersed membrane modules 302

A.5.8.1.2 Dry-arranged membrane modules 302

A.5.8.2 Control of the covering layer 303

A.5.8.2.1 Control of the covering layer in immersed systems 303

A.5.8.2.2 Covering layer control in dry-arranged systems 303

A.5.8.2.3 General facts 304

A.5.8.3 Cleaning strategies 304

A.5.9 Requirements for the influent 306

A.5.9.1 General information 306

A.5.9.2 Mechanical pretreatment 306

A.5.9.3 Mixing and equalizing tank 307

A.5.9.4 Calcium concentration 307

A.5.9.5 Iron and aluminium content 307

A.5.10 Instructions for the design of membrane bioreactors 307

A.5.10.1 General information 307

A.5.10.2 Space requirements 308

A.5.10.3 Elimination rates 308

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A.5.10.4 Aeration 309

A.5.10.5 Hydraulics 309

A.5.10.5.1 Flexibility 309

A.5.10.5.2 Recirculation 309

A.5.10.6 Influence of the temperature 310

A.5.11 Specific features of membrane bioreactors 310

A.5.11.1 Sludge features 310

A.5.11.1.1 Characterization of the sludge 310

A.5.11.1.2 Rheological properties 310

A.5.11.1.3 Excess sludge production 311

A.5.11.1.4 Sludge treatment 311

A.5.11.1.5 Foam development 311

A.5.12 Economic efficiency 312

A.5.12.1 Definition of economic efficiency 312

A.5.12.2 Investment/capital costs 312


A.5.12.4 Comparison of cost-relevant factors 314

A.5.13 Examples in the field of industrial waste water (Europe) 315

A.5.14 Literature 315

A.6 2nd Work report of the DWA Committee of Experts KA-7

“Membrane bioreactor process“ from 19th January 2005 317

A.6.1 Introduction 317

A.6.2 Description of the membrane bioreactor process 318

A.6.3 Instructions for planning and design 322

A.6.4 Sludge treatment 326

A.6.5 Chemical cleaning of the membrane modules 328

A.6.6 Energy demand 329

A.6.7 Upgrading of existing municipal waste water treatment plants 331

A.6.8 Instructions for start-up 332

A.6.9 Costs 333

A.6.10 Annual costs 336

A.6.10.1 Loan servicing and membrane replacement 336


A.6.11 Final remark 336

A.6.12 Advantages and risks of the membrane bioreactor process 337

A.6.12.1 General facts 337

A.6.13 Glossary 337

A.6.14 Literature 341

A.7 Large-scale membrane installations for drinking water treatment in Germany 343

A.8 Glossary 344

A.9 List of abbrevations 346

List of figures 1

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Figure 1-1 Operating principle of micro- and ultrafiltration membranes 28

Figure 1-2 The different fields of application of membrane processes 29

Figure 1-3 Size of typical waste water constituents and the pore size of membranes applied 30

Figure 1-4 Idealized representation of a pore membrane and a solution-diffusion membrane

[according to MELIN 1999] 31

Figure 1-5 Classification of membranes [according to RAUTENBACH 1997] 35

Figure 1-6 Scanning electron micrographs of cross-sections of different membranes 37

Figure 1-7 Top view of the active layer of a polyethylene membrane (MF/UF) [AGGERVERBAND 2002] 37

Figure 1-8 Top view of the broken edge of a polyethylene membrane (MF/UF), the active layer is visible

[AGGERVERBAND 2002] 37

Figure 1-9 Membrane and module forms 38

Figure 1-10 Tube modules [photo: WEHRLE WERK AG] 40

Figure 1-11 Capillary or hollow-fibre modules [photo: KOCH MEMBRANE SYSTEMS] 41

Figure 1-12 Spiral-wound modules [schematic drawing: N. N. 2001], [photo: NADIR FILTRATION GMBH] 42

Figure 1-13 Cushion module [schematic drawing and photo: ROCHEM UF SYSTEME GMBH] 43

Figure 1-14 Disc-tube module (DT module) [PALL 2001] 44

Figure 1-15 New Multibore capillaries from the company inge AG [photo: INGE AG] 45

Figure 1-16 From the membrane element to the membrane stage 46

Figure 1-17 Series connection of modules [according to BAUMGARTEN 1998] 46

Figure 1-18 Parallel connection of modules [according to BAUMGARTEN 1998] 47

Figure 1-19 Arrangement of several modules according to the fir tree structure

[according to RAUTENBACH 1997] 47

Figure 1-20 Schematic representation of a membrane in cross-flow- and dead-end filtration

[according to MELIN 1999] 49

Figure 1-21 Filtration intervals in dead-end operation [according to RAUTENBACH 1997] 49

Figure 1-22 Schematic overview of the filtration resistances on the membrane surface and inside the membrane

[KRAMER, KOPPERS 2000] 51

Figure 1-23 Effect of membrane cleaning on the flow at constant pressure 53

Figure 1-24 Molar masses of selected natural organic constituents in domestic waste water 58

Figure 1-25 Molar masses of selected organic trace substances 59


Figure 2-1 Background – planning – operation of a municipal membrane bioreactor, contents of the chapter

“Membrane technology in municipal waste water treatment“ 63

Figure 2-2 Conventional waste water treatment according to the activated sludge process and possibilities for

the arrangement of a membrane stage at municipal waste water treatment plants [OHLE 2001] 64

Figure 2-3 Flow sheet of a waste water treatment plant with membrane bioreactor process and downstream

membrane stage 65

Figure 2-4 Comparison of the germ load in the effluent of waste water treatment plants [BAUMGARTEN,

BRANDS 2002] 68

Figure 2-5 Schematic representation of the space requirements of a conventional activated sludge plant

(edged in blue) and of a membrane bioreactor (edged in red), example: Nordkanal waste water

treatment plant [ERFTVERBAND 2002] 69

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Figure 2-6 ZeeWeed®-module from the company ZENON 70

Figure 2-7 Arrangement of several ZeeWeed®-modules ZW 1000 in a cassette [photo: ZENON 2004] 71

Figure 2-8 Plate module from the company Kubota 71

Figure 2-9 Basic schematic of the plate module “double-decker” from the company Kubota

[AGGERWASSER GMBH 2004] 72

Figure 2-10 PURON module and module component [photo: PURON AG] 73

Figure 2-11 Membrane module from Martin Systems AG 74

Figure 2-12 Huber VRM® process [photos: HANS HUBER AG, MARTIN SYSTEMS AG] 75

Figure 2-13 Huber VUM® process [HANS HUBER AG] 76

Figure 2-14 Membrane element and membrane module from the company Mitsubishi [photo: ENVICARE®] 76

Figure 2-15 Plate module from the company A3 GmbH [photo: A3 GMBH] 77

Figure 2-16 Membrane module from US Filter Corporation [photo: US FILTER CORPORATION 2004] 78

Figure 2-17 Membrane module from the Keppel Seghers Belgium [photo: KEPPEL SEGHERS BELGIUM NV] 78

Figure 2-18 Membrane system from Weise Water Systems GmbH & Co. KG

[WEISE WATER SYSTEMS GMBH&CO. KG] 79

Figure 2-19 Ceramic plate membranes from the company ItN Nanovation [photo: ItN NANOVATION] 80

Figure 2-20 Membrane module and configuration of the modules in the rack with underlying aeration device

[photos: ItN NANOVATION] 80

Figure 2-21 Basic layout sketch of the rotation disc filter 81

Figure 2-22 Modules of the rotation disc filter in laboratory scale [photo: FRAUNHOFER IGB] 81

Figure 2-23 Specific excess sludge production in membrane bioreactors [ATV-DVWK 2000a] 83

Figure 2-24 Oxygen transfer coefficient (�-values) of the Rödingen and Markranstädt waste water treatment

plants with fine-bubble diffuser aeration [CORNEL ET AL. 2001] 86

Figure 2-25 View and principle of a screening facility for membrane bioreactors (Markranstädt waste water

treatment plant) [HUBER 2002, STEIN 2002a] 87

Figure 2-26 Energy demand of a membrane bioreactor (8,000 PE) with simultaneous aerobic sludge

stabilization [STEIN ET AL. 2001] 91

Figure 2-27 Development of membrane replacement costs [ISA 2002; CHURCHHOUSE, WILDGOOSE 2000] 94

Figure 2-28 Flow sheet of the Seelscheid waste water treatment plant [according to AGGERVERBAND 2004] 99

Figure 2-29 Membrane installation at the Seelscheid waste water treatment plant

[photos: AGGERVERBAND 2004] 99

Figure 2-30 Existing sand filter tanks, to be used for the training installations [photo: AGGERVERBAND 2004] 100

Figure 2-31 Flow sheet of the training installations [according to AGGERVERBAND 2004] 100

Figure 2-32 View of the Büchel pilot plant [photo: ISA RWTH AACHEN] 101

Figure 2-33 Flow sheet of the Büchel pilot plant [BAUMGARTEN 2001b] 101

Figure 2-34 Flow sheet of the membrane bioreactor [according to BAYERISCHES LANDESAMT FÜR

WASSERWIRTSCHAFT 2004] 103

Figure 2-35 Flow sheet of the Eitorf waste water treatment plant [according to GEMEINDEWERKE EITORF 2004] 104

Figure 2-36 Eitorf waste water treatment plant with covered membrane tanks between the buildings in the

foreground 105

Figure 2-37 Membrane installation in container construction for the Xanten-Vynen waste water treatment plant

[photo: A3 GMBH] 106

Figure 2-38 Flow sheet of the Xanten-Vynen waste water treatment plant, including the planned membrane

bioreactors [according to LINEG 2004] 106

Figure 2-39 Flow sheet of the membrane bioreactor [according to CITY OF GUMMERSBACH 2004] 107

Figure 2-40 Flow sheet of the Kohlfurth waste water treatment plant [according to WUPPERVERBAND 2004] 109

List of figures 1

15

Figure 2-41 Flow sheet of the Dormagen waste water treatment plant [according to CITY OF DORMAGEN 2004] 110

Figure 2-42 Aerial photograph of the Swanage waste water treatment plant [photo: AQUATOR GROUP] 111

Figure 2-43 Flow sheet of the Glasgow sludge treatment plant [according to AGGERWASSER GMBH 2004] 112

Figure 2-44 Top view of the sludge treatment plant and of a tank of the membrane installation

[photo: AGGERWASSER GMBH 2001] 113

Figure 2-45 Ebisu Prime Square Building [photo: AGGERWASSER GMBH 2004] 114

Figure 2-46 Waste water treatment plant in the basement of the Ebisu Prime Square Building

[photo: AGGERWASSER GMBH 2004] 114

Figure 2-47 Flow sheet of the waste water treatment plant [according to AGGERWASSER GMBH 2004] 114

Figure 2-48 Flow sheet of the St. Peter ob Judenburg waste water treatment plant

[according to ENVICARE 2002] 115

Figure 2-49 St. Peter ob Judenburg waste water treatment plant [photos: ENVICARE] 116

Figure 2-50 Rotary screen of the fine screen installation 117

Figure 2-51 Flow sheet of the Nordkanal waste water treatment plant [according to ERFTVERBAND 2004] 117

Figure 2-52 Membrane installation at the WWTP Nordkanal 118

Figure 2-53 Monheim waste water treatment plant [photo: BAYERISCHES LANDESAMT FÜR

WASSERWIRTSCHAFT (Bavarian Office for Water Management) 2004] 119

Figure 2-54 Flow sheet of the Monheim waste water treatment plant [according to BAYERISCHES

LANDESAMT FÜR WASSERWIRTSCHAFT 2004] 119

Figure 2-55 Module cassettes during in-air cleaning [photo: CITY OF MONHEIM 2004] 120

Figure 2-56 Process stages at the Markranstädt waste water treatment plant [STEIN 2002a]. 121

Figure 2-57 Process stages at the Markranstädt waste water treatment plant [STEIN 2002a] 122

Figure 2-58 Flow sheet of the Rödingen waste water treatment plant 124

Figure 2-59 View into the two filtration lines during fitting of the ZeeWeed™ cassettes [photo: ERFTVERBAND] 124

Figure 2-60 Schramberg-Waldmössingen waste water treatment plant [photo: STADTWERKE SCHRAMBERG

(municipal utilities) 2004] 125

Figure 2-61 Flow sheet of the Schramberg-Waldmössingen waste water treatment plant [according to

STADTWERKE SCHRAMBERG 2004] 126

Figure 2-62 Membrane installation at the Schramberg-Waldmössingen waste water treatment plant

[photos: STADTWERKE SCHRAMBERG 2004] 126

Figure 2-63 Flow sheet of the Simmerath demonstration plant [according to WVER 2004] 128

Figure 2-64 Membrane installation at the Simmerath waste water treatment plant [photos: PURON AG 2003] 129

Figure 2-65 Flow sheet of the golf course St. Wendel waste water treatment plant [according to ST. WENDEL] 130

Figure 2-66 Module rack at the golf course St. Wendel waste water treatment plant [photos: ItN NANOVATION] 131

Figure 2-67 Flow sheet of the Glessen waste water treatment plant [according to ERFTVERBAND 2004] 132

Figure 2-68 Aerial photograph and flow sheet of the Lowestoft waste water treatment plant [ZENON 2002] 133

Figure 2-69 Photos of the pilot installations and membrane modules at the test field of the Beverwijk waste

water treatment plant [DHV 2004] 135

Figure 2-70 Flow sheet of the Varsseveld waste water treatment plant [according to DHV 2004] 136

Figure 2-71 Flow sheet of the Brescia waste water treatment plant [according to ZENON GMBH 2004] 137

Figure 2-72 Aerial photograph of the Brescia waste water treatment plant [photo: ZENON GMBH 2004] 138

Figure 2-73 View and flow sheet of the membrane bioreactor according to the ZenoGem™ process on the Säntis

[ZENON 2002] 139

Figure 2-74 View of the Busse MF small waste water treatment plant (formerly BioMIR™) [BUSSE 2002] 140

Figure 2-75 Flow sheet of a Busse-MF installation [BUSSE 2002] 141

List of figures1

16

Figure 2-76 Schematic representation of the UltraSept installation from the company Mall [MALL 2002] 142

Figure 2-77 Grey water treatment plant at KfW 143

Figure 2-78 Membrane installation for the treatment of service water in the cellar of KfW

[WEISE WATER SYSTEMS GMBH] 144

Figure 2-79 Plot plan of a small waste water treatment plant with membrane technology installed in a

multicompartment septic tank [HUBER AG 2004] 145

Figure 2-80 Small waste water treatment plant MembraneClearBox™ from Huber AG [photos: HUBER AG 2004] 145

Figure 2-81 Transportation of the container plant by an emergency vehicle and schematic representation of

the plant [A3 GMBH 2004] 146

Figure 2-82 View of a MEMROD ship’s waste water treatment plant according to the membrane bioreactor

process for 250 persons [VA TECH WABAG 2002] 148

Figure 2-83 Ultrafiltration module Pleiade™ for waste water treatment on Queen Mary 2

[photo: ORELIS SA 2004] 148

Figure 2-84 Photo of the Queen Mary 2 149

Figure 2-85 Flow sheet of the waste water treatment plan of Queen Mary 2 [according to ORELIS SA 2004] 149

Figure 2-86 Flow sheet of waste water treatment according to the two-stream solution

[according to ROCHEM UF 2004] 150

Figure 2-87 Membrane bioreactor BioFilt with three lines at 4.5 m3 of permeate per day each [ROCHEM UF 2004] 151

Figure 2-88 Low-pressure reverse osmosis for grey water treatment for 600 m3 of permeate per day

[photo: ROCHEM UF 2004] 151

Figure 2-89 Flow sheet of the Geiselbullach waste water treatment plant [according to AMPERVERBAND 2004] 154

Figure 2-90 Treatment installation at the Geiselbullach waste water treatment plant

[photos: AMPERVERBAND 2002] 155

Figure 2-91 Flow sheet of the Merklingen waste water treatment plant [according to RP TÜBINGEN 2004] 155

Figure 2-92 Pressure tubes of the ultrafiltration plant at the Merklingen waste water treatment plant

[RP TÜBINGEN 2004] 156

Figure 2-93 Flow sheet of the Bondorf-Hailfingen waste water treatment plant [according to BONDORF-

HAILFINGEN WASTE WATER UNION 2004] 158

Figure 2-94 Membrane installation at the Bondorf-Hailfingen waste water treatment plant under construction

[photos: BONDORF-HAILFINGEN WASTE WATER UNION 2004] 158

Figure 2-95 Flow sheet of the Torreele treatment plant [according to ZENON GMBH 2004] 160

Figure 2-96 Flow sheet of the ultrafiltration installation for process water treatment in Katowice

[according to ZENON GMBH 2004] 161

Figure 2-97 Flow sheet of the treatment plant [according to ZENON GMBH 2004] 162

Figure 2-98 General view of the treatment plant [photo: ZENON GMBH 2004] 163

Figure 2-99 Ultrafiltration membrane installation [photo: ZENON GMBH 2004] 163


Figure 3-1 Motive – planning – operation of a membrane installation, overview of the contents of the chapter

“Membrane technology in industrial waste water treatment” 169

Figure 3-2 Objectives and economic interests for the use of a membrane installation in industrial waste water

treatment 170

Figure 3-3 How to proceed in the planning of an installation for industrial waste water treatment 173

Figure 3-4 Factors influencing the economic efficiency of membrane installations 175

Figure 3-5 Flow chart of potato starch production 180

List of figures 1

17

Figure 3-6 Flow chart of the treatment of process- and potato pulp water at Emsland Stärke GmbH

[according to LOTZ 2000] 181

Figure 3-7 Reverse osmosis installation at Durst Malzfabriken GmbH & Co. KG, Gernsheim [LINDEMANN 2001] 183

Figure 3-8 Flow chart of the waste water treatment at BEECK Feinkost GmbH [according to

KOCH-GLITSCH GMBH 2001] 184

Figure 3-9 Ultrafiltration installation at the Grafische Handelsvertretung Peter Leis [LEIS IN EFA 2000] 186

Figure 3-10 Nanofiltration installation at the paper mill Palm, works Eltmann (left) [SCHIRM 2001] and detail of

the tube module arrangement as feed-and-bleed structure (right) [according to SCHIRM 2001] 188

Figure 3-11 Flow sheet of the waste water treatment and processing plant [according to ZENON GMBH 2004] 190

Figure 3-12 Conversion of the waste water treatment plant at PONGS Textil GmbH 191

Figure 3-13 Flow sheet of the membrane bioreactor of the company PONGS [according to A3 GMBH 2004] 192

Figure 3-14 Ultrafiltration installation at the textile finishing plant van Clewe [BÖTTGER 2001] 194

Figure 3-15 Flow sheet of the process water treatment at the vulcanized fibre works GmbH & Co. KG

[AMAFILTER 2001] 195

Figure 3-16 Reverse osomosis installation at the vulcanized fibre works Ernst Krüger GmbH & Co. KG

[photo: AMAFILTER] 196

Figure 3-17 Ultrafiltration installation at the company HT Troplast AG [photo: HT TROPLAST] 197

Figure 3-18 Flow sheet of the waste water treatment process in the laundry ALSCO [according to

WEHRLE UMWELT GMBH 2004] 199

Figure 3-19 Membrane installation in the laundry Alsco [photos: WEHRLE UMWELT GMBH 2004] 200

Figure 3-20 Flow sheet of the treatment plant of Textile Service Mewa GmbH [according to ENVIRO CHEMIE 2004] 201

Figure 3-21 Ultrafiltration plant at Textile Service Mewa [photo: ENVIRO CHEMIE 2004] 202

Figure 3-22 Nanofiltration plant at Textile Service Mewa [photo: ENVIRO CHEMIE 2004] 202

Figure 3-23 Ultrafiltration installation at the company Rasselstein Hoesch [photo: MFT GMBH] 204

Figure 3-24 Ultrafiltration installation at the company Faurecia, Bertrand Faure Sitztechnik GmbH & Co. KG

[KASTEN 2001] 205

Figure 3-25 Mode of operation of the electrolysis membrane [SCHMIDT 2002] 207

Figure 3-26 Ultrafiltration installation at the works Werk Langenberg of Wieland Werke AG [MUNLV 2001] 209

Figure 3-27 Ultrafiltration installation in the DaimlerChrysler works at Düsseldorf [HARMEL 2001] 210

Figure 3-28 Flow sheet of paint-spraying [IMB +FRINGS WATERSYSTEMS GMBH 2004] 211

Figure 3-29 Nanofiltration plant at the Ford works Cologne [photo: IMB+FRINGS WATERSYSTEMS GMBH 2004] 212

Figure 3-30 Aerial photograph of the waste water treatment plant at Schering AG [photos: SCHERING AG 2004] 213

Figure 3-31 Flow sheet of the waste water treatment plant [according to SCHERING AG 2004] 214

Figure 3-32 Optical inspection of a membrane module [photo: SCHERING AG 2004] 215

Figure 3-33 Process combination according to the state of the art for the treatment of landfill leachate without

using membrane processes [ROSENWINKEL, BAUMGARTEN 1998] 216

Figure 3-34 Process combination according to the state of the art for the treatment of landfill leachate using

membrane processes with and without biological pretreatment [completed according to

ROSENWINKEL, BAUMGARTEN 1998] 216

Figure 3-35 Reverse osmosis installation at the landfill Alsdorf-Warden [MAURER 2001] 218

Figure 3-36 Structure of the composite membrane [MAURER 2001] 219

Figure 3-37 Flow sheet of a circuit installation for the treatment of waste water from fish hatchery

[UMWELTBUNDESAMT 2004] 221

Figure 3-38 Flow sheet of the RÖKU process [according to DPC 1997] 222

Figure 3-39 Ultrafiltration unit for the RÖKU process [photo: THERM-SERVICE] 223

Figure 3-40 Flow sheet of bilge de-oiling [according to DEUTSCH 2001] 224

List of figures1

18

Figure 3-41 Water recirculation and treatment at the Aquana Freizeitbad [according to DEGEBRAN®] 226

Figure 3-42 Water treatment at the Freizeitbad Copa Ca Backum [according to L. V. H. T. 2001] 228

Figure 3-43 Flow sheet of the waste water treatment plant at the Kellogg Company in Manchester

[according to WEHRLE UMWELT GMBH 2004] 231

Figure 3-44 Cross-flow ultrafiltration at the Kellog Company in Manchester [photo: WEHRLE UMWELT

GMBH 2004] 231

Figure 3-45 Flow sheet of the membrane bioreactor at Raisio Chemicals [according to HUBER AG 2004] 232

Figure 3-46 Huber VRM® process (rotating modules) [photos: HUBER AG 2004] 232

Figure 3-47 Flow sheet of the waste water treatment plant at Dairygold Food Products, Ireland

[according to WEHRLE UMWELT GMBH 2004] 234

Figure 3-48 Complete plant at Dairygold Food Products with the membrane installation in the foreground

[WEHRLE UMWELT GMBH 2004] 234

Figure 3-49 Flow sheet of the waste water treatment at Dairy Crest, Great Britain [according to


Figure 3-50 Aerial photograph of the malthouse Sobelgra in the Antwerpen harbour [photo: PURON AG] 237

Figure 3-51 Flow sheet of the company-owned waste water treatment plant of the company Sobelgra

[according to PURON AG] 238

Figure 3-52 Schematic representation of the membrane bioreactor (left) and membrane modules (right)

[photo: PURON AG] 238

Figure 3-53 Reverse osmosis installation at the laundry Massop, Kerkrade [ROTH 2001] 239

Figure 3-54 Flow sheet of the membrane bioreactor in Barcelona [according to AGGERWASSER GMBH 2004] 241

Figure 3-55 Membrane bioreactor and membrane modules under construction at the company Sandoz in Spain

[photos: AGGERWASSER GMBH 2004] 241

Figure 3-56 Flow sheet of the membrane bioreactor at SARIA Bio-Industries in Bayet [according to

ZENON GMBH 2004] 243

Figure 3-57 General view of the membrane bioreactor of the animal carcass disposal plant in Bayet

[photo: ZENON GMBH 2004] 243

Figure 3-58 Container with fitted modules at SARIA Bio-Industries in Bayet [photo: ZENON GMBH 2004] 243

Figure 3-59 Flow sheet of the waste water treatment plant at the company TIRME, Spain [according to


Figure 3-60 Waste water treatment plant at the company TIRME [photos: WEHRLE UMWELT GMBH 2004] 245

A Annex 263

Figure A-1 Schematic representation of the basic principle of a membrane process 289

Figure A-2 Classification of membrane and filtration processes 289

Figure A-3 Cross-section of a phase-inversion membrane, example: UF hollow-fibre membrane 292

Figure A-4 Composite membrane 292

Figure A-5 Front view of a tube module with 5.5 mm tubular membranes [photo: X-FLOW] 294

Figure A-6 View of a cushion module [type ROCHEM FM] 294

Figure A-7 Principle of a spiral-wound module 295

Figure A-8 Material and mass fluxes during operation of a membrane installation 298

Figure A-9 Schematic comparison of the conventional activated sludge process with the membrane

bioreactor process 302

Figure A-10 Arrangement of the immersed membrane modules in the aerobic section of the

activated sludge tank 303

Figure A-11 Arrangement of the immersed membrane modules in an external filtration tank 303

List of figures 1

19

Figure A-12 Membrane modules in dry arrangement 303

Figure A-13 Qualitative relationship between necessary membrane surface area, energy demand and flow 304

Figure A-14 Membrane filtration in dry arrangement 318

Figure A-15 Ways of configuring an immersed membrane filtration 319

Figure A-16 Schematic representation of different module constructions 320

Figure A-17 Typical operating modes of the membrane modules 321

Figure A-18 Influence of the solids concentrations on the �-value for fine-bubble pressure aeration installations 325

Figure A-19 Specific energy consumption of the Markranstädt WWTP [STEIN, KERKLIES 2003] 330

Figure A-20 Specific energy consumption of the KA Monheim WWTP [WEDI 2003] 331

Figure A-21 Example for the distribution of construction costs of a membrane bioreactor for approximately

300 m3/h [WEDI 2003] 334

Figure A-22 Orienting net cost guide values for the ready-for-use membrane filtration installation without

structural part [WEDI 2003] 335

List of tables1

20


Table 1-1 Pressure-driven membrane processes in waste water purification 31

Table 1-2 Characteristic features of micro- and ultrafiltration 32

Table 1-3 Characteristic features of nanofiltration 33

Table 1-4 Characteristic features of reverse osmosis 34

Table 1-5 Characteristic values, advantages and disadvantages of module types with tubular membranes 39

Table 1-6 Characteristic values, advantages and disadvantages of module types with flat membranes 39

Table 1-7 Formation of covering layers in membrane filtration [according to BAUMGARTEN 1998] 51

Table 1-8 Methods for reduction and removal of covering layers 52

Table 1-9 Examples of cleaning chemicals and their applications 54

Table 1-10 Molecular separation size and transmembrane pressure of pressure-driven membrane processes 55

Table 1-11 Data on the size of viruses and bacteria 56

Table 1-12 Molar masses of selected natural organic constituents in domestic waste water

[KOPPE, STOZEK 1999] 57

Table 1-13 Molar masses of selected organic trace substances [MUNLV 2004] 59


Table 2-1 Advantages of the membrane bioreactor process compared to the conventional activated sludge process 66

Table 2-2 Performance data of membrane bioreactor plants compared to conventional activated sludge plants

[DOHMANN ET AL. 2002] 67

Table 2-3 Cleaning methods 90

Table 2-4 Savings potentials and additional costs concerning the investments of membrane bioreactors

compared to conventional activated sludge plants 93

Table 2-5 Data of the large-scale membrane bioreactors treating municipal waste water in Germany,

as of December 2004 96

Table 2-6 Membrane bioreactors under construction or in planning stage in Germany, as of December 2005 97

Table 2-7 Minimum requirements, discharge consent and operating values of the Seelscheid waste water

treatment plant [according to AGGERVERBAND 2004] 98

Table 2-8 Input values for the design of the Eitorf membrane bioreactor [according to

GEMEINDEWERKE EITORF (municipal utilities) 2004] 104

Table 2-9 Demands on the effluent quality of the Rurberg-Woffelsbach and Konzen waste water treatment

plants [according to WVER 2004] 108

Table 2-10 Raw waste water and permeate quality [according to AGGERWASSER GMBH 2004] 114

Table 2-11 Influent and effluent concentrations of the waste water treatment plant 115

Table 2-12 Minimum requirements and discharge consent of the Nordkanal waste water treatment plant

[ERFTVERBAND 2004] 116

Table 2-13 Minimum requirements, discharge consent and operating values of the Monheim waste water

treatment plant [BAYERISCHES LANDESAMT FÜR WASSERWIRTSCHAFT 2004] 120

Table 2-14 Minimum requirements, discharge consent and operating values of the Markranstädt waste water

treatment plant [STEIN 2002a] 121

Table 2-15 Minimum requirements and discharge consent of the Rödingen waste water treatment plant

[according to ENGELHARDT ET AL. 2001] 123

Table 2-16 Discharge consent of the Simmerath waste water treatment plant [WVER 2004] 128

Table 2-17 Operating values of the membrane bioreactor in Simmerath [WVER 2004] 129

Table 2-18 Minimum requirements, discharge consent and operating values of the golf course St. Wendel

waste water treatment plant [CITY OF ST. WENDEL 2005] 130

List of tables 1

21

Table 2-19 Demands on the effluent quality of the Glessen waste water treatment plant

[according to ERFTVERBAND 2004] 132

Table 2-20 Key features of the individual pilot installations [DHV 2004] 134

Table 2-21 Raw waste water concentration, operating values and requirements of the Brescia waste water

treatment plant [ZENON GMBH 2004] 138

Table 2-22 Requirements for the effluent quality of small waste water treatment plants and measured effluent

values of the Busse-MF installation 141

Table 2-23 Characteristic values of different membrane modules for the filtration of effluents from the test

installations of Berliner Wasserbetriebe and the test installations at the Geiselbullach, Halfingen

and Merklingen waste water treatment plants 152

Table 2-24 Membrane installations for waste water disinfection in Germany 153

Table 2-25 Demands on the effluent quality and operating values of the Bondorf-Hailfingen waste water

treatment plant [BONDORF-HAILFINGEN WASTE WATER UNION 2004] 157

Table 2-26 Quality of the effluent of the Wulpen waste water treatment plant [ZENON GMBH 2004] 159

Table 2-27 Waste water quality at the inlet and outlet of the ultrafiltration installation for treatment of the

effluent of the Katowice WWTP after secondary clarification up to process water quality

[ZENON GMBH 2004] 161

Table 2-28 Design results according to the approach of the University Group (HSG) for a conventional waste

water treatment plant with TSBB = 12 g/l 164

Table 2-29 Determination of the necessary volumes, taking into account different requirements for the

design of membrane installations 164


Table 3-1 Objectives for the utilization of membrane technology in industrial waste water treatment 171

Table 3-2 Sequence of planning for a membrane installation [according to THEILEN 2000; PETERS 2001] 174

Table 3-3 Sample applications for the use of membrane technology in industrial waste water treatment

in Germany 178

Table 3-4 Quality of the recycling water 2 [ENVIRO CHEMIE 2004] 203

Table 3-5 Inflow values, effluent requirements and operating values of the plant [SCHERING AG 2004] 214

Table 3-6 Sample applications for the use of membrane technology in industrial waste water treatment

outside of Germany 229

A Annex 263

Table A-1 Contacts for development programs of the federal states and selected development programs

concerning “waste water avoidance, closed process water circuits“ 278

Table A-2 Membrane processes and their fields of application 291

Table A-3 Overview of the most current membrane materials for the different membrane processes 293

Table A-4 Features and fields of application of different module types 294

Table A-5 Membrane installations in West European industry 314

Table A-6 Characteristic data of designed membrane bioreactors [WEDI 2002a] 324

Table A-7 Studies on the dewaterability of excess sludge on a large-scale centrifuge 327

Table A-8 Membrane-specific annual cost shares 336

1

22

Introduction

23

What is membrane technology?

Membrane technology is a physical process for the sepa-

ration of material mixtures in which the membranes

function like a filter. The separated substances are neither

thermally nor chemically nor biologically modified. In

waste water treatment membrane technology is also used

in combination with other purification methods, e. g.

biological procedures.

Fields of application

World-wide the field of application of membrane techno-

logy is becoming more and more broad. While its begin-

nings lay in the field of water purification in the desali-

nation of sea and brackish water in arid zones, it is used

for decades also for the separation of valuable materials

from small water volumes, e. g. in biotechnology, in the

pharmaceutical and chemical industry, the metal-work-

ing industry and in the food and beverage industry.

In addition, membrane technology got accepted as effi-

cient and economic procedure for the treatment of high-

strength industrial waste water. Membrane technology

has been tested and applied for the last ten years for the

treatment of comparably low-loaded and big water volu-

mes in drinking water treatment as well as in municipal

waste water treatment (membrane bioreactor process).

Membrane processes are used in drinking water treatment

to improve the retention of particles and to remove micro-

organisms. Ultrafiltration is predominantly used in this

field because not only germs but also viruses are safely

retained. Membrane processes for drinking water prepara-

tion are not treated in detail in this publication. Existing

plants with membrane technology are listed in Annex A7.

The membrane processes microfiltration, ultrafiltration,

nanofiltration and reverse osmosis are classified accord-

ing to the size or molar mass of the separated substances.

Their different molecular separation sizes allow for the

choice of the suited process for the particular task. For

more complex tasks, the combination with other proces-

ses, e. g. biological or chemical processes, is a possibility.

In the same way, two membrane processes may be com-

bined.

Membrane processes in waste water treatment

Due to high efficiency and the possibility of saving costs,

membrane processes currently represent a proven alter-

native to classical procedures for many applications in

the waste water treatment.

The high purification efficiency of membrane processes,

in particular the combination of an activated sludge stage

with downstream micro- or ultrafiltration, makes it pos-

sible to meet the requirements of tertiary waste water

treatment that are legislated for the protection of surface-

and groundwater. Without membrane technology, these

requirements can often only be met by a combination of

different process stages (e. g. activated sludge stage, con-

ventional filtration, disinfection). By using membrane

technology, it is possible in certain cases to reduce the

costs of water supply and waste water treatment as well

as production costs.

Objectives in waste water treatment

In municipal and industrial waste water treatment, mem-

brane processes are applied to satisfy the following objec-

tives:

• retention

(e. g. of solid matter including biomass, of hazardous

material, of dissolved matter by reverse osmosis)

• purification

(e. g. for industrial water treatment, for disinfection by

retention of bacteria)

• concentration

(e. g. for the recycling of valuable substances)

• fractionation

(e. g. for separation into two or more components)

Introduction

Advantages of membrane technology in waste

water treatment

The membrane bioreactor process with immersed mem-

branes can be used for industrial as well as municipal

waste water treatment. Compared to conventional waste

water treatment processes (activated sludge stage, secon-

dary treatment, filtration, disinfection), it has many

advantages which also have economic effects:

• saving of the process stages secondary stage, sand filtra-

tion, UV disinfection,

• the very compact design; compared to the activation

process, the necessary activation volume is only

approx. 30 %,

• the higher purification efficiency by complete reten-

tion of particles and bacteria, and, depending on the

membrane process, also viruses,

• better removal of organic trace substances by a higher

sludge age and the establishing of special micro-orga-

nisms

• the possibility to arrange downstream an additional

membrane stage (nanofiltration or reverse osmosis) to

retain organic trace substances and possibly also dis-

solved substances.

Prospects

Further development and application of membrane tech-

nology in the field of water and waste water treatment

will continue in the next years. The growth forecasts

concerning world-wide application of membrane proces-

ses are approx. 10 – 15 % per year for waste water treat-

ment and about 20 % per year for drinking water treat-

ment (including sea water desalination). (Plants for drink-

ing water treatment existing in Germany are compiled in

Annex 7). Due to continuous development of membrane

materials and module constructions as well as process

design and process engineering, a still broader range of

applications is opened up.

Moreover, the cost-effectiveness of membrane processes

continuously improves compared to other waste water

treatment processes, since the water and waste water costs

generally rise and the specific membrane prices go down.

With view to possibly increasing requirements for the

waste water treatment technology, the attractiveness of

the membrane bioreactor process (micro- or ultrafiltra-

tion) combined with a downstream nanofiltration or

reverse osmosis installation will grow. Due to the high

attainable sludge age and the downstream membrane

stage, the membrane bioreactor process is also suited for

the removal of some organic trace substances.

Structure and contents of this publication

This publication gives an overview of the present use of

membrane processes in municipal and industrial waste

water treatment, in Germany in particular. Membrane

technology is still being developed and the number of

application possibilities continues to increase.

This publication is intended for both specialists and lay-

men. It is less a comprehensive textbook or manual for

the solution of all problems concerning design, building

and operation of a membrane installation than rather an

instrument, which sensitizes the reader to these ques-

tions and offers solutions. The reference to practice and

the relevance of membrane technology to waste water

treatment becomes clear by the description of installa-

tion examples from the municipal and industrial field in

Germany and outside of Germany. The locations of the

installations described are shown in the following figure.

24

Introduction

25

! municipal plants with microfiltration

! municipal plants with ultrafiltration

industrial plants with microfiltration

industrial plants with ultrafiltration

industrial plants with nanofiltration

Sites of the waste water treatment plants with membrane technology in Germany described in this publi-

cation

industrial plants with reverse osmosis

or the combination UF/RO

industrial plants with the combination

UF/NF

industrial plants with the combination

MF/UF/NF/RO

Introduction

26

The contents of this publication is subdivided into several

partial chapters, each of them representing a complete

unit. Therefore they can be read independently from each

other and allow the reader to orient himself according to

the focus of his interests. The following overview sum-

marizes the contents of the individual chapters and shows

the reader the way through the publication.

Annex: Contacts, possibilities for promotion

Guideline

Chapter 1: Basics

Chapter 2: Municipal waste water treatment

Chapter 3:Industrial waste water treatment

Chapter 4: Instructions and standards

Membrane technology in waste water treatment

Structure and contents of this publication

Basics of Membrane Technology 1

Basics of Membrane Technology1

1.1

Basics of Material Separation by means of

Membrane Technology

Material separation by means of membrane technology is

a physical separation process. Compared with other sepa-

ration technologies, this technology has the advantage

that the separated materials are neither thermally nor

chemically or biologically modified. The fields of applica-

tion of membrane processes stretch from simple filtration

of solids, e. g. separation of activated sludge in municipal

waste water treatment, up to the separation of materials

within the molecular range, e. g. retention of dissolved

salts in seawater desalination.

The operating principle of a membrane can be described

in the wider sense like that of a filter. As shown in Figure

1-1, a substance mixture, called feed or raw solution (e. g.

raw waste water) is separated by the membrane. The part

which passes through the membrane almost unhindered is

called permeate or filtrate. To waste water purification

the permeate represents the treated phase. The portion

retained by the membrane is the brine or concentrate.

The driving force for the separation process is the pres-

sure difference between the feed and permeate side, the

so-called transmembrane pressure difference or

transmembrane pressure. It is applied by overpressure on

the side of the feed or low pressure on the side of the

permeate. Dependent on the membrane employed, the

transmembrane pressure is between 0.1 bar and 70 bar,

in special cases it is up to 120 bar.

The characteristics selectivity and capacity are of deci-

sive importance for the economic efficiency of a mem-

brane process. The selectivity describes the ability of a

membrane to differentiate between the components of a

mixture and thus to separate one phase from the other.

By capacity of a membrane, we understand the flow

under specific operational conditions. The flow is defined

as the volumetric flow rate per unit surface area (unit:

L/(m2 · h)).

28

small particleslarge particles

raw solution,waste water, feed

brine,concentrate

membrane permeate,filtrate

Figure 1-1

Operating principle of micro- and ultrafiltration membranes


Another important feature of a membrane is described by

the parameter permeability. It is defined as the quotient

from flow and the accompanying transmembrane pres-

sure (unit: L/(m2· h · bar)). The permeability of a mem-

brane is influenced by the membrane condition and the

filtration characteristics of the waste water (see chapter

1.7). The latter depend on the material composition and

the characteristics of the waste water mixture, e. g. tem-

perature, particle-size distribution and viscosity.

1.2

Membrane Processes in Waste Water Purification

There are various membrane processes which differ in

their molecular separation size and the driving force

which has to be expended. Which process is employed

depends on the waste water composition and the separa-

tion goal.

The separation goal in municipal waste water purification

is above all the separation of the cleaned waste water

from the biomass in order to meet the effluent standards.

In an industrial company, the employment of a mem-

brane process for waste water purification may be fea-

sible, particularly if a useful integration into the produc-

tion process is possible. Besides the treatment of the

waste water, it is also frequently aimed at reusing the per-

meate and possibly the concentrate, so that these can be

recycled into the production process.

In municipal waste water purification, the membrane

processes microfiltration (MF) and ultrafiltration (UF) are

used. For industrial waste water purification, nanofiltra-

tion (NF) and reverse osmosis (RO) are also of impor-

tance. These four processes are therefore described in the

following.

Figure 1-2 indicates the molecular weight and the size of

the materials which can be separated by microfiltration

(MF), ultrafiltration (UF), nanofiltration (NF) and reverse

osmosis (RO).

The size of some waste water constituents and the pore

size of the membranes applied are presented in Figure 1-3.

29

nanofiltration

microfiltration ultrafiltration

reverse osmosis

filtration

aproximate sizelogarithmic scale

molecular weight[g/mol] or [Dalton]no scale

activated sludge flocs

organic acids

100 10 1 0,1 0,01 0,001

200.000 20.000 2001.000.000 10.000100.000500.000

bacteria viruses

diclofenac •

bisphenol A •nonylphenol •

benzo-a-pyren •EDTA •

saccharrose •amoxicilline •

mercury •simazine •

glycine •salt (NaCl) •acetic acid •

phenol •

poliomyelitis virus •

influenza virus •

herpes virus •bacillus subtillis •

escherichia coli •

mumps virus •

Figure 1-2

The different fields of application of membrane processes

polyvalent ion

low-molecular weightorganic substances

monovalent ion

influenza virus

macro-molecular weightorganic substances

activated sludge flocs

escherichia coli


30

mem

bra

ne

typicalpore size:0,4 µm

ultrafiltrationpore size: 0,005 – 0,1 µm

microfiltrationpore size: 0,1 – 5 µm

mem

bra

ne


Figure 1-3

Size of typical waste water constituents and the pore size of membranes applied

Table 1-1 provides an overview of the membrane proces-

ses presented, with driving force and application possibil-

ities. Further details about the individual processes are

given in the following sections 1.2.1 to 1.2.3.

Two mechanisms are essentially responsible for the mass

transfer in membrane processes: transfer by pores and

transfer due to diffusion. In real membranes both trans-

fer modes can occur in parallel; however, the idealized

classification of membranes is as follows:

• pure pore membranes (“porous” membranes) and

• pure solution-diffusion membranes (“dense” mem-

branes)

Separation by pore membranes (MF, UF) is based on a

sieving effect, while differences in solubility and diffusi-

vity are responsible for the selectivity of solution-diffu-

sion membranes (NF, RO) [RAUTENBACH 1997].

The concentration process of a component to be separa-

ted by a membrane is represented in an idealized manner

for a pore membrane and a solution-diffusion membrane

in Figure 1-4. With the pore membrane, the component

to be separated is retained by the membrane due only to

its size. In the course of concentration, a sharp separa-

tion on the membrane surface can be recognized. When

entering into the membrane, the concentration of the

component in the feed drops down to the concentration

in the permeate.

However, with a solution-diffusion membrane a

reduction of the concentration also takes place within

the membrane due to the transportation mechanisms.


31

nanofiltrationpore size: 0,001 – 0,01 µm

reverse osmosispore size: 0,0001 – 0,001 µm

mem

bra

ne


mem

bra

ne


Microfiltration liquid/solid pressure difference 0,1 – 3 bar separation of solid matter from suspensions

Ultrafiltration liquid/liquid pressure difference 0,5 – 10 bar separation of macromolecular or colloids, disinfection

Nanofiltration liquid/liquid pressure difference 2 – 40 bar separation of dissolved organic molecules and polyvalent inorganic ions

Reverse osmosis liquid/liquid pressure difference 5 – 70 bar separation of organic molecules and of all ions

in special cases up to 120 bar

Table 1-1

Pressure-driven membrane processes in waste water purification

Membrane process Phase separation Driving force Application

permeateside

feedside

wiP

wiF

pore membrane solution-diffusion-membrane

wiF concentration of the waste waterconstituents in the feed

wiP concentration of the waste waterconstituents in the permeate

feedside

wiF

wiP

permeateside

Figure 1-4

Idealized representation of a pore membrane and a solution-diffusion membrane [according to MELIN 1999]

Micro- and Ultrafiltration

Microfiltration (MF) and ultrafiltration (UF) belong to the

pressure-driven membrane processes. Concerning operat-

ing pressure and molecular separation size, they are cate-

gorized between nanofiltration and filtration (e. g. sand

filtration). The separation mechanisms of the Mf and UF

membranes are similar and the fields of application may

strongly overlap (Figure 1-2), so that both are described

in this chapter.

According to the principle of a porous filter, by MF

and UF all those particles that are larger than the mem-

brane pores are retained completely. The particles held

back can develop a covering layer on the membrane sur-

face. This layer then holds back smaller particles which,

without a covering layer, would pass through the mem-

brane (process controlled by the covering layer).

Characteristic features of micro- and ultrafiltration are

summarized in Table 1-2.

In waste water purification, micro- and ultrafiltration are

used for the separation and retention of particulate and

emulsified waste water constituents. Typical applications

include:

Municipal waste water treatment

• separation of activated sludge and water

• disinfection

• pretreatment prior to a reverse osmosis plant

• phosphate removal after precipitation

Industrial waste water treatment

• Waste water recycling and reuse as process water

for different purposes

• Treatment of landfill leachate combined with a

biological stage

• Recovery of water-based paint from spray booth

effluents by concentration

• e. g. in the metal-working industry:

· Prolongation of the service life of electro-dipcoat

bathes

· Concentration of water-oil emulsions

· Recycling of degreasing baths


32

Table 1-2

Characteristic features of micro- and ultrafiltration

Mikrofiltration (MF) Ultrafiltration (UF)

Operation mode (see Chapter 1.6) cross-flow- and dead-end-operation cross-flow- and dead-end-operation

Operating pressure 0,1 – 3 bar (transmembrane) 0,5 – 10 bar (transmembrane)

Separating mechanism screening controlled by covering layer, if necessary screening controlled by covering layer, if necessary

Molecular separation size solids > 0,1 µm (see figure 1-2) colloids: 20.000 – 200.000 Dalton*,

solids > 0,005 µm (see figure 1-2)

Membrane types predominantly symmetric polymer or ceramic membranes asymmetric polymer composit or ceramic membranes

(see chapter 1.3) (see chapter 1.3)

Module types spiral-wound, hollow-fibre and tube modules, spiral-wound, hollow-fibre and tube modules,

plate or cushion modules plate and cushion modules

* [Dalton], numerically equivalent to the molecular weight (MW) in [g/mol]

MF UF1.2.1

1.2.2 NF


33

Nanofiltration

Nanofiltration (NF) is a pressure-driven membrane pro-

cess which is preferentially used for the recycling of

aqueous solutions. Concerning operational pressure and

separation size, nanofiltration is categorized between

reverse osmosis and ultrafiltration. By means of NF mem-

branes, the retention rate for particles with a molecular

mass greater than 200 g/mol is high; this corresponds to

a molecule diameter of approx. 1 nm.

Typical of NF membranes is their ion selectivity. The

retention of a dissolved salt is determined by the valency

of the anion. Therefore most salts with monovalent

anions (e. g. Cl-) can pass through the membrane, where-

as multivalent anions (e. g. SO42-) are retained [RAUTEN-

BACH 1997]. Characteristic features of nanofiltration are

represented in Table 1-3.

Up to now nanofiltration has not been used in municipal

waste water treatment.


• Relief of ion exchangers or downstream reverse osmosis

units

• Removal of colour in the waste water of the textile and

the pulp and paper industry

• Demineralization of waste water containing surfactants

In general:

• Retention of multivalent ions (e. g. SO42-, Cd2+, Cr2+),

but permeation of monovalent ions (e. g. Cl-, Na+)

• Retention of organic compounds

• Separation of components with lower and higher mole-

cular weight in aqueous solutions

Table 1-3

Characteristic features of nanofiltration

Nanofiltration

Operating mode (see chapter 1.6) cross-flow-operation

Operating pressure 2 – 40 bar (transmembrane)

Separation mechanism solubility/diffusion/charge (ion selectivity)

Molecular separation size dissolved matter: 200 – 20.000 Dalton* solids > 0.001 µm (see Figure 1-2)

Membrane types asymmetric polymer or composite membrane (see chapter 1.3)

Module types spiral-wound, tube, and cushion modules



Reverse Osmosis

Reverse osmosis (RO) serves to separate components of a

solution. It is based on a pressure-driven process, the

driving force resulting from the difference of the electro-

chemical potential on both sides of the membrane. The

non-porous RO membranes can retain dissolved material

with a molecular weight of less than 200 g/mol com-

pletely, so that reverse osmosis achieves a higher separa-

tion efficiency than nanofiltration. Since dissolved salts

are retained to a very high extent, RO has a history

as a proven membrane procedure, which is already state

of the art for example in the desalination of sea- and

brackish water. Characteristic features of reverse osmosis

are compiled in Table 1-4.

Reverse osmosis has no importance in municipal waste

water treatment. Fields of application are [RAUTENBACH

1997]:


• Concentration of drainage water from mines contain-

ing CaSO4

• Dewatering of flushing water from photo laboratories

for silver recovery

• Treatment of waste water from textile dyeing (cotton

and polyester dyeing)

• Concentration of cellulose washing water

• Recovery of phosphoric acid

• Treatment of waste water from bleacheries

• Treatment of landfill leachate

34

Table 1-4

Characteristic features of reverse osmosis

Reverse Osmosis (RO)

Operating mode (see chapter 1.6) cross-flow-operation

Operating pressure 5 - 70 bar (transmembrane), in special cases up to 120 bar

Separation mechanism solubility/diffusion

Molecular separation size dissolved matter: < 200 Dalton* (see Figure 1-2)

Membrane types asymmetric polymer- or composite membrane (see chapter 1.3)

Modul types spiral-wound, tube, plate, cushion or disc-tube modules


RO1.2.3


35

1.3

Membrane Materials, Structure and Classification

Membranes are classified according to different features

(Figure 1-5), which are briefly explained in the following:

• Origin

• Material

• Morphology and structure

• Manufacturing process

Depending on waste water composition and characteris-

tics as well as operational requirements, different ma-

terials are used for membranes. Membrane materials are

organic (e. g. cellulose, polymer membranes) or inorganic

(e. g. ceramic membranes).

1.3.1

Origin and Materials

Membranes can be of biological and synthetic origin and

differ according to structure, functionality and material

transfer. While biological membranes, e. g. cell mem-

branes, are indispensable for human and animal exist-

ence, in waste water purification only synthetic, solid

membranes are used.

membrane

synthetic

solid

inorganic

non-porous

biologicalorigin

liquid

organic

porous porous

material

morphology

Figure 1-5

Classification of membranes [according to RAUTENBACH 1997]

Organic membranes

At present synthetic polymer membranes are used predo-

minantly because it is possible to select a polymer suita-

ble for the specific separation problem from the existing

huge number of synthetic polymers. Moreover, compared

to other materials, polymer membranes are often chea-

per.

For the separation of a constituent, the structural charac-

teristics of the polymers used, like thermal, chemical and

mechanical stability, and the permeability are decisive.

Examples of organic polymer membranes are for example

polysulfone (PS), polyacrylonitrile (PAN), polyethersul-

fone (PES), polypropylene (PP), polyvinylidene fluoride

(PVDF), acetylcellulose, and polyamide (PA) membranes.

Inorganic membranes

In the recent past inorganic membranes have gained

more and more importance. They are used especially if

the employment of polymer membranes is excluded

because of the characteristics of the raw waste water or

if the organic membrane surfaces have to be cleaned

frequently and intensively due to the waste water com-

position.

Inorganic membrane materials are ceramics, aluminum,

high-grade steel, glass and fiber-reinforced carbon, of

which ceramic membranes at present have the greatest

importance in waste water purification. Compared to

organic membranes, the advantages of ceramic mem-

branes are high resistance against heat and chemicals,

with correspondingly a high regeneration capacity, as

well as reduced aging and long service lives. Disadvan-

tages are above all the higher investments due to the

membrane material and more expensive module con-

structions.

1.3.2

Morphology, Structure and Manufacturing

Concerning the morphology of membranes, we distin-

guish between pore mem-branes and solution-diffusion

membranes (see Figure 1-5 and chapter 1.2). Inorganic

membranes are always pore membranes.

The structure of a membrane may be symmetric or

asymmetric. While symmetric membranes have a nearly

homogeneous structure all over the thickness of the

membrane, asymmetric membranes are made up of two

layers.

The layer on the side of the feed (active layer) determines

the separation behaviour of the membrane, while the

porous layer below serves as support. The supporting lay-

er ensures the mechanical stability of the membrane and

hinders the permeate flow only little. The aim of asym-

metric membrane design is to keep the active layer as

thin as possible and, with this, minimize the filtration

resistance of the membrane. With solution-diffusion

membranes it is therefore possible to obtain flows which

are 50 to 100 times higher than with comparable symme-

tric membranes [MELIN 1999].

Today asymmetric organic membranes are usually manu-

factured as phase inversion or composite membranes.

The active layer and supporting layer of the phase inver-

sion membranes are made from the same material.

However, in the case of composite membranes, the active

layer and supporting layer consist of different materials,

so that both layers can be optimized with a view to cus-

tomizing the characteristics required in each case.

Figure 1-6 shows scanning electron micrographs of phase

inversion membranes (a), (b) as well as of a composite

membrane (c). Figure 1-7 and Figure 1-8 represent the

active layer of a polyethylene membrane at different

resolutions.


36


37

Figure 1-7

Top view of the active layer of a polyethylene

membrane (MF/UF) [AGGERVERBAND 2002]

Figure 1-8

Top view of the broken edge of a polyethylene

membrane (MF/UF), the active layer is visible

[AGGERVERBAND 2002]

denitrifica-tion

symmetricmembrane-layer

200 µm

symmetric polymer membrane (MF) [N.N. 2002a]

activelayer

supportinglayer

7 µm

asymmetric composite membrane(RO) [FRIMMEL, GORENFLO 2000]

activelayer

supportinglayer

7 µm

asymmetric polymer phase inversion membrane(UF) [N.N. 2001a]

Figure 1-6

Scanning electron micrographs of cross-sections of

different membranes


1.4

Membrane Forms and Modules

Depending on the manufacturing process, we distinguish

two basic membrane forms:

• tubular membranes and

• flat membranes

These membranes are arranged in an engineered unit,

the module. Besides the membrane itself, the module is

of decisive importance for the efficiency of a membrane

stage. There are a huge number of different module con-

structions because the modules are adapted in their con-

struction to meet the requirements of the end use.

The basic membrane forms, which depend on the condi-

tions of production, are assigned to the module forms

represented in Figure 1-9. In some special cases this strict

allocation is not permissible, e. g. if some membranes

used in tube modules were manufactured by the tubular

processing of flat membranes. Concerning tubular mem-

branes, we distinguish as module constructions the tube,

capillary and hollow-fibre module. For flat membranes

we distinguish plate, spiral-wound, cushion and disc-tube

modules.

The different module forms can be characterized regard-

ing the arrangement of the separation layer, the compo-

nent density and, with the tubular diaphragms, regarding

the diameter (free flow cross-section) (Table 1-5, Table 1-6).

Due to the different characteristics related to performan-

ce and operation (e. g. operating mode, susceptibility to

blockage, simple backwashing etc.) and the surface-speci-

fic module costs, certain module types are preferentially

used depending on the waste water to be treated. A prere-

quisite for module selection is in each case the selection

of the membrane process and/or the membrane which is

suitable for the separation problem. Table 1-2 (MF and

UF), Table 1-3 (for NF) and Table 1-4 (for RO) can be used

to identify which module types are used in the different

membrane processes.

38

membrane form

module form

tubular flat

tube modul

capillary module

hollow-fibre module

spiral-wound module

cushion module

plate module

disc-tube module

Figure 1-9

Membrane and module forms


The following figures present module forms which are

used particularly in industrial waste water treatment.

They are described with the help of pictures and/or flow

sheets. Further examples and explanations concerning

e. g. the plate and capillary modules used in municipal

waste water treatment are given in chapter 2.1.2.

39

Table 1-5

Characteristic values, advantages and disadvantages of module types with tubular membranes

Tubular membranes

Tube module Capillary module Hollow-fibre module

Arrangement of the inside outside/inside outside/inside

separation layer

Inside diameter 5,5 ... 25 mm 0,25 ... 5,5 mm 0,04 ... 0,25 mm

Component density < 80 m2/m3 < 1.000 m2/m3 < 10.000 m2/m3

Operating mode cross-flow dead-end/cross-flow dead-end

Advantages hardly susceptible to blockage high component density extremely high component density

low pressure loss operation controlled cheap production backwashing possible favourable specific membrane costs

by covering layer is possible on the permeate side high pressure resistance

Disadvantages low component density low pressure resistance susceptible to blockage pressure loss

Table 1-6

Characteristic values, advantages and disadvantages of module types with flat membranes

Flat membranes

Plate module Spiral-wound module Cushion module

Arrangement of the outside outside outside

separation layer

Component density 40 ... 100 m2/m3 < 1.000 m2/m3 ca. 400 m2/m3

Operating mode cross-flow dead-end/cross-flow dead-end/cross-flow

Advantages membranes can be changed separately cheap production few seals little pressure losses on the permeate side

hardly susceptible to blockage high component density hardly susceptible to fouling

Disadvantages many seals long flow path on the permeate side low component density

low component density mechanical cleaning not possible many seals

risk of blockages


Tube modules

Inside a jacket or a pressure tube, several supporting

tubes of smaller diameter which are perforated or perme-

able to the permeate, are combined. The tubular mem-

brane layer is applied on the inside of the tubes. The feed

is pumped through these tubes and is collected in the

outside space between the pressure tube and supporting

tubes and is then withdrawn at a connecting piece on

the pressure tube.

40

permeate collectorpermeate

feed

connectionthread

sealing ringsmembrane-supporting tube

membrane

brine

feed

permeate

Figure 1-10

Tube modules [photo: WEHRLE WERK AG]


41

Capillary or hollow-fibre modules

In a pressure tube, a large number of capillary and/or

hollow-fibre membranes are combined into a module.

Comparable to multichannel tube modules, the capilla-

ries and/or fibres can be fed with the feed stream so that

filtration takes place from inside to outside.

In addition there is a construction for which membrane

capillaries/fibres with an outer coating are used. In this

case, filtration takes place from outside to inside and the

permeate is withdrawn on the inside of the capillaries/

fibres.

More capillary module forms are described in chapter 2.1.2.

hollow fibre

feed: inside

permeate

feed: outside

feed

permeate feed

feed permeate

pressure tube bonding (resin)

Figure 1-11

Capillary or hollow-fibre modules [photo: KOCH MEMBRANE SYSTEMS]


42

Spiral-wound modules

This module consists of one or more membrane bags

which are wound helically with one spacer each (feed

spacer) around the permeate collecting pipe. The mem-

brane bags are closed at three sides and at the open side

the bags are attached to the perforated permeate collec-

tion pipe. The inside of the membrane bags is filled with

a porous plastic textile (permeate spacer), which allows

the permeate to flow between the membranes. The cylin-

dric module resulting from the whirl is supplied to the

front with the feed, which flows through the module in

an axial direction. While the feed flows through the

space outside of the membrane bags resulting from the

feed spacer, the withdrawn permeate flows inside the

membrane bags helically to the permeate collection pipe.

feedspacer

feed flow

central tube

membrane

permeate in thepermeate chanal

permeate spacer

permeate-flow in thecentral tube

Figure 1-12

Spiral-wound modules [schematic drawing: N.N. 2001], [photo: NADIR FILTRATION GMBH]


43

Cushion modules

Cushion modules are constructed by analogy to spiral-

wound modules from membrane bags with intermediate

woven fabric fleece. In this case all sides of the bags are

closed and the permeate is withdrawn through one or

more openings, provided with round seals, in the cushion

provided.

As can be seen in the figure, several cushions can be inter-

connected via the permeate openings. The cushion packa-

ges are then inserted into a pressure tube with modular

character. In its wall is the permeate collection pipe with

connections and seals for the corresponding permeate open-

ings of the cushion packages as well as for the following

components of the pressure tube.

permeate-drainage pin

membranecushion stack

permeate channel (permeate discharge)

pressure tube

spherical shell

spacer

raw water

membrane

drainage fleece onpermeate side

support plate

permeatechannel

spacer1 – 3 mm

(variable channel height)

membrane

permeate drainagepin

drainage fleece onpermeate side

Figure 1-13

Cushion module [schematic drawing and photo: ROCHEM UF SYSTEME GMBH]


44

Disc-tube module (DT module)

The disc-tube module (Figure 1-14) is made of supporting

discs and membrane cushions which are alternately

stacked on a tie rod, so that open flow channels result

between the discs and the membrane cushions on the

side of the raw water. The supporting discs of the DT

module are provided at their outer edge with a sealing

ring which juts out evenly at both sides. An annular gap,

formed by ribs, through which the raw water flows

during operation, a slot for sealing between membrane

cushion and supporting discs, and a lead-through for the

tie rod with permeate discharge slots are arranged centri-

cally. The membrane cushions are made of flat mem-

branes with internal woven fabric fleece and are welded

at the outside.

The preassembled disc-membrane stack is fitted into a

pressure tube. The raw water is fed between the inside

wall of the pressure tube and the sealing rings at the edge

of the discs to the annular gap in the first disc of the

disc-membrane stack and filtered from outside to inside

through the membrane cushions.

The permeate is withdrawn via the round lead-through

in the center of the membrane cushions, the discharge

slots in the supporting discs and a drill-hole in the end

piece of the membrane stack. The open annular gaps and

the flow paths between the membrane cushions and the

discs also allow for the treatment of liquids with higher

colloids or solids loads.

Figure 1-14

Disc-tube module (DT module) [PALL 2001]


45

The membrane system from the company inge AG

Another development is the module from the company

inge AG with new, so-called, Multibore capillaries. As

Figure 1-15 shows, these capillaries have seven drillings

each, which have approximately the inside diameter of

conventional single capillaries. Thus, the mechanical

integrity of the membrane capillaries is increased and

capillary breaks occur more rarely than with single capil-

laries.

The Multibore capillaries are operated according to the

inside-outside principle, i. e. supplied from their inside

with the raw water to be filtered. Thus they are applica-

ble only in the case of small solid contents in the raw

water, comparable to the single capillary modules with

inside flow. In the case of capillary membranes with in-

side flow and small feed channel dimensions, higher

solid contents frequently cause blockages. Therefore, the

preferred field of application of the Multibore capillaries

is drinking water processing.

Figure 1-15

New Multibore capillaries from the company inge AG [photo: INGE AG]


1.5

Arrangement of Modules

A membrane stage is a unit functioning in itself, which

consists of modules, pumps, valves etc. Besides the selec-

tion of a membrane or a membrane module suitable for

the waste water mixture to be separated, the arrangement

and/or connection of the modules is critical to the per-

formance of a membrane stage (Figure 1-16). In waste

water treatment, the volumetric flow to be separated and

the permeate quality or permeate yield to be obtained are

important.

We distinguish two basic connections of modules:

• series connection and

• parallel connection

Series connection is used if the permeate yield from one

module is not sufficient. Several modules are connected

in series, so that according to Figure 1-17, the concentrate

flow of a module serves as feed for the next module and

the permeate of the single modules is brought together.

With parallel connection (Figure 1-18), the feed is dis-

tributed to the individual modules connected in parallel.

The number of modules in parallel connection depends

on required the capacity of the membrane stage. The

modules in parallel connection are called a block. The

waste water-specific permeate yield or the concentration

within a block corresponds to the yield or concentration

that is attained with one module.

While in municipal waste water treatment pure parallel

connection dominates, combinations of both basic con-

nection types are used in industrial waste water treat-

ment in order to achieve the desired purification goal or

the maximum concentration:

46

feed

concentrate

permeate

Figure 1-17

Series connection of modules [according to BAUMGARTEN 1998]

desiredeffluentquality

feed

concentrate

membrane element module modul connection membrane stage

Figure 1-16

From the membrane element to the membrane stage


47

• fir tree structure (Figure 1-19)

• feed-and-bleed structure

Figure 1-19 shows an example of the fir tree structure

which is frequently used (e. g. in the seawater desalina-

tion). The modules within blocks one and two are con-

nected in parallel and all three blocks among themselves

in series. With this structure, the concentrate flow is con-

tinuously concentrated or minimized from block to block

and the permeate yield is correspondingly increased. Since

the permeate is withdrawn from each block, the volume-

tric flow to be treated reduces from block to block. There-

fore, the number of modules required in the following

block is reduced so that, e. g. with tube modules, the

overflow conditions are adapted to the requirements also

in the downstream membrane elements.

If the fir tree structure cannot be used because the feed

flow rate is smaller than is necessary for the module ap-

plied, the feed-and-bleed structure or the recircula-

tion cycle is used within each block. With this structure

the feed flow rate is increased by mixing the concentrate

with a part of the feed by internal recirculation. Thus a

higher concentration or higher permeate yield can be

achieved with one module. This is used for example in

landfill leachate treatment.

feed

concentrate

permeate1st block

2nd block

3rd block

Figure 1-19

Arrangement of several modules according to the fir tree structure

[according to RAUTENBACH 1997]

feed concentrate

permeate

Figure 1-18

Parallel connection of modules [according to BAUMGARTEN 1998]


1.6

Operating Modes

In principle, we distinguish two filtration operating

modes:

• dead-end or static filtration and

• cross-flow or dynamic filtration

Cross-flow operation is used in nanofiltration and reverse

osmosis. In ultra- and microfiltration both operating

modes are possible.

In the cross-flow mode (cross-current filtration) the feed

is pumped parallel to the membrane surface and the per-

meate is withdrawn diagonally to it. In dead-end ope-

ration the membrane is fed orthogonally, comparable to

a “coffee filter”. Figure 1-20 illustrates the differences bet-

ween the two operating modes.

Due to the retention of suspended material, a covering

layer develops on the feed side, which diminishes the fil-

tration capacity. As a result, the permeate flow decreases

with progressive process duration. As preventive measure,

the entire module is submitted in intervals to backwashing.

Figure 1-21 shows the decrease of the permeate flow, VP,

at a constant feed pressure, pF, as set target (left) and the

increase of the feed pressure at a constant permeate flow

as set target (right) over the filtration interval. By remo-

val of the covering layer during the backwashing inter-

val, ideally the original filtration capacity will be reached

again.

In cross-flow operation the formation of a covering layer is

diminished because there is a continuous flow over and

parallel to the membrane. Thus, a state of equilibrium at

the membrane surface between development and remo-

val of the covering layer is achieved by the shear forces.

The overflow is typically generated by pumps. However,

other systems may also be used, such as generating the

overflow by introducing gas below the modules, i. e. by

the ascending gas-feed mixture, or the movement of the

membranes themselves (see chapter 2.1.2). A disadvan-

tage of cross-flow operation compared to dead-end opera-

tion is the higher energy demand as a result of the over-

flow energy which has to be continuously applied.

The term “semi-cross-flow” or “semi-dead-end pro-

cess” is also increasingly used. In this case, process ele-

ments of the two operating modes cross-flow and dead-

end are combined in order to reduce the energy con-

sumption in contrast to the pure cross-flow process. An

example of a semi-cross-flow operation is intermittent

overflow of the membrane according to the cross-flow

principle combined with backwashing intervals so that

the developing covering layer can be removed.

48


49

permeate

feed

feed

permeate

cross-flow operation dead-end operation

Figure 1-20

Schematic representation of a membrane in cross-flow- and dead-end filtration [according to MELIN 1999]

time t

filtrationinterval

backwashinginterval

set target :constant feed presure pF

feed

pre

ssur

e p

F

per

mea

te f

low

Vp

time t

filtrationinterval

backwashinginterval

set target :constant permeate flow Vp

feed

pre

ssur

e p

F

per

mea

te f

low

Vp

Figure 1-21

Filtration intervals in dead-end operation [according to RAUTENBACH 1997]


1.7

Formation of Covering Layers

Municipal and industrial waste waters contain organic

and inorganic matter. During purification of these waste

water by means of a membrane, the constituents of the

feed concentrate and a separation of particles at the

membrane surface occurs due to the selective effect of

the membrane. With increasing operating time, this

results in the development of a covering layer. Covering

layers can be used to a certain extent in a beneficial way

for filtration (e. g. in order to increase the purification

degree), but often they are undesirable because they

diminish the permeate flow and thus the performance of

the membrane.

The reducing performance of the membrane is based on

an increase in the filtration resistance, which increases

the output membrane resistance (Rm) (Figure 1-22).

Concerning the micro- and ultrafiltration membranes,

the increased covering layer resistance results from ad-

sorption (RA), pore blockage (Rp) and the covering layer

formation itself (Rc). However, the increase of the filtra-

tion resistance of the tight nanofiltration and reverse

osmosis membranes is due to a concentration polarisa-

tion (RCP) of dissolved matter, the concentration of which

rises with increasing filtration duration.

Increased resistances due to adsorption (Ra) and pore

blockage (Rp) normally cannot be reduced by measures

such as backwashing or the like, so that during severe

pore blockage another membrane material should be

used. On the other hand covering layer formation can be

decreased or undone by increasing the overflow velocity

or backwashing the membrane with permeate in inter-

vals [PANGLISCH ET AL. 1996].

Measures against covering layer formation and thus for

maintenance of the filtration capacity are treated in the

following chapter.

The formation of covering layers can have different cau-

ses, which also determine the composition of the layer.

We distinguish [BAUMGARTEN 1998]:

• biological fouling (briefly: biofouling)

• colloidal1) fouling

• scaling

Biofouling

Biofilm formation on the membrane surface is caused by

adhesion and the growth of micro-organisms [FLEM-

MING 1995]. Biofouling means that the biofilm causes a

reduction of the performance of the membrane system

by decreasing the specific membrane flow [FLEMMING

2000]. Plant shut-downs should be treated with caution,

since under these conditions the number of bacteria on

the membrane surface may increase dramatically [BAKER

ET AL. 1998].

Colloidal fouling

From the accumulation of colloids results a kind of film

or mucus on the membrane surface, which leads to a

reduction of the filtration capacity.

Scaling

Scaling can be described as coatings on the membrane

formed by inorganic precipitations (crystallization). Usu-

ally they only occur with NF and RO membranes if, for

example, the solubility limit of dissolved salts is exceeded

by excessive concentration on the membrane surface.

Table 1-7 summarizes the substances which can cause the

three types of covering layer presented.

50

1) colloidal = finely spread out, finely dispersed


51

permeate sidefeed side

Rp

Ra

Rm

Rc

Rcp

Figure 1-22

Schematic overview of the filtration resistances on the membrane surface and inside the membrane

[KRAMER, KOPPERS 2000]

Table 1-7

Formation of covering layers in membrane filtration [according to BAUMGARTEN 1998]

Scaling (crystallization)

CaSO4

CaF2

BaSO4

SiO2

Mg(OH)2

Covering layer formation

Fouling

Biofouling

• germs

• bacteria growth due to nutrient supply in the feed

• formation of mucus by micro-organisms

Colloidal fouling

• colloidal silicic acid and silicates

• colloidal hydroxides (e. g. Fe and Mn)

• organic colloids (e. g. humic substances, proteins)


1.8

Measures for Maintenance of the Filtration Capacity

The utilization of membranes in waste water treatment is

practically feasible only if the covering layer formation

(chapter 1.7) is controlled so that safe and economic ope-

ration can be ensured.

The development of covering layers due to fouling or

scaling can be avoided or reduced if the following aspects

Pretreatment measures

In municipal waste water treatment, the pretreatment for

the membrane bioreactor (chapter 2.1.3.2) takes place in

the mechanical stage (e. g. rake, grit chamber, primary

settlement tank). In this stage material which would

disturb the filtration process, such as coarse particles, fats

and fibres, are removed.

Material contents and composition of industrial waste

water vary considerably. The pretreatment measures for a

membrane plant have to be chosen according to the re-

quirements of the waste water composition. Mechanical,

physical, biological and chemical procedures can be used.

Examples are mentioned in Table 1-8.

Optimization of the process configuration

The formation of covering layers is determined essential-

ly by the operating mode – dead-end or cross-flow opera-

tion – and the process control. By operational measures,

such as increasing the backwashing volume or the back-

washing time in dead-end operation, or increasing the

overflow velocity in cross-flow operation, covering layer

formation can be reduced.

However, due to increased energy demand for higher

overflow velocity and because of the permeate loss due

to more frequent backwashing, these measures are not

very economical and can only be optimized during the

operation of a plant.

are considered during construction and operation of the

membrane plant (Table 1-8):

• pretreatment measures

• process configuration

• membrane and module characteristics

• cleaning

52

Table 1-8

Methods for reduction and removal of covering layers

pretreatment

sieve

prefiltration

cooling

neutralisation

preprecipitation

reduction, prevention, removal of covering layers

optimisation of the

process configuration

process design

overflow

flushing method

constructional design

membrane material

structure

module design

module conception

cleaning

cleaning agent

cleaning interval

concentration


Structural design

Membrane material and membrane structure have the

largest influence on the formation of covering layers

since the membranes interact directly with the covering

layer forming materials at the inlet. Depending on mate-

rial properties and the charge of a membrane, contami-

nation at the membrane is adsorbed less or more strongly.

The most important structural characteristics regarding

the covering layer formation are the roughness of the

membrane surface, the pore diameter, porosity (share of

the hollow space2)), and the pore size distribution. The

smoother the surface and the smaller the pore diameter,

the smaller the susceptibility to blockage. Also, the ten-

dency for membrane contamination is, in general, smal-

ler with a homogeneous pore distribution [KRAMER,

KOPPERS 2000]. In recent years numerous efforts have

been made to increase the efficiency of membranes by

modification of their characteristics [LINDAU ET AL.

1998; PIERACCI ET AL. 1998; LINDAU, JÖNSSON 1999;

AMANDA ET AL. 2000].

For example, the module configuration determines how

large a pressure increase can be applied to overcome the

filtration resistance caused by the covering layer. This

pressure increase is allowed only within the scope of the

module-specific maximum operating pressure. It must

also be considered in light of the economic operation of

the membrane stage.

Cleaning

If the desired permeate flow is no longer realizable eco-

nomically, a cleaning plan established by the membrane

manufacturer is applied. Restoration or increase of the

53

cleaning

time

flo

w

cleaning interval irreversiblefouling

withcleaning

withoutcleaning

constant pressure

Figure 1-23

Effect of membrane cleaning on the flow at constant pressure

2) Porosity in [%] is defined as the volume of the hollow space in a mem-brane layer compared to the total volume of the membrane layer


permeate flow is brought about by cleaning with a mem-

brane-compatible cleaning agent. The course of the flow

over time at a constant transmembrane pressure with and

without chemical cleaning is represented in Figure 1-23.

Despite the significant improvement of the flow capacity

by the chemical cleanings, the flow decreases with in-

creasing filtration time. This phenomenon is explained

by irreversible fouling, which cannot be eliminated by

cleaning.

For membrane cleaning, chemical cleaning agents are

used in combination with backwashing (permeate side)

or flushing (feed side). In principle, we distinguish three

types of cleaning:

1. backwashing/flushing of the membrane

2. interim cleaning using chemicals in lower concentra-

tion, e. g. weekly

3. intensive cleaning using chemicals in higher concen-

tration, e. g. biannually

The cleaning agents used for intensive cleaning have a

higher concentration than those used for interim clean-

ing. The cleaning agent is chosen depending on the sub-

stances in the covering layer (Table 1-9).

The effectiveness of cleaning does not only depend on

the cleaning agents applied and their chemical activity,

but is also determined by factors such as temperature, pH

value, contact or reaction time, concentration of the ac-

tive substance, and mechanical forces. The cleaning result

improves with higher temperatures or longer cleaning

times. At higher temperatures the cleaning time can be

reduced, or the temperature can be lower with a longer

cleaning time. In order to adjust the pH value, it is neces-

sary to consider not only the compatibility with the

membrane- or the module material, but also the specific

effectiveness of the cleaning agent in dependence on the

pH.

For handling the cleaning chemicals, the references on

possible hazards of the respective safety data sheets must

be considered. This is of special importance in cases where

the personnel are not familiar (or only to a limited extent)

with the use of hazardous materials, e. g. at waste water

treatment plants.

Moreover it has to be considered that some cleaning che-

micals, after having been used for cleaning, may have

undesirable effects on the permeate quality. After clea-

ning these cleaning solutions have to be collected, if

necessary, and disposed of separately.

54

Table 1-9

Examples of cleaning chemicals and their applications

Covering layer substance

Calcium-, magnesium scaling

Metal hydroxide, inorganic colloids

Organic substances

Bacteria, germs

Cleaning agents applied

Acids, e. g. citric acid, acetic acid

Acids, e. g. citric acid

Anionic surfactants, oxidants, e. g. hypochlorite, hydrogen peroxide,

alkaline cleaning agents, e. g. caustic soda solution

Disinfectants, e. g. hypochlorite; biocides


1.9

Other Aspects Concerning the Use of Membrane

Technology in Waste Water Treatment

Molecular separation size and transmembrane

pressure

The choice of a membrane process depends on the waste

water composition and the separation task. In municipal

The driving force or the transmembrane pressure, which

is necessary for the filtration process, has to overcome

the resistance to filtration. It consists of the resistance of

the membrane, the resistance by adsorption and clogging

of the pores in the membrane, the covering layer at the

feed side and concentration polarization [KRAMER 2000].

The transmembrane pressure of immersed membrane

systems in municipal applications is between 0.05 and

0.2 bar in normal operation. The pressure is generated by

pumps installed at the permeate side. If the tanks with

the membranes are arranged above the permeate collec-

ting tank, it is possible to use the difference of the water

levels, i. e. the hydrostatic pressure, as transmembrane

pressure.

Influences on the filtration process and maintenance

of the performance of the filtration operation

In the filtration process, a covering layer is formed by

particles which are retained by the membrane and accu-

mulate on its surface. Thus the resistance to filtration

increases and the permeate flow is reduced, but the filte-

ring effect is normally improved, so that in some cases it

is possible to attain with a micro-filtration membrane the

separation result of an ultrafiltration process.

In many cases, the structure and thickness of the cover-

ing layer is of higher importance for material separation

than the membrane itself. In particular with microfiltra-

tion processes, the formation of a reversible covering lay-

er formation is even wanted, as long as the flow is not

too strongly reduced, because inside membrane clogging

by smaller particles is avoided. It is of importance that a

steady operation results in which covering-layer-forming

and covering-layer removing effects are compensated.

Even with microfiltration membranes, the covering layer

is able to retain, for example, a high percentage of viruses,

which are much smaller compared to bacteria, although

a retention by the membrane pores is not expected

[MELIN, RAUTENBACH 2004]. Since the size of bacteria

is approx. 0.2 µm up to 10 µm and of viruses approx.

0.02 µm up to 0.250 µm, viruses are retained completely

only by ultrafiltration membranes.

waste water treatment, pressure-driven immersed mem-

brane systems with micro- or ultrafiltration membranes

are predominantly used. The pore size of these mem-

branes ensures the retention of solids and of macromole-

cular or colloidal substances up to the size mentioned in

Table 1-10. The separation of smaller particles or substan-

ces with lower molecular weight requires nanofiltration

or reverse osmosis membranes.

55

Microfiltration solids > 0,1 µm 0,1 – 3 bar

Ultrafiltration 200.000 – 20.000 D * 0,5 – 10 bar

Nanofiltration 20.000 – 200 D * 2 – 40 bar

Reverse osmosis < 200 D * 5 – 70 bar

Table 1-10

Molecular separation size and transmembrane pressure of pressure-driven membrane processes

Membrane process Size of the particles, colloids or molecules to be separated Transmembrane pressure

* Dalton, numerically equivalent to the molecular weight in [g/mol]


Table 1-11 gives an overview of the size of bacteria and

viruses.

To attain stable operation of a membrane installation,

not only coverin-layer-forming and covering-layer-remov-

ing effects have to be compensated, but the development

of fouling must also be limited.

Fouling results from bacteria producing extracellular

polymeric substances (EPS) which mainly consist of poly-

saccharides with incorporated proteins and accumulate

around the cells as mucous capsules. The manifold rea-

sons for the development of these mucous capsules are

not yet completely clarified. Bacteria species producing

mucous EPS are necessary for the development of the

activated sludge floc. By forming a mucous matrix on the

membrane, EPS have a negative effect on the filtration

process. Therefore the process control has to be designed

in such a way that the development of EPS is minimized

as far as possible.

In practice, chemicals are used to counteract the fouling

process. The utilization of an acid, e. g. citric acid, and a

cleaning chemical with oxidative effect, e. g. sodium

hypochlorite or hydrogen dioxide, has proven successful.

To realize chemical cleaning, it is necessary to install a

dosing station for chemicals which is correspondingly

equipped. Cleaning (in situ or on air) can be automated

to a great extent.

Preparation and realization of chemical cleaning require

increased staff employment. For cleaning of the modules

in a separate cleaning chamber, even more staff is needed.

The membrane modules under cleaning are not available

for the filtration process. This has to be considered in the

design of the installation (larger membrane surface area).

According to current knowledge, a precautionary opera-

ting and cleaning strategy, which is adapted to the hy-

draulic load, is technically and economically useful. This

includes planning of a sufficient membrane surface area

and operation of the membranes at moderate transmem-

brane pressure differences.

Within the scope of an optimized operating concept,

buffering of hydraulic peak loads in an upstream balanc-

ing tank may be useful to reduce the membrane surface

area.

56

Table 1-11

Data on the size of viruses and bacteria

Name Length [µm] Width [µm] Diameter [µm]

Bacteria [STARR ET AL. 1981]

Bacteriodes pneumosintes 0,2 < 0,1

Mycoplasma spp. 0,25 0,1

Bacillus subtilis 2,5 0,75

Escherichia coli 2 0,6

Achromatium oxaliferum 100 5

Cristipira pectinis 36 – 72 1,5

Viruses [SCHLEGEL 1976]

Smallpox virus 0,3 0,2

Influenza 0,1

Poliomyelitis 0,02


Performance of micro- and ultrafiltration membranes

The model for material transport in micro- and ultrafil-

tration membranes is based on the idealized pore model,

i. e. bigger particles, activated sludge flocs and bacteria,

substances with a molar mass of more than 20,000 g/mol

are not able to pass through the membrane capillaries

because of their size. Dissolved substances such as acetic

acid or urea cannot be retained, unless they are adsorbed

at substances which are retained. By ultrafiltration mem-

branes, substances with a molar mass of at least 20,000

g/mol can be retained.

In municipal waste water treatment, the membrane bio-

reactor process (a combination of activated sludge pro-

cess and membrane process) is used in order to remove

also dissolved, biodegradable constituents. Degradation

of organic matter with development of biomass and con-

version processes such as nitrification and denitrification

take place in the same way as in the conventional acti-

vated sludge process. The substances adsorbed at the acti-

vated sludge flocs are retained safely by micro- or ultrafil-

tration membranes.

Activated sludge flocs consist of colonies of different bac-

teria species. The species pseudomonas, archobacter, ba-

cillus, micrococcus, aerobacter and in particular zoogloea

are found most frequently. Indications on the size of acti-

vated sludge vary, e. g. with diameters of 50 to 200 µm

[HARTMANN 1983] or 5 to 30 µm [KRIEBITZSCH 1999],

i. e. sized which are also retained by microfiltration mem-

branes.

Performance of nanofiltration and reverse osmosis

membranes

To separate organic components from aqueous solutions,

a nanofiltration or reverse osmosis membrane has to be

used. Nanofiltration membranes achieve considerable

retention performances for substances with a molar mass

of 200 g/mol and more, while reverse osmosis membranes

also retain dissolved organic components with a molar

mass of 100 – 150 g/mol nearly completely. Table 1-12

and Figure 1-24 show the molar masses of some selected

waste water constituents.

57

Table 1-12

Molar masses of selected natural organic constituents in domestic waste water [KOPPE, STOZEK 1999]

Name Chemical formula Molar mass [g/mol]

Natural organic constituents

Makropollutants

Acetic acid C2H4O2 60

Citric acid C6H8O7 112

Sucrose C12H22O11 342

Glycine C2H5O2N 75

Urea CH4ON2 60

Mikropollutants

Estradiol C18H24O2 272

Toluol C7H8 92

Synthetic organic constituents

Trichloroethene C2HCL3 132

Dichloro benzene C6H8CL10 435

Sorbic acid C6H8O4 144


A special feature of nanofiltration membranes is their ion

selectivity. Negatively charged ion groups on or in the

membrane retain dissolved salts with polyvalent anions,

while monovalent anions are able to pass through the

membrane nearly unhindered. In industrial applications

this feature is used to recover valuable material from the

process waste water (e. g. treatment of waste water from

car painting, recovery of dyes in paper mills or in the

textile industry).

For municipal waste water treatment, nanofiltration

membranes open a special perspective for the retention

of organic trace substances.

As resulted from investigations, it is useful to classify the

organic trace substances into three groups with view to

their concentrations in the waste water and their degra-

dation behaviour [MUNLV 2004].

• “Group 1: Substances present in low concentrations

in the waste water” (e. g. Atrazin)

• “Group 2: Substances which are detected in the

inflow and partly in the effluent above the detection

limit and whose concentrations are considerably re-

duced between inflow and effluent“ (e. g. naphtalin,

nonylphenols, bisphenol A)

• “Group 3: Substances which are detected in the

inflow and partly in the effluent above the detection

limit and whose concentrations are not or only slightly

reduced” (e. g. diclofenac)

In Table 1-13 and, some organic trace substances are

selected whose retention can be expected on account of

their molar mass. The real, quantifiable retention perfor-

mance has to be determined by practical tests. At present

intensive studies are realized concerning this subject.

58

reverse osmosis

• glycine• urea• acetic acid

• toluol

nanofiltration

400200 300 500100

molecularweight[g/mol]

• citric acid • trichloroethene • sorbic acid

• estradiol • saccharose • dichloro benzene

Figure 1-24

Molar masses of selected natural organic constituents in domestic waste water


59

reverse osmosis

nanofiltration

molecular weight[g/mol]

• clofibric acid • nonylphenol • bisphenol A

• polycyclic aromatic hydrocarbons • TCEP • EDTA • diclofenac • TCPP • trifluralin

200 300 400

• naproxen • carbamazepin

Figure 1-25

Molar masses of selected organic trace substances

Table 1-13

Molar masses of selected organic trace substances [MUNLV 2004]

Name Chemical formula Molar mass [g/mol]

Bisphenol A C15H20O2 228

EDTA C10H16N2O2 292

Trifluralin C13H16F3N3O4 335

Polycyclic aromatic hydrocarbons C22H12 276

Nonylphenol C15H24O 220

Organic trace substances of group 3

Organophosphates

TCEP C6H12O4P1Cl3 285

TCPP C9H18Cl3O4P 327

Pharmaceuticals

Clofibric acid ClC6H4OC(CH3)2CO2H 214

Carbamazepine C15H12N2O 236

Naproxen C14H14O3 230

Diclofenac C14H11Cl2NO2 296


For operation with high sludge ages, membrane biorec-

tors need considerably smalller activation volumes, com-

pared to conventional plants. It can be assumed that

under these conditions an adaptation of the biomass

takes place which allows increased removal of hardly

removable waste water constituents (cf. e. g. substances of

groups 2 and 3). Complete removal of substances which

possibly are not removed in the membrane biorector

(e. g. substances of group 3) can be attained by direct

downstream arrangement of a nanofiltration stage or a

reverse osmosis. Interconnection of another treatment

stage, as required in conventional activated sludge

plants, is not necessary.

Demands on the operating personnel

A membrane bioreactor differs from a conventional acti-

vated sludge plant with view to operation and process

engineering. At present there is still need for training of

the operating personnel of membrane installations. Con-

cerning the membrane bioreactor process, the Erftver-

band offers a training series at the waste water treatment

plant Nordkanal. In cooperation with MUNLV NRW, the

Aggerverband currently installs a training facility on the

membrane bioreactor process at the site of the waste

water treatment plant Seelscheid.

60

Membrane Technology in Municipal Waste Water Treatment

2

Membrane Technology in Municipal Waste Water Treatment2

Membrane technology has been used for decades in

industrial waste water treatment. In municipal waste

water treatment, however, it has been applied only

for several years.

The main drivers for the recent increased application

of membrane technology in the municipal waste water

treatment market are the new engineering approach con-

cerning membrane modules which are directly immersed

into the activated sludge tank, and further development

of membranes (micro- and ultrafiltration membranes). It

is because of these developments that this technology is

now able to compete with well-established treatment

processes (e. g. the conventional activated sludge process)

and that the purification efficiency has clearly improved.

During the last decades considerable efforts have been

made in the field of waste water treatment, which has

resulted in a significant positive effect on the quality of

water bodies. However, further improvement in water

pollution control has to be realized in the future, specifi-

cally, measures for the removal of germs, bacteria and

viruses from waste water as well as for retention or degra-

dation of micro-pollutants (e. g. substances affecting the

endocrine system or residues from medicaments) must be

addressed.

The following pages provide an overview of the potential

of membrane technology in the municipal waste water

market. The drivers for existing plants to apply membrane

technology will be discussed. The following chapters deal

with these examples as well as with technical and econo-

mic conditions and aspects of planning and operation.

Figure 2-1 serves as guide to the chapter so that the

reader may choose directly the subjects in which he is

interested most.

In the beginning of the chapter the relevant process

engineering is explained in more detail. There exist two

ways of arranging the membrane stage in a municipal

waste water treatment plant (Figure 2-2):

• integration of the membrane stage into the

activated sludge plant, and

• downstream arrangement of the membrane

stage into the effluent of a conventional biological

waste water treatment plant.

In Germany, the integration of the membrane stage

as combination of activated sludge process and membrane

filtration – the socalled membrane bioreactor pro-

cess (chapter 2.1) – is of greatest importance. This pro-

cess is used

• in waste water treatment plants (chapter 2.2), as well as

• in small sewage treatment plants and ship’s sewage

treatment plants (chapter 2.3).

The membrane bioreactor process can be explained as

follows: The membrane stage is used inplace of a secon-

dary clarifier tank to separate the biologically treated

water from the biomass. Depending on the module

system applied, one can distinguish between internal

membrane modules (i. e. fitted into the activated sludge

tank, Figure 2-2, 2a) and external membrane modules

(i. e. installed outside tanks, Figure 2-2, 2b).

Membrane stages arranged downstream of bio-

logical treatment stages (Figure 2-2, 3) are used to obtain

complete retention of solids and farreaching disinfection

of the effluent (see chapter 2.4).

62

Membrane Technology in Municipal Waste Water Treatment 2

63

Figure 2-1

Background – planning – operation of a municipal membrane bioreactor, contents of the chapter

“Membrane technology in municipal waste water treatment“

Procedure

Motive

Target

p. 286

p. 66 ff.

Example

New construction, upgrading, extension of activated sludge stages

Further measures

Information

Concrete examples

Associations

Analysis of theactual situation

p. 286Purification requirements

Local situation

...

Study of variations

p. 286Integration of existing tanks

New construction of tanks

Membrane modules...

p. 70 ffMembrane modules

Economic efficiency

Planning,design,

configuration

p. 82

Design of the membrane bioreactor

Plant configuration

...p. 87 p. 270 ff.

p. 286 f. p. 163Concrete examples

Consulting engineers

Plant manufacturers

Operation

p. 287Cleaning

Energy consumption

Staff

p. 266 ff.

Concrete examples

Plant operators

p. 95 ff.

p. 95 ff.

p. 92 ff.

p. 270 ff.

p. 95 ff.

p. 266 ff.

Consulting engineers

p. 69

p. 64

p. 70 ff.

p. 89 f. p. 89 f.


64

Figure 2-2

Conventional waste water treatment according to the activated sludge process and possibilities for the

arrangement of a membrane stage at municipal waste water treatment plants [OHLE 2001]

raw waste water

conventional process engineering in municipal waste water treatment

effluent

if nec. more far-reaching measurese.g.: NN, SF, UV1

RE/SFF VK BB BB NK

2a

2b

3

integration of the membrane stage in municipal waste water treatment

raw waste waterRE/SFF VK BB

effluent

If nec. FS optional

M

RE/SFF VK BB

If nec. FS optional

M

downstream arrangement of the membrane stage in municipal waste water

raw waste waterRE/SFF VK BB BB NK

effluentM

raw waste water effluentBB

RE⁄SFF screen, grit and grease trapVK primary settlement tankFS fine screen

BB activated sludge tankNK 2nd settlement tankSF sand filter

M membrane stageUV UV treatmentNN post-nitrification stage


With view to water pollution control, membrane techno-

logy represents a future-oriented solution. Thanks to the

high attainable sludge age and another downstream

membrane stage (nanofiltration or reverse osmosis), the

elimination of organic trace substances can also be

expected. Figure 2-3 shows such a process combination.

65

raw water inflow

rakefine screen(optional)

grit and grease

trap

denitrificationstage

nitrificationstage

membrane Stage I(MF/UF)

membrane stage II(NF/UO)

outflow

optionalprocess

supplement

excess sludge

recirculation

Figure 2-3

Flow sheet of a waste water treatment plant with membrane bioreactor process and downstream

membrane stage


2.1

The Membrane Bioreactor Process

2.1.1

Description of the Process and Fields of Application

The membrane bioreactor process is a combination of

biological waste water treatment according to the activa-

ted sludge process and the separation of the sludge-water

mixture by membrane filtration. Waste water treatment

in the true sense takes place by metabolic and conversion

processes in the biological stage (activated sludge pro-

cess). Simplifying we can say that the carbon and nitro-

gen compounds present in dissolved form in the waste

water are converted to CO2 and N2 and integrated into

the biomass. This task is done by micro-organisms which

are found as suspended sludge flocs in the activated sludge

tank.

To separate the treated waste water from the suspended

biomass, membrane stages with pressure-driven micro-

or ultrafiltration membranes are used. The membranes

ensure a complete retention of solids and biomass, so

that a secondary settling tank for phase separation down-

stream of the activated sludge tank is not necessary. The

result is a treated waste water which is free of solids and,

to a far-reaching extent, disinfected. Therefore the em-

ployment of a membrane stage in municipal waste water

treatment is particularly interesting if higher demands on

the quality of the treated waste water are made.

For the membrane bioreactor process, one distinguishes

between internal and external arrangement of the mem-

brane modules. Internal arrangement means that the

membrane modules (Figure 2-2, 2a) are immersed within

the bioreactors into the mixed liquor (immersed system).

With external arrangement the mixed liquor is with-

drawn from the bioreactors and the membrane modules,

usually tubular modules, are fed in cross-flow operation

(Figure 2-2, 2b). For financial reasons only immersed

membrane systems are used in municipal waste water treat-

ment (chapter 2.1.2).

Since the efficiency of phase separation by the membrane

bioreactor process is to a great extent independent of the

settling characteristics of the mixed liquor, the aeration

stage can be operated at much higher biomass concentra-

tion than in conventional plants. With the latter, bio-

mass concentrations of MLSS < 5 g/l are typical, while the

membrane bioreactors working at present are operated at

MLSS concentrations of 9 – 16 g/l. Thus it is possible to

reduce the aeration tank volumes at equal sludge loading

by up to 75 % compared to conventional plants.

Table 2-1 summarizes the main advantages of the use of

the membrane bioreactor process in municipal waste

water treatment.

Considering the aspects mentioned in Table 2-1, today

the membrane bioreactor process proves to be, from the

economic point of view, an advantageous option com-

pared to other process techniques, under the following

general conditions:

66

• complete retention of solid matter:

- improved effluent quality concerning the parameters COD and BOD5

- far-reaching disinfection of the effluent, i. e. secondary settling, filtra-

tion and disinfection plant are replaced

- no influence on the effluent quality by floating or bulking sludge nor

scum formation (possibly lower demand for auxiliary agents)

• smaller aeration tank volumes due to higher biomass concentration

• existing plant components can be used for plant expansions

• less space required for the waste water treatment plant

• expansion of plants by addition of modules

Table 2-1

Advantages of the membrane bioreactor process

compared to the conventional activated sludge

process

Advantages


Demands on the effluent quality

If higher demands are made on the discharge parameters

(standard monitoring or hygienic parameters) (e. g. for

the discharge into “weak“ receiving waters, drinking

water protection areas or bathing water), membrane bio-

Studies on the hygienic quality of the effluent have shown

that by using membrane bioreactors it is possible to com-

ply with the standards of the EU Directive on Bathing

Waters without further treatment measures. To illustrate

the high effluent quality of membrane bioreactors,

the germ load of a conventional waste water treatment

plant [BAUMGARTEN, BRANDS 2002] is compared in

Figure 2-4 to that of the Büchel pilot plant (in each case

mean values from multiple sampling). Concerning the

hygienic effluent parameters, it is evident that the mem-

brane plant is superior to conventional plants.

reactors represent an economically interesting solution.

As shown by Table 2-2, the effluent quality is clearly better

than that of conventional waste water treatment plants.

67

Solids (filterable solids) mg/L 10 – 15 0

COD mg/L 40 – 50 < 30

Ntot mg/L < 13 < 13

Ptot (with simultaneous precipitation) mg/L 0.8 – 1.0 < 0.3

Microbiological quality hygienically alarming bathing water quality

Dry matter content in the g/L < 5 < 20

activated sludge tank

Specific energy consumption kWh/m3 0.2 – 0.4 0.7 – 1.5

Table 2-2

Performance data of membrane bioreactor plants compared to conventional activated sludge plants

[DOHMANN ET AL. 2002]

Parameter Conventional Membrane bioreactor

activated sludge plant


Sewer system

If the catchment area is mainly drained by a separate

sewer system, the membrane surface area to be installed

into the aeration stage of the waste water treatment plant

is much smaller than in plants where waste water from

combined systems is treated. Thanks to lower hydraulic

fluctuations, the membrane stage is optimally used and

thus is competitive with alternative technical methods for

waste water treatment, even if no higher demands on the

effluent quality are made.

However, an increase in sewer infiltration water requires

more membrane surface area. Therefore, membrane pro-

cesses should be used preferentially in applications with

low amounts of sewer infiltration water compared to the

waste water volume.

Local situation

Due to higher biomass concentrations in membrane bio-

reactors, it is possible to reduce the aeration tank vol-

umes by 50 to 75 % compared to conventional plants. If

the surface area available requires compact construction,

a membrane bioreactor may represent suitable technical

solution. This is shown in Figure 2-5 by way of example

for the comparison of variations for the new construc-

tion of the Kaarst waste water treatment plant.

68

1.000.000

100.000

10.000

1.000

100

10

1E. coli

[MPN/100 ml]salmonellae

[MPN/100 ml]faecal streptococci

[MPN/100 ml]total coliforms[MPN/100 ml]

coliphagae[PFU/l]

total number of germs[colony-forming unit]

conventional WWTP membrane bioreactor EU guide value EU limit value

Figure 2-4

Comparison of the germ load in the effluent of waste water treatment plants

[BAUMGARTEN, BRANDS 2002]


Rebuilding or expansion of installations

Existing installations which have to be rebuilt or expanded

(e. g. because of higher demands on the effluent quality or

increased waste water volumes) can be readily converted

to membrane bioreactors. The membrane stage can be

integrated at low cost into existing components of the

plant, so that demolition or new construction of aeration

tanks is not necessary. This is especially advantageous if

an expansion of the surface of the plant to be upgraded is

not possible due to the local situation.

Since in future the costs for installed membrane surfaces

will decrease (chapter 2.1.4), it can be expected that the

economic efficiency of the membrane process will further

increase. The decision of the water boards (Aggerverband,

Erftverband, Kommunale Wasserwerke Leipzig (KWL)),

which have already gained experience with large-scale

application of membrane technology, to include membrane

technology in their efficiency calculations for new pro-

jects or even to give it priority in planning, clearly indica-

tes its competitiveness compared to conventional techno-

logy. According to KWL, even a change towards mem-

brane technology is expected which will not come out on

top because of enhanced purification requirements, but

only because of economic aspects – taking into account

further reductions of the membrane costs as well as pro-

cess optimizations [WALTHER 2001].

69

Figure 2-5

Schematic representation of the space requirements of a conventional activated sludge plant (edged in

blue) and of a membrane bioreactor (edged in red), example: Nordkanal waste water treatment plant

[ERFTVERBAND 2002]


2.1.2

Membrane Modules

For a long time it has been known that membranes are

able to separate activated sludge from water. However,

during only the last ten years, module systems have been

developed which are a relevant process variation, com-

pared to sedimentation, in municipal waste water treat-

ment because of low capital and operating costs.

Until now the so-called low pressure processes using

immersed modules have been the most widespread. Micro-

or ultrafiltration modules are immersed directly into the

mixed liquor and withdraw the biologically treated water

as filtrate at transmembrane pressures of < 0,5 bar in low-

pressure or submergence operation (“gravity flow“). At

present, capillary modules from the company ZENON

and plate modules from the company Kubota have a high

share in the modules being used worldwide on an indus-

trial scale. These modules as well as the latest national

and international developments are presented in the fol-

lowing sections.

Capillary module from the company ZENON, Canada

The hollow fibre module presented in Figure 2-6 (product

name: ZeeWeed®) consists of hundreds of tubular mem-

branes with a diameter of 3 mm oriented vertically be-

tween two plastic blocks (top and bottom header). The

capillary tubes (pore size ~ 0.04 µm) are charged from

the outside with the mixed liquor; the permeate flows

into the interior of the capillary tubes and is discharged

by a collecting channel integrated into the top header.

To minimize the formation of a covering layer, coarse to

medium bubble air is introduced at the bottom header

which generates an up-flow movement of the mixed

liquor and causes the capillary tubes to move between

the headers. Additional covering layer removal is possible

by cyclic backwash of the modules at the filtrate side in

the so-called backpulse mode. Filtration of six minutes

and a backwash time of 30 seconds is a common operat-

ing mode.

70

top header with integratedpermeate collecting channel

membranebundle

rising mixed liquor

support frame with integratedair tube

bottom header

blower

permeate channel

permeatedischarge

supporting layer

membrane

support frame

backwash

air intake

Figure 2-6

ZeeWeed®-module from the company ZENON ,

left: schematic presentation from the operating principle of a module [OHLE 2001],

right: photo of the technical realization as module cassette [photo: ZENON]


During the last years, the module configuration from the

company ZENON has been continuously optimized. A

rather compact configuration has been obtained with the

current capillary module, ZW 500 d (Figure 2-6). The

module cassette presented in Figure 2-7, ZW 1000 (pore

size of the membranes: 0.02 µm), had been designed ori-

ginally for drinking water treatment, but is also used e. g.

for tertiary treatment or for the treatment of the effluent

of a final clarifier or a sand filtration unit.

Plate module from the company Kubota, Japan

The plate modules (Figure 2-8) consist of a support plate

on which the membrane sheet (pore size: ~ 0.4 µm) is

welded at both sides. A drainage and backing fleece is

fixed between the plate and the membrane. The support

plate is provided with drainage channels which come

together in a suction branch for permeate withdrawal.

The individual plates are combined vertically with a

distance of 6 mm parallel to each other to create a plate

package that is fitted into a support frame (Figure 2-8).

The sides of the support frame are closed. The support

frame is installed in an up-flow channel, at the bottom

71

membrane-package

drainage fleece

membrane

suspension

filtratefiltrate collectingchannel

up-flow-channel

pressureaerator

air

suction branch

collecting channels

membranesupport

Figure 2-8

Plate module from the company Kubota,

left: schematic presentation of the operating principle [according to KRAFT, MENDE 1997],

right: photo of the technical arrangement of the plate modules as plate package [photo: KUBOTA]

Figure 2-7

Arrangement of several ZeeWeed®-modules

ZW 1000 in a cassette [photo: ZENON 2004]


of which is arranged a device for exhaustive pressure

aeration. Due to the injected air, the mixture of sludge,

water and air rises and flows over the membrane, en-

suring removal of the covering layer. The filtrate is dis-

charged by low pressure at the filtrate side or by the

hydrostatic pressure of the active water head (“gravity

flow") via the filtrate collecting channel which is connec-

ted with the suction branches of each plate. The covering

layer on the plate is not removed by backwashing on the

permeate side. Filtration is instead interrupted in inter-

vals while the modules are continuously aerated [KRAFT,

MENDE 1997]. The break interval for expansion of the

membranes and removal of the covering layer varies ac-

cording to the waste water composition. In some munici-

pal installations, filtration of nine minutes followed by a

break of one minute has proven to be efficient.

As a further development of the combination of up-flow

channel and plate package design, the so-called double-

decker is now offered for large-scale applications (Figure

2-9). Two plate packages are arranged on top of each

other, so that the air introduced, i. e. the activated sludge

mixture, can be used twice. Therefore the energy demand

for module aeration is considerably reduced

Module system from the company PURON AG

A new immersed module system consisting of capillary

membranes with a pore size of 0.1 µm was developed

about five years ago at the RWTH Aachen University and

is now available for application in water and waste water

treatment. Production and marketing of the new mem-

brane filters are realized by the company PURON which

belongs to the KOCH-GLITSCH group.

The patented basic idea of the PURON module is confi-

guring membrane fibres as bundles which are only fixed

at the bottom, while their closed top ends move freely in

the mixed liquor to be filtered (Figure 2-10).

In the centre of each fibre bundle of a module, a nozzle

is arranged to introduce air for movement and cleaning

of the membranes. The air flows up through the mem-

brane fibre bundle from the inside to the outside. Mem-

72

membrane package at the top

membrane package at the bottom

aeration device

Figure 2-9

Basic schematic of the plate module “double-decker“ from the company Kubota [AGGERWASSER GMBH 2004]


brane coatings or fouling material are discharged from

the module. Hair and fibrous compounds are also slipped

off to the top, which helps to prevent the problem of

their accumulation and sticking to the membrane even

with relatively coarse prescreening. Due to defined air

intake, the aeration time of the modules is reduced to

5 – 10 % of the filtration time, and thus the energy de-

mand for overflow is reduced.

In the technical module of PURON a multitude of these

module components are arranged in parallel. The total

membrane surface area of the PURON module is 504 m2.

The fittings and connections of the module are designed

to be compatible with existing module systems.

Pilot tests have been run since August 2001 at the Aachen-

Eilendorf waste water treatment plant within the scope

of a field study on membrane bioreactors promoted by

“Kompetenznetzwerk Wasser NRW“ (competence net-

work water North-Rhine Westphalia). This pilot study

allows individual components of the membrane module

to be operated under real conditions, i. e. with changing

loads. The experiences from this first pilot study were the

basis for the construction of a technical installation at

the Simmerath waste water treatment plant for 750 PE in

NRW. This technical installation has been operating since

the end of 2002 within the scope of a research and devel-

opment project.

73

filtrate

membrane fibres

filtrate

air

fibre holder

module row

air conduit

filtrate

air bubbles membrane fibre

PURON-module module component

• central air intake• single-sided fixation of membranes• assembly from single membrane bundles

Figure 2-10

PURON module and module component [photo: PURON AG]


Module system from Martin Systems AG

The Martin Systems AG markets a new module system

called siClaro®. According to information from the manu-

facturer, the innovations of this system are the structure

of the filter and the operating mode of the system.

For the modules, flat membranes with a pore width of

35 nm are used. Each membrane is welded on a support-

ing scaffold with an open grate structure. A drainage

fleece is not necessary. The supporting scaffolds with the

spacers necessary for effective cleaning of the membrane

surface are welded to module blocks. Filtrate collectors

are welded on top and bottom of each module block

transversally to the supporting scaffold. Thanks to this

self-supporting construction, the material thickness of

the supporting scaffold is rather small. This allows for a

large number of variations in combining the module

blocks to a connectable module package. For technical

application, several module blocks are connected side by

side and on top of each other. For example, one siClaro®

membrane module of the type FM 643 ready for connec-

tion (see Figure 2-11, right) consists of 12 module blocks

with a total membrane surface area of 72 m2.

By using fine-bubble membrane tube aerators below the

module package, higher oxygen input is attained. Thus

the air input which is additionally necessary to supply

the micro-organisms is reduced. Backwashing with filtrate

is not necessary because the membranes are fixed trans-

versally to the cleaning water-air mixture.

Figure 2-11 shows a scheme of the module (left) and a

module package (right).

74

Figure 2-11

Membrane module from Martin Systems AG, left: schematic representation of a module block,

right: connectable module package [photo: MARTIN SYSTEMS AG]


VRM® process with rotation plate modules and VUM

process from Huber AG, Germany

The VacuumRotationMembrane system (Huber VRM®

process) has been used since 2001 already on an industri-

al scale at the Knautnaundorf, Saxony, waste water treat-

ment plant. The modules (pore size ~ 0.04 µm) consist of

plate segments (plate packages) arranged in parallel, each

of which is provided with a connection to draw off the

permeate (Figure 2-12). The structure of the plate seg-

ments is similar to that of the Kubota plates. The plate

packages are arranged around a rotating hollow shaft and

are connected by permeate collecting pipes by which the

permeate is withdrawn continuously at low pressure.

In the centre of the plate package, air is continuously

introduced radially and rises between the plates. Due to

the rotation of the plate package, the complete mem-

brane surface is overflown by the rising activated sludge

mixture, so that the covering layer is removed.

Huber AG markets the vacuum upstream membrane®

process (VUM® process) (Figure 2-13) primarily for small

and decentralized waste water treatment plants. In this

process, small plate modules with a membrane surface

area of few square metres are used. The individual filter

plates in the module are covered with ultrafiltration

membranes and arranged in parallel. The VUM® mod-

ules are submerged into the liquid to be filtered, and the

filtrate is drawn off directly across the flat membranes

with a pore size of 0.04 µm. The mixed liquor is generated

in a flush box below the module. It flows diagonally to

the filtration flow direction in order to remove the cover-

ing layers from the filtering surfaces. The modules can be

stacked and combined as a module package so that com-

pact filtration units can be easily adapted to each indivi-

dual case.

75

Figure 2-12

Huber VRM® process [photos: HANS HUBER AG, MARTIN SYSTEMS AG], left: view of a filtration unit,

right: filtration unit installed at the Knautnaundorf waste water treatment plant


76

Figure 2-13

Huber VUM® process [HANS HUBER AG], left: view of a module package in two-storey arrangement,

right: view of a module

Figure 2-14

Membrane element and membrane module from the company Mitsubishi [photo: ENVICARE®]


Module system from Mitsubishi AG

Mitsubishi, known among other things for its car produc-

tion, also produces membranes for the filtration of water

and waste water and distributes them packaged in a

module under the designation Sterapore-SUN® (see Figure

2-14). The hollow-fibre membranes are made from poly-

ethylene with a pore size of 0.4 µm. They are fixed hori-

zontally between the permeate-collecting channels and

immersed into the activated sludge. Thus, the hollow

fibres are arranged perpendicular to the up-flow sense of

the activated sludge mixture. In practical operation the

membrane surface is kept free of fouling matter as far as

possible by an air flow which is constantly introduced. In

addition, periodic backwashing of the membranes with

permeate is provided. Up to three membrane modules can

be arranged on top of each other, the relative air require-

ments being lower for three modules than for two.

Membrane system from the company A3 Abfall-

Abwasser-Anlagentechnik GmbH

Another membrane development from NRW is from the

company A3 Abfall-Abwasser-Anlagentechnik GmbH/

Hese Umwelt GmbH. The system is based on the principle

of plate membranes (pore size ~ 0,4 µm) which can be

produced at rather low costs by choosing special material

and employing sophisticated construction principle.

Figure 2-15 shows the view of a prototype and a con-

struction example. Due to a new configuration of the

membrane plate, the membranes developed by the com-

pany A3, unlike the Kubota plate membranes, can be

backwashed on the permeate side. Experience with the

use of the membrane material has been acquired for

several years in the following fields:

• filtration of compost leachate

• filtration of liquid manure

• filtration of fermentation residues from biogas installations

• filtration of activated sludge from textile waste water

treatment plants

• filtration of activated sludge from municipal waste

water treatment plants

77

Figure 2-15

Plate module from the company A3 GmbH [photo: A3 GMBH],

left: photo of the one-storey construction, right: top view of a plate module


Module system from US Filter Corporation

The company US Filter produces and distributes an

immersed membrane system with the product name

MemJetTM that is comparable to the systems from the

companies ZENON and PURON. The membrane modules

consist of bundled capillary membranes (pore size ~

0.2 µm) which are fixed at both ends (Figure 2-16). A

mixture of air and activated sludge is introduced by a

two-phase nozzle at the bottom of the module. Accor-

ding to information from the manufacturer, this arrange-

ment is especially designed to efficiently control the

reversible covering layer and to ensure good intermixing

in the membrane reactor so that deposits and fouling on

the membranes are counteracted. The permeate is with-

drawn at the top header of the module. Figure 2-16

shows a schematic presentation and a photo of the mem-

brane module.

Membrane system from Keppel Seghers Belgium

The membrane system produced and distributed by

Seghers Keppel under the product name Unibrane® is

comparable in form to that of the company Kubota.

The membrane module consists of plate membranes

with a nominal pore size of 0,1 µm manufactured by

the company Toray.

The modules can be installed as one- or two-storey con-

struction, adapted to the conditions of the respective

application. Figure 2-17 shows a top view of the modules

submerged in clear water.

78

Figure 2-16

Membrane module from US Filter Corporation

[photo: US FILTER CORPORATION 2004]

permeate

air

mixedliquor

Figure 2-17

Membrane module from the Keppel Seghers

Belgium [photo: KEPPEL SEGHERS BELGIUM NV]


Membrane system of Weise Water Systems

GmbH & Co. KG

The MicroClear filter module consists of immersed ultra-

filtration modules in which membranes with a pore

size of 0.05 µm are fitted. According to the concrete

application, the module consists of 26 – 40 single filter

plates (see Figure 2-18) arranged in parallel. The filter

plates are available with varying space, depending on the

raw water quality. Coarse to medium bubble air is intro-

duced periodically into the modules according to the

needs, so that the activated sludge mixture flows up.

Thus shear forces occur at the membrane surface which

help to control the reversible covering layer. To remove

the covering layer, filtration is interrupted in intervals

while the modules are continued to be aerated. The raw

water is filtered from outside to inside via the membranes

and the permeate is discharged using a vacuum at the

front side of the module by a collecting tube. Depending

on the necessary capacity, between 1 and 100 MicroClear

filters can be stacked in a frame on top of each other or

side by side (Figure 2-18).

79

Figure 2-18

Membrane system from Weise Water Systems GmbH & Co. KG [WEISE WATER SYSTEMS GMBH & CO. KG],

left: structure of a filter element, right: filter system in two-storey arrangement

spacer

filter plate

membrane

filtrate outlets

The aeration device consists of tube aerators provided

with slots.

To control the covering layer, the membrane modules are

aerated during the filtration of activated sludge from the

bottom with coarse-bubble air. As special advantages of

the ceramic membranes, the manufacturer expects high

thermal and chemical resistance as well as long service

life, thus a broader range of application.

Module system from Fraunhofer IGB, Stuttgart

The rotation disc filter from Fraunhofer Institut für Grenz-


New membrane module developments in Germany

Module system from ItN Nanovation

The membrane system from the company ItN Nanova-

tion consists of immersed modules mounted from cera-

mic plate membranes (Figure 2-19). According to the

manufacturer, the membrane material is �-Al2O3 for the

supporting layer and �-Al2O3, TiO2 or ZrO2 for the active

separating layer. The membranes are available with dif-

ferent molecular separation sizes in the fields of micro-

and ultrafiltration.

One module comprises 86 membrane plates with a spac-

ing of 7 mm between the plates. The active membrane

surface area of a module is approx. 11 m2. Eight modules

can be combined maximally to a rack.

80

Figure 2-19

Ceramic plate membranes from the company ItN

Nanovation [photo: ItN NANOVATION]

Figure 2-20

Membrane module and configuration of the modules in the rack with underlying aeration device

[photos: ItN NANOVATION]


flächen- und Bioverfahrenstechnik (IGB) (Fraunhofer

Institute for Interface and Bioprocess Technology) con-

sists of a cylindric case in which a membrane disc stack is

fitted on a rotating hollow shaft (Figure 2-21). The rota-

tional speed varies between 200 and 500 revolutions per

minute, according to the type and the concentration of

the waste water constituents. The rotation disc filter can

be arranged dry or operated as immersed system.

The membranes are made from a ceramic material

and can achieve relatively high permeate flows. At pres-

ent ceramic discs with an outside diameter of 152 or

312 mm and in six molecular weight separation sizes are

commercially available. Figure 2-22 shows a dry-arranged

lab-scale module with pressure casing.

In immersed arrangement, the rotation disc filter is used

without the pressure casing. The permeate passes the

separating layer on the membrane disc from outside to

inside and is withdrawn by the hollow shaft. The cover-

ing layer is controlled by centrifugal force that causes the

laminar boundary layer sticking to the filtering disc to

flow radially to the outside. The result is continuous

renewal of the covering layer.

81

rotating hollow shaft

membrane filter discs

cylindric casing

inflow

solid outlet

filtrate

Figure 2-21

Basic layout sketch of the rotation disc filter

Figure 2-22

Modules of the rotation disc filter in laboratory

scale [photo: FRAUNHOFER IGB]


The results from pilot plant operation have shown that

the rotation disc filter is insensitive to clogging and accu-

mulation and sticking of fibrous material which reduce

the performance of membranes. Therefore, it is also sui-

ted for the filtration of digested waste water sludge diges-

tion. At present a demonstration plant for filtration of

waste water sludge is operated at the Heidelberg waste

water treatment plant. In 2005, a large-scale installation

for sludge filtration will be built at the Tauberbischofs-

heim waste water treatment plant. At both plants, cera-

mic membranes with a pore size of 0.2 µm are used.

Other module systems for the separation of

activated sludge and water

Besides the module systems described in the previous sec-

tions, there are others that, like some of those mentioned

above, are not yet applied on a large scale in municipal

waste water treatment in Germany. However, some

manufacturers have references in Europe, America, and

Asia (e. g. the modules for immersed systems from the

companies Rhodia and Norit). For several years the num-

ber of manufacturers and new module developments has

been steadily increasing.

2.1.3

Planning and Operation of Membrane Bioreactors

The “new” membrane filtration process has important

design-specific, constructive and operational differences

compared to conventional waste water treatment. The

most important aspects are summarized in this section.

They are based on the findings from the first years’ of

operation of large-scale installations, a large number of

lab-scale and semi-technical studies, including findings

from The Netherlands (field test Beverwijk) [V.D. ROEST

ET AL. 2002], and the publications of the ATV-DVWK

committee of experts KA 7 – Membrane Bioreactor Pro-

cesses [ATV-DVWK 2000a, DWA 2005].

This committee with representatives of operators, manu-

facturers and scientists, elaborates a standard for mem-

brane bioreactors analogous to with the standard ATV-

DVWK-A 131, so that a binding regulation can be expect-

ed after some years. In anticipation of this standard, the

deviations from design, planning and operation of con-

ventional activated sludge stages are focused on in this

section. The following items are discursed:

• pretreatment of the raw waste water (mechanical waste

water treatment)

• process design and calculation of the biological and

membrane filtration stages (reactor volume and mem-

brane surface area)

• design of the aeration equipment

• design of sludge treatment

• operation of the membrane stage including membrane

cleaning and

• variations in boundary conditions and safety in the

case of disturbances

2.1.3.1

Design

The design of a membrane bioreactor can be realized

according to the design principles for conventional acti-

vated sludge stages, i. e. to the standard ATV-DVWK-A 131

[ATV-DVWK 2000c] or to the approach of the University

Group [DOHMANN ET AL. 1993]. In addition, the Insti-

tute for Environmental Engineering of the RWTH Aachen

University will author in the first half of the year 2005

an upgrade of the design tool “ARA-BER”, whose devel-

opment is financed by the Land North-Rhine Westphalia.

In conventional design, an iterative process is used to

design the volumes of activated sludge tanks and secon-

dary settlement tanks because of the interactions bet-

ween both process steps. This is not necessary in the case

of membrane bioreactors. Under the boundary condi-

tions listed in the following sections it is possible to

design the membrane stage and the activated sludge

tanks to a great extent independent from each other.

Chapter 2.5 contains an example for the design of a

membrane bioreactor based on the following recommen-

dations.

82


For sludge ages < 30 days, the activated sludge tanks

are designed according to the proven design method of

ATV or the University Group approach mentioned above.

For higher sludge ages, the recommendations of the ATV-

DVWK committee of experts KA 7 “Membrane Bioreac-

In Germany, up to now all existing and planned large-

scale membrane bioreactors for municipal waste water

treatment are designed for sludge loadings of BTS,BOD5

� 0,08 kg BOD5/kg ,TS·d. This design value is chosen to

achieve nitrogen removal at simultaneous aerobic sludge

stabilization (sludge age > = 25 d).

In the design of activated sludge tanks, the total solids

content (TSBB) and the sludge volume index (SVI) in the

activated sludge stage are considered in dimensioning

the volumes of the activated sludge and secondary settle-

ment tanks. For membrane bioreactors this is not the

case. In principle, the TSBB can be independently chosen

to determine the volume of the activated sludge tank.

However, in practice TSBB design values in the range of

10 – 15 g/l have proven to be well-suited to the opera-

tion of membrane bioreactors, because in this range the

mixed liquor has good filterability characteristics, and

the oxygen input can be managed in an economic way.

The sludge volume index, SVI, has no relevance for

membrane bioreactors.

As a result of the higher TSBB content of 10 – 15 g/l in

membrane bioreactors, according to module types and

recommendations of the manufacturers, at equal sludge

loadings, the activated sludge tank volumes are three to

four times smaller, compared to conventional activated

sludge stages, at equal sludge loadings. The smaller volume

tors” [ATV-DVWK 2000a], presented in Figure 2-23, have

to be considered since, due to the higher sludge age, the

usual approach for determining the excess sludge produc-

tion is not valid.

83

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

exce

ss s

lud

ge

[kg

TS/

kg B

OD

5]

0.001 0.01 0.1 1

sludge loading [kg BOD5/(kg·TS·d)]

1.2

1.0

0.8

0.6

0.4

design rangeTS0/BOD5

minimal excess sludge production nutrient removal tTS=15d

Figure 2-23

Specific excess sludge production in membrane bioreactors [ATV-DVWK 2000a]


of the activated sludge tanks as well as the volume of the

final clarifiers which does not exist in the case of mem-

brane installations are relevant to the buffering capacity

and the degradation efficiency because of shorter hydrau-

lic retention periods.

In order to comply with discharge standards for nitrogen,

it is therefore necessary to maintain for the critical design

case a minimum retention period in the activated

sludge tank. The recommendation of a necessary minimum

retention period of 6 h (or 8 h for more far-reaching

demands) at a design temperature of 10 °C for the critical

design case can be undercut, if the necessary volume of

the membrane installation would be larger than the

volume of the activated sludge tanks which results in

conventional design with a volume allowance of up to

50 % (with a chosen TSBB = 10 – 15 g/l in the activated

sludge stage). It has to be considered absolutely that the

nitrification volume of the membrane installation (with

VDeni, MBR / VNitri, MBR = 1), due to the volume limitation

(VMBR, max = 1,5 · VBB, conventional, 10-15 g TS/l ), will not be smaller

than the necessary nitrification volume with conventional

design (at a chosen TSBB = 10 – 15 g/l in the activated

sludge stage). The necessary tank volumes can be provided

by designing larger activated sludge tanks or by designing

supplemental balancing tanks. The recommendations

concerning the necessary retention period, the relation

between nitrification and denitrification volume of the

membrane installation as well as the volume limitation

to the 1.5-fold volume of the activated sludge tanks with

conventional design (at a chosen TSBB = 10 – 15 g/l in the

activated sludge stage) are based on simulation studies

carried out at the Institute of Environmental Engineering

of RWTH Aachen University. The effluent concentrations

of a fictitious conventional waste water treatment plant

and a ficititious membrane bioreactor with a connection

size of 100,000 PE were modelled with varying membrane

bioreactor volume. Assuming that the standard parameter

set (e. g. BORNEMANN ET AL. for the Activated Sludge

Model No. 1) is also valid for membrane bioreactors and

considering a fluctuation factor of 1.7 and a given design

load, the resulting effluent concentrations of both simu-

lated waste water treatment plants were comparable, at a

membrane bioreactor volume which leads to a hydraulic

retention period of 6 h for the critical load case.

The critical load case may occur during combined water

flow as a result of flushing water hammers with NH4-N

peak concentrations occurring in parallel in the inflow.

However, if there are no such peak concentrations at

combined water flow, but only peak concentrations at

dry weather flow depending on the time of the day, the

critical load case has to be explained with the help of

concentration hydrographs recorded during a representa-

tive period.

The recommendation of a minimum retention time of

6 h for the decisive load case and at a design temperature

of 10 °C represents the current state of knowledge. With

the help of the knowledge acquired with the operation

of membrane bioreactors, the current recommendations

for the design of membrane bioreactors are further devel-

oped.

The smaller reactor volume of membrane bioreactors has

an effect not only on possible breaking through of peak

inflows, but also on the capacity of the denitrification

stage. In large-scale membrane bioreactors, typical facili-

ties are constructed up to now with upstream denitrifica-

tion tanks. As a result of the smaller activated sludge

tank volume, undesired effects may occur, e. g. increased

oxygen carry-over from the nitrification or filtration zone

to the denitrification zone. This effect is reinforced by

high recirculation rates from the filtration zone.

In order to reduce the effects of increased oxygen carry-

over, the volume of the denitrification zone has to be

equated with that of the nitrification zone (VDN : VN = 1),

in contrast to the design of conventional activated sludge

stages. In order to take different operating states into

account, part of the denitrification zone should be design-

ed as a variable zone. This zone with a size of approx.

30 – 50 % of the denitrification zone, must be arranged

in the activated sludge tank according to the require-

ments of operation. It is also possible to credit the filtra-

tion zone for the nitrification volume. In this case it is

necessary to consider the operating mode of module

aeration as well as the lower oxygen input value (refer to

section “Demand for aeration of the membrane modules”).

84


To avoid oxygen carry-over into the denitrification zone

and to optimize oxygen utilization in the nitrification

zone, relaxation zones should be provided upstream of

the sludge recirculation flow.

If the filtration zone is separated from the other zones, it

might be useful not to recycle the return sludge into the

nitrification tanks rather than the denitrification tanks.

In this configuration it is possible to control both inter-

nal cycles – recirculation sludge from the nitrification

stage into the denitrification stage and return sludge from

the membrane stage – independently from each other.

The measures mentioned may contribute to reduce the

VDN/VN ratio.

In order to obtain phosphorus effluent values according

to the discharge standards, phosphate precipitation

should be carried out according to the proven recom-

mendations (e. g. ATV-DVWK-A 131, N. N. 2000b]). Nor-

mally a precipitant is dosed into the activated sludge

stage, i. e. simultaneous precipitation takes place. The

increased specific excess sludge volume resulting from

simultaneous phosphate elimination by precipitating

salts can be determined according to the ATV standard

A 202 [OHLE 2001].

Design of the membrane filtration stage

By analogy with the conventional activated sludge pro-

cess, the phase separation, i. e. the membrane stage, has

to be dimensioned for membrane bioreactors. In con-

trast to conventional activated sludge stages, the typical

membrane bioreactor design total solids content TSBB of

10 – 15 g/l has a non-quantifiable influence on the

dimensioning of the membrane surface to be installed.

The following factors have to be taken into account in

dimensioning and calculation of the membrane

stage and the membrane surface area required:

• maximum inflow to the membrane bioreactor and the

maximum effluent flow

• the performance data of the membrane modules utilized

(surface-specific flow) depending on the features of the

medium to be filtered (temperature, viscosity, etc.)

The membrane surface should be dimensioned in such a

way that the surface-specific flows allow for a constant

operation of the membrane modules, even in the case of

peak flows. Short events, i. e. for a few hours, where the

maximum flow is exceeded, are possible but should be

avoided with a view to long-term maintenance of a

high permeability. With new or cleaned membranes,

the permeability rates are usually in a range of more than

150 – 200 L/(m2· h · bar). In-tensive cleaning is normally

necessary at a permeability < 100 L/(m2· h · bar).

If the design concept for the installation is that one or

more module cassettes or filtration lines are permanently

in a cleaning cycle (e. g. in larger installations), the sur-

faces being cleaned must be excluded when dimensioning

the membrane surface area.

When determining the necessary membrane surface area,

internal process water quantities, e. g. from screen clean-

ing, have also to be considered.

Experience acquired with membrane bioreactors in ope-

ration has shown that it is possible, with the membrane

modules commercially available, to apply a net design

flux of 25 L/(m2· h ) at temperatures of the mixed liquor

of 8° C, based on the effluent flow of the complete instal-

lation. With a design temperature of 10° C this range may

be higher by 15 % [ATV-DVWK 2000a].

Design of the aeration equipment

With the membrane bioreactor process, the higher TS

content in the activated sludge tank leads to higher

viscosity of the mixed liquor compared to conventional

activated sludge stages. This has an influence on the

material transfer and the oxygen transfer coefficient �,

as shown by Figure 2-24.

85


This factor has to be considered in the design of the

aeration equipment for oxygen transfer. Oxygen transfer

measurement in the activated sludge stages of the Mark-

ranstädt and Rödingen waste water treatment plants have

shown a decrease in the �-value with rising solid matter

content (Figure 2-24). �-values of 0.75 have been measured

with a TS content of 7 g/l, they decreased to 0.4 with a

TS content of 17 g/l.

If TSBB = 12 g/l is selected as the basis for the calculation

of a membrane bioreactor, an �-value of 0.6 should be

chosen for the oxygen transfer. This corresponds approxi-

mately to the �-values of conventional installations with

fine bubble aeration [CORNEL ET AL. 2001].

The necessary blower power for the overflow of the

membrane modules can be estimated as 7.5 – 25 W

per m2 of membrane surface installed, depending on the

module. Since the demand for aeration as well as the

aeration strategies (coarse or medium bubbles, perma-

nent, intermittent) strongly depends on the concepts of

the module manufacturers, the design of the aeration is

normally realized by the manufacturers. Further reduc-

tions of the aeration demand of membrane stages can be

expected as a result of improved module concepts (see

chapter 2.1.2).

The oxygen transfer taking place together with the

aeration of the membrane modules can be credited for

the biological degradation. The respective �-value should

be assessed as 0.17 – 0.20 (TSBB = 16 – 10 g/l) [SEYFRIED

2002].

Sludge treatment

First experiences acquired with the treatment of sludge

from membrane bioreactors have shown that the sludge

qualities do not differ very much from aero-bically stabi-

lized sludge from conventional installations. Tests for

dewatering aerobically stabilized sludge at the Rödingen

waste water treatment plant and the Büchel pilot plant

have shown that dried solid matter contents of 25 – 30 %

can be obtained with the usual aggregates (chamber filter

press, centrifuge), under equal operating conditions and

with a comparable demand for flocculants [ENGEL-

HARDT ET AL. 2001; N. N. 2003c; DICHTL, KOPP 1999;

86

1.0

0.8

0.6

0.4

0.2

0

alp

ha

valu

e[-]

Markranstädt

5 10 15 20

TS content [g/l]

Rödingen

Figure 2-24

Oxygen transfer coefficient (�-values) of the Rödingen and Markranstädt waste water treatment

plants with fine-bubble diffuser aeration [CORNEL ET AL. 2001]


BRANDS ET AL. 2000; VAN DER ROEST 2001; DRENSLA

ET AL. 2001].

Concerning the digestibility of sludge from membrane

bioreactors, similar values as for sludge from conventio-

nal plants have been determined for simultaneous

aerobic sludge stabilization with the help of the specific

digester gas production [BRANDS ET AL. 2000; VAN DER

ROEST 2001].

2.1.3.2

Mechanical Design and Planning

Concerning mechanical design and planning, membrane

bioreactors do not differ considerably from conventional

activated sludge plants. This is also true for possible failure

scenarios which have to be considered e. g. for approval

planning. Therefore only those aspects that additionally

have to be taken into account compared to conventional

municipal waste water treatment plants are mentioned in

the following.

Mechanical pretreatment

For the membrane bioreactor process, mechanical treat-

ment of the inflowing waste water is especially important.

From experience with large-scale installations it is known

that the membrane modules used are susceptible to accu-

mulation and sticking of fibrous material and therefore

to clogging [BAUMGARTEN 2001a]. This results in an

insufficient flow across the membrane surface which leads

to a reduction of the performance or may even cause

damage of the membranes [ENGELHARDT ET AL. 2001].

Therefore all undesired material such as grease, hair or

other coarse matter has to be removed from the raw

waste water. This has to be done much more carefully

than in conventional activated sludge plants. The quality

of pretreatment does not only depend on the features of

the influent, but also on the membrane module used. For

capillary membranes, mechanical pretreatment consist-

ing of a fine screen in the inlet zone (3 – 5 mm), follo-

wed by a sand and grease trap as well as a fine sieve with

a slit width of < 1 mm is recommended [MEYER 2001;

DRENSLA 2001]. Experiences with plate membranes have

shown that pretreatment with a 3 mm screen as well as a

sand and grease trap is sufficient because they show less

tendency to accumulation and sticking of fibrous matter

[N. N. 2000c].

In order to meet the requirements for pretreatment for

membrane bioreactors, the screen manufacturers have

already developed new products. An example is the

membrane screen offered by the company Huber AG

(Figure 2-25) for finest screening of the raw waste water

in the inlet to a membrane bioreactor stage.

87

Figure 2-25

View and principle of a screening facility for

membrane bioreactors (Markranstädt waste water

treatment plant) [HUBER 2002, STEIN 2002a]


Design of the installation with view to failure

scenarios

Compared to conventional activated sludge plants, in the

case of membrane bioreactors failures have to be consi-

dered which affect the performance of the membrane

stage. Total breakdown of the membrane stage is the worst

case scenario for these installations, similar to the failure

of the secondary settlement tanks in conventional plants.

Therefore the pretreatment stages (screen, sand and grease

trap and, if necessary, separator for light density material)

of membrane bioreactors, being critical to the long-term

functioning of the membranes, have to be designed with

careful attention to breakdowns caused by common failure

scenarios that can be excluded in the design of conven-

tional municipal plants. Accidents in the catchment area

of the waste water treatment plant must also be considered.

In the case of critical influents due to accidents in the

catchment area of waste water treatment plants, the inlet

of the membrane bioreactor stage has to be closed, if

necessary, to avoid intoxication of the biomass as well as

damage to the membranes. This can be realized by special

sensors (e. g. conductivity sensors) in the inlet zone of the

waste water treatment plant so that sewers with storage

capacity and overflow, and stormwater overflow tanks

(e. g. unused primary settlement tanks) can be activated

in the case of accidents. The storage volume should be

calculated in such a way that in the case of combined

waste water flow, the influent to the membrane bioreac-

tor can be stored for two hours. In this case the mixing

and equalizing tank volume mentioned in chapter 2.1.3.1

can be taken into account with a view to maintaining

the minimum retention period. However, the impound-

ment or storage volume which is necessary to comply

with the standards for combined water treatment (ATV

standard A 128) must not be set off with the buffer vol-

ume to be installed.

It is also possible to build scum-boards and discharge

devices so that in the case of critical and unauthorized

indirect discharges, e. g. oil, petrol etc., a direct charge of

the membranes can be prevented.

Design of the installation with view to the arrange-

ment of membrane surfaces and reactors

In the case of new constructions, the membrane stage

should be designed in principle in two lines which are

hydraulically uncoupled, i. e. separate tanks including the

peripheral equipment, in order to allow for separate opera-

tion of each line for the complete inflow from the activated

sludge tank. The system has to be dimensioned hydrauli-

cally for these inflow volumes. Allowances for the permeate

capacity of the membranes are necessary if the capacity

reserves of the membranes have already been completely

utilized in the design of the installation for Qmax.

The same is true for installations with three or four lines,

for which the operational breakdown of one line has to be

considered in planning. Concerning multiple-line (> 4)

installations, the membrane stages should be calculated

in such a way that the maximum water volumes can be

treated, under design conditions, by 80% of the membrane

surface area available.

The mechanical design of the membrane stages should be

realized in such a way that in the case of necessary mem-

brane replacement, the above mentioned minimum mem-

brane surface in waste water treatment plants < 10,000 PE

(corresponding to a combined water flow of Qm < approx.

246 m3/h, i. e. a daily in-flow of Qd < approx. 2,250 m3/d)

can be quickly removed and installed, replaced or cleaned,

if necessary. The membrane suppliers have to ensure that

the membrane surfaces required are available and ready for

installation within two or three working days. Concerning

single-line installations, it must be possible to install the

membrane surfaces during operation (filled tanks).

For plants with more than 10,000 PE (corresponding to a

combined water flow of Q m > approx. 246 m3/h or a daily

inflow of Q d > approx. 2,250 m3/d)1), both requirements

mentioned in the last sections are of secondary importance

because even with indirect discharges caused by failures,

damaging of the complete membrane stage is rather im-

probable as a result of dilution effects. Moreover, larger

installations can be designed with multiple lines if suffi-

cient capacity reserves are available.

88

1) Assumptions according planning standard ATV-DVWK-A 131 [ATV-DVWK 2000c]: xs = 14 h/d, xf = 24 h/d, specific infiltration water flow = 0.5·QS,

Qm = 2·QS+Qf


Measurement, control and regulation technique

Besides the measurement, control and regulation techni-

que applied today at municipal waste water treatment

plants, additional parameters to be measured have to be

considered when using membrane technology. In parti-

cular, the permeability of the membranes has to be ob-

served and recorded separately for each line. This is neces-

sary in order to ensure that cleanings are carried out in

time so that a sufficient permeate capacity is maintained.

Within the scope of these measurements, suction pressure

and flow have to be recorded online, considering con-

struction measures and hydrostatic influences on the

pressure measuring. Inhibiting influences in flow measure-

ment have to be excluded.

For operation and cleaning of the modules, the require-

ments according to the recommendations of the manu-

facturers (e. g. pause control, backwash periods and volume

flows, alarm in the case of module aeration failure) have

to be taken into account.

Power supply

For possible power failures, a stand-by power supply

should be provided similar to conventional plants, in

case a two-side current input to the waste water treat-

ment plant is not possible. Anyway the process control

technique as well as the permeation have to be supplied

with power, and the power demand for minimum module

aeration (about 25 – 30 % of the design value) has to be

ensured.

Buffer tanks or reserves in the freeboard height are also

possible which allow for impoundment operation during

a short period.

Membrane cleaning

To maintain the filtration capacity, regular cleaning of

the membrane modules is necessary, which may take place

either in the activated sludge tank/filtration tank or in

separate tanks. Depending on the concept of the mem-

brane manufacturers, heating for the separate tank or the

cleaning solution has to be provided.

Since the cleaning agents to be used have caustic, oxidiz-

ing or corrosive effects, requirements concerning the

choice of materials for tanks (e. g. plastic sealings) and

aggregates (e. g. high-grade steel, PE) as well as for safety

at work (e. g. discharge devices for gases (chlorine), accord-

ing to the recommendations of GUV or DVGW for MAC

values) have to be considered in planning.

Appropriate tanks or stockrooms have to be provided for

the storage of the chemicals necessary for the cleaning

solutions.

2.1.3.3

Operation

Measures for maintenance of the filtration capacity

For safe operation of a membrane bioreactor, the mainte-

nance of a sufficient filtration capacity is of similar im-

portance as the maintenance of the settlement features

of activated sludge in a secondary settlement tank. While

in conventional plants the settlement features of the acti-

vated sludge can be influenced only to a limited extent

(e. g. floating sludge, bulking sludge or problems with

foaming), the filtration capacity of membrane bioreactors

can be maintained by regular operational measures, i. e.

membrane cleanings.

Cleaning is necessary for all membranes available on the

market, since in spite of sufficient pretreatment and module

aeration, the permeability of the membrane modules and

thus the flow performance at constant transmembrane

pressure, starting from a design flow rate of e. g. 25 L/(m2·h),

decreases continuously during operation. This reduction

of the performance is due to an increase in the resistance

to filtration by organic and inorganic covering layers on the

membrane surface and clogging of the membrane pores,

which cannot be avoided by operational measures such

as overflow and possible backwash of the membranes.

For maintenance or intensive cleanings, acid, alkaline

and oxidative cleaning agents are used which are suited

to restore the original filtration capacity.

In each case the instructions of the membrane or module

manufacturer have to be observed, since the cleaning

89


methods may vary considerably according to the specific

module.

Maintenance cleanings are performed in situ in the

activated sludge. They take place regularly once or twice

a week using low concentrations of cleaning agents (e. g.

150 mg/L of active chlorine). They are used for example

for ZeeWeedTM and Puron modules. During an extended

backwashing phase, the cleaning agent is added to the

permeate and pumped into the modules which are

immersed into the mixed liquor.

Intensive cleanings with higher concentrations of

chemicals (e. g. 500 – 2,000 mg/L of active chlorine) have

to be performed every 3 to 6 months, depending on the

degree of contamination. By analogy to maintenance

cleanings, the modules are cleaned while they are im-

mersed (in situ) or in separate tanks (ex situ). With

At present the use of sodium hypochlorite as cleaning

agent provides the best results. However, high concen-

trations of cleaning agents may have negative effects

such as damage of the biomass and foaming of the acti-

vated sludge stage, so that overdosing must be avoided.

Especially in the case of in-situ cleanings, negative effects

on the effluent quality may occur due to e. g. increased

AOX concentrations in the permeate. But this can be pre-

vented by permeate recycling into the biological stage. In

the course of studies on the pretreatment of rinsing

waters from extensive external cleaning, pretreatment

methods are being developed which shall reduce the AOX

concentration in the rinsing waters and avoid foaming in

the waste water treatment plant [DRENSLA, SCHAULE

2004].

At present less critical cleaning agents such as hydrogen

peroxide or citric acid are being tested in some mem-

brane bioreactor installations, so that soon alternatives

for sodium hypochlorite will be available.

installed modules, cleaning takes place in the activated

sludge, in cleaning solution or on air. In this case the

filtration tanks are emptied so that the modules are

suspended freely.

External cleaning (ex situ) is realized at cleaning solution

temperatures of 30 – 35 °C. For better mixing, the mem-

brane can be aerated during the cleaning process, so that

the chemicals are distributed more evenly. External clean-

ing provides the best result, but this method requires

higher operating expense [DRENSLA, SCHAULE 2004].

Table 2-3 summarizes the cleaning methods for immersed

membrane systems.

Due to the high concentrations of chemicals, intensive

cleanings may damage organic membrane materials and

thus have negative effects on the membrane service life.

90

in the activated sludge The chemicals are dosed from the permeate side.

in the cleaning solution The tanks are emptied and filled with the cleaning Cleaning in a separate cleaning cell, the

solution, the cleaning solution is dosed from the chemicals are dosed from the feed side at

feed side. temperatures of 30 – 35 °C.

on air The water level is lowered, the chemicals are

dosed from the permeate side.

Table 2-3

Cleaning methods

Membrane modules installed (in situ) Membrane modules removed (ex situ)


Energy demand

In existing membrane bioreactors, specific energy con-

sumption rates of 0.8 to 2.0 kWh/m3 of permeate were

determined. Approximately 50 – 80 % of this value is

used for module aeration, which, however, provides most

of the oxygen transfer necessary for biological treatment.

The throughput of the installation, the TS content (oxy-

gen transfer coefficient) and the waste water temperature

have been identified as the main factors influencing the

specific energy demand. At present, the specific energy

demand of membrane bioreactors is still higher than that

of conventional waste water treatment plants, but the

effluent quality concerning hygiene-relevant parameters

is better. For the Markranstädt and Monheim waste water

treatment plants, the specific energy demand related to

the average inflow volume in the range of 0.8 kWh/m3 –

0.9 kWh/m3 [DWA 2005]. The fluctuation ranges for dif-

ferent parts of the specific energy demand (e. g. cross-flow

aeration, permeate/recirculation, additional demand for

aeration) are indicated in the DWA working report [DWA

2005] (see Annex 6).

Figure 2-26 presents by way of example the specific

energy consumption rate of the Markranstädt waste

water treatment plant as a function of the throughput.

The energy consumption rate of the membrane stage

(suction pumps and module blowers), the recirculation

pumps, the agitators, the fine-bubble blowers, and the

inlet structure have been considered.

While the energy consumption of recirculation pumps,

agitators and inlet pump station are nearly independent

of the throughput, clear dependencies exist for the opera-

tion of the membrane stage and the fine-bubble aeration.

It has been shown that with larger waste water flows

to be treated, the specific energy consumption rate of the

membrane stage is 22 % lower than for a smaller through-

put. The same tendency is observed for the specific ener-

gy demand of the fine-bubble aeration. In this case the

energy demand can be reduced by 48 %. Energy is saved

by increasing the performance of the fine-bubble aera-

tion and switching off the coarse-bubble aeration during

91

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

spec

ific

en

erg

y d

eman

d [

kWh

/m3 ]

membrane stage(suction pumps)and module aeration

recirculation pumps

agitators

fine-bubble aerators

inflow pumping station

1,000-1,500

plant throughput [m3/d]

2,000-2,500 > 3,000

0.12

0.21

0.05

0.16

0.88

0,090.01

0.14

0.85

0.1

0.11

0.69

0.01 0.010,01

Figure 2-26

Energy demand of a membrane bioreactor (8,000 PE) with simultaneous aerobic sludge stabilization

[STEIN ET AL. 2001]


filtration pauses, or by reducing the performance of the

fine-bubble aeration at continuous coarse-bubble aeration

during filtration [STEIN ET AL. 2001].

Due to ongoing optimizations in plant operation as well

as module design and overflow, further reduction of the

energy consumption rate can be expected. Early develop-

ments such as the introduction of intermittent aeration,

two-storey arrangement of modules on top of the air

injection device, and operation of rotating membranes

has already resulted in a reduction of overflow-specific

energy costs by approx. 50 %. The Kommunale Wasser-

werke Leipzig (municipal waterworks) expect that the

energy consumption for MBR treatment will ultimately

be reduced to the range of conventional plants [STEIN

ET AL. 2001].

Manpower requirements and qualification

Besides training and sensitization of personnel for addi-

tional problems which result from the operation of a

membrane bioreactor (e. g. concerning membrane opera-

tion, cleaning, emergency operation in case the measure-

ment, control and regulation systems break down), there

are no extra demands on staff qualification.

Experiences from the Rödingen waste water treatment

plant (3,000 PE) have shown that the personal expendi-

ture after start-up, repair of faults and a training period is

at present approximately 0.5 man-days per day. This

value is in the range of conventional plants of comparable

size run by the Erftverband [DRENSLA 2001].

During the start-up period of the Markranstädt waste

water treatment plant (8,000 PE), the necessary working

time expenditure was assessed as unsatisfactorily high.

This was due in particular to failures of the peripheral

equipment of the membrane stage. After improvement of

the operational stability, the working time expenditure is

now in the range of conventional activated sludge plants

or only slightly greater with a maximum of one additional

working hour per day [STEIN 2002a].

2.1.4

Investments and Operating Costs

2.1.4.1

Investments

The investments for the construction of a membrane bio-

reactor consist of the costs for the components of mecha-

nical pretreatment, biological waste water treatment and

biomass separation and, if necessary, for excess sludge

treatment. From the experience acquired to-date, the

savings potentials and additional costs for the investments

compared to conventional waste water treatment techno-

logy can be summarized as follows in Table 2-4.

Starting from the typical costs for conventional waste

water treatment technology [BOHN 1993; GÜNTHERT,

REICHERTER 2001], the savings made in process engineer-

ing (smaller tank volumes, secondary settlement and pos-

sibly more tertiary treatment steps become unnecessary)

with the membrane bioreactor process can be divided

among the investments for additional expenditures as well

as for the membrane separation stage itself. According to

RAUTENBACH ET AL. [2000], the savings potential for the

components of a membrane bioreactor which are not part

of the membrane stage were 20 – 30 % for a plant size of

100,000 PE (compared to a conventional activated sludge

plant with secondary settlement and sand filtration).

Assuming a typical specific cost at that time of 200 euro per

m2 of membrane surface installed (including peripheral

equipment such as pipes, suction pumps, measurement,

control and regulation equipment), nearly the same total

investment for both variations were required.

The results of the tender process for the construction of

the Kaarst waste water treatment plant (80,000 PE) in 2001

have turned out favourably for membrane technology. The

offers submitted for membrane technology (20.3 – 22.1

million euro) were 1.7 – 3.4 million euro lower than those

for a comparable conventional plant without advanced

treatment (23.7 million euro) [ENGELHARDT 2002].

Based on the costs of membrane bioreactors built to-date

and on the results of tenders for new projects, the follow-

ing categories can be used to assess the investment:

92


The inhabitant-specific costs have to be assessed be-

tween 250 and 1,400 euro. This margin is mainly due to

different drainage systems. With combined systems, the

complete installation has to be dimensioned for the com-

bined waste water flow (usually 2·QT). Conversely, the

membrane stage of plants with separate systems only need

half of the membrane surface area compared to a com-

bined system. Moreover, the surface-specific costs of the

membrane modules decrease with increasing installation

size, and therefore have to be considered in direct depend-

ence on the total investments.

The share of investments for the membrane stage

(including peripheral equipment, machinery and piping)

in the total costs is in the range of 30 – 60 %. This wide

range also depends on the drainage system. Additional

influencing factors are the underlying membrane and

module costs, which during the last years have shown a

downward trend. Moreover, in the course of further tech-

nical development an increase in the performance of the

modules can be expected, so that the membrane surface

area to be installed, and thus the specific costs for the

membrane stage, will decrease.

At present, specific module costs for the first invest-

ment (including peripheral equipment) of 75 – 150 euro

per m2 of membrane surface can be assessed. These values

vary according to membrane manufacturers and the surface

used. Based on the developments made in the course of

the last years, an increase in the number of module system

suppliers can be expected. Rising sales as well as increased

competitive pressure will also have positive effects on the

module costs. Figure 2-27 shows the development of the

membrane replacement costs over the last decade and

a forecast for the year 2005 according to CHURCHHOUSE,

WILDGOOSE [2000]. In addition, the module-specific

costs on the basis of the tender results of different German

waste water treatment plants are listed. According to this

cost curve, more significant cost reductions can be expec-

ted in future. For the Monheim waste water treatment

plant, for example, membrane replacement costs of 58 or

50 euro/m2 after a membrane service life of 7.5 or 8 years,

respectively, have been assessed [RESCH 2002; STEIN

2002b].

93


Biological treatment

Biomass separation/

advanced treatment

Sludge treatment

activated sludge tank volumes 3 to 4 times smaller because

of operation at increased TS content of 12 to 16 g/L

secondary settlement tank not necessary downstream

processes for further treatment of the biologically treated

waste water at higher demands on the effluent (sand

filtration, disinfection) not necessary

usually no anaerobic sludge stabilization (digester) because

the biomass is aerobically stabilized

finer mechanical pretreatment

• hollow-fibre membranes ≤ 1 mm

• plate membranes ≤ 3 mm

necessary to protect the membrane modules

costs for the membrane stage are higher than for con-

ventional secondary settlement tanks due on the one

hand to the costs of the membrane modules themselves

and on the other hand to peripheral equipment (measure-

ment, control and regulation equipment, piping, suction

pumps, compressors, cleaning facilities etc.)

higher energy costs due to aerobic sludge stabilization,

no utilization of digester gas from primary and secon-

dary sludge (with plants > 50.000 PE)

Table 2-4

Savings potentials and additional costs concerning the investments of membrane bioreactors compared to

conventional activated sludge plants

Process stage Savings potential Additional costs


2.1.4.2

Operating and Maintenance Costs

The annual operating and maintenance costs related to

waste water volumes or the population connected consists

of different cost types. Compared to the costs of conven-

tional waste water treatment processes, the following dif-

ferences result for the membrane bioreactor process:

1. Energy costs:

Operation of a membrane stage requires more energy

than that of conventional plants. From the operation

of existing installations ≥ 3,000 PE, energy consump-

tion rates of 0.8 – 1,4 kWh per m3 of waste water treat-

ed have been determined. For the Nordkanal waste

water treatment plant, an energy demand approx. 60 %

(0.8 kWh/m3) greater than for conventional plants

(0.46 kWh/m3 with anaerobic sludge stabilization and

0.51 kWh/m3 with aerobic sludge stabilization) can

be expected [ENGELHARDT 2002].

2. Membrane cleaning:

To maintain the filtration capacity, the membranes

have to be cleaned regularly. Therefore, the costs for

chemicals (about 0.25 – 1.00 euro/(m3· a) and additio-

nal labour costs have to be taken into account.

3. Maintenance:

The typical cost for the maintenance of conventional

plants increases for membrane bioreactors due to the

additional expenditure for maintenance of the mem-

brane stage. The costs to be assessed result from the

real membrane service life (i. e. guaranteed by the

manufacturer; assumed up to now: 5 – 8 years, in

some cases 10 years [WOZNIAK 2002]) and from the

anticipated membrane replacement costs. The main-

tenance costs decrease with longer service life and

falling module costs.

94

450

400

350

300

250

200

150

100

50

0

mem

bra

ne

rep

lace

men

t co

sts

o/m

2

1990year

1995 2000 2005

1 Specific net costs for installed membrane surface area (without peripheral equipment, first installation), calculated back on the basis of theresults of the call for tenders; according to information from the manufacturers, low costs can be expected for membrane replacement.

2 Estimation of the operator [STEIN 2002b]

KA Monheim9.700 PE

KA Rödingen1

3.000 PE

GKW Nordkanal1

80.000 PE

KA Markkleeberg2

30.000 PE

KA Markranstädt1

8.000 PE

according to Churchhouse (2000) gathering ISA RWTH (2003)

Figure 2-27

Development of membrane replacement costs [ISA 2002; CHURCHHOUSE, WILDGOOSE 2000]


4. Waste water charges:

As a result of the treatment efficiency of membrane

stages, a reduction in the pollution load discharged

into water bodies can be expected.

The expenditure for the construction of a membrane

stage can therefore be cleared with the waste water

charges paid to-date, provided that the requirements

according to § 10 section 3 of the Waste Water Char-

ges Act are met.

Since the higher energy and maintenance costs exceed

the reduction in waste water charges, higher operating

costs of membrane bioreactors can be expected on the

whole. A comparison of operating costs has been realized

for the Nordkanal waste water treatment plant on the

basis of the offers [ENGELHARDT 2002]. According to

this study, the assessed waste-water-specific operating

costs of the membrane bioreactor (0.24 – 0.25 euro/m3)

were higher by approx. 15 % than that of the conventio-

nal solutions offered (0.20 – 0,22 euro/m3). Ranges for the

costs per year, related to energy demand and waste water

volume, for aeration and recirculation, the necessary

chemicals etc. are indicated in the DWA working report

“Membrane bioreactor process” (see Annex A 6 [DWA

2005]).

In this case it has to be taken into account that plants

with differing effluent qualities are compared in cost

determination. In order to obtain the same effluent qua-

lity with conventional activated sludge plants as with

membrane bioreactors, an additional treatment stage

(e. g. disinfection stage) has to be arranged downstream

of the conventional plant. Under this condition the ope-

rating costs of membrane bioreactors should be the same

or lower.

Moreover, further technical developments of the mem-

brane modules will lead in future to a reduction of the

energy costs and improvement of the performance, so

that the population-specific treatment costs will also

decrease.

2.2

Concrete Examples of Membrane Bioreactors

In the following chapters, membrane bioreactors for the

treatment of municipal waste water are described which

already have been realized or are under planning. The

concrete examples are arranged according to the loca-

tions (in or outside Germany) and the membrane process

applied (microfiltration or ultrafiltration). Large-scale

plants, pilot plants, small waste water treatment plants,

ship’s waste water treatment plants and mobile plants are

described.

In Germany, at present nine large-scale membrane biore-

actors with capacities between 700 and 80,000 PE are

operated. Five more installations will be put into opera-

tion by the end of 2005. Ten plants will then exist in the

state North-Rhine Westphalia (NRW). All installations

built in NRW have been promoted by funds from the state.

The state makes available additional funds for new appli-

cations and more far-reaching scientific studies which

especially aim at optimizing the treatment capacity and

the operating cost.

Table 2-5 gives an overview of the most important data

for the plants in Germany, which will be described in

detail in the following sections.

95


96

Table 2-5

Data of the large-scale membrane bioreactors treating municipal waste water in Germany,

as of December 2004

Operator

Federal State

Plant

Capacity

Membrane

manufacturer

Module type

Process

Membrane

surface area

Bioreactorvolume

Maximum inflow

Sewer system

Start-up

Pretreatment

Special feature

Erftverband

North Rhine-

Westphalia

WWTP Nordkanal

80,000 PE

ZENON

capillary module

ultrafiltration

84,480 m2

9,200 m3

1,881 m3/h

combined system

December 2003

screen (5 mm)

grit and grease trap

rotary screen (0.5 mm)

Aggerverband

North Rhine-

Westphalia

WWTP Seelscheid

10,500 PE

Kubota

plate module

microfiltration

12,480 m2

2,310 m3

356 m3/h

combined system

August 2004

step screen (3 mm)

grit chamber

expansion at the site of

the WWTP

City of Monheim

Bavaria

Monheim WWTP

9,700 PE

ZENON

capillary module

ultrafiltration

12,320 m2

1,640 m3

288 m3/h

combined system

July 2003

fine screen (1 mm)

grit channel

Municipal Waterworks

Leipzig

Saxony

Markranstädt WWTP

at present 8,000 PE

up to 12,000 PE

ZENON

capillary module

ultrafiltration

7,360 m2

approx. 1.800 m3

180 m3/h

combined system

January 2000

two-stage screen

(up to 1 mm)


Erftverband

North Rhine-

Westphalia

Rödingen

3,000 PE

ZENON

capillary module

ultrafiltration

4,846 m2

480 m3

135 m3/h

combined system

June 1999

screen (3 mm) grit and

grease trap sieving of

the recirculation sludge

(0.5 mm) in partial flow

Operator

Federal State

Plant

Capacity

Membrane

manufacturer

Module type

Process

Membrane

surface area

Bioreactorvolume

Maximum inflow

Sewer system

Start-up

Pretreatment

Special feature

Municipal Services

Schramberg

Baden-Württemberg

Schramberg WWTP

2,600 PE

ZENON

capillary module

ultrafiltration

4,400 m2

730 m3

90 m3/h

combined system

May 2004

screen (5 mm)

fine screen (0.5 mm)


Aggerverband

North Rhine-Westphalia

Büchel WWTP

1,000 PE

Kubota

plate module

microfiltration

960 m2

190 m3

40 m3/h

combined system

August 1999

screen (3 mm) grit

chamber, optional

primary treatment

pilot plant

Municipal Waterworks

Leipzig

Saxony

Knautnaundorf WWTP

at present 900 PE

up to 1,800 PE

Martin Systems AG

plate module

ultrafiltration

756 m2

68 m3

23 m3/h

separate system

October 2001

two-stage screen

(3 mm, 1mm)


Wasserverband

Eifel-Rur (WVER)

North Rhine-Westphalia

WWTP Simmerath

700 PE

PURON

capillary module

ultrafiltration

1,000 m2

136 m3

being studied

combined system

2003

fine screen (3 mm)

pilot plant


The positive experiences acquired to-date with membrane

technology and the membrane bioreactor are the reason

for water boards and municipalities to take the membrane

bioreactor process into consideration when planning new

or up-grading existing plants as an alternative to conven-

tional waste water treatment processes. Especially those

operators (Wasserverband Eifel-Rur (WVER), Erftverband)

who have acquired experience with membrane technology

are planning or building more membrane bioreactors

(Table 2-6).

Moreover, the application of the membrane bioreactor

process is studied at a large number of other sites in

Germany. The waste water plants at the sites Xanten-

Vynen (LINEG) and Richtheim (Municipality of Richt-

heim in cooperation with Bayerisches Landesamt für

Wasserwirtschaft (Bavarian Office for Water Manage-

ment)) are mentioned here by way of example, which

will also be described in the following chapters.

97

Table 2-6

Membrane bioreactors under construction or in planning stage in Germany, as of December 2005

Operator

Federal State

Plant

Design capacity

Planned start-up

State

Membrane

manufacturer

Module type

Process

Membrane surface

area

Bioreactor volume

Maximum inflow

Pretreatment

Special features

WVER

North Rhine-

Westphalia

WWTP Rurberg

6,200 PE

2005

commissioned

Kubota

plate module

microfiltration

approx. 13,440 m2

approx. 750 m3 planned

349 m3/h

fine screen (3 mm)

grit chamber

finest screen (0.5 mm)

discharge into

Rurtalsperre (Rur valley

reservoir)

WVER

North Rhine-

Westphalia

WWTP Konzen

9,700 PE

2005

commissioned

Kubota

plate module

microfiltration

23,040 m2

approx.1,700 m3 planned

587 m3/h

fine screen (3 mm)

grit chamber

finest screen (0.5 mm)

City of Eitorf

North Rhine-

Westphalia

WWTP Eitorf

11,625 PE

2005

commissioned

Kubota

plate module

microfiltration

10,240 m2

1,200 m3

288 m3/h

fine sieve


partly industrial waste

water

Linksniederrheinische

Entwässerungs-

Genossenschaft

North Rhine-

Westphalia

WWTP Xanten-Vynen

2,000 PE (only

membrane installation)

2005

commissioned

A 3 GmbH

plate module

microfiltration

2,000 m2

40 m3/h

screen (3 mm)

expansion of the WWTP

at the site

Erftverband

North Rhine-

Westphalia

WWTP Glessen

9,000 PE

2005

planning stage

not yet determined

not yet determined

micro-/ultrafiltration

12,320 m2 planned

approx.1,700 m3 planned

268 m3/h

screen (6 mm)

grit-/grease trap

fine sieve (0.5 mm)

expansion of the WWTP

at the site

MF2.2.1

MF2.2.1.1


Waste Water Treatment Plants with Microfiltration

Membrane Installations in Germany

Seelscheid Waste Water Treatment Plant and

Training Centre

From 1974 to 1976, the Seelscheid waste water treatment

plant had been designed for 3,000 PE. In a second stage,

from 1991 to 1992, it was expanded to a capacity of

7,500 PE. The design at that time provided a final expan-

sion up to 10,500 PE so that some structures, in particu-

lar the pipes, were designed for that size. Upgrading of

the waste water treatment plant to 10,500 PE according

to the activated sludge process would have been very

expensive due to limited space. In 2003, the membrane

bioreactor suggested itself as a more effective alternative

with lower space demand.

For the expansion, two fine screens (3 mm spacing) were

installed in the existing screen building in order to ensure

trouble-free operation of the waste water treatment plant,

especially of the membrane installation. Each of both

fine screens is able to treat the maximum waste water

flow of 99 L/s, resulting in a redundant system. The

aerated grit and grease trap, which existed before the last

upgrade, has a volume of V = 104 m3. The calculated

hydraulic retention time in this structure is more than

17 min. in the case of stormwater flow and more than

35 min. during dry weather flow. After having passed the

grit chamber, the waste water flows into the activated

sludge tank which is built as a circular tank with differ-

ent zones. The waste water flows centrally into an an-

aerobic zone (V = 500 m3) for increased biological phos-

phorus removal. The outside zone of the activated sludge

tank (V = 1.160 m3) is used for denitrification. Part of the

tank (500 m3) can be aerated and used for nitrification,

depending on time and load.

The intermediate settling tank was decommissioned to

build the new three-line membrane stage on this surface,

which was commissioned in July 2004. The three mem-

brane tanks with a total volume of approx. 800 m3 serve

for nitrification. In each of the three tanks, 13 plate

membrane modules (type EK 400) from the company

Kubota are installed. The total membrane surface area is

12,480 m2. The recirculation flows and the aeration are

controlled by fuzzy logic.

At present, the necessary transmembrane pressure differ-

ence is produced in gravity flow and can be supported

by permeate pumps. The filtrate is fed into a storage tank

(V = 100 m3). From there it is discharged by the existing

pipes into the Wenigerbach (a creek). Part of the treated

waste water is used as process water at the waste water

treatment plant. The concentrate is recycled into the

denitrification zone or optionally into the aerobic zone.

The minimum requirements, the values of the discharge

consent and the operating values after four months of

operation are listed in Table 2-7.

The investment for upgrading of the Seelscheid waste

water treatment plant was approx. 4.6 million euro,

supported by funds from MUNLV.

98

Table 2-7

Minimum requirements, discharge consent and operating values of the Seelscheid waste water treatment

plant [according to AGGERVERBAND 2004]

Parameter

CSB

BSB5

NH4-N

Ntot

Ptot

AOX

Unit

mg/L

mg/L

mg/L

mg/L

mg/L

µg/L

Minimum requirements

90

20

10

18

2

no information

Discharge consent

40

10

3

18

0.8

50

Operating values

< 20

no information

< 0.1

< 5

–

–


99

feed

alternative

recirculation

fine screen3 mm

fine screen3 mm

denitri-fication-tank

nitri-fication-tank

anaerobictank

sludge

permeatestorage

blowerinstallation

process water

gritchamber

membrane stage/nitrification

receivingwater

Figure 2-28

Flow sheet of the Seelscheid waste water treatment plant [according to AGGERVERBAND 2004]

Figure 2-29

Membrane installation at the Seelscheid waste water treatment plant [photos: AGGERVERBAND 2004],

left: membrane tanks, right: machine cellar of the membrane installation


Training centre at the Seelscheid waste water

treatment plant

The Aggerverband (water board) will establish at the site

of the Seelscheid waste water treatment plant a modern

training centre for membrane technology. This will be

done in cooperation with the Ministry for Environment

and Nature Conservation, Agriculture and Consumer Pro-

tection (MUNLV) of the state North-Rhine Westphalia,

the Bildungszentrum für die Entsorgungs- und Wasser-

wirtschaft (BEW) (Training Centre for Water Management

and Waste Water Disposal), the Deutsche Vereinigung für

Wasserwirtschaft, Abwasser und Abfall (DWA) (German

Association for Water Management, Waste water and

Waste), the Deutsche Gesellschaft für Membrantechnik

(DGMT) (German Association for Membrane Technology)

and the RWTH Aachen University. The centre is supported

by funds from the state North-Rhine Westphalia. Besides

training rooms and eight laboratory working places, four

membrane bioreactors with upstream denitrification and

various membrane systems will be installed in the tanks

of the former sand filtration system in order to realize

practical training (see Figure 2-31 and Figure 2-30).

The training courses are intended for environmental

technicians, sanitation masters and future engineers from

universities. Completion of the training centre is scheduled

for the year 2005. The training centre is promoted by

funds of the federal state North Rhine-Westphalia.

100

raw wastewater

optionalinflow

fine screen3 mm

fine screen0,75 mm

to treatment plant

raw wastewater

denitri-fication

nitrification/membrane stage

recirculation

recirculation

recirculation

recirculation

blowerinstallation

blowerinstallation

blowerinstallation

blowerinstallation

Figure 2-31

Flow sheet of the training installations [according to AGGERVERBAND 2004]

Figure 2-30

Existing sand filter tanks, to be used for the trai-

ning installations [photo: AGGERVERBAND 2004]


Büchel Pilot Plant

Within the scope of a research project “Upgrading of the

Büchel waste water treatment plant using membrane

technology” promoted by the Ministry for Environment

and Nature Conservation, Agriculture and Consumer

Protection (MUNLV) of the state North-Rhine Westpha-

lia, the Aggerverband (water board) has operated from

1999 to 2001 a membrane bioreactor pilot plant. This

R&D project was realized on behalf of Aggerverband by

the Institute of Environmental Engineering of RWTH

Aachen University and ATEMIS (consulting engineers).

The reason for the project was the necessary expansion

of the Büchel waste water treatment plant from the

existing capacity of 12,000 PE to 25,000 PE. Besides the

limited space available, stringent demands on the effluent

quality made by the district government Cologne, due to

the situation of the plant in a nature reserve, had also to

be taken into consideration. Therefore, the Aggerverband

searched for an alternative to conventional waste water

101

nitrification and membrane container V=80m3 permeate

nitri-/denitrification-tank V=100m3

feed

membrane stage 1 membrane stage 2

RS

blowerstationmembranereactor

blower stationnitrification

Figure 2-33

Flow sheet of the Büchel pilot plant [BAUMGARTEN 2001b]

Figure 2-32

View of the Büchel pilot plant [photo: ISA RWTH

AACHEN]. Foreground: filtration container. Back-

ground, left: activated sludge tank of the pilot

plant. Background, right: primary settling tank of

the overall plant

MF2.2.1.2


treatment technology. After detailed cost comparisons,

the membrane bioreactor process turned out to be the

most interesting alternative. The Aggerverband decided

to run a pilot plant within the scope of expansion plan-

ning in order to acquire experience with this technology.

The pilot plant was situated at the site of the Büchel

waste water treatment plant and is fed with a partial flow

of the mechanically pretreated waste water from the exi-

sting plant. Mechanical pretreatment consisted of a

step screen (3 mm), an aerated grit and grease trap and a

primary settling tank. To feed the pilot plant, the partial

flow could be taken either upstream or downstream of

the primary settling tank.

The waste water was pumped by a lifting pump into the

denitrification zone of the pilot plant. Nitrification took

place only in the zone of the downstream membrane

stage (Figure 2-33) because under normal conditions the

air injected for the overflow of the membranes is sufficient

for complete nitrification. If this was not ensured, single

zones in the upstream denitrification tank could be aerated

and used for nitrification.

The membrane stage consisted of two filtration lines

which could be operated independently from each other.

Each line is equipped with four plate packages contain-

ing 150 plate modules from the company Kubota. The

treated waste water was withdrawn by suction from the

filtration modules.

After a start-up period during which faults of the mecha-

nical installation were remedied, the plant was operated

nearly trouble-free. After a six-month operating phase

where each of the filtration stages was operated with net

specific flows of 27 L/(m3·h), the transmembrane pressure

increased from approx. 80 mbar to average values of

approx. 150 mbar due to fouling. Therefore, chemical

in-situ cleaning had to be carried out in order to ensure

the throughput of the plant. With this it was possible to

restore the original membrane capacity nearly completely

[WOZNIAK, BAUMGARTEN 2001, BAUMGARTEN

2001b].

After conclusion of the pilot tests, an expansion at the

site of the Büchel waste water treatment plant according

to the conventional activated sludge process was pre-

ferred for economic reasons. However, as a result of the

experience acquired with membrane technology, the

Aggerverband favoured under technical aspects the fur-

ther use of membrane technology for municipal waste

water treatment. Thus the experience acquired was in-

cluded in the meantime e. g. in the expansion of the large-

scale Seelscheid waste water treatment plant of the

Aggerverband (see chapter 2.2.1.1). For future new con-

structions or expansions of plants, too, this technology

will be included in the studies of technical processes.

102


Richtheim Waste Water Treatment Plant

In Bavaria, many decentralized waste water treatment

plants are situated in regions with stricter requirements

for water pollution control (e. g. karstland) or discharge

into sensitive receiving waters, so that advanced waste

water treatment may be useful or necessary, e. g. by sand

filtration and UV disinfection, ozonation or membrane

technology.

Within the scope of a research project promoted by the

Landesamt für Wasserwirtschaft (LfW) (State Office for

Water Management) in Bavaria, different processes for

the treatment of municipal waste water in decentralized

waste water treatment plants are studied at three sites.

The study focuses on the attainable effluent quality,

operational liability and expenditure.

The Richtheim waste water treatment plant is used to

perform the studies on the membrane bioreactor process.

It has a treatment capacity of 100 PE.

An inflow shaft, installed for the separation of coarse and

floating matter, serves as primary settling tank for coarse

and floating matter. The pretreated waste water then

flows by gravity into the membrane bioreactor. The plate

modules from the company Kubota (2 module packages

with 80 m2 membrane surface area each), which include

aeration, are installed in a prefabricated shaft which serves

as the membrane bioreactor. The oxygen demand is

covered completely by aeration of the membrane mod-

ules. Figure 2-34 shows the flow sheet of the installation.

103

feed

primary treatment

blowerinstallation

membrane stageflow

receivingwater

Figure 2-34

Flow sheet of the membrane bioreactor [according to BAYERISCHES LANDESAMT FÜR WASSERWIRTSCHAFT

2004]

MF2.2.1.3

MF2.2.1.4


Eitorf Waste Water Treatment Plant (Commissioned)

The Eitorf waste water treatment plant receives municipal

waste water from the municipality of Eitorf, parts of the

city of Hennef and the waste water from commercial and

industrial enterprises. For expansion of the capacity of

the plant from 33,000 PE up to now to approx. 46,500 PE

(value prognosticated for the year 2010), process variants

using membrane technology were developed within the

scope of a study [NOLTING, KAZNER 2005]. Based upon

the comparison of the costs per year, the construction of

a membrane bioreactor turned out to be the most favour-

able solution for the expansion of the capacity for the

treatment of a partial waste water flow.

The installation was originally intended for the joint tre-

atment of a high-loaded waste water flow from textile

finishing with strong coloration and high AOX concen-

trations (see Table 2-8). In order to increase the treatment

efficiency concerning these parameters (effluent require-

ment for AOX: 50 µg/L), simultaneous addition of pulver-

ized activated carbon was tested successfully in the run-

up on an industrial scale for the conventional plant

[KAZNER 2003] and on pilot scale for a membrane bio-

reactor [BAUMGARTEN 2005].

104

feed

receivingwater

primary treatmentfine screen3 mm

gritchamber

fine sieve1 mm

75 %

25 %

biological reactor

sludge

clarifier

variabletank

denitrifi-cation

recirculation

4-linemembrane stagewith nitrification

Figure 2-35

Flow sheet of the Eitorf waste water treatment plant [according to GEMEINDEWERKE EITORF 2004]

Table 2-8

Input values for the design of the Eitorf membrane bioreactor [according to GEMEINDEWERKE EITORF

(municipal utilities) 2004]

Parameter Qd Qh QM COD BSB5 TKN NH4-N Ptot AOX

Inflow to the membrane bioreactor 1,800 145 288 1,152 486 108 62 13 0,4

m3/d m3/h m3/h kg/d kg/d kg/d kg/d kg/d kg/d


Due to operations-related closure of the dye-works, this

waste water flow will cease in future. A high-loaded waste

water flow from the food industry will be introduced

instead.

The membrane bioreactor consists of a denitrification

tank (V = 300 m3), a variable zone equipped with aerators

(V = 300 m3) for denitrification or nitrification and four

nitrification tanks (150 m3 each), in which immersed plate

modules from the company Kubota (type EK 400, double-

decker modules) with a total membrane surface area of

10,240 m2 are installed.

The investments for the construction of the membrane

bioreactor, which was commissioned in September 2005,

were 3.9 million euro, subsidized in part by the Ministry

for Environment and Nature Conservation, Agriculture

and Consumer Protection of the federal state North

Rhine-Westphalia (MUNLV NRW).

105

Figure 2-36

Eitorf waste water treatment plant with covered membrane tanks between the buildings in the foreground


Xanten-Vynen Waste Water Treatment Plant

(Commissioned)

In 1972, the Xanten-Vynen waste water treatment plant

was designed, according to the design principles at that

time, for 6,000 PE and triple dry-weather flow. Today the

biological stage is approved for 3,300 PE. At present,

approx. 3,160 PE are connected. Thus, the degree of capa-

city utilization is more than 95 % and has to be expanded

to 4,989 PE, due to anticipated population growth. The

connected quarters Vynen and Marienbaum are drained

for the most part by a combined sewer system. Only one

modern estate is drained by a separate system. The inflow

to the waste water treatment plant is exclusively of muni-

cipal origin.

Within the scope of a three-year research project, a two-

line membrane bioreactor at the Xanten-Vynen waste

water treatment plant will be equipped with the plate

membrane system from the company A3 and operated in

106

feed

screen gritchamber

screen system3 mm

biological reactor

sludge

clarifier

recirculation

effluent polishingpond

blowerinstallationrecirculation

denitrifi-fication

membrane stagenitrification

denitrifi-fication

membrane stagenitrification

receivingwater

Figure 2-38

Flow sheet of the Xanten-Vynen waste water treatment plant, including the planned membrane

bioreactors [according to LINEG 2004]

Figure 2-37

Membrane installation in container construction

for the Xanten-Vynen waste water treatment plant

[photo: A3 GMBH]

MF2.2.1.5


Piene Waste Water Treatment Plant

(in Planning Stage)

The construction of a waste water treatment plant with a

treatment capacity of 170 PE according to the membrane

bioreactor process is being planned for the quarter Piene

of the city of Gummersbach.

Until now, the waste water of Piene is treated by three-

chamber septic tanks. The treated waste water is discharged

into a “weak” receiving water, The discharge consent

requires a COD effluent concentration of < 70 mg/L and

a BOD5 concentration of < 10 mg/L. Due to the situation

described above, a decision was made in favour of the

membrane bioreactor process. Figure 2-39 shows the flow

sheet of the membrane bioreactor.

It is planned to pretreat the waste water by a rotary

screen with a spacing of 3 mm. The following buffer tank

wih a volume of 40 m3 serves to buffer peak flows in the

case of combined water flow and to store the excess sludge.

From the storage tank the waste water is fed into the

activated sludge stage (V = 40 m3) in which the immersed

membrane modules are integrated. It is intended to use

plate membrane packages from the company Kubota

with a total membrane surface area of 320 m2.

107

parallel (see Figure 2-38). The total capacity of the two-line

membrane bioreactor will be approx. 2,000 PE.

Both membrane bioreactors will be operated under real

conditions in parallel to the existing activated sludge stage

to compare the cleaning efficiency of both systems. The

three-year test period has the following objectives:

• To prove evidence of the operational safety and capacity

of the installation

• To study the economic efficiency of the membrane

system

• To determine an optimum operating and cleaning

management program

Both membrane installations are manufactured identically

and fitted in one container each (Figure 2-37). For mecha-

nical pretreatment, a screen with an aperture size of 3 mm

is planned. The activation volume is 100 m3 each. Each

membrane installation is designed for a dry weather flow

of 12.5 m3/h and a stormwater flow of 40 m3/h and has a

membrane surface area of 2,000 m2. The membrane instal-

lation will be commissioned still in 2005.

feed

buffer tank

biological reactormembrane stage

fine screen3 mm

sludge

receivingwater

Figure 2-39

Flow sheet of the membrane bioreactor [according to CITY OF GUMMERSBACH 2004]

MF2.2.1.6

MF2.2.1.7


Rurberg-Woffelsbach and Konzen Waste Water

Treatment Plants (Commissioned)

The Rurberg-Woffelsbach and Konzen waste water treat-

ment plants of Wasserverband Eifel-Rur (WVER) (water

board) are being expanded to a treatment capacity of

6,200 PE and 9,700 PE, respectively. At present, both

expansion measures are realized. The plants will be put

into operation at the end of 2005.

The current demands on the effluents of the Rurberg-

Woffelsbach and Konzen waste water treatment plants

are listed in Table 2-9. The Rurberg-Woffelsbach waste

water treatment plant discharges into the Rur reservoir

which is used for recreation purposes, and the Konzen

waste water treatment plant uses the Laufenbach (a

creek) as receiving water which is situated in the drin-

king water catchment zone. These were the reasons for

the use of a membrane bioreactor at both sites.

In future, the Rurberg-Woffelsbach waste water treatment

plant will be designed for a dry weather flow of 175 m3/h

and a stormwater flow of 349 m3/h. The Konzen waste

water treatment plant will treat a dry weather flow of

245 m3/h and a stormwater flow of 587 m3/h.

The process concept for both plants includes mechanical

pretreatment by a fine screen with a spacing of 3 mm,

followed by a grit and grease trap and a fine screen with

a spacing of 0.5 mm. The fine screen will be redundant.

At the Rurberg-Woffelsbach waste water treatment plant,

biological waste water treatment takes place in an upstream

denitrification tank and a combined nitrification/mem-

brane tank.

At Konzen, an activated sludge tank both for denitrifica-

tion and nitrification precedes the membrane chamber.

Additional nitrification volume is available in the mem-

brane chamber. Both installations are equipped with plate

membrane modules from the company Kubota. At the

Rurberg-Woffelsbach waste water treatment plant, a

membrane surface area of 13,440 m3 will be installed,

and of 23,040 m3 at the Konzen plant. For these mem-

brane surface areas, 42 and 72 membrane-modules,

respectively, of the type EK 400 are provided. In this

region, the membranes have to cope with a waste water

temperature in winter of less than 6 °C.

According to the submittal results, the investments for

the Rurberg-Woffelsbach plant are approx. 5.5 million

euro (without planned lake duct, pumping station and

engineering) and 7.5 million euro for the Konzen plant

(without combined water treatment and engineering).

Taking into account a subsidy of 50 % by the federal

state North Rhine-Westphalia for the membrane-specific

costs, the expansion of both waste water treatment

plants by the membrane bioreactor process is less

expensive than conventional upgrading.

108

Table 2-9

Demands on the effluent quality of the Rurberg-Woffelsbach and Konzen waste water treatment plants

[according to WVER 2004]

Parameter Unit Demands on the effluent of the Demands on the effluent of the

Rurberg-Woffelsbach WWTP Konzen WWTP

CSB mg/L 80 50

BSB5 mg/L 20 15

NH4-N mg/L 10 3

Ptot mg/L 0.5 0.2

MF2.2.1.8


Kohlfurth Waste Water Treatment Plant,

Process Water Treatment

The Kohlfurth waste water treatment plant has a design

capacity of 156,000 PE. It treats mainly municipal waste

water by the conventional activated sludge process with

following anaerobic sludge treatment (see Figure 2-40).

Concerning nitrogen removal, the Kohlfurth waste water

treatment plant was designed for a monitoring value of

18 mg Ninorg/L. In future, it has to comply with a monitor-

ing value of 13 mg Ninorg/L. With full capacity utilization

of the plant, at present it cannot be assured that this

requirement is met in the qualified random sample. This

was the reason in autumn 2003 to plan a new treatment

facility for the process water from sludge dewatering.

At the Kohlfurth waste water treatment plant, the daily

sludge liquor quantity from sludge dewatering is 300 m3

with a NH4-N concentration of 700 – 1,000 mg/L. As new

treatment concept, the membrane bioreactor process was

chosen. The potential for autotrophic deammonification

in the membrane bioreactor will be studied in particular.

The sludge liquor is stored temporarily in a buffer tank.

It flows for nitritation into the first aeration reactor with

a volume of 200 m3. Autotrophic deammonification will

take place in the second aeration reactor (V = 180 m3).

Two thickeners which are no longer used, serve as reac-

tors for the activated sludge stage.

The two-line membrane installation arranged downstream

of the activated sludge stage is installed in a separate

reactor. Each line contains two module packages (from

the company Kubota, type EK 400) with a total membrane

surface area of 720 m2. The permeate of the membrane

installation is fed into the return sludge pumping station

and, with this, into the activated sludge stage of the

Kohlfurth waste water treatment plant.

The plant is working since January 2005. After a test ope-

ration phase, the operating mode of autotrophic deam-

monification as well as of conventional denitrification

will be studied.

109

primary treatment biologicalreactor

sludge

clarifier

denitri-fication

nitrifi-cation

feed

screengritchamber

denitri-fication

carbon source

gritfiltration

coarse sludge

pre-thickening

digester digester

post-thickening

chamberfilter press

sludge liquor

filtrate

membranestage

storage

sludgeliquor

recirculation

flow

receivingwater

Figure 2-40

Flow sheet of the Kohlfurth waste water treatment plant [according to WUPPERVERBAND 2004]

MF2.2.1.9


Dormagen Waste Water Treatment Plant,

Process Water Treatment (Commissioned)

The Dormagen waste water treatment plant has a design

capacity of 80,000 PE and treats predominantly municipal

waste water. After mechanical pretreatment, the waste

water is treated according to the activated sludge process.

The sludge is anaerobically treated (see Figure 2-41).

The process water from sludge treatment consists of the

sludge liquor from the digester and the post-thickener as

well as the centrate water from the centrifuges. It is stored

temporarily in a balancing tank. The NH4-N concentra-

tion of this process water is approx. 800 mg/L, which

corresponds to a waste water load of approx. 15,000 PE.

Due to this load, the waste water treatment plant reached

its capacity limits from time to time. This was the reason

in autumn 2003 to plan a new sludge water treatment

plant.

The concept using the membrane bioreactor for the treat-

ment of the sludge water turned out to be favourable in

terms of technology and economic efficiency. The mem-

brane installation is planned with two lines and will con-

tain eight module packages from the company Kubota

(type EK 150) with a total membrane surface area of 960 m2.

The existing grit chamber will be converted to a nitrifica-

tion and denitrification stage in which the process water

from the storage tank is fed. The membrane installation

will be fitted in a container on the existing grit chamber.

The permeate of the membrane installation will be fed into

the inflow of the activated sludge tank for treatment.

The plant is under construction and will be put into

operation in 2005.

110

recirculation

clarifier

feed

thickening digester digester

post-thickening

sludge liquor

... water

membranestage

storage

sludgeliquor

recirculation

flow

gritchamberscreen primary treatment

denitri-fication

nitrifi-cation

bio-P nitrifi-cation

denitri-fication

sludge

blowerinstallation

centrifuge

if nec.sludgeliquor

receivingwater

Figure 2-41

Flow sheet of the Dormagen waste water treatment plant [according to CITY OF DORMAGEN 2004]

MF2.2.2


Installations Outside of Germany with

Microfiltration Membranes

Membrane technology has been used in municipal waste

water treatment since the nineties. The first large-scale

plants were built mainly in North America and Japan.

About 90 % of these installations have a capacity of less

than 100 m3/d. A larger plant with a design capacity of

about 5,700 m3/d is situated in Powell River, Canada. The

installations in North America and Asia are used nearly

exclusively to treat waste water from separate systems, at

differing cleaning requirements in the individual coun-

tries. Therefore, the experience acquired at those plants is

transferable only to a limited extent to European condi-

tions.

However, since 1998 the use of membranes in the field of

municipal waste water treatment has increased worldwide.

Beyond many small installations, the first large-scale

waste water treatment plant in Europe (with a capacity

of 1,900 m3/d) was put into operation in 1998 at Porlock,

England. In 2000, the Swanage waste water treatment

plant (Figure 2-42) on the South coast of England follow-

ed, with a capacity of 13,000 m3/d and 23,000 inhabi-

tants connected. Until the end of 2001 this was the largest

membrane bioreactor treating municipal waste water.

The installation, equipped with the Kubota system, is

situated directly on the beach and is hardly visible as a

result of complete casing.

In Great Britain, the membrane bioreactor process is well

established not only with a view to technical but also to

economic aspects, so that a possible use of this process is

examined in the case of each new construction or expan-

sion of a plant.

In other European countries, e. g. in Italy/Lake Garda, or

in Belgium, the first membrane bioreactors are being

planned or are under construction.

111

Figure 2-42

Aerial photograph of the Swanage waste water treatment plant [photo: AQUATOR GROUP]

MF2.2.2.1


Glasgow Waste Water Treatment Plant, Scotland

The Glasgow central sludge treatment plant treats sludge

of industrial as well as municipal origin. Between 7,800

and 12,800 m3 of sludge with an average TS content of

2 – 2.5 % are treated daily, consisting not only of sludge

quantities produced locally, but also of sludge from the

cities Shieldhall, Dulmuir, Paisley, Dalmarknock, Glasgow

Catchment and Daldowie.

Sludge dewatering takes place in 12 centrifuges operated

in parallel, following a 5 mm screen and storage tank of

30,000 m3. The sludge is thickened to a TS content of

30 % TS and then dewatered in six dryers to 90 – 92 % TS.

About 200 – 450 m3 of sludge water are produced per day,

80 % of this quantity resulting from the centrifuges and

20 % from the dryers. This sludge water has COD con-

centrations of 3,000 – 4,000 mg/L and NH4-N concentra-

tions of 200 – 300 mg/L, which corresponds to a load of

approx. 180,000 PE related to NH4-N.

The sludge water is treated by a three-line fine screen

(bar distance: 3 mm). Biological treatment takes place in

an upstream-arranged denitrification tank (V = 2,300 m3)

and four nitrification tanks operated parallel (Vtotal =

9,400 m3), in which the membrane modules are immersed.

The four-line membrane installation consists of 128 plate

membrane modules of the type EK 400 from the company

Kubota with a total membrane surface area of 20,480 m2.

Effluent concentrations of 40 – 60 mg/L COD and

0.1 – 0.4 mg/L NH4-N are reached. The NO3-N effluent

concentration is 30 mg/L on average.

The sludge treatment plant presented in Figure 2-44 has

been operated since the year 2002.

112

sludge water

recirculation

fine screen3 mm

fine screen3 mm

nitrification, membrane stage

fine screen3 mm

blowerinstallation

denitrification

receivingwater

Figure 2-43

Flow sheet of the Glasgow sludge treatment plant [according to AGGERWASSER GMBH 2004]


113

Figure 2-44

Top view of the sludge treatment plant and of a tank of the membrane installation

[photo: AGGERWASSER GMBH 2001]

footprint membranes

aeration device


Ebisu Prime Square Building Waste Water

Treatment Plant, Japan

The Ebisu Prime Square Building is a tower block in Tokyo

where all office rooms, sales space and restaurants are

housed on a total surface of 70.000 m2 (Figure 2-45).

When the tower block was built, a membrane bioreactor

was installed in the basement. The waste water is treated

to a degree that the permeate can be used as process water

for a laundry and for toilet flushing.

Figure 2-47 shows the flow sheet of the waste water treat-

ment plant. The composition of the raw waste water and

the permeate is listed in Table 2-10.

The installation was put into operation in April 1997 and

is dimensioned for a permeate volume flow of 189 m3/d.

Equipment, maintenance and operation of the installa-

tion are realized by the company Kubota. Until now, the

plate modules have been cleaned chemically once or twice

a year. The TS content is kept between 15 and 20 g/L.

The transmembrane operating pressure is between 0.05

and 0.1 bar.

114

Figure 2-45 (left): Ebisu Prime Square Building

Figure 2-46 (right): Waste water treatment plant

in the basement of the Ebisu Prime Square

Building [photos: AGGERWASSER GMBH 2004]

feed

blower

membrane stage

fine screen

permeate for laundryand toilet flushing

concentratedisposal

Figure 2-47

Flow sheet of the waste water treatment plant [according to AGGERWASSER GMBH 2004]

Table 2-10

Raw waste water and permeate quality [according to AGGERWASSER GMBH 2004]

Parameter Unit Raw waste water Permeate

COD [mg/L] 60 < 3

BOD5 [mg/L] 40 < 2

Ptot [mg/L] – n. n.

Ntot [mg/L] – < 1

filterable solids [mg/L] 140 – 180 n. n.

MF2.2.2.2

MF2.2.2.3


St. Peter ob Judenburg Waste Water Treatment

Plant, Austria

With the waste water treatment plant of the municipality

St. Peter ob Judenburg (1,500 PE), the first experiences

with membrane technology in the treatment of muni-

cipal waste water in Austria have been acquired. For cost

reasons, the waste water treatment plant was initially

planned and approved by the authorities as water treat-

ment lagoons. Although the lagoons had been dimen-

sioned rather large, the plant did not meet the treatment

capacity required by the Austrian Emission Ordinance

(Emissionsverordnung (EmV) 210/1996) “Limitation of

waste water emissions from waste water treatment plants

in settlement areas“.

Within the scope of a research project realized in 2001

and 2002, it could be demonstrated and implemented in

the following that the existing plant can meet the legal

standards without important constructional alterations

by using new aeration and mixing concepts combined

with immersed membrane filtration in the nitrification

tank (Table 2-11).

By installation of a wooden partition, the lagoon was

divided into an activation zone and a secondary settle-

ment zone. Both zones are connected by two overflows

in the partition. In the secondary settlement zone, the

activated sludge settles and is discharged by the sludge

hopper at the bottom. Culvert siphons lead to a pump

shaft with a submerged pump which recycles the activa-

ted sludge into the activation zone or withdraws it from

the system.

To obtain complete nitrification, a separate nitrification

tank made of reinforced concrete is installed downstream

of the lagoon. The existing components for the growth

of biomass have been removed and replaced by immersed

membrane modules from the company Mitsubishi. A

total membrane surface area of 945 m2 is installed in

9 cassettes. Since the completion of the research project

in 2002, the St. Peter ob Judenburg waste water treat-

ment plant has been operated successfully according to

the process concept presented above (Figure 2-48). Figure

2-49 shows the membrane modules and the lagoon.

115

feed

blowerinstallation

membrane stage

fine screen3 mm

grit chamber BB

recirculation

NK

settling pond 1receivingwater

Figure 2-48

Flow sheet of the St. Peter ob Judenburg waste water treatment plant [according to ENVICARE 2002]

Table 2-11

Influent and effluent concentrations of the waste water treatment plant

Parameter Unit Influent Effluent lagoon Permeate

COD [mg/L] 300 – 700 100 – 300 < 30

NH4-N [mg/L] 25 – 45 25 – 35 < 1.0

UF2.2.3


Waste Water Treatment Plants in Germany with

Ultrafiltration Membranes

Nordkanal Waste Water Treatment Plant

When the expansion of the Nordkanal waste water treat-

ment plant became necessary, the original site had to be

given up due to the spatial development of the City of

Kaarst. A new plant had to be built at another site. The

Erftverband decided on the membrane bioreactor process

because positive experience had been acquired with this

process at the Rödingen waste water treatment plant. The

waste water treatment concept was developed in close

coordination with the Ministry for Environment and

Nature Conservation, Agriculture and Consumer protec-

tion (MUNLV) of the state North-Rhine Westphalia. Due

to its size, this plant represents new planning dimensions

and has demonstration character throughout Europe.

The plant is designed for a capacity of 80,000 PE and a

combined water flow of 1,881 m3/h. It was commissioned

in 2003. The demands on the effluent quality are com-

piled in Table 2-12.

116

Figure 2-49

St. Peter ob Judenburg waste water treatment plant [photos: ENVICARE],

left: membrane module, right: lagoon

Table 2-12

Minimum requirements and discharge consent of the Nordkanal waste water treatment plant

[ERFTVERBAND 2004]

Parameter Unit Minimum requirements Discharge consent

COD mg/L 90 90

BOD5 mg/L 20 20

NH4-N mg/L 10 10

Ntot mg/L 18 18

Ptot mg/L 2 2

UF2.2.3.1


117

At the site of the old waste water treatment plant, the

waste water is pretreated by a coarse screen and pumped

to the new Nordkanal plant, situated a distance of 2.5 km

away, where the waste water is mechanically pretreated

by two step screens (5 mm spacing) operated in parallel

and two aerated grit and grease traps also operated in

parallel. Then the waste water is treated by two rotary

screens operated in parallel with an aperture size of 0.5 mm

(Figure 2-50) to protect the membranes in the nitrifica-

tion stage. The emergency circuit of the rotary screens is

made safe by a fine screen with an aperture size of 1 mm,

so that the membranes are protected from the input of

coarse material into the activated sludge tank. Figure 2-51

shows the flow sheet of the Nordkanal waste water treat-

ment plant.

The activated sludge stage has four lines, each of which

consists of upstream denitrification tanks, a variable tank

zone for either denitrification or nitrification, and of the

nitrification tanks with immersed membrane modules,

flow

recirculation

rotaryscreen0,5 mm

emergencybypassscreen 1mm

rotaryscreen0,5 mm

blowerinstallation

feed

gritchamber

screen

step screen5 mm

nitrificationmembrane stage

step screen5 mm

gritchamber

denitri-fication

variable-zone

denitri-fication

variable-zone

denitri-fication

variable-zone

denitri-fication

variable-zone

Figure 2-51

Flow sheet of the Nordkanal waste water treatment plant [according to ERFTVERBAND 2004]

Figure 2-50

Rotary screen of the fine screen installation


designed as activated sludge tanks with circulating flow.

The nitrification tanks are cased. The total volume of the

activated sludge tanks is 9,200 m3. The sludge is stabilized

aerobically. As a result of flow simulations, agitators and

baffles were integrated into the activated sludge tanks

with circulating flow.

The membrane installation has been realized with eight

lines and equipped with capillary membranes from the

company ZENON (ZW 500c). A total filter surface area of

approx. 85,000 m2 has been installed because the District

Government Düsseldorf demanded to provide a reserve

of 25 % for the membrane filtration. For external chemi-

cal cleaning, a separate cleaning chamber is available.

The investment for the new construction of the Nord-

kanal waste water treatment plant was 21.5 million euro.

Approx. 6.6 million euro of this amount had been taken

over by the federal state North-Rhine Westphalia.

Monheim Waste Water Treatment Plant

The waste water treatment plant of the city of Monheim

is situated in the sensitive karstland of the district Donau-

Ries. It treats not only the waste water from the city of

Monheim, but also from the municipalities of Rögling

and Tagmersheim. The treated effluent is discharged into

the Gailach which infiltrates into the karst 6 km down-

stream of Monheim. In 1998 and 1999, first concepts for

the discharge of waste water into the karst subsoil were

developed.

Within the scope of the large-scale pilot project “Waste

water treatment Gailach valley“, the Free State of Bavaria

supported the financing of the construction of a mem-

brane bioreactor at the site of the Monheim waste water

treatment plant. The investment for the membrane bio-

reactor was approx. 7.6 million euro, of which 5.8 mil-

lion euro were granted as subsidy by the state Bavaria.

Figure 2-53 shows the Monheim waste water treatment

plant.

The Monheim waste water treatment plant is designed for

a capacity of 9,700 PE, based on a peak flow of 288 m3/h

and an average daily waste water flow of 2,400 m3/d.

As shown in the flow sheet of the Monheim waste water

treatment plant (Figure 2-54), the mechanical pretreat-

ment stage has two lines. Each line consists of a fine sieve

with an aperture size of 1 mm and a grit chamber. 75 %

of the maximum inflow can be treated by each line. The

mechanically pretreated waste water flows into the acti-

vated sludge stage with a total volume of 1,660 m3, which

is also built in two lines. Each line consists of an upstream

denitrification and a nitrification tank as well as two

membrane chambers which have been provided with a

coating resistant to chemicals to protect the concrete.

The tanks for denitrification and nitrification have a

volume of 340 m3 each, while each of the four membrane

chambers has a volume of 75 m3. The sludge is stabilized

aerobically.

118

Figure 2-52

Membrane installation at the WWTP Nordkanal

UF2.2.3.2


The membrane stage was designed for a specific filtration

capacity of 22–24L/(m3·h) of combined flow. This volume

can be increased at short notice up to 31 L/(m3· h) when

one membrane chamber is shut down. According to this

design, the membrane stage contains 28 module cassettes

from the company ZENON (type ZW 500c) with a total

membrane surface area of 12,320 m2 filter. Filtration takes

place at a TS content of 12 g/L. Since the filtration lines

are installed in four separate chambers, chemical clean-

ing of the modules can be realized by pumping off the

activated sludge without removing the modules (on air).

The specific energy demand of the waste water treatment

plant is about 1 kWh per m3 of waste water. The man-

power requirement corresponds to that of a conventional

plant.

119

feed

membrane stage

gritchamber

denitrifi-cation

nitrifi-cation

flow

sieve 1 mm

sieve 1 mm

gritchamber

recirculation recirculation

recirculation recirculation

receivingwater

blowerinstallation

Figure 2-54

Flow sheet of the Monheim waste water treatment plant [according to BAYERISCHES LANDESAMT FÜR

WASSERWIRTSCHAFT 2004]

Figure 2-53

Monheim waste water treatment plant [photo:

BAYERISCHES LANDESAMT FÜR WASSERWIRTSCHAFT

(Bavarian Office for Water Management) 2004]


Using the membrane process at the Monheim waste water

treatment plant, the requirements for the effluent quality

are safely met, as can be taken from Table 2-13.

At present, the operation of the Monheim membrane

bioreactor is accompanied by a research program. Main

items of this study include testing and optimization of

the membrane bioreactor process and investigating the

effects of waste water discharge on the Gailach and the

groundwater.

120

Figure 2-55

Module cassettes during in-air cleaning

[photo: CITY OF MONHEIM 2004]

Table 2-13

Minimum requirements, discharge consent and operating values of the Monheim waste water treatment

plant [BAYERISCHES LANDESAMT FÜR WASSERWIRTSCHAFT 2004]

Parameter Unit Minimum requirements Discharge consent Operating values

COD mg/L 90 75 15

BOD5 mg/L 20 15 1.2

NH4-N mg/L 10 5 0,1

Ntot mg/L – 18 10

Ptot mg/L – 1 0.6


Markranstädt Waste Water Treatment Plant

The Markranstädt waste water treatment plant is situated

in the southwest of Leipzig. It is one of more than 30

waste water treatment plants of Kommunale Wasserwerke

Leipzig (Municipal Waterworks). It was designed for

12,000 PE; the actual degree of capacity utilization is

approx. 8,000 PE.

The reason for a new construction of this plant was the

planned closure of the obsolete waste water treatment

plant which no longer complied with the requirements.

The deciding factors for the construction of a membrane

bioreactor were the limited surface area of the site and

increased demands on the effluent quality (Table 2-14)

due to a “weak” receiving water.

121

Table 2-14

Minimum requirements, discharge consent and operating values of the Markranstädt waste water

treatment plant [STEIN 2002a]


COD [mg/L] 90 50 35

BOD5 [mg/L] 20 10 5

NH4-N [mg/L] 10 5 1

Ntot [mg/L] 18 18 15

Ptot [mg/L] 2 2 1

Filterable solids [mg/L] no information no set target no information

Figure 2-56

Process stages at the Markranstädt waste water treatment plant [STEIN 2002a],

left: inflow chamber to the membrane bioreactor with overflow edge to combined water treatment,

right: combined water treatment tank

UF2.2.3.3


122

Figure 2-57

Process stages at the Markranstädt waste water treatment plant [STEIN 2002a],

left: step screen, right: nitrification and denitrification tanks

The plant has a hydraulic capacity of 180 m3/h. From the

intercepting sewer of the combined sewer system, the waste

water is fed by a lifting pump via the inflow chamber

(Figure 2-56, left) to the mechanical pretreatment stage.

The two-line mechanical pretreatment stage consists

of a step screen (3 mm spacing) (Figure 2-57, left) and a

grit and grease trap. By a distributor the waste water

flows into the two-line activated sludge stage. It is

operated as upstream denitrification (VDN = 2 · 435 m3)

with downstream nitrification (VN = 2 · 435 m3). All tanks

are equipped with agitators. In addition, aggregates for

fine-bubble aeration are installed over the whole surface

area of the bottom of the nitrification tanks.

The membrane modules for biomass separation from the

company ZENON are arranged at the inner longitudinal

sides in the upper zone of the nitrification tanks with a

depth of 7 m. The total filter surface area of 7,360 m2 is

distributed in four lines, two each in both nitrification

zones. Between the longwise arranged nitrification tanks

a cleaning shaft for external module cleaning is installed.

The modules can be removed by a fixed crane.

Besides the waste water treatment plant, a combined

water treatment plant was built in parallel at the same

site. The waste water quantities which exceed the capacity

of the membrane stage during combined water flow are

stored temporarily and pretreated in parallel in two tanks

which serve as settling and storage tanks. These waste

water quantities are fed to the membrane installation

during periods with smaller inflow volumes. Thanks to

the combined water treatment plant, the necessary mem-

brane surface area could be considerably reduced because

it had not to be designed for the maximum inflow quan-

tity, but only for 1.1 · Q T.

Since the plant was commissioned in 2000, much knowl-

edge has been acquired concerning the optimization of

process engineering and control [MEYER 2001]. Improve-

ment of mechanical pretreatment was especially impor-

tant. The screen installed initially was replaced by a com-

bination of coarse screen (5 mm spacing) and fine sieve

with an aperture size of < 1 mm.


Rödingen Waste Water Treatment Plant

The waste water treatment plant is situated in the territory

of the municipality of Titz in the district of Düren in the

immediate vicinity of the opencast mining Hambach. Its

catchment area comprises a predominantly rural region

with smaller villages which do not discharge commercial

or industrial waste water. Groundwater depletion due to

mining prevents the contact of the receiving water with

the groundwater so that in dry periods the water level of

the receiving water is very low. Therefore, an important

portion of the receiving water is supplied by the effluent

from the Rödingen waste water treatment plant. On

account of this fact, the district government sets high

standards for the discharge of waste water into this re-

ceiving water (see monitoring values in Table 2-15).

For this reason, a new construction of the Rödingen

waste water treatment plant, which up to now consisted

of an activated sludge stage with intermittent denitrifica-

tion and simultaneous precipitation for phosphorus

removal, was indispensable. Upgrading by conventional

technology would have required investments of approx.

6.1 million euro for the construction of large activated

sludge tanks and a downstream floc filtration.

The Erftverband, as the responsible water board, decided

on the construction of a membrane bioreactor because in

1996 first knowledge on the operating mode, the effluent

quality to be attained and operational liability was ac-

quired in the course of successful operation of a pilot plant

using this technology. One million euro of the total costs

of 2.8 million euro for the first large-scale installation in

Germany, which was put into operation in the middle of

1999, were taken over by the state North-Rhine Westphalia.

The installation is designed for a daily waste water flow

of 450 m3. With combined water flow, up to 135 m3 per

hour are treated.

The inflow to the plant is mechanically pretreated by a

fine screen with a spacing of 3 mm, followed by an aerated

grit chamber (Figure 2-58). The waste water is then fed to

the two bioreactors which are operated with intermittent

nitrification/denitrification.

When the mixed liquor has passed the biological stage,

it flows into the two-line filtration stage, from where

the treated water is withdrawn by immersed microfiltra-

tion modules. The concentrated mixed liquor remaining

in the filtration zone, which has a TS content higher by

4 g/L than in the rest of the activated sludge tank is pum-

ped back into the bioreactors.

Each of the two filtration lines (Figure 2-59) consists of

six cassettes each with 8 modules from the company

ZENON. The total membrane surface area is 4,846 m2. A

combined specific water flow of approx. 28 L/(m3·h) has

been calculated as design capacity for the membranes.

The background for this higher than typical design speci-

fic flow rate were measures waiting to be done in the

sewer system in order to reduce the infiltration water

123

Table 2-15

Minimum requirements and discharge consent of the Rödingen waste water treatment plant

[according to ENGELHARDT ET AL. 2001]


COD mg/L 110 35 < 25

BOD5 mg/L 25 8 < 3

NH4-N (at 5 °C) mg/L – 2 < 0,5

Ptot mg/L – 0.5 < 0.3 (simultaneous precipitation)

AOX µg/L – 50 < 50

UF2.2.3.4


rate. Therefore, smaller inflow volumes are expected with

resulting flow rates < 28 L(m3 · h).

To maintain the filtration capacity, the modules are not

only submitted to normal backwashing (300 – 500 sec. fil-

tration, 30 sec. backwashing) and weekly intermediate

cleaning, but also to intensive chemical cleaning twice a

year. For this purpose the modules are removed from the

filtration tank and cleaned chemically, from inside and

outside, in a separate heatable container. With this, the

permeability of the membranes, and possibly necessary

capacity reserves, are restored.

Within the scope of a research project promoted by the

state North-Rhine Westphalia, the operation of the first

German large-scale membrane bioreactor was accompa-

nied by scientists. The aim was to acquire more far-

reaching knowledge for new constructions of membrane

bioreactors, in particular about the operating mode of

124

V= 200m3 V= 200m3

nitrification andmembrane containerV=80m3

nitri-/denitrifi-cation tank 1

blowerstationmembranereactor

feed

nitri-/denitrifi-cation tank 2

grit and oilchamber

screen3 mm

membranefiltration

membranefiltration

RS

recirculation

blower stationnitrification

partial flowtreatment

fine sieve0,5 mm

permeate

Figure 2-58

Flow sheet of the Rödingen waste water treatment plant

Figure 2-59

View into the two filtration lines during fitting of

the ZeeWeedTM-cassettes [photo: ERFTVERBAND]


the membrane modules in order to reduce the energy

demand of module aeration. The following measures

have been realized successfully:

• single filtration lines are switched on or off depending

on the water volume to be filtered

• discontinuous aeration of the membrane modules

• intermittent operation of the activated sludge stage to

get small recirculation flows

Moreover, it turned out that the waste water needs better

mechanical pretreatment because accumulation and

sticking of fibrous material occurred on the hollow-fibre

membranes. For this reason, a partial flow of the activa-

ted sludge is treated by sieving between the activated

sludge tank and the filtration tank (see Figure 2-58) to

remove fibres and coarse material which get into the acti-

vated sludge stage despite mechanical pretreatment

[ENGELHARDT ET AL. 2001].

Schramberg-Waldmössingen Waste Water

Treatment Plant

The Schramberg-Waldmössingen waste water treatment

plant had been operated from 1995 to 1998 at the limit

of its capacity. The consent for operation was limited to

31st December 1998. Since the effluent is discharged into

the „weak“ and sensitive receiving water Heimbach (a

creek), discussions with the supervising authority had

determined in 1996 that the operation of a conventional

waste water treatment plant without a tertiary treatment

stage would no longer be approved at this site. Before

expanding the plant, several alternatives were studied,

including connection to and upgrading of neighbouring

waste water treatment plants. However, in 2001 it was

decided to expand the plant at the same site with the

membrane bioreactor process, because this was the most

ecologically and economically favourable solution.

The waste water treatment plant (Figure 2-60) is designed

for 2,600 PE and a waste water flow of up to 90 m3/h.

As presented in the flow sheet of the plant (Figure 2-61),

mechanical pretreatment is carried out by a screen (5 mm

spacing) and a grit chamber. Two slot sieves (0.5 mm spa-

cing) operated in parallel are arranged downstream of the

grit chamber to protect the membrane stage. The activa-

ted sludge stage comprises an upstream denitrification

tank (V = 250 m3), a nitrification tank (V = 480 m3) and

the membrane bioreactor.

The two-line membrane stage is equipped with 10 module

cassettes (type 500 c) from the company ZENON (see

Figure 2-62). The membrane surface area of approx.

4,400 m3 in total treats an average permeate flow of

2,160 m3/d.

The investment for the waste water treatment plant

amounted to 2.8 million euro. The state Baden-Württem-

berg prioritized this project and provided a subsidy of

34 % within the scope of the general promotion of waste

water treatment projects, so that the plant could be com-

missioned in 2004. For one year the University of Stutt-

gart assists with and documents the operation of the

plant and determines its treatment capacity.

125

Figure 2-60

Schramberg-Waldmössingen waste water treat-

ment plant [photo: STADTWERKE SCHRAMBERG

(municipal utilities) 2004]

UF2.2.3.5


126

feed

receivingwater

fine screen0,5 mm

nitrification,membrane stage

fine screen0,5 mm

blowerinstallation

denitri-fication

nitri-fication

gritchamber

screen5 mm

recirculation

Figure 2-61

Flow sheet of the Schramberg-Waldmössingen waste water treatment plant [according to STADTWERKE

SCHRAMBERG 2004]

Figure 2-62

Membrane installation at the Schramberg-Waldmössingen waste water treatment plant [photos: STADT-

WERKE SCHRAMBERG 2004], left: view of the membrane tanks, right: membrane module

UF2.2.3.6


Knautnaundorf Waste Water Treatment Plant

The Knautnaundorf waste water treatment plant of Kom-

munale Wasserwerke Leipzig (Municipal Waterworks) is

the newest membrane bioreactor put into operation in

Germany. With a capacity of 900 PE (expandable up to

1,800 PE) and a peak inflow of 23 m3/h, it is the smallest

“large-scale” membrane installation for municipal waste

water treatment. Although no increased demands on

waste water treatment were made at this site, the mem-

brane bioreactor process came out on top in the tender

results against conventional solutions because of lower

investment requirements. An important feature of this

site is the fact that it is fed by a separate sewer system.

As such, it was possible to reduce the investment for the

membrane stage compared to plants working with a com-

bined sewer system [WALTHER 2001].

The process engineering is comparable to that of the

installations described above. The following special fea-

tures have to be mentioned:

• For the first time the immersed system from the com-

pany Martin Systems was used in the membrane stage

(see chapter 2.1.2, figure 2-11). With a membrane sur-

face area of 756 m2, the performance of a German-

developed membrane can be proven on technical scale.

• The mechanical pretreatment stage is equipped with a

two-stage screen. The finest screen with an aperture

size of 1 mm in the second stage will retain all unde-

sired matter from the filtration zone.

• The bottom of the nitrification tank is fully equipped

with aerators for the plate membranes to ensure opti-

mal oxygen input.

After successful start-up in October 2001 and start of

regular operation for several weeks, the plant had to be

shut down due to a non-authorized discharge (diesel oil)

in order to settle claims for damages. At present, state-

ments on the operational behaviour of the installation

cannot be made because the plant has only been return-

ed to operation in April 2002.

127


128

feed

fine screen3 mm

grit andoil chamber

fine screen1 mm

biological reactor

sludge

clarifier

membrane stage

recirculation

receivingwater

blowerinstallation

nitri-fikation

denitri-fikation

Figure 2-63

Flow sheet of the Simmerath demonstration plant [according to WVER 2004]

Simmerath Pilot Plant

The Wasserverband Eifel-Rur (WVER) (water board) opera-

tes a waste water treatment plants in the low mountain

region of Eifel. Since the plants are situated in drinking

water catchment areas, more stringent demands on their

effluent quality are made. Low waste water temperatures

in winter and a large amount of sewer infiltration create

additional challenges for waste water treatment. At the

Simmerath site, the WVER operates a waste water treat-

ment plant for 15,000 PE. Table 2-16 shows the demands

on the effluent quality of the membrane bioreactor.

Starting from these boundary conditions, a membrane

bioreactor pilot project was started in 2003 at the Simme-

rath waste water treatment plant, which is operated by

WVER and designed for 15,000 PE. The project is pro-

moted by the Ministry for Environment and Nature

Conservation, Agriculture and Consumer Protection

(MUNLV) of the state North Rhine-Westphalia.

Within the scope of the pilot project, a membrane biore-

actor was installed in a separate building on the site of

the Simmerath waste water treatment plant. It is equip-

ped with immersed capillary membranes from the com-

pany PURON which are tested in technical scale under

real conditions (Figure 2-64). The membrane bioreactor is

designed for a capacity of 750 PE. It treats a partial flow

of the effluent from mechanical pretreatment (rotary

screen with an aperture size of 3 mm) of the Simmerath

waste water treatment plant. Without further presieving

this partial flow is fed into the membrane bioreactor,

which consists of an activated sludge tank with a volume

of 136 m3, which is divided into an upstream denitrifica-

Table 2-16

Discharge consent of the Simmerath waste water treatment plant [WVER 2004]

Parameter COD BOD5 NH4-N Ntot Ptot AOX

Discharge consent 40 mg/l 10 mg/l 3 mg/l 18 mg/l 0.8 mg/l 50 µg/l

UF2.2.3.7


Knowledge on the clogging behaviour as well as on the

problems with fibrous matter in membrane installations

was acquired. Different treatment concepts were tested

concerning their efficiencies. The treatment results of the

plant were documented and evaluated. It was discovered

that the denitrification process was influenced by the

O2 load recycled from the membrane chamber. This prob-

lem was solved by changing the process configuration.

At present, a second research period is active to test, among

other things, further developed membranes and to opti-

mize the integration of the membrane modules into the

process engineering of the waste water treatment plant.

129

tion stage with subsequent nitrification and the down-

stream membrane stage with a volume of 20 m3. The TS

content in the tanks is between 10 and 14 g/L.

The membrane stage consists of two module cassettes with

a filter surface area of 500 m2 each, which are immersed

and operated in two separate chambers. The sludge from

the membrane stage is recycled either into the denitrifi-

cation or the nitrification zone. The permeate of the mem-

brane stage is fed into the in-flow of the Simmerath plant.

Over the course of the test period, the membrane modul-

es and their operation were continuously optimized so

that the operation of the membrane installation clearly

improved. The operating values of the membrane bio-

reactor are listed in Table 2-17.

Figure 2-64

Membrane installation at the Simmerath waste water treatment plant [photos: PURON AG 2003],

left: denitrification and nitrification tanks with the hall for the membrane installation,

right: membrane cassette

Table 2-17

Operating values of the membrane bioreactor in Simmerath [WVER 2004]

Parameter COD BOD5 NH4-N Ntot Ptot AOX

Operating values < 30 mg/L no Information < 1 mg/L < 8 mg/L < 2 mg/L – µg/L


St. Wendel Golf Course

For several months, the City of St. Wendel has operated

at the site of the local golf course a new waste water treat-

ment plant according to the membrane bioreactor pro-

cess, which is currently treating the sanitary waste water

of the golf course and the restaurant. At present the waste

water flow is approx. 3 m3/d. Next year the hotel belong-

ing to the golf course will be finished so that the load

of the waste water treatment plant will reach the design

capacity of approx. 150 PE. 15 m3 of waste water will

then be treated per day. Currently approx. 3 m3 of waste

water per day are treated in the new waste water treat-

ment plant. This volume will increase to 15 m3/d, when

reaching the design capacity. The waste water treated in

this plant is infiltrated at the golf course. It is also possi-

ble to use it for golf course irrigation.

The construction and operation of the membrane biore-

actor are supported financially within the scope of a re-

search project promoted by the Ministry of the Environ-

ment of the federal state Saarland. A special innovation

represent the ceramic plate membranes (molecular sepa-

ration size ~ 0.1 µm) from the company ItN Nanovation

which are used for the first time in Germany for munici-

pal waste water treatment. Within the scope of the rese-

arch project, the performance and the service life of the

ceramic membranes will be examined. Especially con-

130

waste water

biological reactormembrane stage infiltrationpermeate

storage

buffertank

fine screen3 mmfine screen

3mm

Figure 2-65

Flow sheet of the golf course St. Wendel waste water treatment plant [according to ST. WENDEL]

Table 2-18

Minimum requirements, discharge consent and operating values of the golf course St. Wendel waste

water treatment plant [CITY OF ST. WENDEL 2005]

Parameter Unit Minimum requirements Operating values

COD mg/L 150 18

BOD5 mg/L 40 < 4

Total number of Bakteria coli cfu/100 mL < 100

UF2.2.3.8


cerning the service life, it is expected that the ceramic

membranes have a clear advantage compared to polymeric

membranes.

The waste water treatment plant consists of a buffer tank

with a volume of 7 m3, a rotary screen with an aperture

size of 3 mm, an activated sludge stage with a volume of

approx. 20 m3 and a downstream permeate storage tank.

The waste water flows from the buffer tank and the rotary

screen into the activated sludge stage in which the im-

mersed membranes are installed. The membranes are

aerated from below by slotted tubes. Thus the air is not

only used to control the covering layer on the mem-

branes, but also for aeration of the activated sludge stage.

Since the tanks are completely intermixed, sludge recy-

cling can be spared. Due to the small waste water volume

flow, the TS content in the activated sludge stage current-

ly is about 4 g/L. The design capacity has been calculated

with a TS content of 12 g/L.

The membrane stage consists of a rack with three mod-

ules. Each module has a membrane surface area of 11 m2,

so that a total membrane surface area of 33 m2 is install-

ed. For capacity expansion, the stage will be upgraded by

more modules.

The operating and cleaning concept of the membrane

stage using immersed ceramic membranes can be compa-

red with that of immersed membrane systems on poly-

mer basis. But due to the more solid ceramic membranes,

it is possible, among other things, to use higher trans-

membrane pressure differences, higher pressure levels

during backwashing and higher concentrations of clea-

ning chemicals.

The investment of the plant was approx. 400.000 euro,

75 % of which were taken over by the federal state Saar-

land. Besides the costs for the membrane bioreactor it-

self, this sum of 400.000 euro comprises, among other

things, the costs for connection, an appropriate building

for the site and a sludge mineralization plant.

131

Figure 2-66

Module rack at the golf course St. Wendel waste water treatment plant,

left: top view, [photo: ItN NANOVATION], right: side view [photo: ABWASSERWERK ST. WENDEL]


Glessen Waste Water Treatment Plant

(Planning Stage)

The design capacity of the Glessen waste water treatment

plant (Erftverband) is currently 5,000 PE. The effluent is

discharged into a receiving water which infiltrates into

the groundwater of a drinking water catchment zone.

Therefore, the demands on the effluent quality are higher

than the minimum requirements for waste water treat-

ment plants of this size category (see Table 2-19).

In order to comply in future, too, with the demands on

the effluent quality, the waste water treatment plant is

expanded using existing plant components. In this con-

nection a waste water treatment plant with a pressure

pipe in a distance of 4 km will be also connected, so that

the design capacity of the plant at the Glessen site after

132

feed

gritchamber

fine screen5-6 mm

nitri-ficationtank

denitri-ficationtank

membrane stage/nitrification

recirculation

blowerinstallation

receivingwater

0.5 mm

screeningsystem

0.5 mm

Figure 2-67

Flow sheet of the Glessen waste water treatment plant [according to ERFTVERBAND 2004]

Table 2-19

Demands on the effluent quality of the Glessen waste water treatment plant

[according to ERFTVERBAND 2004]

Parameter Unit Minimum requirements for Discharge consent

WWTP of size category 3

COD mg/l 90 30

BOD5 mg/l 20 6

NH4-N mg/l 10 1.5

Ptot mg/l – 0.6

UF2.2.3.9


expansion will be 9,000 PE. With dry weather flow, the

daily waste water quantity is 2,394 m3.

The Glessen waste water treatment plant is in the plan-

ning stage. The concept (Figure 2-67) provides mechanical

pretreatment by a single-line screen with a spacing of

6 mm. The grit chamber, with a volume of 53 m3, is

planned with a single line, followed by the two-line fine

screen with a spacing of 0.5mm. The membrane bioreactor

will be operated with simultaneous denitrification and

aerobic sludge stabilization. The activated sludge tank with

Installations Outside of Germany with

Ultrafiltration Membranes

The largest membrane bioreactor in the world up to the

year 2004, and one of the most modern plants in Eng-

land, is the Lowestoft waste water treatment plant which

was put into operation in the beginning of 2002 with a

capacity of 46,000 PE (only for the membrane bioreactor)

(Figure 2-68). For this plant as well as for the Campbeltwon

waste water treatment plant (Scotland, 6,000 – 9,000 PE),

the ZenoGemTM system is used.

circulating flow for nitrification and denitrification has a

total volume of 1,680 m3.

Planning is based on membranes from the company

ZENON installed in four tanks with 7 modules each of the

type 500 c and a total membrane surface area of 12,320 m3.

The TS content will be 12 g/L. The membrane installation

was designed for a specific filtration capacity of 22 L/(m2 ·h),

which will have to be increased to approx. 30 L/(m2· h)

in case a membrane line has to be shut down on short

notice. The former secondary settling tank with a volume

of 560 m3 will be used as an equalization tank.

133

inflow

inletstructure

distributor lamellaseparator

membrane bioreactor 1

membrane bioreactor 2 permeatestorage tank

backflush pumps

to inletstructure

vacuum pumps

distributor

ZeeWeedTM

ZeeWeedTM

Figure 2-68

Aerial photograph and flow sheet of the Lowestoft waste water treatment plant [ZENON 2002]

UF2.2.4

UF2.2.4.1


Pilot Plants at the Beverwijk Waste Water

Treatment Plant, The Netherlands

From 2000 to 2004, the consulting engineers DHV and

the Stichting Toegepast Onderzoek Waterbeheer (Stowa)

have realized at the Beverwijk waste water treatment plant

(capacity: 450,000 PE) the decisive research project con-

cerning the membrane bioreactor process in The Nether-

lands. Over the course of these four years, various module

systems (ZENON, Kubota, X-Flow, Mitsubishi, Memfis,

The research project at the Beverwijk waste water treat-

ment plant has been successfully completed [VAN DER

ROEST ET AL. 2002]. The large-scale plant at Varssefeld

has been planned and built on the basis of the results

from Beverwijk.

Toray and Huber) have been tested with a view to their

capacity and suitability in practice.

The tests have been carried out on a test field built espe-

cially for this purpose with separate membrane bioreac-

tors. The overview in Table 2-20 shows the important key

features of the individual test installations.

134

Table 2-20

Key features of the individual pilot installations [DHV 2004]

Manufacturer

Huber

Kubota

Memfis

Mitsubishi

Toray

X-Flow

ZENON

ZENON

ZENON

Type

plate

plate

plate

hollow fibre

plate

tubular

hollow fibre

(module ZW 500a)

hollow fibre

(module ZW 500c)

hollow fibre

(module ZW 500d)

Pore size

[µm]

0.038

0.4

0.05

0.4

0.08

0.03

0.035

0.035

0.035

Membrane surface

[m2]

360

240

112

314

137

220

184

55

90

Permeate flow

[m3/h]

15

10

5

7

5

9

8

3

5

Test period

10/03 – 07/04

05/00 – 07/02

05/02 – 06/03

05/00 – 03/02

02/03 – 02/04

05/00 – 04/02

03/00 – 10/02

03/01 – 03/03

11/02 – 08/03


135

Figure 2-69

Photos of the pilot installations and membrane modules at the test field of the Beverwijk waste water

treatment plant [DHV 2004]

From left to right: Huber, Huber

From left to right: Kubota, Kubota, Mitsubishi, Mitsubishi

From left to right: X-Flow, X-Flow, Zenon, Zenon

From left to right: Memfis, Memfis, Toray, Toray

UF2.2.4.2


Varsseveld Waste Water Treatment Plant,

The Netherlands

The membrane bioreactor at the Varsseveld waste water

treatment plant is the first large-scale implementation of

this process in The Netherlands. It will be put into opera-

tion in the beginning of 2005. Since April 2004, a pilot

plant has been operated within the scope of a research

project at the site of the Varsseveld waste water treatment

plant with a permeate flow of 3.5 m3/h to study process

optimizations for the large-scale plant. In parallel, the

large-scale plant has been built. The project is realized and

assisted by the water board Rijn en IJssel, the Stowa, DHV

and other institutions. The research project is financed

by the Stowa and the EU LIFE program (see also possibili-

ties for promotion by EU in the annex).

The connection size of the Varsseveld waste water treat-

ment plant is 23,150 PE with a maximum waste water

volume flow of 755 m3/h. Waste water treatment plants

in The Netherlands are faced with a hydraulic load in the

case of stormwater flow which is greater by a factor three

compared to the average waste water load. This is also

true for the Varsseveld waste water treatment plant. An

average daily waste water volume of 5,000 m3/d was de-

termined. The supervisory authorities demand effluent

concentrations of < 5 mg/L for nitrogen and < 0.15 mg/L

for phosphorus.

The membrane installation was built with four trains

(Figure 2-70). A total membrane surface area of 20,160 m2

of the company ZENON (module type: ZW 500 d) has

been installed. The calculated specific stormwater flow is

37.5 L/(m3 · h) of permeate. The membrane installation

can be increased with additional modules, if necessary.

The investment for the Varsseveld waste water treatment

plant amounts to 10 million euro.

136

feed

recirculation

gritchamber

circulation tank with aerated zoneand upstream denitrification

fine screen6 mm

outlet

fine screen0,8 mm

membrane stage

Figure 2-70

Flow sheet of the Varsseveld waste water treatment plant [according to DHV 2004]

UF2.2.4.3


Brescia Waste Water Treatment Plant, Italy

The Brescia waste water treatment plant is an example for

the advantage of the membrane bioreactor process in the

case of necessary plant expansion at limited space available.

Since 1980, the Brescia waste water treatment plant existed

as three-line activated sludge plant. Each of the three

lines consisted of primary clarification, activated sludge

tank, secondary clarification and dosing station for chlo-

rine. Due to more stringent demands on the Ntot effluent

concentration (< 15 mg/L), the waste water treatment

plant had to be expanded in 2000. Upgrading the con-

ventional activated sludge process would have required

the construction of very large tank volumes for a denitri-

fication system which was not possible with the space

available. With the membrane bioreactor process, a plant

expansion has been achieved with alteration of only one

treatment line (Figure 2-71).

The secondary clarification tank was replaced by a four-

line membrane stage. 160 membrane cassettes of the type

500C (capillary membranes) from the company ZENON

with a total surface area of 70,400 m2 are installed. 50 %

of the waste water volume flow of the Brescia waste water

treatment plant (about 40,000 m3/d) is treated by the

137

membrane stage

clarifier

recirculation

sludge

flow

feed

primary treatment

fine screen3 mm

gritchamber

fine screen3 mm

gritchamber

primary treatment

nitrifi-cation

denitrifi-cation

nitrifi-cation

denitrifi-cation

recirculation

sludge

recirculation

nitrifi-cation

denitrifi-cation

clarifier

recirculation

receivingwater

existing plant expansion

Figure 2-71

Flow sheet of the Brescia waste water treatment plant [according to ZENON GMBH 2004]


membrane bioreactor line. The remaining 50 % are treat-

ed by the two conventional lines. Today the Brescia

waste water treatment plant has a treatment capacity of

approx. 150,000 PE. Figure 2-72 shows an aerial photo-

graph of the Brescia waste water treatment plant.

Thanks to the conversion finished in 2002, the effluent

values of the plant improved considerably. The raw waste

water concentration for some parameters, the operating

values of the plant and the demands on the effluent qua-

lity are listed in Table 2-21.

138

Figure 2-72

Aerial photograph of the Brescia waste water treatment plant [photo: ZENON GMBH 2004]

Table 2-21

Raw waste water concentration, operating values and requirements of the Brescia waste water treatment

plant [ZENON GMBH 2004]

Parameter Unit Raw waste water Operating values Requirements

concentration

COD mg/L 505 20 < 125

BOD5 mg/L 255 10 < 25

TS mg/L 290 not detectable 2

TKN mg/L 50 2 < 15 (Ntot)

Turbidity mg/L >50 < 10 no data


Säntis Waste Water Treatment Plant, Switzerland

On the peak of the Säntis, a top station with restaurant

and telecommunication centre is situated. To purify waste

water and to treat waste water for non-potable drinking

water purposes, the existing small waste water treatment

plant was replaced in 2000 by membrane technology

according to the ZenoGemTM process. The installation is

operated by Swisscom and Säntis-Schwebebahn AG

(Funicular AG).

Thanks to the compact structure of the membrane tech-

nology, the installation could be integrated into the exist-

ing building with very restricted space. It distinguishes

itself by high cleaning efficiency (effluent values: COD

< 30 mg/L, NH4-N < 2 mg/L) at extreme temperatures and

a high inflow dynamics due to rapid load changes at up

to 8,000 visitors per day.

139

kitchen waste water

sludge storagesettlement

grease separator sieve screw

buffer tanks

other inflow

permeatetank

disinfectionrailtransportation

nitrificationwith ZeeWeedTM

denitrification

effluent

Figure 2-73

View and flow sheet of the membrane bioreactor according to the ZenoGemTM process on the Säntis

[ZENON 2002], situation of the membrane bioreactor on the Säntis and view of the modules [ZENON 2002]

UF2.2.4.4

MF2.3.1


2.3

Small Waste Water Treatment Plants, Mobile

Installations and Ships Waste Water Treatment

with Membrane Technology

Small or domestic waste water treatment plants are used

in Germany as long-term solution depending on the regula-

tions of the water legislation of the individual states. In

North-Rhine Westphalia, § 53 section 4 Landeswassergesetz

(law on water) is decisive. According to this article, private

property-related waste water treatment is permissible only

for properties outside of coherently built-up areas.

According to an assessment by OTTO [2002], until the

year 2006 up to 4 million German citizens will remain

unconnected to a central sewer system and therefore are

responsible themselves for waste water disposal. In North-

Rhine Westphalia, at present about 580,000 inhabitants

are not connected to central sewer systems or waste water

treatment plants. They treat their waste water by approx.

130,000 small waste water treatment plants and cesspits

without outlet [MUNLV 2005].

With further technical development, membrane filtration

is becoming more and more accepted in the field of small

waste water treatment plants.

With membrane technology, small waste water treatment

plants are able to attain higher cleaning efficiencies at

high operational safety (Table 2-22). Besides ultrafiltra-

tion of the treated waste water, the operator can also use

the treated water as non-potable water for domestic pur-

poses, e.g. for toilet flushing or garden irrigation. In addi-

tion to ecological advantages, cost savings by reducing

the drinking water demand for non-potable water appli-

cations may be decisive to use this process concept.

In the meantime, several manufacturers offer or are devel-

oping corresponding systems. At present, the inhabitant-

related investments are between 1,000 and 1,500 euro

per inhabitant, depending on the size of the installation.

In addition, costs of 60 – 110 euro per inhabitant per year

arise for operation and maintenance.

In the following sections, the most fully developed systems

are presented which include numerous references.

Busse-MF Installation from the Company Busse

The company Busse Innovative Systeme GmbH produces

and sells an installation with membrane technology

which is the first small or domestic waste water treatment

plant with type approval (Z-55.3-60) by Deutsches Insti-

tut für Bautechnik (DIBt) (German Institute for Construc-

tion Engineering).

The production started in autumn 1999. In the meantime,

more than 250 installations (as of 2005) are operated

with this technology worldwide with connection capaci-

ties from 2 to 32 PE. They are used for the treatment of

waste water from detached houses and multiple dwelling

units, office buildings, restaurants and hotels in Germany

and 10 more countries [BUSSE 2005]. By using membra-

nes, the Busse-MF system is very compact, as can be seen

in Figure 2-74, which is typical for a Busse-MF installa-

tion fitted in the cellar of a residential building.

As shown by the flow sheet in Figure 2-75, the system

consists of two tanks. The first tank (primary settling) is

connected directly to the downpipe for waste water trans-

portation. It serves to separate coarse matter and to store

waste water and sludge temporarily. From the central

140

Figure 2-74

View of the Busse MF small waste water treatment

plant (formerly BioMIRTM) [BUSSE 2002]


tank zone, the liquid phase is pumped by a mammoth

pump, which is protected by a plastic network, into the

second tank (activated sludge tank) where biological

waste water treatment and phase separation take place

using immersed plate modules from the company Kubota.

The transmembrane pressure difference necessary for per-

meate discharge is generated by the hydrostatic pressure

of the water head between the permeate outlet and filling

level of the activated sludge tank. Thus there is no need

for a suction pump to withdraw the permeate.

The plant is usually installed in the cellar or the garage.

It is also possible to use an existing pit as an upstream

waste water storage tank and coarse matter separator. In

this case, only the downstream activated sludge stage has

to be upgraded with membrane filtration.

The treatment capacity is sufficient to meet the de-

mands according to the approval principles for small waste

water treatment plants of DIBt [N.N. 2002d], as was alrea-

dy proven by independent studies [ROSENWINKEL ET

AL. 2001; KRAUME ET AL. 2000]. Table 2-22 shows a

comparison of the limit values according to DIBt [N.N.

2002d] and the mean values of qualified random samples

and 24-h-composite samples taken each month over a

one-year test period [ROSENWINKEL ET AL. 2001]. It can

be seen that the effluent values remain below the stand-

ard values.

141

waste water frombathroom, kitchen,toilet

ventilation byexisting shaft

condenser

mammouth pumpwith coarse-matterseparator

intermediate storage ofwaste water and sludge

activated sludge stagewith filtration unit

permeate

Figure 2-75

Flow sheet of a Busse-MF installation [BUSSE 2002]

Table 2-22

Requirements for the effluent quality of small waste water treatment plants and measured effluent values

of the Busse-MF installation

Parameter Unit Minimum requirements Limit values according Effluent values

to DIBt 2000 for installations Busse-MF installation

with nitrification [N.N. 2002d] [ROSENWINKEL ET AL. 2001]

COD mg/L 150 90 39

BOD5 mg/L 40 20 2.4 *

NH4-N mg/L – 10 (at > 12 °C) 4.5

Filterable solids mg/L – 50 0.65 *

* higher effluent values are due to algae growth in the filtrate collecting tank

MF2.3.2


UltraSept Installation from the Company Mall

Another system is the UltraSept installation marketed by

the company Mall GmbH (Figure 2-76). More than 50 of

these plants with a size of 6 to 40 connected inhabitants

are operated in Germany.

The installation consists of three compartments arranged

according to the principle of a three-compartment septic

tank. The first two compartments are used for the pretreat-

ment of the waste water according to the principle of a

multicompartment septic tank. The third compartment is

the largest. It contains the activated sludge stage and the

filtration unit for the discharge of the treated waste water.

For a membrane module, a module from the company

Weise is used.

The installation is usually lowered completely into a pit

excavated for this purpose. In case a multicompartment

septic tank already exists, it is possible to upgrade the

existing tank with membrane technology to improve the

effluent quality. This alternative is less expensive than a

new installation.

142

feed

emergency

overflow

Mall UltraSeptapplied for national technical approval

connection for outlet, aeration, control lead

mechanical stage

rubber seal (elastomer gasket)

biological stage

float switch

suction duct

aeration lead

membrane module (physical stage)

Figure 2-76

Schematic representation of the UltraSept installation from the company Mall [MALL 2002]

MF2.3.3


Small Waste Water Treatment Plant for 4 PE

in North-Rhine Westphalia

Within the scope of a pilot project for decentralized waste

water treatment and treatment of non-potable water for

domestic purposes, a small waste water treatment plant

according to the UltraSept process is operated in the nor-

thern Eifel (low mountain region in North Rhine-West-

phalia). The plant is installed at the part-time cattle breed-

ing farm of a four-member family.

The membrane bioreactor has a nominal capacity of

900 L/d and is fed with an actual waste water volume of

900 L/d. In addition to the waste water treatment plant,

two storage tanks for further utilization of the treated

waste water have been installed which buffer the differ-

ences between the production of and the demand for

non-potable water for domestic purposes.

Kreditanstalt für Wiederaufbau (KfW),

Service Water Treatment

At the Kreditanstalt für Wiederaufbau in Frankfurt (KfW),

a combination of a fixed-bed activated sludge stage and a

membrane stage is used for the treatment of grey water

in such a way that it can be reused as service water. The

grey water is composed of the shower water from the

employees’ apartments and the waste water from the tea-

houses and the kitchen of the board of management.

At first, the kitchen waste water is pretreated by a grease

trap, and hairs etc. are removed mechanically from the

shower waste water (Figure 2-77). Both pretreated waste

water flows are fed into an activated sludge stage.

The biological stage is realized as fixed-bed activated

sludge stage with special components for biomass growth

A small tank with a volume of 0.6 m3 is used to cover the

demand for non-potable water in the house. The tank is

installed below ground to prevent the new formation of

germs in the water during storage. The connections to the

domestic piping are realized according to the technical

principles of rainwater utilization.

The non-potable water which is not needed directly in

the house, is stored in a long-term storage tank which, in

the case of this pilot project, is constructed as a foil pond

with a volume of 36 m3. The water stored there is used to

clean the cow-sheds and to irrigate the garden [KLEMENS

2002].

143

shower waste water

processwaterstorage

ultrafiltration

kitchen waste water

sieve

greaseseparator

fixed bedactivation

toilets

buffertank

storage

Figure 2-77

Grey water treatment plant at KfW

UF2.3.4

Small Waste Water Treatment Plant Membrane

ClearBoxTM and Huber HoneyCombTM from the

Company Huber AG

The company Hans Huber AG markets the small waste

water treatment plant MembraneClearBoxTM and the

HoneyCombTM system, which are used in particular for

decentralized waste water treatment in rural areas. Both

systems can be installed as expansion kits in existing or

new multicompartment septic tanks (Figure 2-79). The

process consists of the three steps pre-treatment, activa-

tion and membrane filtration. The MembraneClearBoxTM

(MCB) can be used for up to 8 PE and the HoneyCombTM

system for 9 – 150 PE.

The first compartment serves for primary treatment and

the second serves for primary treatment or as buffer tank,

before the waste water is fed in free over-flow into the

third compartment, which is built as an activated sludge

tank. The assembly kit and an aeration system are install-

ed in this tank. Depending on the size of the plant, the

assembly kit consists of a varying number of plate mod-


developed by the company ACO Passavant. After having

passed this stage, the waste water is fed into a storage

tank and then filtered by an ultrafiltration installation, a

MicroClear plant from the company Weise Water Systems

GmbH (Figure 2-78). The installation is equipped with

immersed plate modules with a total membrane surface

area of 44 m2. An average permeate volume of 500 L is

filtered per hour by the membrane stage. Compared to

other membrane bioreactors with suspended biomass, this

plant receives waste water with rather low TS content,

formed only by the sludge output from the components

for biomass growth. Therefore, the plate membrane mod-

ules have relatively small spacings between the plates of

2.5 mm.

The treated water is fed into a storage tank. As service

water it is used among other things for toilet flushing in

the administration building and in the apartments of the

employees.

ules, the so-called VUM modules (VacuumUpstream

Membrane), which are equipped with ultrafiltration mem-

branes. The clear water withdrawn by a vacuum pump

can either be used as non-potable domestic water, dis-

charged or infiltrated. The related aggregate and control

unit (Figure 2-80) can be installed close to the septic tank

in a heated control cabinet or in the cellar of the neigh-

bouring residential building. The MCB plants are equipped

with a remote control, which in case of a breakdown sends

an information via SMS, e-mail or fax.

According to information from the manufacturer, the

operation of existing small waste water treatment plants

has shown that the COD can be reduced by more than

95 % and ammonia nitrogen by approx. 98 %. The energy

consumption for a 4-PE plant is about 2 kWh/d. In some

plants, the excess sludge production has clearly decreased,

e.g. in one plant from initially approx. 0.09 kg TS/(m3 · d)

to only 0.015 kg TS/(m3 · d) after a longer operation period.

Even after more than one year of operation, excess sludge

removal was not necessary.

144

Figure 2-78

Membrane installation for the treatment of service

water in the cellar of KfW [WEISE WATER SYSTEMS

GMBH]

UF2.3.5


145

1. settling tank with overflowfor coarse desludging

2. settling tankwith overflow

emergencyoverflow

aeration 3. activated sludge tankmembrane filtration

permeate discharge

inflow

1. settling tank with overflowfor coarse desludging

inflow

2. settling tankwith overflow

3. activated sludge tank

membrane filtration

aeration

Figure 2-79

Plot plan of a small waste water treatment plant with membrane technology installed in a multicompart-

ment septic tank [HUBER AG 2004]

Figure 2-80

Small waste water treatment plant MembraneClearBoxTM from Huber AG [photos: HUBER AG 2004],

left: aggregate and control unit, right: MCB expansion kit, consisting of plate module and aerator

MF2.3.6


Mobile Installations for the Use in Military Camps

Missions of the German Armed Forces take place at various

locations in Germany and abroad for limited periods of

time. As such, long-term planning is often impossible. In

most cases, local infrastructure cannot be used so that

water supply and waste water disposal structures have to

be mobile, easy to handle and usable all over the world.

Moreover, they have to comply with the legal prescrip-

tions and the requirements of the troops employed.

On account of these requirements, the Bundesamt für

Wehrtechnik und Beschaffung (Federal Office for Defence

Technology and Provision), Koblenz, has charged A3

Abfall-Abwasser-Anlagentechnik GmbH (process techno-

logy for waste and waste water), Gelsenkirchen, to design

and build a mobile waste water treatment plant which is

fitted into a 20-inch container (see Figure 2-81). The plant

is able to treat the waste water of 300 soldiers at ambient

temperatures between -32 °C and +49 °C to such an ex-

tent that it can be discharged or infiltrated in place. Thanks

to the containerized construction, the plant can be used

at any time and in any location worldwide and transport-

ed by nearly any means of transportation (Figure 2-81).

The waste water to be treated is pumped via a grinding

unit to the container. Feeding from outside takes place by

automatically heated and isolated tubes to ensure opera-

tion of the plant in cold areas. The membrane bioreactor

fitted into the container includes six immersed plate mem-

brane modules from the company A3 GmbH with a total

membrane surface area of 120 m2. The filtrate is withdrawn

by a frequency-controlled suction pump and pumped to

the discharge point. A plant of this construction type has

been running since the beginning of 2004.

146

Figure 2-81

Transportation of the container plant by an emergency vehicle and schematic representation of the plant

[A3 GMBH 2004]

MF2.3.7


Ships’ Waste Water Treatment Plants with

Membrane Technology

Waste water discharge from ships used for civilian or mili-

tary purposes is regulated by national and international

law. The governing body responsible for international

legislation is the International Maritime Organization

(IMO). The discharge of ships’ waste water is regulated in

Annex IV of the IMO rules and standards (MARPOL 73/78).

As defined in these standards, the direct discharge of

waste water is not permitted, unless it has been treated

and disinfected by an officially approved installation.

Annex IV has been put into force in September 2003, after

the necessary conditions had been fulfilled in 2002 (trans-

fer into national legislation by a sufficient large number

of countries).

For inland navigation ships, the regulation concerning the

discharge of waste water will change with Article 9.01 of

the Agreement on Collection, Handing over and Accept-

ance of Waste in Rhine and Inland Navigation of the

Zentralkommission für die Rheinschifffahrt (Central Com-

mission for Rhine Navigation) [ZKR 2000]. According to

this article, the discharge of domestic waste water will

not be permitted from 1st January 2005 for cabin ships

with more than 50 sleeping places and from 1st January

2010 for passenger ships which are licensed for the trans-

portation of more than 50 passengers. The contracting

countries therefore commit themselves to establish ade-

quate receiving stations until the dates defined above.

The prohibition of waste water discharge is not valid for

passenger ships which are equipped with a licensed ship’s

waste water treatment plant. This agreement has not yet

come into force (as of August 2005) because it has not yet

been ratified by each single member state.

Up to now, grey water (waste water from showers, hand

basins, floor inlets) and kitchen waste water has histori-

cally been fed directly (without biological pretreatment)

into the disinfection cell of the waste water treatment

plant. For biological treatment of black water (waste

water from toilets) on ocean ships, at present activated

sludge plants, often arranged as cascades, are used for

preliminary treatment prior to disinfection.

The waste water is usually fed to the conventional plants

in surges, depending on the moment of waste water pro-

duction. The waste water flows into the first aerated acti-

vation chamber. After a reaction time which results from

the plantspecific hydraulics, it flows as mixed liquor into

the second activation chamber. It is aerated again to en-

sure further degradation of the organic waste water pollu-

tants. The waste water is then fed to the secondary sett-

ling tank and finally to the disinfection cell.

The process technology described above has some weak

points in particular for the application on board of ships

because it has been directly copied from conventional

municipal waste water treatment. The specific boundary

conditions on ships were often neglected. Special prob-

lems occur in secondary settlement because sedimenta-

tion is considerably disturbed by the movement of the

ship and continuous low-frequency vibrations resulting

from the ship’s engines. The result is regular occurences

of sludge being discharged from the secondary settling

tank into the sea. Also, the development of organic halo-

genated compounds during the disinfection of the efflu-

ent by means of chlorine bleach liquor is another critical

issue related to water pollution.

Since enclosed space on board of ships is extremely expen-

sive, all systems to be installed – including waste water

treatment plants – must be as small as possible.

The use of installations with microfiltration membranes

for waste water treatment has been successfully tested by

some projects [BRÜSS, RICHTER 2001]. Figure 2-82 shows

an example of such a plant. Waste water treatment plants

with membrane technology have the advantage that the

activated sludge plant can be operated at a dry matter

content TS BB of up to 20 g/L so that the aeration tank

volume can be reduced to a quarter compared to a con-

ventional plant. Also, by using microfiltration in the bio-

logical reactor, it is no longer necessary to provide a secon-

dary settlement zone. Separation of the activated sludge

is ensured by the membranes independent of the settling

characteristics of the mixed liquor. In addition, the efflu-

ent quality is clearly better, and chlorination of the waste

water for disinfection becomes unnecessary because of

germ retention.

147

UF2.3.8


Cruise Liner Queen Mary 2

With a length of 325 m, a capacity of 2,620 passengers

and a crew of 1,250 persons, the Queen Mary 2 is one of

the biggest passenger cruisers in the world. Figure 2-84

shows a photo of the passenger cruiser Queen Mary 2.

In the hold of Queen Mary 2, the grey and black waters

are treated by a membrane bioreactor according to the

current state of technology. Decisive factors for the choice

of this installation were its compact construction and

high treatment capacity with the possibility to reuse or

to discharge the treated waste water. Thus the ship is

allowed to navigate in protected waters.

The daily waste water flow to be treated is approx. 1,100 m3.

After mechanical pretreatment by a hydrocyclone and a

fine screen with an opening size of 1 mm, the waste water

is fed into the activated sludge stage, which consists of

two tanks for denitrification and nitrification with a volu-

me of 150 m3 each. Solid-liquid separation takes place in

cross-flow operation mode in an ultrafiltration installa-

tion. The total membrane surface area, consisting of two

modules with plate membranes (PleiadeTM) from the com-

pany Rhodia (see Figure 2-83), is 700 m2. The permeate

Waste water treatment with membrane technology for

inland passenger ships, which must be adapted to the

boundary conditions of shipbuilding and operation, is

being studied at present within the scope of a projects

promoted by the Ministry for Environment and Nature

Conservation, Agriculture and Consumer Protection of

the federal state North Rhine-Westphalia (MUNLV NRW).

After successful tests with pilot plants (in the years 2002

–2004), the operation of a large-scale membrane bioreactor

will be studied on board of the event ship RheinEnergie

of Köln-Düsseldorfer Deutsche Rheinschifffahrt AG.

148

Figure 2-82

View of a MEMROD1) ship’s waste water treatment

plant according to the membrane bioreactor pro-

cess for 250 persons [VA TECH WABAG 2002]

Figure 2-83

Ultrafiltration module PleiadeTM for waste water

treatment on Queen Mary 2 [photo: ORELIS SA 2004]

1) MEMbrane Reactor Operation Device


volume flow is approx. 50 m3/h. For further reduction of

organic matter and for disinfection, an activated carbon

filter and a UV installation are installed downstream of the

ultrafiltration system. It is planned to reuse about 50 % of

the waste water treated by this process combination as

non-potable water on the cruise liner.

149

Figure 2-84

Photo of the Queen Mary 2

feed

hydrocyclone

membrane system

fine filter1 mm

150 m3 UV-disinfection

sludge

activatedcarbon

150 m3

biological reactor

recirculation

sludge

outlet

Figure 2-85

Flow sheet of the waste water treatment plan of Queen Mary 2 [according to ORELIS SA 2004]

UF RO2.3.9


Grey and Black Water Treatment on Ships

The concept for waste water treatment used today on ships

is the one-stream solution which consists of mixing grey

water (from showers, handbasins, laundry) and black water

(from toilets) and combined treatment by membrane bio-

reactors. Immersed membrane modules, which are also

used in municipal waste water treatment, are applied.

Ultrafiltration installations with externally arranged mo-

dules with open channels at the raw-water side have also

been designed.

For large waste water volumes, e.g. on cruise liners with

more than 1,000 passengers, the two-stream solution can

be more effective. The grey water is treated by low-pres-

sure reverse osmosis membranes. The permeate is availa-

ble for technical purposes. The black water, the concen-

trate from low-pressure reverse osmosis and the kitchen

waste water are treated by a membrane bioreactor. The

filtrate can be discharged or reused in applications with

lower quality demands. The development of the two-

stream solution was influenced by knowledge and ex-

periences from the treatment of industrial waste water

by membrane processes and the “do-not-mix rule“. The

“do-not-mix rule” says that, in general, it is easier and

more efficient to treat waste water with different compo-

sition and clear concentration differences by different

processes. Figure 2-86 shows the two-stream solution

which has been implemented on 25 ships.

The membrane technology from the company Rochem

UF, presented by way of example, is based on ultra-

filtration and ultrafiltration + low-pressure reverse

osmosis. It is shown in Figure 2-87.

150

grey water

process water

blowerinstallation

ultrafiltration

black water

reverse osmosis

membrane bioreactor

discharge/sullage

blowerinstallation

Figure 2-86

Flow sheet of waste water treatment according to the two-stream solution [according to ROCHEM UF 2004]


151

Figure 2-87

Membrane bioreactor BioFilt with three lines at 4.5 m3 of permeate per day each [ROCHEM UF 2004]

Figure 2-88

Low-pressure reverse osmosis for grey water treatment for 600 m3 of permeate per day

[photo: ROCHEM UF 2004]


2.4

Downstream Membrane Stage for Waste

Water Disinfection

2.4.1

Process Description and Fields of Application

The use of a membrane stage at the outlet of a waste water

treatment plant is applied to achieve disinfection of the

effluent to comply with higher standards (e.g. EU Bath-

ing Water Directive) or to reuse the treated waste water.

Disinfection by a membrane stage has advantages com-

pared to conventional processes such as UV treatment,

ozonation or chlorination. Namely, no undesired bypro-

ducts develop and the formation of chemical resistance

of bacteria and viruses is not supported [DORAU 1999].

For the most part, the waste water from the outlet of the

waste water treatment plant is pre-sieved with a molecu-

lar separation size of 500 µm before it is fed into the

membrane stage. Additional pretreatment is not neces-

sary. Removal of dissolved phosphate compounds after

disinfection can be achieved by arranging a dosing sta-

tion for precipitants upstream of the separation stage

[DITTRICH ET AL. 1998] to retain the precipitation sludge

in the downstream membrane stage.

2.4.2

Membrane Modules Used

Test studies (test installations of Berliner Wasserbetriebe

at the Berlin Ruhleben waste water treatment plant

[DITTRICH ET AL. 1998], plant at the Geiselbullach waste

water treatment plant [SCHILLING 2001] and tests at the

Hailfingen and Merklingen waste water treatment plants

[MAIER, VOGEL 2003]) have proven the suitability of dif-

ferent micro- and ultrafiltration modules for secondary

effluent disinfection. Table 2-23 presents the characteris-

tic values of the modules used for large-scale operation.

152

Table 2-23

Characteristic values of different membrane modules for the filtration of effluents from the test installa-

tions of Berliner Wasserbetriebe and the test installations at the Geiselbullach, Halfingen and Merklingen

waste water treatment plants

Manufacturer

Membrane process

Material

Module type

Nominal molecular

separation size

Mode of operation

Operating pressure

(transmembrane)

Specific flow

Backwashing

WWTP

Berlin-Ruhleben

[according to

DITTRICH ET AL. 1998]

MemBrain

ultrafiltration

ceramics

multichannel tube

module

0.05 µm

dead-end

0.5 – 2.0 bar

approx. 63 L/(m2· h)

with filtrate

(filtrate side)

WWTP

Berlin-Ruhleben

[according to

DITTRICH ET AL. 1998]

Memtec

microfiltration

PP1)

capillary module

0.1 µm

dead-end

0.5 – 1.5 bar


with compressed air

(filtrate side)

WWTP Geiselbullach

[according to

SCHILLING 2001]

ROCHEM

ultrafiltration

PAN2)

cushion module

50 / 200 kD

dead-end

0.5 – 2.0 bar


with filtrate (filtrate

side) and compressed

air (feed side)

WWTP

Bondorf-Hailfingen

ZENON

ultrafiltration

PVDF3)

capillary module

0.02 µm

dead-end

0.05 – 0.3 bar



side) and compressed

air (feed side)

WWTP

Merklingen

X-flow

ultrafiltration

PES4)

capillary module

150 kD

dead-end

0.5 – 2.0 bar



side)

1) Polypropylen 2) Polyacrylnitril 3) Polyvinyldiflourid 4) Polyethersulfon

UF2.4.4


2.4.3

Operating Experience

The effluent quality measured at the test installations at

the Berlin Ruhleben waste water treatment plant proves

that the limit values of the EU Bathing Water Directive

can be readily met with membrane treatment [DITTRICH

ET AL. 1998].

According to first experiences with the modules applied

up to now, specific flows of 35 – 70 L/(m2 � h) can be ap-

plied as a basis [DITTRICH ET AL. 1998; SCHILLING 2001].

To maintain the filtration capacity, High personnel and

financial expenditure for chemical cleaning must be con-

sidered.

First information on the treatment costs was acquired

with the help of semi-technical tests at Berliner Wasser-

betriebe. According to this information, in 1998 the spe-

cific total net costs for two different plant configurations

were between 0.25 euro/m2 and 0.42 euro/m2 of filtrate

[DITTRICH ET AL 1998]. In comparison, the costs of con-

ventional processes, e.g. consisting of sand filtration and

subsequent UV treatment, are between 0.15 euro/m2 and

0.31 euro/m2 [DOHMANN 1997].

Large-Scale Applications in Germany for Waste

Water Disinfection by Ultrafiltration

In Germany, three membrane installations are operated

currently which serve for further treatment of the effluent

from a conventional waste water treatment plant (Table

2-24). A technical installation has been operated since

July 2000 at the Geiselbullach waste water treatment plant

(Bavaria) of the Amperverband (water board). It treats the

effluent from the conventional waste water treatment

plant up to process water quality so that it can be used as

process water at the waste water treatment plant. Thus it

is no longer necessary to use groundwater for this purpose.

In 2004, two more membrane installations for down-

stream tertiary waste water treatment have been commis-

sioned after preliminary tests at the Hailfingen waste water

treatment plant of the waste water union Bondorf-Hail-

fingen and at the Merklingen waste water treatment plant

of the municipality of Merklingen. They are described in

the following sections.

153

Table 2-24

Membrane installations for waste water disinfection in Germany

Operator Amperverband Municipality of Merklingen Waste Water Union of

Bondorf-Hailfingen

Federal state Bavaria Baden-Württemberg Baden-Württemberg

Installation Geiselbullach WWTP Merklingen WWTP Bondorf-Hailfingen WWTP

Capacity 250,000 PE 2,300 PE 9,000 PE

Membrane manufactur Rochem X-Flow ZENON

Modul typs cushion module capillary module capillary module

Process ultrafiltration ultrafiltration ultrafiltration

Membrane surface area 480 m2 420 m2 7.560 m2

UF2.4.4.1


Geiselbullach Waste Water Treatment Plant

Up to now, groundwater has been used as process water at

the Geiselbullach waste water treatment plant. The conser-

vation of this resource and closure of the process water

cycle, combined with a reduction of the waste water quan-

tity, were the reasons for further treatment of the effluent

of the waste water treatment plant and its reuse as process

water. Moreover, it was necessary to find an alternative to

the use of groundwater for cooling of the district-heating

power stations because of continuous problems with the

development of coatings on the heat exchangers due to the

iron and manganese concentrations in the water. The safe

and hygienic quality of process water treated by a mem-

brane process, compared to UV disinfection, was the reason

to decide on this technology.

After mechanical pretreatment, the waste water is treated

in the activated sludge stage which consists of a denitrifica-

tion zone, increased biological phosphorus removal and

a nitrification zone. A sand filtration unit is arranged

downstream of the final clarification (Figure 2-89).

The raw water for process water treatment is withdrawn

after sand filtration by means of a submerged pump install-

ed in the outlet shaft of the waste water treatment plant,

which pumps the raw water into the storage tank of the

membrane installation. For pre-treatment, a filter with a

molecular separation size of 500 µm and a flocculant

dosing unit for iron(III) chloride sulphate is arranged up-

stream. The pretreated water is fed into the ultrafiltra-

tion installation. It consists of cushion modules from the

company Rochem with 480 m2 of membrane surface area

in total, installed as cushion membranes in 60 pressure

tubes (Figure 2-90). The permeate volume flow is approx.

(V = 60 m3). The storage serves to ensure a sufficient pro-

cess water quantity in order to cover the peak loads with

up to 120 m3/h for some minutes. The specific energy

consumption of the installation is indicated with 0.5 kWh

per m3 of treated process water [SCHILLING 2001].

The investment for the process water treatment plant was

410,000 euro. The specific operating costs amount to

approx. 0.65 euro per m3 of treated process water. The

installation was commissioned in July 2000. Start-up and

optimization of the process technology engineering cover-

ed the period up to the year 2002.

154

primarytreatment

anoxic

sludge

clarifier

feed

screen gritchamber

anaerobic

recirculation

excesssludge

aerobicvariable

Ringlacecords

sand filtration

ultra-filtrationprocess water for

cooling the CHP

flocculant

storagetank

filter

receivingwater

Figure 2-89

Flow sheet of the Geiselbullach waste water treatment plant [according to AMPERVERBAND 2004]

UF2.4.4.2


Merklingen Waste Water Treatment Plant

The Merklingen waste water treatment plant, designed for

2,300 PE, is situated in the mountain region of Swabian

Jura. In the case of dry weather flow, about 300 m3 of waste

water per day are treated. During wet weather flow, this

quantity may increase to 2,000 m3/d.

Due to the special geological conditions of the Swabian

Jura, the treated waste water is discharged directly by an

infiltration shaft into the subsoil. The discharge location

is situated in the zone III of a water protection zone, so

that further treatment of the effluent became necessary.

155

sludge

feed

screengritchamber

concentrate

membrane system

nitrificationsimultaneous denitrification

clarifier storage

sand filter

sand filter

activatedcarbon

permeatstorage

Figure 2-91

Flow sheet of the Merklingen waste water treatment plant [according to RP TÜBINGEN 2004]

Figure 2-90

Treatment installation at the Geiselbullach waste water treatment plant [photos: AMPERVERBAND 2002],

left: pressure tubes of the membrane installation, right: process water storage tank


Since July 2004, part of the treated waste water from the

effluent of the plant has been treated by two different

process technologies (ultrafiltration and slow sand filtra-

tion). An accompanying scientific program serves to com-

pare both technologies for advanced waste water treat-

ment with specific consideration of their capacity to re-

move filterable solids, bacteria etc.

As presented in Figure 2-91, the waste water is fed into

the activated sludge tank with a total volume of 366 m3

after having passed a rake screen with a spacing of 5 mm

and a grit channel. Denitrification takes place simultane-

ously with nitrification, the sludge is aerobically stabilized.

Following secondary clarification, one part of the waste

water is treated by a slow sand filter, the other one by

ultrafiltration (Figure 2-92). The membrane installation

contains pressure-driven capillary membranes from the

company X-flow with a molecular separation size of

150 kD. The total membrane surface area in 12 pressure

tubes is approx. 420 m2. The membranes are operated in

a dead-end process with inside-outside filtration. The maxi-

mum specific filtration capacity has been calculated as

60 L/m2· h.

The investment for the ultrafiltration system was about

530,000 euro. The state Baden-Württemberg has support-

ed the installation with a subsidy of 70 %.

156

Figure 2-92

Pressure tubes of the ultrafiltration plant at the Merklingen waste water treatment plant [RP TÜBINGEN 2004]

UF2.4.4.3


Bondorf-Hailfingen Waste Water Treatment Plant

The Bondorf-Hailfingen Waste Water Union was estab-

lished in 1971 for the treatment of the waste water from

the Associated Municipalities Bondorf and of the district

Hailfingen of the city of Rottenburg on Neckar. In 1974

the mechanical-biological Bondorf-Hailfingen waste water

treatment plant was built. From 1995 to 1999 it was up-

graded to achieve nitrogen elimination. Today the waste

water treatment plant with a design capacity of 9,000 PE

is operated according to the activated sludge process with

upstream denitrification, nitrification, biological phos-

phorus removal and aerobic sludge stabilization.

The dry weather flow to the waste water treatment plant

is 36 L/s on average, the storm weather flow is 67 L/s.

The plant is equipped with a mixing and compensating

tank (V = 1.690 m3), a screen (6 mm spacing), a grit and

grease trap, activated sludge tanks (V = 2.330 m3) and two

secondary settling tanks with a total volume of 1,190 m3

(Figure 2-93).

The positive results of the tests with three different mem-

brane installations in July and August 2003 were the rea-

son for the construction of a large-scale membrane instal-

lation with modules from the company ZENON which was

commissioned in December 2004. The installation is built

in two lines, each equipped with membrane cassettes of

the type ZW 1000. The pore size of the membranes is

0.02 µm on average. The total membrane surface area of

approx. 6,700 m2 generates a permeate volume flow of

approx. 3,100 m3/d.

The investment for the complete plant including build-

ing and civil engineering was about 1.25 million euro.

The state Baden-Württemberg supported the installation

with a subsidy of approx. 50 %.

The treated waste water is discharged into the Kochhart-

graben (Kochhart ditch). In summer, the flow of the Koch-

hartgraben is very low or it carries water only downstream

of the waste water treatment plant, respectively. In the

further course of the Kochhartgraben, the water infiltra-

tes into the subsoil. The plant is situated in a water pro-

tection area of the zone II a.

Due to this special situation, the geological conditions

and the need for groundwater protection, the water

management authorities made special demands on the

effluent quality concerning phosphate content, filterable

solids and disinfection (Table 2-25).

157

Table 2-25

Demands on the effluent quality and operating values of the Bondorf-Hailfingen waste water treatment

plant [BONDORF-HAILFINGEN WASTE WATER UNION 2004]

Parameter Unit Effluent final clarification Effluent membrane Requirements

Operating values installation

COD mg/L 30 < 25 60

BOD5 mg/L 4 < 4 15

NH4-N mg/L – – 5

Ntot mg/L – – 13

Ptot mg/L 1.1 0.3 0.3*

Filterable solids mg/L 15 - 30 n. n. < 5

Hygienics bathing water quality disinfection

* 24 h composite sampler


158

recirculation

feed

screengritchamber

bio-P deni-/nitrifikation tank clarifier

mixing andcompensating tank

blowerinstallation

receivingwater

membrane system

excess sludgestorage

sludge

clarifier

Figure 2-93

Flow sheet of the Bondorf-Hailfingen waste water treatment plant [according to BONDORF-HAILFINGEN

WASTE WATER UNION 2004]

Figure 2-94

Membrane installation at the Bondorf-Hailfingen waste water treatment plant under construction

[photos: BONDORF-HAILFINGEN WASTE WATER UNION 2004], left: building with membrane installation,

right: tank for membrane modules

UF2.4.5.1


Large-Scale Applications Outside of Germany for

Waste Water Disinfection by Ultrafiltration

At present, few experiences exist in Germany with large-

scale membrane filtration of the effluent of secondary

treatment. However, some large-scale installations have

been built worldwide, e.g. in the U.S.A., Great Britain

and Australia [N.N. 2001; N.N. 1996; N.N. 1992]. Some

examples are described in the following sections.

Torreele, Belgium

To ensure that groundwater is used as basis for drinking

water at the Belgian North Sea shore, the groundwater

must remain uninfluenced by seawater. For this purpose,

a concept was developed in 2000 which comprises the

processing of treated waste water and subsequent infiltra-

tion into the dunes. This water serves for ground water

recharge under the dunes and thus prevents the infiltra-

tion of salt water. After approx. 40 days of underground

passage, it is reused as raw water for drinking water pre-

paration.

The treated waste water from the Wulpen plant is used as

feed water for this process. At the waste water treatment

plant Wulpen, the waste water is treated according to the

conventional activated sludge process with upstream de-

nitrification. The effluent values are compiled in Table 2-26.

The waste water treated by the Wulpen plant is fed via a

channel into the ultrafiltration processing plant which

consists of mechanical pre-filtration, a five-line ultrafil-

tration installation and a three-line reverse osmosis

system with downstream UV disinfection (Figure 2-95).

The plant from the company ZENON has an average treat-

ment capacity of 250 – 400 m3 permeate volume flow per

hour. The ultrafiltration plant has five lines. 25 cassettes

of the type ZW 500c are installed which treat up to

9,000 m3 of waste water per day. One part of the treated

waste water from ultrafiltration (about 10 %) is infiltrated,

the other part is further treated by reverse osmosis. The

reverse osmosis membranes have been provided by the

company Dow. The concentrate from the membrane

stage is discharged into the sea via a brackish water chan-

nel, approx. 90 % of the permeate is infiltrated.

The total investment of the processing plant was about

4.5 million euro. The energy demand for operation is

currently about 0.9 kWh per m3 of permeate [VAN

HOUTTE ET AL. 2004].

159

Table 2-26

Quality of the effluent of the Wulpen waste water treatment plant [ZENON GMBH 2004]

Parameter Unit Mean Maximum

COD mg/L 54 162

Cl mg/L 340 1,140

Suspended solids mg/L 5 19

Turbidity NTU 2 11

TS mg/L 1,130 1,950

UF2.4.5


160

outlet

membrane stage

fine screen

fine screen

clarificationof WWTPWulpen

storage storage

NaOCl

blowerinstallation

infiltration

storage

reverse osmosis

storage

UV-disinfection

pond

90 %

10 %

Figure 2-95

Flow sheet of the Torreele treatment plant [according to ZENON GMBH 2004]

UF2.4.5.2


Katowice Treatment Plant, Poland

In Katowice, the effluent from the Katowice waste water

treatment plant is treated up to process water quality and

then used as cooling water for the Katowice power plant

situated at a distance of 12 km. The treatment takes place

with the help of a three-line ultrafiltration installation

from the company ZENON (Figure 2-96). Table 2-27 shows

the waste water quality at the inlet and outlet of the mem-

brane installation.

The ultrafiltration plant consists of 18 cassettes of the

type ZW500 and prepares approx. 5,600 m3 of process

water in total per day is processed, which is used as

additional cooling water for the cooling tower of the

Katowice power plant.

161

powerstation

additionalwater

clarifier

feed

blowerinstallation

blowerinstallation

blowerinstallation

membrane system

Figure 2-96

Flow sheet of the ultrafiltration installation for process water treatment in Katowice

[according to ZENON GMBH 2004]

Table 2-27

Waste water quality at the inlet and outlet of the ultrafiltration installation for treatment of the effluent

of the Katowice WWTP after secondary clarification up to process water quality [ZENON GMBH 2004]

Parameter Unit Inlet Outlet

COD mg/L 35 - 51 27 - 34

BOD5 mg/L 2 - 32 < 2.0

Suspended solids mg/L 6 - 32 < 1.0

Turbidity NTU 10 - 50 < 0.1

UF2.4.5.3


Bedok Waste Water Treatment Plant, Singapore

The Bedok NEWater is the first of four planned plants

which treat waste water to meet the local industrial water

demand. The plant purifies the treated final effluent from

a municipal waste water treatment plant. To ensure the

water quality for reuse of the waste water in industrial pro-

duction, a decision was made In December 2001 on an

overall process concept consisting of ultrafiltration,

reverse osmosis and UV disinfection (Figure 2-97).

Figure 2-98 shows the waste water treatment plant with

the buildings for ultrafiltration and reverse osmosis.

The treated effluent from the waste water treatment plant

flows through a 0.5-mm sieve and is then fed into the

five-line ultrafiltration installation. To prevent the devel-

opment of germs in the membrane tanks, chlorine is added.

The installation is equipped with 70 capillary modules of

the type ZW 500c and has a capacity of 42,500 m3/d after

a first upgrade. Two expansions are already in the plan-

ning stage, so that the total capacity after completion

will be 117,000 m3/d.

The filtrate is discharged by a pump at a low pressure of

0.05 – 0.4 bar and fed into a reverse osmosis installation

for demineralization. Finally it is submitted to UV disin-

fection as a security measure. The concentrate is recycled

into the waste water treatment plant.

The water produced according to the multi-barrier system

is called “NEWater”. It is used as process water for the

electronic industry, for semiconductor manufacture and

also as cooling water for service buildings. A small per-

centage of the NEWater is also used for drinking water

preparation.

162

outlet

treatmentplant

UV-disinfection

fine sieve0,5 mm

ultrafiltration system

chlorinereverse osmosis

to industry

concentrate toWWTP

blowerinstallation

blowerinstallation

blowerinstallation

blowerinstallation

blowerinstallation

Figure 2-97

Flow sheet of the treatment plant [according to ZENON GMBH 2004]


163

2.5

Example for the Design of a Membrane Bioreactor

2.5.1

Design Basis

The basis for the following calculation is the approach of the University

Group (HSG).

Design basis: Type of plant: simultaneous aerobic sludge stabilization

without pretreatment

Population equivalent = 100,000 PE

specific waste water volume ws = 130 L/(E·d)

Daily inflow Q d = 19,500 m3/d

Sewer infiltration water flow Q f = 6,500 m3/d

Combined water flow Q m = 2.128 m3/h

Peak flow factor waste water xs = 14

Pretreatment = none

Fluctuation factor = 1.70

Dry matter content in the activated sludge tank TSBB = 12 g/L

alpha value � = 0.6

Resolubility factor (part of TKN in excess sludge) rX = 0

Sludge age tTS = 25 d

Temperature in the activated sludge tank T = 10 °C

Simultaneous phosphate precipitation with Fe(III)Cl

The design of secondary settling tanks is not necessary for membrane

bioreactors.

Figure 2-98

General view of the treatment plant [photo: ZENON GMBH 2004]

Figure 2-99

Ultrafiltration membrane installation

[photo: ZENON GMBH 2004]


A waste water treatment plant of the size class 5

(> 100,000 PE) has to comply with the following

monitoring values:

Ninorg. = 13 mg/l

NH4-N = 10 mg/l

Ptot. = 1 mg/l

Norg. = 2 mg/l

A printout of the calculation results of the activated

sludge stage with the design program ARA-BER is enclosed

as chapter 2.5.4. Moreover, interim results are given in

order to explain the progression of design (see Table 2-29).

2.5.2

Interpretation of the ARA-BER Calculation

According to the Design Recommendations

for Membrane Bioreactors

The basis for the design of membrane bioreactors are the

tank volumes determined for a conventional waste water

treatment plant either according to ATV-DVWK-A 131 or

to the approach of the University Group (HSG), consider-

ing already a TS content which is typical for membrane

bioreactors. The data determined for the exemplary in-

stallation are listed in Table 2-28.

Due to the smaller reactor volume of membrane bioreac-

tors, undesired effects may occur, e.g. increased oxygen

carry-over from the nitrification or filtration zone into

the denitrification zone. To reduce these effects, the di-

mension of the denitrification zone (VDeni, MBR) should cor-

respond approximately with the dimension of the nitrifi-

cation zone (VDeni, MBR / VNitri, MBR = 1). The bigger of these

volumes of the conventional design (VDeni, conv,12 g TS/L or

VNitri,conv, 12 g TS/L) has to be equated with the corresponding

volume of the membrane bioreactor, since a smaller nitri-

fication or denitrification volume of the membrane instal-

lation (VDeni, MBR or VNitri, MBR) has to be included, compared

to a conventional design. To take special operating state

into account, a variable zone (Vvario) in the dimension of

30–50 % of the denitrification volume should be designed,

which can be arranged in the activated sludge tank ac-

cording to the needs of operation.

Moreover, a minimum retention time thydraulic ≥ 6 h (with

increased demands: thydraulic ≥ 8 h) has to be observed in

the case of certain boundary conditions. It is possible to

undercut the recommended retention time if the volume

required to maintain the recommended retention time is

bigger than the volume of the activated sludge tank of

the membrane installation, which in conventional design

has been determined with TSBB = 12 g/L and enlarged in

addition by 50 %.

164

VDeni, MBR : VNitri, MBR = 1

VMBR, tot. ≤ 1,5 � VBB, conv, 12 g TS/l

thydraulic ≥ 6 h

8,770 m3 > 5,520 m3

=> 2 � 8,770 m3 = 17,540 m3

Here assumption: xQmax = xS

=> xQmax = 14 h/d

=> Qcritical load case = Qd/xQmax

VBB, MBR = 17,540 m3

VNitri, MBR = 8,770 m3

VDeni, MBR = 8,770 m3

VBB, MBR = 21,435 m3

VBB, MBR = 8,357 m3

Table 2-29

Determination of the necessary volumes, taking into account different requirements for the design of

membrane installations

Requirements for MBR Interim result MBR

Table 2-28

Design results according to the approach of the

University Group (HSG) for a conventional waste

water treatment plant with TSBB = 12 g/l

VBB, conv, 12 g TS/L = 14.290 m3

VNitri, conv, 12 g TS/L = 8.770 m3

VDeni, conv, 12 g TS/L = 5.520 m3

VDeni, conv, 12 g TS/L / VBB, konv, 12 g TS/L = 0.386


After determination of the necessary volumes consider-

ing the different design criteria for membrane installa-

tions, the interim results are compared to determine the

decisive volume.

The Table shows that for this example the resulting vol-

ume is bigger than the volume necessary to maintain the

minimum retention time, considering the maximum

volume allowance of 50 % for the volume of the activa-

ted sludge tank in conventional design (VBB, conv, 12 g TS/L).

For this reason, the criterion VMBR, tot < 1,5* VBB,conv,12 g TS/L

is not decisive in this case. Now it has to be examined

whether the nitrification or denitrification volume is suf-

ficient. Due to the criterion of maximum retention time,

the required volume in this example is much smaller

than would be necessary for the compliance with the cri-

terion VDeni, MBR / VNitri, MBR. Therefore the criterion of mini-

mum retention time neither can be decisive for the design

of the membrane installation.The volumes decisive for

the example are listed in the following Table.

VBB,MBR = 17,540 m3

of which VNitri,MBR = 8,770 m3

VDeni,MBR = 8,770 m3

contained in it: Vvario,30% = 2,631 m3

or: Vvario,50% = 4,385 m3

In this case it is not possible to arrange compensating

volume because the total volume is required for the bio-

chemical processes. The resulting total retention time

with critical design inflow of Q critical load case = Q d/xQmax

= 1,393 m3/h is 12.6 h.

2.5.3

Design of the Membrane Filtration Stage

The surface areas of membrane filtration stages are de-

signed according to the permeate flow.

The membrane modules available on the market at pre-

sent have a design flow (net flow) of 25 L/(m3 · h) at 8 °C.

At a design temperature of 10 °C, the design flow may be

increased by 15 % (" design flow = 28.75 L/(m3 · h).

Necessary membrane surface area for the example in-

stallation:

Necessary information:

Design maximum flow Q m = 2,128 m3/h (in contrast to

the design of the reactor volume, the combined water

flow is always decisive in the determination of the neces-

sary membrane surface area of municipal membrane bio-

reactors!)

Design specific flow of 28.75 L/(m3 · h)

In addition, 1 % of the membrane surface area installed

must be maintained as reserve for cleaning measures (on

approx. 200 working days per year, 1 % of the surface area

is cleaned, i. e. the total membrane surface area is cleaned

twice a year).

From this results a necessary membrane surface area of

74,758 m3.

165


2.5.4

Printout of the Design Results with ARA-BER:

Waste water treatment plant: membrane installation 100,000 PE

Type of installation: simultaneous aerobic sludge stabilization

Total volume: 17,530 [m3]

Nitrification volume: 8,765 [m3]

Denitrification volume: 8,765 [m3]

VDeni / Vtot : 0.500 [-]

Design temperature: 10.0 [°C]

Mean TS concentration: 12.00 [kg/m3]

Aerobic sludge age: 15.35 [d]

Total sludge age: 25.00 [d]

Effluent values:

NH4-N (peak) (design value) 10.0 [mg/L]

NH4-N (mean) (design value) 2.0 [mg/L]

NO3-N (average) (design value) 6.6 [mg/L]

Dry weather flow Q t 1,199 [m3/h]

Combined water flow Q m 2,128 [m3/h]

Daily flow Q d 19,500 [m3/d]

Backcharges:

BOD5 0.0 [kg/d]

TKN 0.0 [kg/d]

Ptot. 0.0 [kg/d]

Part of TKN in excess sludge = rX 0.00 [-]

TKN backcharge from rX 0.0 [kg/d]

Precipitation with: iron(III) salt

Precipitant dosage 17.42 [g/m3]

Attainable P effluent value 1.00 [mg/L]

No calculation of secondary settling tanks

166

Membrane Technology in

Industrial Waste Water Treatment

3

Membrane Technology in Industrial Waste Water Treatment3

3.1

Brief Overview

The application of membrane processes in industry has

its origin in the field of production, with most references

in the beverage industry and in the pharmaceutical in-

dustry and for the production of ultra-pure water [BROCK-

MANN 1998]. Due to rising costs for process water and

for waste water discharge as well as increasing environ-

mental awareness in industry, membrane processes are

now used more frequently for the treatment of industrial

waste water.

In industrial production, waste water is often produced

discontinuously and its composition may vary signifi-

cantly. Joint treatment of high-strength industrial waste

water in municipal waste water treatment plants gives

rise to problems, especially when the treatment efficiency

of the municipal plant is limited or its biological treat-

ment capacity is not sufficient. In these cases separate

treatment or pretreatment of industrial waste water is

required for which membrane processes, as process- and

production-integrated measures, can make an important

contribution.

The following chapter deals with the use of membrane

technology in industrial waste water treatment. Motives,

objectives and decision criteria for the use of membrane

technology are discussed, cost-benefit analyses are made,

and successful examples from practice are briefly described.

Figure 3-1 on the next page shows the contents of the

chapter. It presents the most important steps from the

motives and planning stage to the operation of a mem-

brane installation. With the help of references to page

numbers and short check lists the reader is able to focus

on individual sections of the chapter according to his

interest.

For successful operation of a membrane installation,

detailed planning and pilot-scale testing by specialists is

necessary, taking into account the existing boundary

conditions. Therefore the annex contains a list of con-

tacts for concrete planning intentions.

168

Membrane Technology in Industrial Waste Water Treatment 3

169

Figure 3-1

Motive – planning – operation of a membrane installation,

overview of the contents of the chapter “Membrane technology in industrial waste water treatment”

Procedure

Motive

Objective

p. 288

p. 170 ff.

Examples

Reduction of costs

Compliance with the standards

Information

Analysis of the actual situation

p. 288Incoming material flows

Outgoing material flows

Selection of processes

p. 288Separation processes

Membrane technology...

p. 174 ff.

p. 279 f.

Economic analysis

Comparison of processesCost-benefit relationPossibilities for promotion

Planning and pilot-scale testing

p. 174

Preliminary tests

Laboratory tests

Choice of membranes

...p. 174 p. 270 ff.

p. 289ConsultantsIndustrialsPlant manufacturersCleaning agent producer Membrane producer

Operation and control

p. 289Operator model

Owner-operated enterprise

p. 280 ff.

Concrete examples

Internet portalwww.pius-info.de

p. 177 ff.

p. 280 ff.

Effizienz-Agentur NRW

PIUS®-Check

Independent consultants

p. 172

p. 172

p. 177


170

Avoidance of waste water

• Closure of circulation systems• Recycling of process water from

waste water

Optimization of treatmentprocesses

• Utilization of processes for com-pliance with effluent standards

• Improvement of effluent parameters

Reduction of space or volumerequirements for waste water

treatment

• Protections of sites

Recovery of reusable material

• For reutilization in the productionprocess

• As secondary raw material for processing

• For marketing

Minimization of discharge costs

• By production of pure material (e.g.non-polluted water or solvents)

• By concentration of pollutants

Reutilization of biomass

• By separation in the production inbiotechnical processes

• In biological waste water treatmentby recycling into the aeration reactor

Objectives

Economic interests

Figure 3-2

Objectives and economic interests for the use of a membrane installation in industrial waste water treatment

3.2

Objectives and Applications in Different Industrial

Branches

Membrane processes in industrial waste water treatment

can be arranged downstream of or integrated into the

production process. Besides compliance with legal

standards (for discharge into public sewer systems or

into water bodies), this technology is also used for econo-

mic reasons (Figure 3-2). Typical objectives for the appli-

cation of membrane technology in industry include:

• separation of reusable material, auxiliary agents, by-

products and solvents directly at the source of origin

• recirculation of partial flows

• avoidance of large high-strength waste water flows

• reuse of the concentrates as raw material or as secondary

raw material, or low-cost discharge


171

Food industry

Tanneries

Paper mills

Fibre industry (e. g. vulcanized fibre)

Textile industry

Plastics industry

Laundries

Metal industry, electroplating

Printers, paint shops

Car production

Petrochemical industry

Power stations

Mining industry

Navigation

Various branches, e. g. tanneries, breweries,

paper and textile industry

• Treatment of waste water for use as process water

• Higher protein output (potato starch production)

• Separation of precipitated heavy metals from waste water and reuse as recycling water

• Compliance with effluent standards


• Recovery of reusable material (ZnCl2)

• Process water treatment

• Recovery of size baths and indigo dyes

• Separation of colour pigments


• Separation of softeners and reuse of the treated waste water as process water

• Treatment of the waste water and reuse as process water

• Separation of oil and emulsions [DRIESEN ET AL. 1998] and recycling

• Recovery of scouring baths

• Treatment of rinsing water

• Recovery of coloured pigments

• Separation and concentration of mixed pigments to reduce the discharge costs

• Process water treatment

• Recovery of coloured pigments

• Treatment of reaction- and washing water [THEILEN 2000]

• Treatment of boiler feed water [THEILEN 2000]

• Treatment of mine water and radioactive surface water [THEILEN 2000]

• Separation of oil and emulsions

• Biological waste water treatment using ultrafiltration and microfiltration processes for biomass

separation (membrane bioreactor process)

Table 3-1

Objectives for the utilization of membrane technology in industrial waste water treatment

Industrial branch Examples of objectives

These process objectives may lead directly to cost-saving,

e. g. by

• reduction of the waste water load and possible reduction

of waste water levies for indirect dischargers or the waste

water charge for direct dischargers,

• savings of water and reusable material, if e. g. process

water is recycled or recovered.

The treatment of small specific volume flows may also

be profitable in cases where reusable material is saved or

recovered. Various objectives for the use of membrane

technology in industrial waste water treatment are sum-

marized in Table 3-1.


3.3

Decision Criteria

Due to continuously rising costs for drinking- and pro-

cess water as well as for waste water discharge together

with increasing environmental awareness, industrial en-

terprises more and more frequently implement internal

measures to minimize the waste water load and quantity.

Such internal measures can be realized by using various

processes and process combinations. The choice of a

technically and economically suitable process requires

• structured analysis of the existing conditions and

• clear definition of the objective.

Figure 3-3 shows the methods and criteria of decision-

making for the selection of a suitable process. Since

membrane technology in industrial waste water treat-

ment is the focus of attention, the decision tree presents

two alternatives – membrane technique or alternative

processes – from which only membrane technology is

studied in more detail.

Prerequisite for the selection of a successfully and econo-

mical membrane process is a comprehensive analysis of

the production processes, the water used and the waste

water produced. If after first assessment of the boundary

conditions the use of membrane technology proves to be

technically feasible in an enterprise, an adequate installa-

tion can be planned. Planning has to be carried out

step by step, so that the final result will be adapted

most favourably to the separation problem. The planning

stages for the realization of a large-scale installation are

presented in the flow sheet (Figure 3-3).

172

Each planning phase comprises other detailed decision

criteria which should be examined individually and coor-

dinated by the entrepreneur together with the membrane-

and plant manufacturer. As a rule, existing knowledge

about the waste water to be treated should be used, and

tests on different scales are imperative.

Table 3-2 summarizes the working steps which can be

carried out on the different scales. Careful planning is

critical for successful operation of each membrane instal-

lation.


173

separation ofsubstance mixture

production ofprocess water

separation ofbiomass

identification of the flow(s) to be treated

avoidance or reductionpossible?

realization ofmeasures

terms of reference/objective

yes

no

quality requirements

possibilities for reuse

raw waterquality (physical and chemical)

reusable and hazardous materialquantity produced

boundary conditions

concept of treatment strategy

alternativeprocesses

yes

under certaincircumstances

draft of the flow sheet

identification ofmembrane material

assessment of membraneperformance

is the processexpected to be profitable? no

yes

energy costsmembrane replacement

cleaning agentsnumber of cleanings

staff/service

choice of membrane (membrane material, membrane geometry)

positive test results ?

yes

preliminary tests (laboratory)

choice of module

pilot teststechnical optimizationmodule formpretreatment

hydraulic conditions

economic optimizationoperating costs

overall economic efficiency

technicallyoptimized ?

economicallyoptimized ?

no no

yesyes

large-scale installation

control of operation

benefitrecovery of reusable material

saving of discharge costssaving of water and waste

water costs

costsinvestments

operating costs

filtrate performance

retention rates

economic efficiency

cleaning and backwashingintervals

pressure conditionsdevelopment of covering layer

membrane techniquepossible ? no

hydraulic efficiency

pretreatment/combination with other processes

no

separation ofreusable material

…

Figure 3-3

How to proceed in the planning of an installation for industrial waste water treatment


3.4

Economic Efficiency of Membrane Installations

in Industrial Waste Water Treatment

An important decision criterion for the choice of a waste

water treatment process is its economic efficiency. It can

be assessed, for example, with the help of a cost-benefit

analysis and requires knowledge or estimation of the

costs and the resulting benefits.

From the examples in chapters 3.5 and 3.6 it is clear that

membrane technology (membrane processes and mem-

brane bioreactors) is used in most different industrial

branches for the treatment of waste water. These concrete

examples contain information about investments and

operating costs as well as the resulting amortization period,

as far as these data are accessible to the general public.

These indications only apply to the individual case. In

general, transfer to other installations of the same type is

not possible because the specific boundary conditions

(e. g. production process and techniques) influence the

costs in a significant way.

Due to some important factors of influence on costs and

economic efficiency (Figure 3-4) of a membrane installa-

tion, this chapter can give only qualitative information

on the costs. These factors are explained below.

174

Laboratory

Pilot scale

Planning of the installation

Large-scale installation

• Complete analysis of the waste water to be treated

• Choice of the membrane in a test cell installation

• Approximate determination of the most important process-engineering parameters such as trans-

membrane pressure and flow velocity

• First tests on membrane cleaning

Operation of a pilot installation:

• Choice and test of the modules, module connection

• Process optimization

On-site under operating conditions:

• Cleaning intervals and demand for chemicals

• Energy demand

• Product quality in continuous operation

• Analysis of the test results

• Design of the installation

• Analysis of economic efficiency

• Control and optimization

– of the operating parameters

– of the energy demand

• Determination of the overall efficiency (cost-benefit relation)

Table 3-2

Sequence of planning for a membrane installation [according to THEILEN 2000; PETERS 2001]

Scale Working steps


End use, or tasks and objectives

• Membrane installations are designed for a specific task

or treatment objective. In many cases, treatment beyond

this objective is possible, but often involves additional

costs.

Boundary conditions

• The waste water characteristic determines the required

investment and operating costs of a membrane installa-

tion. The waste water treatment costs may significantly

differ, even for enterprises of the same branch. It is not

useful to give numerical values because this might lead

to inaccurate assessment of the economic efficiency of

a membrane installation.

• The cost-benefit relation of a membrane installation

may be positive or negative, depending on a large num-

ber of boundary conditions. These are for example the

water and waste water charges, the design capacity, pos-

sibilities and costs for waste disposal, etc. More exam-

ples for boundary conditions influencing the costs are

presented in.

175

tasks/objectives

boundary conditions

...freshwaterprice

waste watercharges

energy costshydraulicefficiency

waste waterquantity

qualityrequirement

location

planning and pilot tests

membrane bioreactor membrane process

investments

• membrane material• membrane surface• module form• peripherical equipment

operating costs

• operating mode• annual operating period• energy demand• cleaning• cleaning agent• cleaning interval• membrane replacement• discharge costs• personal maintenance• insurance• costs for the building

benefit

• protection of the plant location• compliance with limit values• reduction of waste water charges• reduction of discharge costs• recirculation• recovery of reusable material

Figure 3-4

Factors influencing the economic efficiency of membrane installations


Planning, pilot tests and choice of the membrane

process

• Since each industrial enterprise produces a specific

waste water, a detailed planning and pilot test phase is

necessary to examine the possible use of a membrane

process and to assess the costs. The expense for pilot

tests, which may vary considerably, also belongs to the

costs for a membrane installation. Detailed planning

and comprehensive pilot tests contribute to avoiding

uneconomical design of the installation, to recognize

possible operating problems and to counteract them in

advance by corresponding design and operative

management.

• The type of the membrane process has an effect on the

investments and the operating costs. The membrane

bioreactor has been assessed since 1997 as an economic

treatment process for concentrated waste water, e. g.

some industrial waste waters [ROSENWINKEL ET AL.

1997], while up to now this is true only to a limited

extent for municipal waste water applications.

For each plant, investments and operating costs have to

be distinguished. Both categories can be subdivided into

more individual factors.

The amount of investments depends among others

on the membrane material, i. e. the module costs, and

the membrane surface area installed. This is especially

true for large installations. Membrane material, surface

and form are chosen for the individual case considering a

number of criteria. STROH ET AL. [1997] compared for

two applications – clarification of fruit juice and oil/water-

emulsion filtration – the amount of investment and ope-

rating costs resulting from the use of polymer and cera-

mic membranes. It turned out that the investment and

the power demand for ceramic membranes are higher,

but that the costs for replacement of the membranes at

the same time are lower because of their longer service

life. Related to a cubic meter of filtrate, the use of cera-

mic membranes may be more favourable in one case,

while the use of polymer membranes is more favourable

in another one. The authors therefore emphasize that

without exact relation to a concrete case, only general

assessment is possible. With further developments in the

field of membrane technology (membranes, modules,

energy demand, etc.) the costs for the different materials

and modules will also change. With view to the product

and market development, it is expected that the prices

for membranes in general will decrease.

To ensure profitability of a membrane installation, full

use of the membrane surface by an optimal operating

mode is essential because the costs rise with increasing

membrane surface area. However, doubling of the mem-

brane surface area does not result in a doubling of the

costs, since the expense for peripheral equipment of the

installation, such as measurement and control technique,

has larger impact on smaller installations [e. G. VOSSEN-

KAUL, MELIN 2001].

The operating costs comprise several components. An

important component is the energy cost which depends

on the annual operating period and the operating mode

(cross-flow or dead-end). The energy demand of installa-

tions working in dead-end mode is lower than that of

installations operated in classical cross-flow mode.

Depending on each single case, the costs for membrane

cleaning must not be neglected. Optimized cleaning

methods (chemicals, cleaning intervals) contribute to

minimize these costs and possibly extend the service life

of the membranes. The longer the service life of the mem-

branes, the lower the costs for membrane replacement.

The service life of membranes may significantly vary de-

pending on the membrane material, waste water compo-

sition, pretreatment, operating period and operating mode

(chapters 3.5 and 3.6, Concrete examples). In some cases

(e. g. treatment of landfill leachate), service lives of five

years and more are standard.

Moreover, the operating costs also include the discharge

costs, insurance, personnel and maintenance costs. Per-

sonnel and maintenance costs are assessed in most cases

as flat rate in percent of the investment costs, but they

also depend on the size of the installation. For example,

a study of the economic efficiency of installations for

sludge water treatment has shown that this value as a rule

should be corrected: for small installations it is higher, for

large installations it is lower [VOSSENKAUL ET AL. 2000].

176


The breakdown of investments and operating costs is not

necessary for the user of an installation run according to

an operator model, e. g. “BOO” (Build-Own-Operate).

With this accounting method, the user of the installation

reimburses the quantity of treated waste water according

to a volume-specific price which already includes all costs

of waste water treatment.

The expenditure for a membrane installation is always

seen in relation to the benefit and the savings expected.

The benefit may consist of the protection of the enter-

prise location, compliance with limit values or the reduc-

tion of waste water charges and discharge costs. Savings

can be made by recirculation (recycling of process water

or recovery of reusable material). In some cases these

savings are very high, so that the membrane installation

is amortized after a rather short time. But the amount of

savings compared to the expenditure and the amortiza-

tion time to be expected have to be examined for each

single case.

3.5

Sample Applications of Plants in Germany

In the following subsections the employment of different

membrane processes in various industrial branches in

Germany is presented with the help of exemplary instal-

lations which have been built on industrial scale and are

operating successfully or a in planning stage. Some of

these installations have been realized with the financial

backing of the Ministry for Environment and Nature

Conservation, Agriculture and Consumer Protection of

the federal state North Rhine-Westphalia (MUNLV NRW).

Examples from international practice are described in the

subsections of chapter 3.6.

Diverging from the sorting of the installations for muni-

cipal applications (see chapter 2.2), the examples are

sorted according to their use in industrial branches,

because combinations of different membrane processes

are also used in industrial waste water treatment. A short

introduction into the respective industrial branch prece-

des the description of the example installations. As intro-

ductory overview for each concrete example, the mem-

brane process applied, the objectives attained or the

benefit of the installation are indicated.

All examples described in the following sections are com-

piled in Table 3-3. The addresses of the companies and

enterprises are listed in the annex.

Statements on the total economic efficiency of the pro-

cesses described are made for the following concrete ex-

amples as far as information was available. For the total

economic efficiency of a membrane installation, besides

the construction, the choice of the operating parameters

is decisive above all and which can be optimized in detail

only when the installation is finished. Since some of the

examples described are rather new or in planning stage,

only limited operating experience exists for some of the

installations, especially concerning the service life of the

membranes. Only after a longer practical operating peri-

od, experience will show how successful and economic

membrane processes are in each single case.

The installations described are examples for large-scale

realization of the membrane process. Normally they can-

not be transferred as a standard solution to another enter-

prise of the same industrial branch. The employment of

membrane technology has to be examined for each sin-

gle case concerning technical feasibility as well as econo-

mic efficiency.

177


178

Potato starch

industry

Malthouses

Food industry

Printing industry

Paper mill

Textile industry

Textile industry

Textile industry

Fibre industry

Plastics industry

Laundry

Laundry

Metal proces-

sing industry

Metal proces-

sing industry

Metal proces-

sing industry

Metal proces-

sing industry

Table 3-3

Sample applications for the use of membrane technology in industrial waste water treatment in Germany

Branch of

industry

Emsland Stärke

Durst Malz -

H. Durst Malz-

fabriken

Beeck Feinkost

Peter Leis

Paper mill Palm

Drews Meerane

Silk weaving

mill Pongs

Gerhard van

Clewe

Vulcanized fibre

Troplast

Laundry Alsco

Textil Service

Mewa

Rasselstein

Hoesch GmbH

Faurecia, Bert-

rand Faure Sitz-

technik

Electroplating

Enterprise

Rudolf Jatzke

Wieland Werke

Company

Emlichheim

Gernsheim

Hamburg

Solms

Eltmann

Meerane

Mühltroff

Hamminkeln-

Dingden

Geldern

Troisdorf

Kaiserslautern

Groß Kienitz

Andernach

Stadthagen

Bielefeld-Senne-

stadt

Langenberg

Location

1997

1997

1994

1998

1999

2001

2004

UF/NF/RO: 1997

MF: 2001

1997

1998

2000

1998

1999

2000

1993

1998

Start-up

RO

RO

UF

UF

NF

UF

MF

MF/UF/

NF/RO

RO

UF

UF/NF

UF/NF

UF

UF

Membrane

electrolysis

UF

Membrane

process

Tube modules

Spiral-wound

modules

Tube modules

Ceramic tube

modules

Spiral-wound

module

Immersed capil-

lary modules

Plate modules

MF: tube modules

UF: ceramic

tube modules

NF/RO: spiral-

wound modules

Spiral-wound

modules

Ceramic tube

modules

UF: tube module

NF: spiral-wound

module

UF: ceramic

tube modules

NF: spiral-

wound modules

Ceramic tube

modules

Flat membranes

2 cells per dialy-

sator

Capillary modu-

les

Modules

5,000

1,333

100

2.4

15,000

2,200

320

MF: 225

UF/NF/RO: no

information

312

38

UF: 44

NF: 180

UF: 60

NF: 135

4.56

1.1

44

Membrane

surface area m2

3.5.1.1

3.5.1.2.1

3.5.1.3

3.5.2

3.5.3.1

3.5.4.1

3.5.4.2

3.5.4.3

3.5.5

3.5.6

3.5.7.1

3.5.7.2

3.5.8.1

3.5.8.2

3.5.8.3

3.5.8.1

Chapter


179

Treatment of

waste water

from car pain-

ting

Treatment of

waste water

from car pain-

ting

Pharmaceutical

industry

Landfill leachate

Fish hatchery

Power plants

De-oiling of bilge

water

Swimming pool

Swimming pool

Table 3-3

Sample applications for the use of membrane technology in industrial waste water treatment in Germany

DaimlerChrysler

Ford Werk

Schering

Alsdorf-Warden

landfill

Pilot installation

GuD Dresden

Aquana Freizeit-

bad

Freizeitbad

Copa Ca Backum

Düsseldorf

Köln

Bergkamen

Alsdorf

Dresden

Würselen

Herten

1998

2001

2003

1999

2004

1996

1989

1998

1998

UF

NF

UF

RO

MF

UF

UF

UF/RO

UF

Plate modules

no information

Capillary modu-

les

Disc-tube

modules

Plate modules

Ceramic multich-

annel elements

Tube modules

UF: capillary

modules

RO: spiral-

wound modules

Hollow-fibre

modules

30

no information

15,840

460

21

15.2

23.6

UF: 42

RO: 140

300

3.5.9.1

3.5.9.2

3.5.10

3.5.11.1.1

3.5.11.2

3.5.11.3

3.5.11.4

3.5.11.5.1

3.5.11.5.2

3.5.1

Food Industry

The generic term food industry is comprised of a large

number of branches, such as the milk or meat processing

industry, processing of vegetables, finished products, the

beverage industry etc. Correspondingly, the waste waters

of the individual branches vary in their composition.

They have in common only high organic loads.

In the following the use of membrane technology for the

treatment of waste water from the food industry is described

for three branches – potato starch production, delicatessen

production and malt production – and presented with

the help of concrete examples.

Besides waste water treatment, membrane technology is

also used in the food industry for other purposes, such as

concentration (e. g. of juice, milk, whey, egg whites), fil-

tration (e. g. of juice, wine, beer) and alcohol removal

from beer. The alcohol fraction resulting from alcohol

removal is a suitable substrate for denitrification in waste

water treatment (as a methanol substitute).

Branch of

industry

Company Location Start-up Membrane

process

Modules Membrane

surface area m2

Chapter


3.5.1.1

Potato Starch Production

In the Federal Republic of Germany, starch is produced

from maize, potatoes, wheat and rice. Of these raw mate-

rials the potato has the highest water content. For starch

production, the potatoes are carefully prewashed and then

ground, separated from the pulp water (0,76 m3 of pulp

water per ton of potatoes) and washed out. The starch is

produced from the ground potatoes, and the pulp water

is generally used to produce potato protein (Figure 3-5).

The residual pulp water is used for irrigation of farmland

or evaporated. Potato pulp, which contains fine-ground

peelings, cell walls, starch residues and pulp water, is de-

watered. In Germany and the Benelux Countries, potato

pulp has been used for many years as fodder for dairy

cattle and young stock, and also partly for fat stock.

The entire production process results in sweeping and

washing water, pulp water and starch washing water. The

amount of washing water is about 1.8 to 2.8 m3 per ton

of starch. Characteristic constituents are potato pulp

water ingredients, fibres and mineral components (earth,

sand etc.).

Potato starch is only produced only during a certain sea-

son. The Fertilizer Ordinance (1996) dictates the storage

of potato pulp and irrigation water between 15th Novem-

ber and 15th January (even longer in the case of frost)

and limits the application in autumn to a maximum of

80 kg Ntot/ha.

The concentration of the pulp water and closing of the

internal water cycle are suitable measures to manage the

production limitations defined above. This can be obtained

with the help of different procedures (e. g. membrane

technology).

180

potatoes

fibres potato pulp water

protein precipitation

soluble matter

potato protein

potato pulp

grater fractionation (wet procedure)

starch

Figure 3-5

Flow chart of potato starch production

RO3.5.1.1.1


The company Emsland Stärke GmbH is the most impor-

tant producer of potato starch in Germany and is one of

the world’s leading manufacturers of finished starch pro-

ducts, potato protein, amino acids and sugar products

such as glucose syrup. The parent plant in Emlichheim,

established in 1928, has 405 employees. For the produc-

tion of potato starch, starch derivates and potato protein,

water with drinking water quality is used and ultimately

disposed of as waste water (sweeping and washing water,

derivate waste water).

In 1997, a reverse osmosis installation from the com-

pany Stork was commissioned in the Emlichheim plant

in order to reduce the quantity of waste water to be

disposed of, to conserve drinking water and to recover

more protein. The potato pulp water from starch produc-

tion is separated in the cross-flow mode at an operating

pressure of 40 bar. Tube modules with a total membrane

surface area of 5,000 m2 filter a feed volume flow of

140 m3/h. With daily backwashing and cleaning with

commercial enzymatic cleaning agents, the service life of

the membranes is about 6,000 hours. During the produc-

tion campaign (about 120 days per year), the installation

works 24 hours per day, so that the membranes have to

be replaced after approx. two campaigns.

181

potatoes

starch factory

evaporation

waste watertreatment plant

for fumes condensate

water supply

treatment

fibres

potato pulpwater reverse osmosis

protein production

potato pulp

permeate forpotato washing

potato protein

process water

fumes condensate

excess

brinefertilizer

feedmolasses

receiving water

process waste water

Figure 3-6

Flow chart of the treatment of process- and potato pulp water at Emsland Stärke GmbH

[according to LOTZ 2000]

Food Industry, Emsland Stärke GmbH

Start-up

Objectives

Membrane surface

Modules

Permeate volume flow

Pretreatment

Benefit

1997

Reduction of the waste water- and drinking water volume, higher protein yield

5,000 m2

Tube modules

62 m3/h

Separation of fibres and pulp water

Savings of energy, water, waste water, at the same time higher protein yield

Membrane process Reverse osmosis


The permeate (about 62 m3/h) from the reverse osmosis

system is used to wash the potatoes, while potato protein

is produced from the brine. The remaining potato pulp

water is evaporated. The vapour condensates are fed to a

dedicated waste water treatment plant and recycled after

further treatment at drinking water quality into the pro-

duction process (see also Figure 3-6).

Thanks to the closed water cycle, more than 500,000 m3

of water are saved per year (250,000 m3 of washing water

by the permeate of the reverse osmosis installation and

more than 250,000m3 by closing the cycle with the vapour

condensates). Other advantages of the membrane instal-

lation are a drastic reduction in the waste water volume

and a higher protein yield.

3.5.1.2

Malt Houses

Malt is used as a raw material to produce alcohol from

starch-containing materials. Today a large number of brew-

eries get malt from commercial malthouses which pre-

dominantly use barley (about 2.5 million tons per year

[GUTSCH, HEIDENREICH 2001]) and partly wheat for

malt production. The malt production process can be

broadly subdivided into the steps cleaning, soaking, ger-

minating and kiln-drying [KRAFT, MENDE 1997]. Due to

high water consumption for washing and soaking, malt-

houses have to pay high costs for freshwater and waste

water disposal [GUTSCH, HEIDENREICH 2001].

For waste water whose pollution load comes mainly from

the production of malt from cereals and which is dis-

charged directly into a receiving water, the limit values

according to Appendix 21 of the Waste Water Ordinance

[ABWV 2002] are valid. Depending on the production

process applied, the waste water quantities and concen-

trations may vary significantly from one malthouse to

the other. Waste water constituents include suspended

substances (dust, earthy constituents, residues from cere-

als and husks), sugar, nitrogen-containing substances

(soluble proteins, vegetable fibrin), inorganic matter, and

possibly rubber and polyphenols.

For the treatment of malthouse waste water, membrane

technology can be used in various combinations which

have to be adapted to the specific case. Besides the exam-

ple described below, treatment by microfiltration in low-

pressure operation combined with a biological stage and

a closed process water cycle is also possible [KRAFT,

MENDE 1997].

182

RO3.5.1.2.1


Malthouse Durst Malz –

H. Durst Malzfabriken GmbH & Co. KG

The Heidelsheim company H. Durst Malzfabriken GmbH

& Co. KG is specialized in malt production for Pilsner

beer, but also furnishes special malt for other types of

brewing. 25 people are employed in the works in Gerns-

heim, one of the four plants which combined produce

about 230,000 tons of malt per year.

Large waste water quantities and disposal costs were the

motives for Durst Malz to cooperate with Schwander GmbH

at Bad Vilbel, which together with Frings Recycling-Anla-

gen GmbH (today: imb+frings watersystems gmbh) de-

veloped the patented FriSch-Verfahren® (FriSch process)

for the treatment of process water in the malt and bever-

age industry.

Promoted by Hessische Landes- und Treuhandgesellschaft

(HLT) Wiesbaden, today Investbank Hessen (IBH), an in-

stallation for the treatment of the malthouse waste water

was commissioned in 1997 at Gernsheim (Figure 3-7).

Since that time a daily amount of 700 m3 of water, con-

sisting of the barley soaking water and the washing water

of the production plants, is treated.

The malthouse waste water has a high COD content of

approx. 2,500 to 3,000 mg/l. By biological (SBR process1))

and physical-chemical (ferric chloride precipitation)

treatment, followed by fine filtration, this concentration is

reduced to 30 mg/l in the influent to the reverse osmosis

installation. Subsequently, spiral-wound modules in the

reverse osmosis installation (imb+frings watersystems

gmbh) with a total filter surface area of 1,333 m2 remove

all undesirable malting residues from the water at an

operating pressure of approx. 10 bar. The permeate com-

plies with the requirements of the Drinking Water Ordi-

nance and is recycled into the barley soaking process.

The remaining brine (about 25 – 30 % of the total inflow

to the membrane installation) is treated in the municipal

waste water treatment plant. In order to ensure the opera-

tion of the spiral-wound modules, an antiscaling agent is

used and the modules are backwashed daily with citric

acid.

The employment of the membrane installation led to a

reduction in the water demand and to considerable cost

savings concerning the waste water surcharge. Another

advantage is the modular construction of the installation,

as it can be adapted without causing problems to varying

production parameters.

183

Start-up

Objectives

Membrane surface area

Modules


Pretreatment

Benefit

1997

Reduction of waste water quantities and costs

1,333 m2


about 470 m3/d

Biological treatment (SBR), precipitation

Savings of freshwater and cost reduction in waste water treatment and disposal


1) SBR process: Sequencing-Batch-Reactor process. All phases of the treatment process run in succession in one reactor.

Figure 3-7

Reverse osmosis installation at Durst Malzfabriken

GmbH & Co. KG, Gernsheim [LINDEMANN 2001]

UF3.5.1.3


The company BEECK Feinkost GmbH & Co. KG produces

delicatessen and salad dressings. More than 200 people

are employed at the site in Hamburg.

Tanks and equipment used in the preparation of delicates-

sen and salad dressings, tanks and equipment are regular-

ly cleaned using water and cleaning agents. During this

process solids as well as emulsified fats and oils get into

the waste water and give rise to high COD concentrations.

Treatment of the waste water by a grease trap was not suf-

Food Industry

BEECK Feinkost GmbH & Co. KG

ficient to comply with the COD discharge limit, and a sur-

charge for excess COD concentrations was paid by the

plant.

In order to reduce the waste water fees, an ultrafiltration

installation from the company KOCH-GLITSCH GmbH

was commissioned in 1994. First of all, the solids are se-

parated by prefiltration from the waste water (Figure 3-8).

The prefiltered water is fed to a tank from which the ultra-

filtration installation is charged. The installation is equipped

184

Start-up

Objectives


Modules


Pretreatment

Benefit

1994

Comply with the COD limit values and reduce the waste water fees (surcharge for heavy polluters)

100 m2

Tube modules

Depending on the production, 3.5 – 6 m3/h

Prefiltration

Saving of waste water fees

Membrane process Ultrafiltration

waste water

particles

100 %

pump shaft

prefiltration

tank 80 m3

disposal 1 %

collecting tank

ultrafiltration

sewer system 99 %

concentrate

measuring/monitoring

neutralisation

concentrate

filtrate

recirculationafter disconnectionof the inflow

Figure 3-8

Flow chart of the waste water treatment at BEECK Feinkost GmbH [according to KOCH-GLITSCH GMBH 2001]

UF3.5.2


with tube modules made of PVDF2) membranes with a

molecular separation size of 250,000 Dalton (KOCH-

GLITSCH GmbH), which are operated in cross-flow mode.

About 3.5 to 6 m3 of waste water per hour (depending on

the production) are filtered by 100 m2 of membrane sur-

face area at an operating pressure of max. 6.2 bar.

Depending on the production, the inflow to the tank is

closed so that the waste water is further concentrated by

recycling it to the ultrafiltration installation. The concen-

trate (1 % of the inflow) is disposed of, while the filtrate

(99 % of the inflow) is neutralized and discharged into

the sewer system.

The Grafische Handelsvertretung Peter Leis (graphical com-

mercial agency) at Solms, with five employees, supplies

printers with print drums and chemicals, e. g. cleaning

oils for printing machines.

One of the services of the company consists of voluntary

return of used adsorption oils from its clients. Therefore

a procedure has been developed which serves to convert

the polluted adsorption oils into a valuable reusable pro-

duct. This was done in cooperation with the companies

CARO Umwelttechnik GmbH (contact via NERAtec AG)

and Altenburger Elektronic GmbH.

Since autumn 1998, a membrane installation has been

operating to separate the components oil, water, dye par-

ticles and paper dust. The system consists of a micro-sett-

ling filtration step to remove coarse matter, an oil separator

and an ultrafiltration process to purify the oil phase.

Ceramic tube modules (from the company Tami) with a

total membrane surface area of 2.4 m2 produce about 30 L

permeate per hour at an operating pressure of approx. 3 bar.

On average, the ultrafiltration installation (Figure 3-9)

works 6 to 8 hours per day. Cleaning of the membranes

by removal and burning out becomes necessary after a

throughput of approx. 5,000 L. The service life of the

membranes ends on average after 20,000 L. The filtrate is

reused as recycled high-quality adsorption oil, the con-

centrate is recycled into the settling filtration stage.

The membranes are cleaned chemically once a week.

With this operating mode, the service life amounts to

4 – 5 years.

The installation has not only ecological advantages, but

is also profitable: By saving the surcharge for heavy pol-

luters, the investment for the installation is amortized

after three years.

185

Printing Industry, Peter Leis

Start-up

Objectives


Modules


Pretreatment

Benefit

Autumn 1998

To manufacture a reusable product from polluted adsorption oils

2.4 m2

Ceramic tube modules

30 L/h

Micro-settlement filtration to remove coarse matter, oil separator

Saving of waste water disposal costs and new adsorption oils


2) polyvinylidene fluoride


Besides positive effects on the environment by closing

the product cycle, there are also economic advantages

from the use of this process combination. The yearly costs

for waste water disposal were halved, and the use of new

adsorption oils was reduced to only 25 % from which the

customers profit. Under the present operational condi-

tions, the amortization of the investment of 51,000 Euro

will be two years. These operational conditions were at-

tained about 1.5 years after start-up of the installation.

3.5.3

Paper Mills

Paper mills belong to the group of major industrial water

users. Water is needed for the production of printing pa-

per for the press to process the fibrous raw material as

well as for the production process in the paper machine

itself. The water is taken for the most part from rivers

and lakes and discharged after biological treatment. In

Germany the production of paper and cardboard is about

20 million tons per year, resulting in an average waste

water quantity of 10m3 per ton of final product [VDP 2004].

For the discharge of waste water from paper and cardboard

production into receiving waters, Appendix 28 of the

Waste Water Ordinance [ABWV 2002] is valid.

For the production of new printing paper form waste pa-

per, the applied printing ink has to be removed. Besides

water and air, auxiliary agents such as soap, sodium hydro-

xide, water glass, hydrogen peroxide and complexing agents

are needed. For the production of magazine paper it is

necessary to bleach the fibrous material.

In general, the waste waters from paper mills are highly

loaded organically. Their composition and other consti-

tuents, however, strongly depend on the raw material

used and the type of paper produced, therefore they may

differ considerably. Today membrane processes are still of

secondary importance in the treatment of waste water

from paper mills. In particular, the waste waters from

waste paper processing are nearly calcium-saturated which

leads to scaling. Moreover, they show high lignin contents

and a high percentage of fibrous material. Therefore the

use of membrane technology and of necessary pretreat-

ment measures have to be carefully examined and planned.

186

Figure 3-9

Ultrafiltration installation at the Grafische Handelsvertretung

Peter Leis [LEIS IN EFA 2000]


The paper mill Palm with its headquarters at Aalen-Neu-

kochen, Baden-Württemberg, belongs to the leading Euro-

pean manufacturers of newspaper printing paper and raw

paper for the production of corrugated cardboard. In the

works Eltmann in Bavaria, 250 employees produce news-

paper printing paper from 100 % waste paper.

From material processing and paper production results

waste water with COD and AOX loads, containing also

salts and dyes. In order to comply with the demands

for direct dischargers, the waste water is treated since

December 1999 by biological processes, followed by sand

filtration, and is then submitted to nanofiltration in

cross-flow mode by an installation from Wehrle Werk AG.

The installation has been promoted by the Deutsche Aus-

gleichsbank on behalf of the Federal Ministry for the Envi-

ronment, Nature Conservation and Nuclear Safety (BMU).

The polyamide-based spiral-wound modules (KOCH-

GLITSCH GmbH) used in nanofiltration are arranged in a

feed-and-bleed configuration (see chapter 1.5 and Figure

3-10). At an operating pressure of 3 to 7 bar, a total mem-

brane surface of 15,000 m2 treats a feed volume flow of

max. 195 m3 per hour. The output is 90 %, i. e. 175 m3 of

permeate per hour, which at present is still discharged

into the receiving water. Recycling of the permeate and

its use as process water are being planned. The concen-

trate is treated by lime milk and coagulants, an optimiza-

tion of this treatment is being planned, too.

At present, the modules are backwashed daily. Once a week

(depending on the operating pressure) they are chemical-

ly cleaned, so that the service life of the membranes is

estimated to be 2 – 3 years. These operating parameters of

membrane backwashing are still being optimized.

The membrane installation at the works Eltmann ensures

compliance with the discharge standards and thus serves

above all environmental protection. The planned closure

of the water cycle and utilization of the permeate as pro-

cess water will help to save freshwater, thus economic ad-

vantages are expected.

187

Paper Mill Palm, Works Eltmann

Start-up

Objectives


Modules


Pretreatment

Benefit

December 1999

Compliance with the standards for direct dischargers

15,000 m2


about 175 m3/h

Biological treatment, sand filtration

Compliance with the discharge standards; saving of process water after closure of the water cycle

Membrane process Nanofiltration

UF3.5.3.1


3.5.4

Textile Industry

In Germany there are about 1,100 textile factories, approx.

150 of which are finishing works, which are, for the most

part, small to medium-sized businesses [GESAMTTEXTIL

2000]. From the different fields of production result pro-

cess waters whose composition reflects the diversity of

plant structures and production programs which vary

with the seasons of the year. The discharge of these pro-

cess waters gives rise to increasing costs.

The variety of processes in textile finishing hardly allows

general statements on the water consumption. However,

approx. 60 – 80 L of waste water, partly strongly coloured,

results from the finishing of 1 kg of textiles [MARZIN-

KOWSKI 1999]. Waste water from the cleaning of dye

preparation tanks is highly concentrated. On the other

hand, waste water from dyeing is loaded with dyes in

lower concentrations. With only a few exceptions, these

dyes are not biologically degradable or only partially de-

gradable under aerobic conditions [BRAUN ET AL. 1997].

Since many medium-sized textile finishing enterprises are

indirect dischargers, problems arise in municipal waste

water treatment due to the parameters COD and colour

[GUTSCH, HEIDENREICH 2001]. Direct dischargers have

to comply with the limit values according to Appendix 38

of the Waste Water Ordinance [ABWV 2002]. Besides pre-

cipitation, flocculation and chemical oxidation, membrane

technology can also be used to obtain further removal of

colour from textile waste water.

However, the great variety of waste waters from textile

finishing does not allow one to consider membrane pro-

cesses an economical and technically sound solution for

all applications in this field. Possible employment and

performance of membrane technology requires individ-

ual adaptation to each single case and location and should

be confirmed by detailed pilot tests. The treatment and

disposal of the brine are important considerations in the

overall economic efficiency of the process [MACHEN-

BACH 1998].

188

feed

concentrate

permeate

concentrate

permeate

concentrate

permeate

concentrate

permeate

concentrate permeate

1st circulation

2nd circulation

3rd circulation

4th circulation

Figure 3-10

Nanofiltration installation at the paper mill Palm, works Eltmann (left) [SCHIRM 2001] and detail of the

tube module arrangement as feed-and-bleed structure (right) [according to SCHIRM 2001]


Various process combinations for the treatment of textile

waste water are being tested or have been applied in

practice:

• To realize a closed water cycle in textile finishing, com-

bination of a biological stage (immersed biodisks),

cross-flow microfiltration and adsorption on activated

carbon (complete decolourization) have been tested

[WAIZENEGGER ET AL. 2000].

• Tests have proven the suitability of nanofiltration for

the treatment of waste waters from the textile industry.

Moreover, it was possible to close the water cycle by a

combination of ultra- and nanofiltration as well as to

The company Drews Meerane GmbH runs a textile finish-

ing plant from which high-strength waste water results.

The COD concentrations are between 1,000 and 1,500mg/L.

Moreover, the waste water is strongly coloured due to the

presence of by well water-soluble azo dyes.

The new concept for water and waste water management

intends separate treatment of partial flows with higher

and lower loads. A total of approx. 1,500 m3 of waste wa-

ter per day is treated by the waste water treatment and pro-

cessing plant. The share of the higher loaded waste water

is about 60 %. The COD concentrations in the higher

loaded flows are around 1,400 mg/L, in the lower loaded

flows approx. 1,100 mg/L.

The lower loaded waste water is treated by anaerobic and

aerobic processes, followed by sludge separation in a la-

mella separator (Figure 3-11). Finally the treated waste

water is discharged to the municipal waste water treat-

ment plant.

treat the concentrates in a biological fixed-bed reactor.

In Germany, this process combination has not yet been

realized on an industrial scale [SCHÄFER ET AL. 1997;

GUTSCH, HEIDENREICH 2001].

• In a large-scale plant, waste water from dyeing is treated

by a combination of a biological stage, adsorption, down-

stream reverse osmosis and activated-carbon filtration,

so that it can be directly discharged. The largest part of

the treated water is recycled into the production pro-

cess as all-purpose process water [BRAUN ET AL. 1997].

189

Textile Industry, Drews Meerane

Start-up

Objectives


Modules


Pretreatment

Benefit

2001

Reuse of the treated waste water

2,200 m2

Immersed capillary membranes

~ 34 m3/h

Bent-sieve screen

Reduction of fresh water consumption and of the waste water quantity, cost savings


UF3.5.4.1


At first the higher loaded waste water is treated in an

anaerobic reactor to break down the azo dyes and other

dyes. The resultant products are much smaller and are

yellow up to colourless.

The waste water is then treated by an anaerobic process.

By means of the downstream lamellar clarifier, thickened

sludge is separated and recycled into the anaerobic reactor.

Complete separation of the solid and the liquid phase

takes place in the down-stream ultrafiltration system

with immersed capillary membranes from the company

ZENON. The membrane installation consists of six cas-

settes of the type 500c with a total membrane surface

area of 2,200 m2. Treatment of the higher loaded waste

water by this process combination achieves a reduction

of the COD concentration of 90 %. After final decoloura-

tion with ozone, part of the filtrate from the membrane

installation is used as recycled water with an average

COD concentration of 160 mg/L mainly in textile print-

ing processes for rinsing and cleaning purposes.

Thanks to this waste water treatment system, the COD

load to the nearby municipal waste water treatment plant

was reduced by approx. 500 kg/d. The economic efficien-

cy of the processing plant, compared to the conventional

waste water treatment plant operated in parallel, is achieved

at a recycling quote of approx. 26 %. The recycling quote

really achieved is much higher.

The project was promoted by Deutsche Bundesstiftung

Umwelt (German Federal Foundation for the Environ-

ment) and received in 2002 the Technology Promotion

Award of the Braunschweig Chamber of Industry and

Commerce.

190

flow to municipaltreatment plant

lamella separator

waste water treatment plant

lamella separator

waste water treatment plant

excess sludge

recirculationmembrane stage

ozonisation

well water

treated waste water

production

aerobicreactor

anaerobicreactor

aerobicreactor

anaerobicreactor

excess sludge blowerinstallation

Figure 3-11

Flow sheet of the waste water treatment and processing plant [according to ZENON GMBH 2004]

MF3.5.4.2


Since 1993, the PONGS Textil GmbH in Mühltroff pro-

duces and finishes large-dimensioned special clothes with

a width of up to 6,20 m, among other things. For this pur-

pose, sized warps and weft threads are used.

Before further processing, the raw material is washed to

remove sticking size baths as well as waxes and oils which,

in general, are hardly biodegradable. The washing tem-

perature is between 60 °C and 95 °C, depending on the

substances sticking to the raw material.

Due to increasing production and waste water quantities

and the resulting discharge costs, the textile company

was faced in 1999 with the decision either to relocate the

production to another site or to implement a process

concept that ensures waste water treatment in spite of

significant load variations and applies the reuse of a large

part of the treated waste water in the production process.

With the aim to lower the costs for the upgrading of the

existing waste water treatment plant, a concept was devel-

191

Silk Weaving Mill PONGS

Start-up

Objectives


Modules


Pretreatment

Benefit

2004

Reuse of the waste water/closure of water, circuits

320 m2

Double-decker modules/plate membranes

~ 2.5 m3/h

Vibrating screen

Expansion of the waste water treatment capacity Savings of costs for fresh water and waste water

discharge

Membrane process Microfiltration

Figure 3-12

Conversion of the waste water treatment plant at PONGS Textil GmbH, left: conversion of the existing

trickling filter to a membrane bioreactor [photo: A3 GMBH 2004], right: new membrane bioreactor

[photo: A3 GMBH 2004]

membran bioreactor


oped in 1999 – 2000 that included converting the existing

trickling filter to a membrane bioreactor. Figure 3-12 shows

the conversion of the old trickling filter to a membrane

bioreactor (left) and the new membrane bioreactor (right).

This membrane bioreactor, realized as cascade, was run

until another capacity enlargement in 2004. It consisted

of two tanks arranged in series which were intensively

aerated. The second tank was equipped with immersed

membrane modules from the company A3. The filtration

capacity of the installation could be maintained for six

months without chemical cleaning of the membrane

modules. Depending on process needs, the treated waste

water was used as process water in the textile company

or discharged into the sewer system of the municipality.

The successful operation of the plant showed that the

treatment of waste water from desizing by membrane

bioreactor processes is technically feasible and also cost-

effective. Enlargement of the capacity, necessary due to

increasing production capacity, was realized in 2004 with

the membrane bioreactor process, too.

The daily waste water flow to this installation is approx.

60 m3 with COD concentrations from 8,000 mg/L to

15,000 mg/L. The waste water from the company PONGS

is buffered in a mixing and compensating tank and flows

via a vibrating screen with a molecular separation size of

100 µm to the membrane bioreactor stage. The activation

volume is 240 m3. The membrane installation consists of

four double-decker modules (plate membranes) from the

company A3. The pore size of the membranes is approx.

0.4 µm, the total membrane surface area is 320 m2.

A large part of the treated waste water is reused in the

production process. The company PONGS has set a treat-

ment target of COD concentrations < 200 mg/L for the

reuse of the treated waste water. This target is attained

with COD effluent concentrations of less than 100 mg/L.

192

processwaste water

blowerinstallation

membrane stage

vibrating screen100 µm

production

mixing andcompensatingtank

sewersystem

Figure 3-13

Flow sheet of the membrane bioreactor of the company PONGS [according to A3 GMBH 2004]

MF UF UF RO3.5.4.3


In 1954 the company Gerhard van Clewe has been estab-

lished at Hamminkeln-Dingden. In 1973 the enterprise

was expanded by a dye-works. Today, 190 employees in

total are occupied with the finishing of textiles of all types.

In textile finishing plants, different process waste waters

result from the production areas of pretreatment, dyeing,

dye preparation, washing machines, and finishing. Their

discharge gives rise to increasing costs. In order to reduce

these costs, the company van Clewe tried at first to reduce

as far as possible the water consumption in the finishing

process. As a result, the concentrations in the waste water

increased, and it was no longer possible to comply with

the limit values for AOX and heavy metals for the dis-

charge into the municipal waste water treatment plant.

Based on the results of a large number of tests with a pilot

plant, a large-scale membrane installation from the com-

pany CSM Filtrationssysteme GmbH & Co. KG, Bretten,

was commissioned in 1996. Following expansion of the

installation in 1997, which was promoted by Deutsche

Bundesstiftung Umwelt, Osnabrück, and scientifically as-

sisted by the University of Wuppertal, both partial flows

from the dye-house are fed separately to the membrane

installation. At operational pressures between 5.5 and 27

bar, the permeate output is max. 12 m3 per hour. The per-

meate is recycled to the pretreatment stage and the dye-

house.

The three-stage membrane installation which works in

the cross-flow mode serves to treat the partial flow con-

taining the waste water from cotton dyeing and mesh

finishing. It comprises the stages ultrafiltration (con-

struction and calculation by RIK, Dülmen), nanofiltra-

tion and reverse osmosis. To separate fluff and other

coarse matter, a screen (discotrainer) has been arranged

up-stream. In the ultrafiltration stage (Figure 3-14), cera-

mic tube modules from the company atech innovations

gmbh separate fine-particulate and dissolved polymeric

substances from the waste water. The filtrate passes a

downstream bag filter (protecting function) before it is fed

to the nanofiltration stage. In this stage, decolourization

and partial demineralization are obtained using spiral-

wound modules made from synthetic polymer from the

company Osmonics. The largest part of the salt and most

of the COD load are removed by reverse osmosis using

spiral-wound modules made from polymer membranes

(company Osmonics).

193

Textile Finishing Works Gerhard van Clewe GmbH & Co. KG

Start-up

Objectives


Modules


Pretreatment


Start-up


Modules


Pretreatment

Benefit

1997

no information

Ceramic tube modules (UF), spiral-wound modules (NF and RO)

12 m3/h in total

Screen filtration (discotrainer) upstream of the ultrafiltration to separate fluff and other coarse particles,

bag filter upstream of nanofiltration

Saving of process water and reduction of waste water costs

Membrane process Ultrafiltration, nanofiltration, reverse osmosis

2001

Reduction of the costs for waste water discharge and compliance with the requirements for indirect dischargers

225 m2

Tube modules

2.5 m3/h

Dosing of liquid polymer and clay minerals to increase the particle size (improvement of the separation capacity)


The second partial flow has a smaller volume and is less

polluted. It consists of waste water containing pigment

dyes from dye preparation and dye coating, waste water

from the tenter driers as well as from the purification of

waste air from the tenter driers. Since the beginning of

2001, this partial flow is fed to a microfiltration stage

after dosing of clay minerals and coagulants to increase

the particle size and to improve the separation capacity.

The microfiltration has been designed by MDS Prozess-

technik GmbH and calculated by the company BKT Burg-

gräf GmbH. The installation is equipped with tube mod-

ules (Microdyn Modulbau GmbH) made from polymer

mebranes and works in the cross-flow mode. The mem-

brane surface with an area of 50 m2 in total processes a

permeate volume flow of 2.5 m3 per hour. The tube mod-

ules are backwashed periodically, and fully-automated

chemical cleaning takes place once a week.

After reverse osmosis, the permeate is colour-free and

contains only 3 % of the original COD load. This quality

is sufficient to reuse the permeate from the membrane

stage (single-stage and three-stage) as process water. Thus

a recycling rate of up to 50 % of the total waste water

amount is obtained. The concentrate from all stages is

evaporated, dried by film driers and discharged into an

incineration plant for household waste.

Only the membranes of the ultrafiltration stage have to

be backwashed every three minutes. With this operating

mode, the ultrafiltration membranes have been in service

for seven years without showing loss of capacity (as of

August 2005). The service lives of the nanofiltration and

reverse osmosis membranes are 1.5 years. They have to

be cleaned only on the weekend with special membrane

cleaning agents.

Besides compliance with the standards for indirect dis-

chargers, the membrane installation helps to save about

50 % of the waste water costs by a closed process water

cycle.

194

Figure 3-14

Ultrafiltration installation at the textile finishing

plant van Clewe [BÖTTGER 2001]

RO3.5.5


Vulcanized fibre is a versatile material produced from re-

newable raw material. It is manufactured from non-glued

cotton linters and pulp under the action of a zinc dichlo-

ride solution. The material is antistatic, elastic and of low

weight.

The 50 employees of the Ernst Krüger GmbH & Co. KG

at Geldern produce, among other products, seals, guides

for weaving machines and stamped parts from vulcanized

fibre for the car industry, electrical industry and textile

industry. An important production step is the washing

off of zinc dichloride by several baths connected in series,

from which results waste water containing a residual zinc

dichloride concentration.

Approx. 30,000 m3 of rinse waste water are generated per

year in the production process. The waste water was typi-

cally treated by conventional precipitation and floccula-

tion processes. The plant was interested in finding alter-

native treatment processes to reduce cost. In a prelimina-

ry study the Research Institute for Water and Waste Ma-

nagement (FiW) compared different processes and estab-

lished the contact with Amafilter Deutschland GmbH.

Since 1997 not only ultrapure water for rinsing purposes

but also a high-quality zinc dichloride solution for the

process bath have been recovered. This is made possible

by prefiltration and downstream reverse osmosis

(Amafilter Deutschland GmbH), which works continuously

195

Start-up

Objectives


Modules


Pretreatment

Benefit

1997

Cheap alternative for reduction of the rinsing water quantity and treatment of the zinc-dichloride waste water

312 m2


4 m3/h

Prefiltration

Saving of precipitation agents and flocculants, freshwater, waste water and zinc dichloride


equalization oflosses

5m3/h

concentrate1m3/h

permeate4m3/h

zinc dichlorideevaporator

water bath lye bath parchmentizing bath 70% ZnCl2

reverse osmosis

Figure 3-15

Flow sheet of the process water treatment at the vulcanized fibre works GmbH & Co. KG

[AMAFILTER 2001]

Fibre Industry, Vulcanized Fibre


in the effluent of the water bath (Figure 3-15 and Figure

3-16). The spiral-wound modules with a total filter sur-

face area of 312 m2 treat a permeate volume flow of 4 m3

per hour, at an operating pressure of 25 bar. Practical

operation has shown that the service life of the mem-

branes is greater than three years (up to six years). When

the membranes had to replaced for the first time, another

type of membrane was chosen which resulted in an

increase of the capacity.

The permeate of the reverse osmosis installation has the

quality of fully demineralized water so that it can be re-

cycled to the water bath. The brine contains the zinc di-

chloride which is reused in the lye bath of the production

process.

Thanks to the financial backing of 50 % by a promotion

program3) of the federal state North-Rhine Westphalia, the

installation has been amortized after approx. four years.

The employment of the reverse osmosis installation in

continuous vulcanized fibre production as well as the

integration of other waste water flows and the cooling

water to reverse osmosis have economic and ecological

advantages. By closure of the water cycle the waste water

quantity was reduced by 80 % in total, and the freshwa-

ter demand by 90 % (about 18,000 m3 per year). Due to

this reduced demand, the costs for freshwater conditio-

ning (softening of well water) decreased.

Moreover, precipitation and flocculation agents are saved,

and through targeted recovery the zinc dichloride remains

in the production cycle, which minimizes the additional

demand for this chemical.

196

Figure 3-16

Reverse osomosis installation at the vulcanized fibre works Ernst Krüger GmbH & Co. KG [photo: AMAFILTER]

3) Promotion program (1997 – 1999) „Initiative ökologische und nachhaltige Wasserwirtschaft NRW“ (Action group Ecological and Sustainable Water

Management) [MURL 1996]

UF3.5.6


Since the beginning of the 20th century, special plastic

material has been produced by the company HT Troplast

AG in Troisdorf. Today the company has 1,500 employees

at this location, about 180 of them working in the Trosi-

fol branch, which produces safety-glass films for the car

industry and the building industry. In the course of the

production process, Trosifol, a flexible film on the basis

of polyvinyl butyral resin, is cooled. During this process,

undissolved plasticizers (oily) get into the cooling water.

To separate the plasticizers from the process water, the

company decided in 1998, after study of various proces-

ses and discussions with the company Amafilter Deutsch-

land GmbH, to commission an ultrafiltration installa-

tion with an upstream filter for the separation of coarse

matter (coarse filter, screen filter, cartridge filter). The

ultrafiltration installation is equipped with ceramic tube

modules fro the company atech innovations gmbh and

is completed with a heat exchanger for water cooling

(Figure 3-17).

The membrane surface area with a size of 38 m2 works in

cross-flow mode at an operating pressure of 4 bar and pro-

cesses a feed flow of 10 m3 per hour. 95 % of the inflow

are yielded as filtrate and fed back into the water cycle.

The concentrate is discharged by the waste water system.

The service life of the membranes is expected to be more

than 10 years.

Besides ecological advantages, the installation is also pro-

fitable. By reduction of the volume and the closed water

cycle, waste water costs and groundwater resources are con-

served, as the water consumption is reduced by 75 – 80 %.

Moreover, safe and low-maintenance process design has

contributed to the fact that the installation has been

amortized after 2.5 – 3 years, in spite of the rather high

investment of 348,000 Euro, which is due to full automa-

tion and corresponding control technology.

197

Figure 3-17

Ultrafiltration installation at the company

HT Troplast AG [photo: HT TROPLAST]

Plastics Industry, Troplast

Start-up

Objectives


Modules


Pretreatment

Benefit

1998

Recirculation of the cooling water which has come into contact with the product

38 m2


approx. 9.5 m3/h

Coarse filter, screen filter, cartridge filter

Saving of freshwater and reduction of waste water costs



3.5.7

Laundries

Waste water from laundries can be loaded with danger-

ous pollutants. At present, laundry waste water is typical-

ly discharged with or without previous treatment into

municipal waste water treatment plants. There are still a

few laundries which discharge the waste water without

treatment into receiving waters [GUTSCH, HEIDENREICH

2001]. For the treatment of low-loaded waste water from

laundries (e. g. washing of hospital and hotel textiles),

which is then recycled, membrane filtration processes are

often used in addition to biological treatment systems

and their combinations with chemical precipitation

[MENGE 2001]. Installations for closing the water cycle

in laundries comprise either a combination of microfil-

tration and nanofiltration or a reverse osmosis system

[MENGE 2001].

Appendix 55 of the Waste Water Ordinance [ABWV 2002]

is valid for waste water which is discharged directly into

a water body and whose pollution load mainly results

from washing of dirty textiles, carpets, mats and fleeces

in commercial enterprises and public institutions. For

waste water from dry cleaning of textiles, carpets and

products made from fur and leather, Appendix 52 of the

Waste Water Ordinance [ABWV 2002] is valid.

198

Laundry Alsco

Start-up

Objectives


Modules


Pretreatment

Benefit

2000

Waste water treatment

44 m2

Tube modules

6.5 m3/h

Vibrating screen

Pretreatment prior to nanofiltration


Start-up

Objectives


Modules


Pretreatment

Benefit

2000

Waste water treatment

180 m2

Spiral-wound module

~ 6 m3/h

Ultrafiltration

Savings of costs for freshwater and waste water discharge


UF NF3.5.7.1


Since May 2000, the company ALSCO has operated a

commercial laundry in Kaiserslautern. To separate the

partial flow, the laundry volume is allocated to special

engine groups which are connected by a pipeline system,

so that the waste water of the partial flows can be col-

lected and treated separately (Figure 3-18).

The waste water from the partial flow “mat cleaning/blue

laundry” consists of 30 m3/d of waste water from blue

laundry and 45 m3/d from mat cleaning. With a working

period of five days per week, the annual waste water quan-

tity from “mat cleaning/blue laundry” is 18,750 m3/a.

The partial flow “white laundry”, which comes from the

washing of work clothes, towels and flatwork, is about

95 m3/d. This waste water is collected and fed to a cooling

tower for temperature reduction, followed by neutralisa-

tion by means of CO2. The treated waste water of the

white laundry is discharged by the sewer system into a

municipal waste water treatment plant.

The waste water of the partial flow “mat cleaning/blue

laundry” is collected in an underground tank with a vol-

ume of approx. 5 m3. From there it is fed to a vibrating

sieve to separate fluff and other coarse particles. After

having passed the vibrating screen, the waste water is

cooled down to a temperature of 38 °C by a condensation

cooling tower and pumped into an aerated volume com-

pensating tank which holds approx. 65 m3. From there it

is fed into the activation reactor which also holds 65 m3.

After treatment in the activated sludge stage, the

waste water and the activated sludge are thickened in the

cross-flow ultrafiltration system to a solid matter content

of approx. 4 %. About 10 m3 of wet sludge per month are

discharged to a waste water treatment plant at a local

chemical industry.

The ultrafiltration plant (Figure 3-19) contains four

pressure pipes with 11 m2 of membrane surface area each

and two empty pipes for future expansion. The mem-

brane modules are equipped with organic tube modules

from the company Berghof with a free duct of 10.2 mm.

The permeate volume flow is approx. 6.5 m3/h.

199

blowerinstallation

washingwater neutrali-

sationwhitelaundry

recirculation

biologicalreactor

coolingtower sewer system

nano-filtration

ultra-filtration

wet sludgeconcentrate

concentrate tothe sewer system

process water recycling

tank

tankvolumecompensatingtank

coolingtower

blue laundryand mats

vibratingsieve

Figure 3-18

Flow sheet of the waste water treatment process in the laundry ALSCO

[according to WEHRLE UMWELT GMBH 2004]


The COD concentration in the waste water from mat

cleaning/blue laundry is 2,800 mg/L on an average and

maximally 5,000 mg/L. The COD concentration in the

permeate from the ultrafiltration system is between 80

and 150 mg/L. AOX compounds do not occur because

chlorine bleach liquor is not used in the washing process.

The permeate from the ultrafiltration meets the require-

ments according to Annex 55 of the Waste Water Decree

and can be discharged into the local sewer system. The

specific energy consumption of the ultrafiltration is

approx. 4.0 kWh per m3 of permeate.

To reduce the fresh water and waste water costs at the

laundry, the waste water treated by ultrafiltration is further

treated by nanofiltration and reused as washing water.

The single-stage nanofiltration plant is equipped with

spiral-wound modules from the company Desal. The per-

meate is used again as washing water. The concentrate

flow (10 – 15 m3/d), which meets the requirements for in-

direct dischargers and those made by the local waste water

statutes, is discharged together with the waste water from

the white laundry into the municipal waste water treat-

ment plant.

The costs of membrane cleaning have been determined

as approx. 1 – 2 Cent/m3 of waste water.

The service life of the membranes has been calculated as

4 – 6 years. With a service life of four years, membrane re-

placement costs of about 0.15 Euro per m3 of waste water

will become necessary.

According to the supplier of the plant (Wehrle Umwelt

GmbH), the specific operating costs of the ultrafiltration

system as sum of energy-, membrane replacement- and

cleaning costs are approx. 0.40 Euro per m3 of waste

water.

200

Figure 3-19

Membrane installation in the laundry ALSCO [photos: WEHRLE UMWELT GMBH 2004],

left: ultrafiltration installation, right: complete installation

UF NF3.5.7.2


At the site Groß-Kienitz, the textile service Mewa cleans

very dirty work clothes from the industrial branches

metal industry, mechanical engineering firms, motorcar

repair shops, etc. On account of legal constraints, the

waste water treatment process had to be upgraded in

1997. According to Annex 55 of the Waste Water Ordi-

201

Textile Service Mewa GmbH

Start-up

Objectives


Modules


Pretreatment

Benefit

1998

Closed washing water circuits

60 m2


~ 4 m3/h

Prefiltration / fluff sieve

Reduction of the fresh-water demand and savings of detergents


Start-up

Objectives


Modules


Pretreatment

Benefit

1998

Closed washing water circuits

135 m2


~1,5 m3/h

Ultrafiltration

Reduction of the fresh-water demand


prefiltrationbuffer andprecipitation

ultra-filtration 1

1,5 m3/hrecycling water 1for preliminary andgeneral washing

concentrate toexternal discharge

concentratestorage

ultra-filtration 2

sewer system

nano-filtration

1,5 m3/hrecycling water 2for process water

feed

Figure 3-20

Flow sheet of the treatment plant of Textile Service Mewa GmbH [according to ENVIRO CHEMIE 2004]


nance, heavy metals and hydrocarbons have to be re-

moved before the waste water can be discharged into the

public sewer system.

A treatment plant has been run since 1998 at the site of

the laundry. The treatment plant treats 100 m3 of laundry

waste water per day to such an extent that it can be re-

used in the washing process. Figure 3-20 shows the flow

sheet of the treatment plant.

After having passed a prefiltration and precipitation stage,

the waste water flows into the first ultrafiltration stage

which consists of six modules with 47 ceramic bars each

(Figure 3-21)

By filtration over the total membrane surface area of

approx. 60 m2, a permeate volume flow of approx. 4 m3/h

is attained. About 30 % of the permeate volume flow of

the ultrafiltration plant is reused as recycling water 1.

The quality required for the recycling water 1 is COD <

1,000 mg/l and a residual mineral oil content of < 20 mg/L.

Due to the residual organic load it can be used only to a

limited extent in the preliminary and main washing pro-

cesses. However, about 20 % of washing agents can be

saved thanks to the high detergent content in the recyc-

ling water.

The remaining permeate of the first ultrafiltration stage

further treated by a downstream nanofiltration stage con-

sisting of spiral-wound modules with a total membrane

surface area of 135 m2 (Figure 3-22)

About 1.5 m3 of permeate are produced per hour (recyc-

ling water 2). The recycling water 2 is treated to such an

extent (see Table 3-4) that it can be used for rinsing pur-

poses in the main washing process. Thus the freshwater

demand is lowered.

With this multi-stage waste water treatment process, the

total recycling efficiency of the waste water volume flow

is approx. 70 %.

202

Figure 3-22

Nanofiltration plant at Textile Service Mewa

[photo: ENVIRO CHEMIE 2004]

Figure 3-21

Ultrafiltration plant at Textile Service Mewa

[photo: ENVIRO CHEMIE 2004]


3.5.8

Metal Processing Industry

In the metal processing industry, metal surfaces and also

non-metal surfaces (as far as they become metallized) are

treated by aqueous solution, emulsions, slimes, and also

fused salts (mechanically, chemically, electrochemically

and thermally). The various waste waters resulting from

these processes are mainly loaded with inorganic pollu-

tants and characterized by their high metal content. In

addition, they contain organic substances such as mine-

ral oils (especially found in cutting fluids), varnish com-

ponents, mineral greases, chlorinated hydrocarbons and

other solvents.

For the discharge of waste water from the metal industry,

Appendix 40 of the Waste Water Ordinance [ABWV 2002]

as well as the requirements of the municipal statutes and

the Ordinance on Indirect Discharges are valid. Compli-

ance with the limit values is only possible after internal

treatment of the process waste waters, otherwise they

have to be discharged as hazardous waste, which is rather

expensive.

Lowering the costs for discharge and raw material is the

primary motive of an enterprise to buy an internal pro-

cess- or waste water treatment plant which at the same

time contributes to protect the environment. A possible

solution to reduce the waste water quantity to be dis-

charged and, with this, the discharge costs is the treat-

ment, i. e. concentration of the liquid waste by membrane

filtration and vacuum evaporation [SPECHT 1997]. The

resulting permeate may be recycled and used again in the

process. If permeate and concentrate are completely re-

used, the process is waste-water-free. However, it is not

possible to achieve waste-water-free operation “off the

peg”, because treatment techniques as well as auxiliary

material used in production, e. g. cleaning agents, have

to be coordinated and adapted to the production facili-

ties [SPECHT 1997]. Comprehensive preliminary tests

help to avoid mistakes and to save costs.

203

COD mg/L 100

Conductivity µs/cm 500

Bacteria colony-forming units/mL 100

Table 3-4

Quality of the recycling water 2 [Enviro Chemie 2004]

Parameter Unit Concentration


The Rasselstein Hoesch GmbH with its headquarters at

Andernach and production works at Andernach and Dort-

mund holds a top position among the European tinplate

producers. Tinplate is cold-rolled blackplate with a thick-

ness between 0.12 mm and max. 0.49 mm, which is main-

ly used as packaging material.

In the cold-rolling process, palm oil is used which has to

be removed before further processing by a degreasing

process. The waste water from this process is organically

loaded due to the palm oil. This waste and the waste

water from the cleaning of the degreasing facility, which

is necessary in regular intervals, and the new preparation

of the degreasing bath require considerable quantities of

degreasing agents.

These were the reasons for commissioning in 1999 an

ultrafiltration installation (Figure 3-23), in cooperation

with the company Membran-Filtrations-Technik-GmbH

(MFT). Ceramic tube modules working at an operating

pressure between 6 and 8 bar remove the palm oil from

the degreasing baths. The ultrafiltration membrane with

a surface area of 4.56 m2 processes a feed flow of 1 m3 per

hour. It is cleaned automatically after 120 hours (using at

first alkaline, then acid products, followed by backwash-

ing with water). The installation has been operating now

for 1.5 years (as of June 2001); the service life of the

membranes is expected to be five years.

The filtrate (about 90 % of the feed) is recycled as clean

degreasing solution directly into the bath, while the con-

centrate is fed to rolling grease treatment and afterwards

discharged thermally.

After some initial operating problems, the advantages of

the installation became evident: With constant process

bath quality, the waste water quantity is reduced thanks

to recirculation of 9 m3 per hour. In addition, drinking

water and chemicals are conserved. Also, the COD load is

reduced by 24 % and with this the discharge costs. Accord-

ing to calculations, the total investment of 358,000 Euro

will be amortized after 1.5 years.

204


Rasselstein Hoesch GmbH

Start-up

Objectives


Modules

Feed volume flow

Pretreatment

Benefit

1999

Reduction of the palm oil load in the waste water, i. e. the number of cleanings of the degreasing

facility and of new preparations of the degreasing baths are reduced

4.56 m2


1 m3/h (approx. 90 % of the feed are yielded as filtrate)

none

Saving of freshwater and chemicals, reduction of the waste water quantity and of the discharge costs


Figure 3-23

Ultrafiltration installation at the company

Rasselstein Hoesch [photo: MFT GMBH]

UF3.5.8.1

UF3.5.8.2


The flat plastic membranes with a molecular separation

size of 30.000 Dalton are wound on supporting structures

made from high-grade steel. The total filter surface area is

1.1 m2 and processes a filtrate flow of 0.3 m3 per hour, at

an operating pressure of 2 bar. The membranes are cleaned

twice a week and replaced after approx. 12 months. Since

the filtrate is recycled into the production process, only

the concentrate has to be discharged. With this operating

mode, the service life of the degreasing baths was extended

from two weeks to six months.

205


Faurecia, Bertrand Faure Sitztechnik GmbH & Co. KG

Figure 3-24

Ultrafiltration installation at the company Faure-

cia, Bertrand Faure Sitztechnik GmbH & Co. KG

[KASTEN 2001]

Start-up

Objectives


Modules


Pretreatment

Benefit

October 2000

Saving of costs by extension of the service life of the degreasing baths and ensuring of a constant product

quality

1.1 m2

Flat membranes wound on support structures made from high-grade steel

0.3 m3/h

Grease and oil separation

Saving of freshwater, waste water and degreasing chemicals as well as reduction of waste water levies


The company Faurecia Autositze GmbH & Co. KG has de-

veloped into an international business group which sup-

plies the car industry. Today the Faurecia group has about

100 works in 25 countries. In the works Stadthagen, about

800 employees produce metal fittings and seat components

(seat- and seat back frameworks) for the car industry.

Cathodic dip coating of the frameworks requires upstream

degreasing by special chemicals. The impurities removed

from the metal surfaces enter the degreasing bath and con-

tinuously reduce the cleaning efficiency, until the clean-

ing effect is no longer sufficient. At this stage, the degreas-

ing bath has to be replaced.

In order to save costs by prolongation of the service life

of the degreasing baths and to ensure a constant product

quality, the company Faurecia decided to use a process

combination with membrane technology. The waste water

from the degreasing of the seat frameworks is pretreated

in a tank in which fats and oils float, and heavy pollu-

tants as well as metal sludges are collected and separated

weekly via a special discharger. After a retention time of

three hours, the oil content in the oil-water mixture drops

to 0.2 %. The mixture is then fed to the ultrafiltration in-

stallation built by the company Atec Automatisierungs-

technik GmbH (Figure 3-24).

Since October 2000, the ultrafiltration installation sepa-

rates more oil quantities by means of a patent-protected

cross-flow process using agitators (Atec-Overflow-System).


Besides its ecological advantages, the ultrafiltration in-

stallation provides also economic benefit by saving de-

greasing chemicals, water and waste water. The demand

for chemicals was reduced by 85 %, the water demand by

water-free, as it serves to recover iron and to oxidize chro-

mium. Thanks to this installation by the company Ato-

tech, the service life of the chromium baths is theoreti-

cally unlimited.

In membrane electrolysis, a transport of charged parti-

cles through ion-selective membranes as well as electrode

reactions such as reduction or oxidation take place (see

Figure 3-25).

The ion-selective membrane separates the anolyte (chro-

mic acid) from the catholyte (polycarboxylic acid). Only

the cations, e. g. metallic impurities, are able to pass the

membrane. Due to the potential applied, the cations are

transported through the membrane to the cathode where

they are reduced and separated as metal. At the same time

the chromium (Cr3+) reduced during the chromizing pro-

cess is oxidized at the anode (Cr6+) and recycled. Since

this oxidation process goes faster than the ion transport

to the cathode, only a very small part of the chromium

passes the membrane.

In the electroplating enterprise Rudolf Jatzke at Bielefeld-

Sennestadt, managed since 1979 by the owner Klaus

Wickbold, 14 employees work in the field of hard chro-

mium plating. The work pieces, partly special models for

customers from all branches, are protected by chromium-

plating against wear and corrosion. During this process,

metal cations, especially iron and chromium(III), are

removed by etching from the surface of the workpiece

and get into the electrolyte. This has negative effects on

the quality and requires continuous cleaning or regular

discharge and new preparation of the highly toxic solu-

tions.

Up to now, a cation exchanger had been used to treat the

solutions, resulting in large quantities of waste water with

a heavy-metal load whose discharge required again large

quantities of chemicals. For this reason a membrane elec-

trolysis installation (called chromium dialysator) has been

developed in cooperation with the University of Bielefeld

and later with the University and Polytechnic of Pader-

born, promoted by Deutsche Bundesstiftung Umwelt, Os-

nabrück. This plant has been operating since 1993 waste-

90 %, and the discharge costs were reduced by 90 %, so

that the installation will be amortized after less than two

years, according to the calculation of the person respon-

sible for surface- and environmental technology.

206

3.5.8.3


Electroplating Enterprise Rudolf Jatzke

Start-up

Objectives

Membrane surface area 1)

Modules


Pretreatment

Benefit

1993

Extension of the service life of the electrolytic solution and reduction of the demand for chemicals

approx. 0.25 m2

2 cells per dialysator (standard)

no information

none

Saving of freshwater, reduction of the demand for chemicals, reduction of the heavy-metal sludge quantity

Membrane process Membrane electrolysis

1) The output of the chromium dialysator is not a function of the membrane surface area, but of the current quantity (the current density being the limiting

factor). If the current becomes too great, the membrane is destroyed.


Compared to the cation exchange installation used be-

fore, the yearly water de-mand is reduced by 28,000 m3

and the demand for chemicals by 25,000 kg. Only 750 kg

of harmless citric acid are used instead of 10,000 L of sul-

phuric acid. Also, 7.5 t of heavy-metal sludge are avoided.

Besides these environmentally relevant advantages, a re-

duction of the annual power consumption by 10 % results

from the conversion to continuous coating processes,

which also results in improved product quality.

In 1997, a European patent was issued for the membrane

electrolysis process. Membrane electrolysis is not only

applicable for chromium baths, but also for a large num-

ber of other processes (chromatizing, pickling).

In addition to the membrane electrolysis installation, the

company Jatzke is equipped with a computer-controlled

water cycle and vacuum evaporation system for the rins-

ing water. In 2000, the company Jatzke received the first

price of the Effizienz-Agentur NRW (EFA) for production-

integrated environmental protection.

207

anode

chromium bath (anolyt)

met

allic

po

lluti

on

s

cathode

membrane

Fe3+

Cu2+

Zn2+

Ni2+

(Cr3+)

Cr6+

Cr3+

Figure 3-25

Mode of operation of the electrolysis membrane

[SCHMIDT 2002]

UF3.5.8.4


The works Langenberg of the Wieland-Werke AG is a cold-

rolling mill where 361 employees are occupied with the

processing of rough-rolled belts from copper and copper

alloys to finished high-grade products (including for the

electronics industry).

After each rolling process, the belts are given the neces-

sary characteristics in annealing installations and acid-

treatment plants. Afterwards the surface of the belts is

cleaned mechanically by brushing machines. In the past,

the waste water from these brushing machines (about

80 m3/h) was treated jointly with other process waste

waters by neutralisation, precipitation/flocculation and

gravel filtration. A partial flow was recycled into the pro-

cess. In this configuration, 46 m3/h of waste water still

have to be discharged into the public sewer system and

have to be replaced by freshwater from a river.

In 1998, a concept for water saving was realized in the

works Langenberg which had been tested before in detail.

This was done in cooperation with the company Dr.-Ing.

Peters Consulting für Membrantechnologie und Umwelt-

technik (CMU), Neuss, and der RWW Wassertechnologie

GmbH, Nettetal, and with a financial subsidy from the

Land Nord-Rhine Westphalia4). According to this concept,

the waste water from the brushing machines is treated by

ultrafiltration in dead-end mode, after having passed a

paper belt- and a cartridge filter. Each of the four brushing

machines integrated into this concept forms an internal

“local” water cycle with an ultrafiltration installation

(Figure 3-26). The capillary modules from X-Flow have a

total filter surface area of 44 m2 and produce up to 6 m2

of filtrate per hour, at a transmembrane pressure of up to

max. 1 bar. The filtrate is reused in the brushing machines.

The particle-containing water (0.5 m3/h per installation)

from backwashing of the ultrafiltration is fed into the

internal water cycle. With this, the water quantity in this

cycle as well as the freshwater demand and the consump-

tion of neutralization and precipitation agents is reduced

by 60 %. The resulting sludge, which contains copper, is

used in the iron and steel industry.

208

Start-up

Objectives


Modules


Pretreatment

Benefit

1998

Water saving

44 m2

Capillary modules

up to 6 m3/h

Paper belt-, cartridge filter

Saving of freshwater and reduction of the waste water quantity


Start-up

Objectives

Modules


Pretreatment

Benefit

2001

Water savings

Cushion modules

approx. 24 m3/d

Ultrafiltration

Savings of completely demineralized water and reduction of the waste water quantity


4) Development program (1997-1999) “Action group for ecological and sustainable water management NRW“

RO

Metal Processing Industry, Wieland Werke AG

Figure 3-26

Ultrafiltration installation at the works Werk

Langenberg of Wieland Werke AG [MUNLV 2001]


After successful conclusion of a pilot test for the demine-

ralization of the filtrate from these ultrafiltration installa-

tions by low-pressure reverse osmosis, which was assisted

by ROCHEM UF-Systeme GmbH, Hamburg, and CMU,

Neuss, the water cycles at the brushing machines were

expanded in 2001 by corresponding RO installations.

These are equipped with the FM (flat membrane) module

(cushion module). The permeate is deionized as far as

possible so that completely deionized water, which is

very expensive, for the rewashing process can be saved.

The enterprise described above is the first cold-rolling

mill for non-ferrous metals which uses ultrafiltration in

dead-end operation and low-pressure reverse osmosis.

The use of these methods represents an improvement in

the state of the art for this field.

The environmentally relevant investments (229,800 Euro,

with a subsidy of the Land NRW of 100,000 Euro) are

profitable: Besides the waste water quantity which now is

only approx. 4 m3 per hour, the water consumption, too,

was clearly reduced (by up to 90 %) by internal recircula-

tion. Moreover, by ultrafiltration as well as low-pressure

reverse osmosis the particular and dissolved substances

are removed as far as possible from the individual water

cycles, so that the surfaces of the final products are of

constant high purity.

209

UF3.5.9.1


In the DaimlerChrysler AG plant in Düsseldorf, 5,400

employees are occupied with the production of goods

vehicles. The car bodies are painted by applying three

layers, each applied in a separate process. The second

paint layer, the so-called filler, absorbs rockfalls and

equalizes small anomalies in the bodywork.

In former times, the filler was sprayed on the car body

using a pressure-driven manual system. With this proce-

dure, half of the paint ended up as “overspray” beside

the car body and had to be discharged at high costs as

flocculated and dewatered paint sludge.

By conversion of the painting process, the percentage of

overspray was clearly reduced. At the same time, a water-

soluble paint was used which is applied in a closed cycle

and a paint recycling process.

The recycling installation from the company Eisenmann

Lacktechnik KG for water-soluble paint has been in ope-

ration since 1998. The ultrafiltration installation is an

important component of the process along with prefiltra-

tion and chemical conditioning (Figure 3-27). Plate mod-

ules made of polymer membranes (company Rhodia)

separate the paint particles from the water phase at an

operating pressure of between 3.5 and 4.5 bar.

Depending on the solid matter content, the membrane

surface area of 30 m2 processes a permeate flow of 1,060

to 1,400 L/h. The membranes are backwashed after one

or two weeks and cleaned chemically once a year. 10 % of

the membrane surface area is replaced per year. The fil-

trate is used to improve the quality of the circulating

water in the system, while the concentrate is reused as

recycled paint for the painting of car bodies.

The use of membrane technology for paint recycling

shows that ecological advantages may also be of econo-

mic benefit. Thanks to reprocessing, about 30 tons of

210

3.5.9

Treatment of Waste Water from Car Painting

Treatment of Waste Water from Car Painting, DaimlerChrysler AG

Start-up

Objectives


Modules


Pretreatment

Benefit

1998

Reduction of the discharge costs for paint sludges

30 m2

Plate modules

1.0 – 1.4 m3/h

Prefiltration, chemical conditioning

Saving of paint, reduction of hauls because paint sludge is no longer produced


Figure 3-27

Ultrafiltration installation in the DaimlerChrysler

works at Düsseldorf [HARMEL 2001]

NF3.5.9.2


paint are saved per year. Moreover, the discharge of the

50 tons of paint sludge (70 % of this paint line) produced

up to now is no longer necessary, which means that dis-

posal costs are saved. Besides the environmentally rele-

vant aspects, these savings are so great that the invest-

ment of nearly 358,000 Euro will be amortized probably

after 3.5 years.

211

Treatment of Paint Waste Water from the Production of Spare Parts in the Ford Works, Cologne

Start-up

Objectives


Modules


Pretreatment

Benefit

2001

Recycling of valuable substances, Reuse of the permeate and the concentrate in the production process

No information

No information

~ 2 m3/h

Fine screen

Reduced fresh-water consumption, lower waste water loads, reduced chemicals cost, lower total costs


concentrate for discharge

car components to be painted

UF NFRO UF

rinsing bathsrinsing bathsrinsing bathsdegreasing phospating

1st step: degreasing 2nd step: phospating 3rd step: painting

cathodicdipcoat

Figure 3-28

Flow sheet of paint-spraying [IMB + FRINGS WATERSYSTEMS GMBH 2004]


212

After degreasing, the car components are phosphated and

then flushed. The process waste water from flushing have

been treated since 2001 by a nanofiltration plant. One

objective is the recycling of heavy metals and phosphates.

Thus, the concentrate is used as replenisher for phosphat-

ing. The permeate is used with additives to flush the car

components after degreasing. Approximately 2 m3/h of

process waste water is treated by the nanofiltration plant

(Figure 3-29). The service life of the membranes is approx.

3 years.

Thanks to the operation of the nanofiltration plant, fresh-

water and chemical consumption were lowered and the

waste water load was reduced. The total costs of the pro-

cess were lowered by 15 %.

The process concept presented above comprises as a final

step the recirculation of the anolyte in paint-spraying

(cathodic dipcoat) by single- or multistage reverse osmo-

sis and the prolongation of the service life of the dipcoat

bathes by treatment of the liquid by means of an ultrafil-

tration plant. The realization of these measures for further

reduction of the fresh-water and chemical demand is in

the planning stage.

Especially in the car industry it is useful to treat and to

recycle single process water flows because small volume

flows can be treated effectively and valuable substances

can be recovered. These valuable substances are found,

among other places, in the process water flows resulting

from the paint-spraying of car components.

The company imb+frings watersystems gmbH has devel-

oped in cooperation with Henkel Surface Technologies a

process concept for the recycling of water and valuable

substances from paint-spraying for the Ford works in

Cologne. The concept provides separate treatment for

each of the process water flows from degreasing, phos-

phating and paint-spraying (Figure 3-28). The treatment

of waste water from phosphating by nanofiltration

has been already implemented.

The process waste water from the degreasing bath for

cleaning of the car parts are treated by an ultrafiltration

plant. The permeate is used for flushing. Thus the fresh-

water and chemicals consumption can be reduced. The

concentrate is discharged as waste water.

Figure 3-29

Nanofiltration plant at the Ford works Cologne

[photo: IMB + FRINGS WATERSYSTEMS GMBH 2004]

UF3.5.10


The foundations for the company Schering were laid in

1851 by Ernst Schering who opened the “Green Pharma-

cy” in the north of Berlin. Today Schering AG employs

approx. 26,000 people in 140 subsidiaries in the develop-

ment and production of drugs as a main field of activity.

At the Bergkamen site, active agents are made as a basis

of drug production. Due to changing batch production,

the composition of the waste water varies depending on

the production process. Until 2003, the waste water was

temporarily stored after pretreatment in a mixing and

equalizing tank and then discharged into the nearby

municipal waste water treatment plant.

To ensure waste water treatment according to the state of

the art and satisfying the quality requirements of the re-

ceiving water body, Schering AG tested the possibility of

an industrial waste water pretreatment plant with mem-

brane bioreactor technology. This process turned out to

be economically end ecologically efficient. The membrane

installation, which is nationwide the largest for the treat-

ment of industrial waste water, has been in operation since

2003 (see Figure 3-30). Since 1st July 2004, the treated

waste water has been discharged directly.

The membrane bioreactor at the Bergkamen site treats on

average 3,500 m3 of waste water per day. Its composition

is presented in Table 3-5.

213

Pharmaceutical Industry, Schering

Start-up

Objectives


Modules


Pretreatment

Benefit

2003

Optimized waste water treatment according to the state of the art

15,840 m2

Cassettes/capillary membranes

~ 150 m3/h

Primary settling

Reduction of waste water disposal costs


Figure 3-30

Aerial photograph of the waste water treatment plant at Schering AG [photos: SCHERING AG 2004],

left: general view, right: side view of the membrane installation


Figure 3-31 shows the flow sheet of the waste water treat-

ment. The first stage consists of to primary settling tanks

connected in series with a volume of 1,000 m3 each. They

serve to neutralize the waste water, to dose precipitants

and flocculants and to separate solids and precipitation

products.

The three-line activated sludge stage with a total volume

of 9,000 m3 is realized with upstream denitrification and

nitrification, followed by the membrane installation with

four lines. The membrane installation consists of 36 mem-

brane cassettes of the type ZW 500c from the company

ZENON (Figure 3-32). It has a total membrane surface

area of 15,840 m2. After membrane filtration, the treated

waste water is discharged into the receiving water.

214

Table 3-5

Inflow values, effluent requirements and operating values of the plant [SCHERING AG 2004]

Parameter Unit Inflow (mean values) Effluent requirements* Operating values

COD mg/l 3,500 > 90 % reduction compliance with the requirements

BOD5 mg/l 1,500 below detection limit

Ntot mg/l 95 < 50 mg/l compliance with the requirements

Ptot mg/l 8 < 2 mg/l compliance with the requirements

* according to Annex 22 of the Waste Water Ordinance

waste water

recirculation

membrane stage

nitri-fication

denitri-fication

waste waterbuffer tank

neutralisationand primarytreatment stage

emergencycatchbasin

excess sludge

sludgestorage

receivingwater

Figure 3-31

Flow sheet of the waste water treatment plant [according to SCHERING AG 2004]


Two aerated sludge storage tanks with a total volume of

1,700 m3 have been built to manage the excess sludge.

Three tanks with a total volume of 20,500 m3 are available

as emergency catch basins.

The investments for the new construction of the plant,

which mainly comprised the activated sludge tanks and

the membrane installation, were approx. 10 million Euro,

1.6 million Euro of which had been granted as funds by

the state North-Rhine Westphalia.

Besides gas and odour, landfill leachate is one of the main

emissions from landfills for municipal waste. During the

amendment of the Federal Water Act in 1986, it has been

defined for the first time as “waste water which has to be

treated” [HENSS, OPITZER 1995]. In general it is highly

polluted by organic and inorganic matter, and the load

may vary considerably over the life of the landfill.

Various processes and process combinations exist for the

treatment of landfill leachate [ATV 1993, VDMA 1994] to

produce a permeate which can be discharged without

restriction (Waste Water Ordinance, Appendix 51 [ABWV

2002]). Often a single process is not sufficient to achieve

the desired result.

During the last years, two process combinations for the

treatment and processing of landfill leachate have domi-

nated [PETERS 1996]:

• the combination of a biological stage and oxidation or

activated carbon (Figure 3-33) and

• the combination of reverse osmosis, high-pressure re-

verse osmosis; if necessary nanofiltration and discharge

of the residues.

Besides these process variations, others are also used, e. g.

the extension of the biological pretreatment stage (from

the first bullet) by an integrated membrane stage.

The reverse osmosis process belongs to the state of the

art in leachate treatment [ATV 1993]. Many years of con-

tinuous operation of numerous large-scale installations

prove that the organic and inorganic constituents present

in dissolved form in the leachate can be separated by 98 –

99 % with the help of reverse osmosis, at relatively low

expense, if modules and installation systems are adapted

215

3.5.11

Miscellaneous

3.5.11.1

Landfill Leachate

Figure 3-32

Optical inspection of a membrane module

[photo: SCHERING AG 2004]


216

biological pretreatmentraw leachate membrane process

(reverse osmosis/nanofiltration)

oxidation

activated carbon

recycling

controlled infiltration into the landfill body,for a certain time and locally limited

incinerationevaporation

dryingintegration

elimination

residue

treated leachate

concentrate

gravel filterraw leachate

residue

treated leachate

nitrogenremoval

incineration

integration

nitrogencompound

residue

membrane process(reverse osmosis)

evaporation

activated carbon

controlled infiltration into the landfill body,for a certain time and locally limited

recycling

concentrate

elimination

Figure 3-34

Process combination according to the state of the art for the treatment of landfill leachate

using membrane processes with and without biological pretreatment

[completed according to ROSENWINKEL, BAUMGARTEN 1998]

carbon source

biological pretreatmentraw leachate

oxidation (ozon)

treated leachate

regeneration

activated carbon

energyexcess sludge

Figure 3-33

Process combination according to the state of the art for the treatment of landfill leachate

without using membrane processes [ROSENWINKEL, BAUMGARTEN 1998]


to the specific problem [PETERS 1998, PETERS 2000].

Operating results obtained with semi-industrial and large-

scale membrane installations for leachate treatment have

been documented and analyzed by BAUMGARTEN [1998].

Studies realized by THEILEN [2000] have shown that a

combination of conventional filtration (bag or cartridge

filter) and one or two membrane stages is very well suited

for the treatment of raw leachate. By means of a first mem-

brane stage (e. g. cushion or tube modules) and a second

stage which is possibly required (cushion or spiral-wound

modules), a permeate is produced from the high-loaded

leachate which has nearly surface water quality. Figure

3-34 presents process combinations for the treatment of

landfill leachate using membrane processes (reverse osmo-

sis, nanofiltration) with and without biological pretreat-

ment according to the state of art.

However, in leachate treatment, too, membrane processes

meet with their limits due to the development of irrevers-

ible covering layers. Since the leachate matrix is very

complex, these process limitations cannot be determined

on the basis of analytical results, but have to be deter-

mined onsite for each individual leachate [ROSENWINKEL,

BAUMGARTEN 1998].

Using membrane technology, there are three alternative

strategies for managing the leachate concentrates

[PETERS 2000]:

• incineration of the concentrate in installations which

are especially equipped and certified for the discharge

of high-loaded liquids,

• integration of the concentrate into various materials,

followed by deposition of the dry residues on the land-

fill,

• controlled infiltration of the concentrate into the land-

fill body (for a certain period and locally limited) in

order to improve the biochemical degradation process

of the organic waste and to accelerate the immobilisa-

tion of the organic material.

The third alternative leads to an increase of the gas pro-

duction and, with this, to accelerated reduction of the

organic material in a landfill. Comprehensive studies as

well as knowledge acquired from many years of experi-

ence confirm that over the long term no noticeable

changes in the leachate quality are observed [PETERS

2000].

217


The company Abfallwirtschaft Kreis und Stadt Aachen

GmbH (AWA) (Waste Management for the District and

the City of Aachen) operates the central landfill Alsdorf-

Warden (commissioned in 1976), where only inorganic

waste is deposited. Within the scope of its capacity, the

central landfill also accepts inert material from external

corporations.

For leachate treatment, two installations are used. One of

them is a two-stage reverse osmosis installation which is

described in the following.

The two-stage reverse osmosis installation (Figure 3-35)

for leachate treatment is owned and operated since 1995

by the company Pall.

Both stages are equipped with so-called DT modules (disc

tube modules) from the company Pall. To protect the

installation, a gravel filter for the separation of coarse

matter and a cartridge filter are arranged upstream. The

installation comprises 60 modules in total, 44 of which

are used in the leachate stage, 13 in the first concentrate

stage (120 bar) and 3 in the second concentrate stage

(150 bar). Each module has a membrane surface area of

approx. 7.6 m2, so that a total membrane surface area of

about 460 m2 is available. At present, 5 m3 of leachate are

treated per hour, 92 – 95 % of which is yielded as per-

meate. The permeate is fed to the waste water treatment

plant, and the brine is discharged externally.

The membranes used are composite membranes with an

active layer from polyamide (Figure 3-36). Cleaning of

the membranes is required once or twice a week. Replace-

ment of the membrane has not yet been necessary since

starting up the installation.

Landfill leachate is treated exclusively for ecological rea-

sons. Thus the benefit of the two-stage reverse osmosis

system is ensuring environmentally oriented operation

and possible aftercare of the landfill.

218

Alsdorf-Warden Landfill

Start-up

Objectives

Membrane surfacee area

Modules


Pretreatment

Benefit

1999

Treatment of the leachate, and thus protection of the landfill

approx. 460 m2

Disc tube modules

approx. 4.8 m3/h

Gravel filter for separation of coarse matter and gravel filter

Ensuring of the leachate treatment

Membrane process Two-stage: reverse osmosis, high-pressure reverse osmosis

Figure 3-35

Reverse osmosis installation at the landfill Alsdorf-

Warden [MAURER 2001]

RO3.5.11.1.1

ultra-thin active layerfrom modified polyamide

microporous intermediate layerfrom polysulfone

0,2 µm

supportingfabric frompolyester

40 µm

120 µm

Figure 3-36

Structure of the composite membrane [MAURER 2001]


In North-Rhine Westphalia there are many other sites

(e. g. Essen, Cologne, Mönchengladbach) where landfill

leachate is treated by membrane technology and biologi-

cal treatment or other processes (e. g. adsorption on acti-

vated carbon).

219

MF3.5.11.2


Since the middle of the seventies, considerable efforts

have been made in the field of fresh-water aquaculture to

develop innovative, non-polluting and resource-conserv-

ing technologies for economic and environmentally

compatible intensive fish hatchery The development of

so-called closed-circuit plants was of special importance.

Since the middle of the nineties, the membrane bioreac-

tor technology has been available as an innovative pro-

cess for the realization of closed-circuit plants. The suita-

bility of this process for the treatment of waste water from

fish hatcheries was confirmed by studies with a pilot plant

membrane bioreactor (see Figure 3-37) that was installed

on the test facility of the Umweltbundesamt at Berlin-

Marienfelde.

The pilot plant consists of a tank for fish hatchery, which

is approx. 4 m high and made from fibreglass-reinforced

plastic, and the treatment plant. A pump feeds the water

together with the settled sediment (throughput: 1.7 L/s)

in intervals from the tank into the denitrification stage,

which consists of three PE tanks equipped with agitators.

The volume of the denitrification stage can be adjusted

to satisfy the requirements of the test operation by a ver-

tically adjustable overflow. Thus, the volume in the deni-

trification stage can be varied between 0.4 and 1.4 m3.

Nitrification takes place in the membrane stage with a

volume of approx. 1 m3. This tank contains the membrane

module consisting of 35 filter plates with a total filter

surface area of 21 m2. The pore size of the membranes is

0.4 µm. Below the filter module, air exhaust devices are

arranged which serve to clean the filter surface area and

to supply the sludge with oxygen. A second module exists

which can be used to double the filter surface area.

To ensure an internal sludge circuit between nitrification

and denitrification, the circulation pump feeds sludge

from the filter tank into the denitrification stage.

The permeate pump sucks the treated water through the

membranes and recycles it into the fish hatchery tank.

The pump operates constantly, apart from regular pauses

serving for better cleaning of the filter surface areas. The

water exchange rate for the fish hatchery tank is deter-

mined by the turn-on and pause times of the pump and

on the volume flow which can be chosen between 1 and

8 m3/d.

The excess sludge and the waste water flow from the fish

hatchery tank which is not recycled are discharged into

the waste water treatment plant.

The work up to market maturity is continued in a project

of Deutsche Bundesstiftung Umwelt (DBU) (German Fede-

ral Foundation Environment).

220

Fish Hatchery

Start-up

Objectives


Modules


Pretreatment

Benefit

2004, pilot plant

Reuse of the waste water / closure of water circuits

21 m2

One-decker plate modules

~ max. 8 m3/h

Not necessary

Savings of costs for fresh water and waste water discharge


UF3.5.11.3


The Dresden gas and steam turbine heating power station,

Nossener Brücke, was built in 1995. It has an electric out-

put of 270 MW, a thermal output of 455 MW of heating

water and 25 MW of steam. Since 1997 the power station

belongs to the DREWAG. In the middle of the operating

year 1996, turbine oil got into the long-winded and

branched intermediate cooling water system of the power

station. This free oil has deposited at different heat-ex-

changing surfaces which resulted in deterioration of the

heat transfer and thus of the cooling performance of in-

dividual pieces of equipment.

221

tank

membrane stagenitrification stage

recirculation

DN 1 DN 2 DN 3

denitrification stage

recycling flowfresh water

blowerinstallation

waste water totreatment plant excess sludge

Figure 3-37

Flow sheet of a circuit installation for the treatment of waste water from fish hatchery

[UMWELTBUNDESAMT 2004]

Power Stations, Dresden Gas and Steam Turbine Heating Power Station (GuD)

Start-up

Objectives


Modules

Filtrate volume flow

Pretreatment

Benefit

1996

Cleaning of oil-contaminated cooling water or heating circuits by separation of emulsified oil from the

circuit water by means of ultrafiltration

15.2 m2

Ceramic multichannel elements

Up to 2.5 m3/h

Cartridge filter < 1 µm

Rehabilitation of the cooling or heating capacity of oil-contaminated cooling or heating circuits

without downtimes of the power station



Exchange of the cooling water quantity of approx. 90 m3

and flushing of the cooling water system would not have

been sufficient to clean the cooling system because it con-

sists of pipes of various diameters and different aggregates

with hydraulic dead zones. Alternatively, it would have

been necessary to change out all components of the pro-

cess equipment separately and to flush them. Besides the

expenditure for cleaning of the individual aggregates,

temporary shut-down of the power station would have

been required.

In order to solve the problem, a process was developed

jointly by the THERM-SERVICE für Kraftwerke und Indus-

trie GmbH and the DPC, Dr.-Ing. Peters Consulting für

Membrantechnologie und Umwelttechnik, using the

module technology of atech innovations GmbH. This

patented process was introduced under the designation

“RÖKU (Reinigung ölkontaminierter Kühlwasserkreisläu-

fe mit Ultrafiltration und Emulgierung bei laufendem

Blockbetrieb – Cleaning of oil-contaminated cooling

water circuits by ultrafiltration and emulsification at

running block operation)”. Compared to the conventional

procedure, the costs are lower and cost-intensive down-

times are avoided. Figure 3-38 shows the flow sheet of

the RÖKU process.

A RÖKU plant is conceived as a mobile unit and can be

adapted with high flexibility to the local condition. It

consists of the main components prefiltration, raw water

storage tank, ultrafiltration unit (Figure 3-39) with four

modules connected in series with 3.8 m3 of membrane

surface area each, circulation tank, filtrate tank, and a

CIP device for cleaning of the membranes.

In the case of the Dresden gas and steam turbine power

station, the oil sticking to the surfaces of the cooling wa-

ter circuit was emulsified with the help of a specifically

chosen emulsifier which was added to the cooling water.

This emulsion was treated by the ultrafiltration unit con-

nected in bypass. It is equipped with ceramic membranes

and operated in cross-flow mode. The treatment took

place in batches. The permeate, which still contained

part of the emulsifier, was recycled into the circuit. The

concentrate, in which the oil micro-droplets separated

from the emulsion, was discharged. In this way, about

1,600 L of oil were removed from the intermediate cool-

ing water circuit of the Dresden gas and steam turbine

heating power station. After having attained the desired

residual oil content, the emulsifier is removed from the

circuit water, which is accordingly conditioned.

222

cartridge filter

ultra-filtration

raw waterstorage

cooling watercirculation oil-loaded cooling water

circulationtank

permeatetank

oil discharge

cooling water without oil

concentrate

emulsifier

Figure 3-38

Flow sheet of the RÖKU process [according to DPC 1997]

UF3.5.11.4


Other examples for the use of this ultrafiltration-based

process were the rehabilitation in the heating power sta-

tion Zolling of Isar-Amper Works in 1997 (separation of

approx. 1,000 L of lubricating oil from the intermediate

cooling water circuit with a content of 300 m3) and in

1998 the cleaning of an intermediate cooling water cir-

cuit with a content of 130 m3 and 400 heating elements

in a hospital at Rottweil (removal of 2,600 L of lubricat-

ing oil).

Various types of oily residues result from navigation (in-

land or other navigation), which accumulate in the bilge,

the deepest place in the machine room of a ship. This

oily waste water, called bilge water, is a mixture of oil,

lubricating grease, fuel residues, cooling water, condensed

water, antifreeze and anticorrosive agents, cleaning agents,

as well as river or sea water in unknown concentrations

[FURTMANN ET AL. 2001]. Therefore, the bilge water has

to be pumped out periodically, i. e. the oil-water mixture

from the bilge has to be eliminated. In the past, the bilge

water was pumped out into a water body, but this has

been prohibited since 1963.

223

De-oiling of Bilge Water

Start-up

Objectives


Modules


Pretreatment

Benefit

1989

Discharge of bilge water

23.6 m2

Tube modules

3 m3/h

Oil separation

Saving of volume on the ship, contribution to environmental protection


Figure 3-39

Ultrafiltration unit for the RÖKU process

[photo: THERM-SERVICE]


In order to ensure the discharge of the bilge waters, the

riparian Federal States of river Rhine have established in

1965 the Bilgenentwässerungsverband (bilge drainage as-

sociation). This is a corporation under public law, which

is under legal supervision of the Land North-Rhine West-

phalia. To fulfil its duties, the association makes use ot

the Bilgenentölungsgesellschaft mbH (bilge de-oiling

company), which accepts and treats the bilge water free

of charge from all ships (independent of their country of

origin).

The Bilgenentölungsgesellschaft mbH was established in

1961 and employs 25 people. It is responsible for bilge

de-oiling of all inland navigation ships in the Federal

Republic of Germany south of Münster. (For Hamburg,

Bremen and Berlin, other institutions have taken over

this task.) The company operates several bilge de-oiling

boats which separate the oil from the water phase by

gravity separators and, in addition, since 1989, by ultra-

filtration.

The bilge water is sucked off and preseparated by a cas-

cade oil separator (see Figure 3-40). The oil phase is col-

lected in a tank and, according to the water content,

reprocessed or submitted to thermal treatment. The ther-

mal treatment is performed by other companies.

The water phase is fed to an ultrafiltration system (from

the company Berghof) operated in cross-flow mode. Tube

modules with polymer membranes and a molecular sepa-

ration size of 100,000 Dalton separate more oil from the

water phase at an operating pressure of 7 bar. The total

membrane surface area (23.6 m2) produces 3.0 m3 of fil-

trate per hour, which according to the permission of the

responsible water authority complies with the limit

values and is discharged directly into a water body.

The concentrate is fed again to the ultrafiltration system

and is further concentrated. After several passes, only a

few litres of oil-containing concentrate are left which are

also collected in the oil tank and either reused or dis-

charged. Depending on their operation, the membranes

are backwashed once or twice a week. Practice has shown

that the service life of the membranes is about 15,000

operating hours.

224

ultrafiltration

concentrate

recirculation after closingthe influent

separator

permeate

sucking-offfrom the bilge

oil phase

collecting tank forused oil

water phase

deliveryashore

Figure 3-40

Flow sheet of bilge de-oiling [according to DEUTSCH 2001]

UF RO3.5.11.5.1


3.5.11.5

Swimming Pools

In swimming-pool water, in addition to small pollutants,

also water-soluble and emulsifiable substances (e. g. sweat,

residues of skin cream and suntan lotions) accumulate

and must not exceed certain concentrations. In usual

swimming-pool operation, this is managed by dilution

with drinking water which is pumped into the filled pool.

Due to this pumping and water displacement by bathing

people, water – splash water – flows off via the overflow

launder into a splash-water tank. After having passed a

conditioning facility, the filtered water is fed back into

the swimming-pool.

From time to time the filter has to be cleaned by back-

washing (mostly with splash water). The sludge water

from backwashing is collected and discharged into the


Between 30 L [DIN 19643] and 120 L of water per guest

are consumed by discharge of water into the sewer sys-

tem and addition of fresh drinking water.

Due to water evaporation and refilling, the water hard-

ness, consisting of lime and magnesium salts, increases.

From chlorination and correction of the pH, other salts

develop. Moreover, big swimming-pool companies with

brine pools face the problem that brine is carried over to

the normal swimming-pool water.

Established in 1998, the city of Würselen is 100 % respon-

sible for this leisure facility with 30 employees.

In order to reduce the large freshwater quantities which

are necessary in conventional filtration, an ultrafiltration-

and reverse osmosis installation (degebran® GmbH Anla-

genbau) was planned and commissioned in 1998 in the

course of the new construction of Aquana Freizeitbad.

The plant is not integrated into the pool-water cycle, but

serves to recover about 70 % of the large water quantity

which is necessary for backwashing of the sand filters.

For this purpose, two membrane filtration stages operate

in series to treat sludge water (from filter backwashing),

shower water, water from washbasins and rainwater. In

addition they remove substances such as organic chlorine

compounds, washing and cleaning agents and urine com-

ponents (Figure 3-41). The membrane systems operate in

cross-flow mode. After prefiltration, back-washable capil-

lary membranes with a total filter surface area of 72 m2

separate in the first ultrafiltration stage solid pollutants

and suspended substances. From this filter cycle, 10 % of

concentrate is continuously withdrawn and discharged as

waste water. The filtrate is fed to the second stage, the

225

Swimming Pool, Aquana Freizeitbad GmbH & Co. KG

Start-up

Objectives


Modules


Pretreatment

Benefit

1998

Reduction of the freshwater quantities needed

42 m2 (UF), 140 m2 (RO)

Capillary modules (UF), spiral-wound modules (RO)

In total (UF and RO) 5 m3/h

Prefiltration

Saving of freshwater and energy for heating

Membrane processes Ultrafiltration (UF), Reverse osmosis (RO)


reverse osmosis installation, where spiral-wound

modules (140 m2 filter surface area) also reject dissolved

substances. The permeate of this second stage is recycled

via activated-carbon adsorption into the swimming-pool

water cycle, while the brine, which contains more salts,

is used as process water. The total capacity of the system

is 5 m3 per hour.

Thanks to this process, up to 80 % of the freshwater

quantity used before, needed as filling water, is saved.

In addition the energy demand is reduced because it is

possible to recycle the permeate in warm state into the

pool cycle without additional heating. The amortization

period of the investment of 383,000 Euro is calculated at

three years.

226

ultrafiltration

concentrate

reverse osmosis

brine as processwater

filtrate

activated carbonadsorber sludge water

showerwaste

splash water tank

rainwaste

raw water

swimming-pool

normal operation filter backwashing

permeate

prefilter

clean water

overflowchannel

Figure 3-41

Water recirculation and treatment at the Aquana Freizeitbad [according to DEGEBRAN ®]

UF3.5.11.5.2


The Freizeitbad Copa Ca Backum (leisure facility) is oper-

ated by the Hertener Stadtwerken GmbH (municipal ser-

vices). With the objective to reduce the freshwater de-

mand and to ensure a hygienic water quality, the Herte-

ner Stadtwerke GmbH and the L.V.H.T.-Institut5), Essen

(scientific assistance) developed a process for the treat-

ment of waste waters from public swimming-pools and

commercial plants. Since August 1998, this process com-

bination, which includes membrane technology, has been

used in the Freizeitbad Copa Ca Backum for the treatment

of pool water, sludge water and shower water.

The used water from bathing and part of the shower water

are collected in a raw-water tank, where particulate sub-

stances settle and are separated by a screen (Figure 3-42).

The downstream ultrafiltration installation serves for

pre-liminary treatment of the combined process water.

Polymeric hollow-fibre membranes (Pall system) separate

in dead-end mode undissolved particles and turbidity as

well as oils, fats and ointments, so that only dissolved

substances are fed to the following process stages. In

total, the six modules with a filter surface area of 50 m2

each process a permeate volume of 10 m3 per hour.

To remove the developing covering layer from the mem-

brane, backwashing every half hour (by reversing the flow),

combined with air cleaning (hourly), is necessary. Che-

mical (alkaline) cleaning of the membranes is performed

every four weeks. With this operating mode, the service

life of the membranes is expected to be five years.

After additional treatment stages (oxidation as well as

adsorption on activated carbon and final disinfection

with chlorine), the filtrate has drinking water quality. It

is collected in a storage tank and used as pure water for

filling of the swimming pool or for filter backwashing.

The sludge water from filter backwashing is discharged

into the raw-water tank and flows together with the used

pool water and the shower water through the treatment

cycle described above. Water losses resulting from the

treatment and through evaporation or carry over in the

bath are compensated for by feeding freshwater.

Although freshwater is regularly fed, the salt content in

the swimming-pool water may increase by up to 10 – 15 %

in a year, due to recirculation of the backwashing water

and evaporation losses. But this is not relevant since ac-

cording to DIN 19643 the complete pool volume must be

exchanged once a year.

227

Swimming Pool, Freizeitbad Copa Ca Backum

Start-up

Objectives


Modules


Pretreatment

Aftertreatment

Benefit

August 1998

Reduction of the freshwater quantity needed and ensuring disinfected water

300 m2

Hollow-fibre membranes

10 m3/h

Sedimentation, particle separation by screening

Oxidation, adsorption, disinfection

Saving of freshwater and energy


5) L.V.H.T.- Lehr- und Versuchsgesellschaft für innovative Hygiene-Technik mbH, Institut für angewandte Bau- und Bäderhygiene GmbH, Essen


In the process combination presented above, the mem-

brane technology is only employed as an upstream treat-

ment stage. The economic advantages, such as savings of

freshwater and energy, are therefore related to the whole

system. With adherence to freshwater savings of 60 %

and the forecasted energy savings of 50 %, the plant will

be amortized after approx. 3 – 5 years.

228

oxidationultrafiltrationfiltrate

final disinfection

swimming-pool

adsorption

raw water storage tanksludge water frombackwashing

sludge water

shower water

backwashing water

filling water

Figure 3-42

Water treatment at the Freizeitbad Copa Ca Backum [according to L. V. H. T. 2001]


229

3.6

Sample Applications of Plants Outside of Germany

The use of different membrane processes in Germany is

described in the subsections of chapter 3.5. The subsec-

tions of this chapter deal with examples from internatio-

nal practice. The examples are sorted in the same way as

in chapter 3.5 according to the branches of industry in

which the installations are used. All examples described

in the following are listed in Table 3-6.

Food industry

Chemical

industry

Food industry

Food industry

Malthouses

Laundries

Pharmaceutical

industry

Animal carcass

disposal

Mechanical-bio-

logical waste

treatment

Table 3-6

Sample applications for the use of membrane technology in industrial waste water treatment outside of

Germany

Branch of

industry

Kellogg

Raisio Chemicals

Dairygold

Dairy Crest

Sobelgra n. v.

Laundry Massop

Sandoz/

BIOCHEMIE

SARIA

Tirme

Company

Manchester

(Great Britain)

Veurne

(Belgium)

Mitchelstown

(Ireland)

Davidstow Camel-

ford Creamery

(Great Britain)

Antwerpen

(Belgium)

Kerkrade

(The Netherlands)

Barcelona

(Spain)

Bayet

(France)

Mallorca

(Spain)

Location

2004

2004

2000

2003

2004

1998

2003

2000

2004

Start-up

UF

UF

UF

UF

UF

RO

MF

UF

UF

Membrane

process

Tube modules

Immersed

rotating plate

modules

Tube modules

Tube modules

Immersed capil-

lary modules

Spiral-wound

modules

Immersed plate

modules

Immersed capil-

lary modules

Tube modules

Modules

5 � 216

1,188

648

486

8,000

250

1,440

1,800

100

3.6.1.1

3.6.1.2

3.6.1.3

3.6.1.4

3.6.1.5

3.6.2

3.6.3

3.6.4.1

3.6.4.3

ChapterMembrane sur-

face area m2


3.6.1

Food Industry

Muesli Production at the Kellogg Company,

Great Britain

Depending on the production batch, the waste water

may contain solids which are removed by a rotary screen.

However, cocoa powder cannot be separated by sieving.

In this case, the waste water containing cocoa powder is

detected by turbidimetry and is subsequently fed into a

decanting centrifuge for the separation of solid matter.

The liquid phase is fed to the biological treatment stage

where the dissolved organic constituents are degraded.

The biological treatment stage is realized according to the

activated sludge process, combined with externally arrang-

ed ultrafiltration for biomass separation according to the

BIOMEMBRAT® process from Wehrle Umwelt GmbH.

The five-line ultrafiltration installation (Figure 3-44) is

operated in cross-flow mode. It produces 60 – 80 m3 of

permeate per hour. Depending on the waste water quantity,

the individual UF lines can be connected or disconnected.

The resulting excess sludge is mixed with the cocoa-

containing waste water in the aerated storage tank of the

decanting centrifuge. The solids are subsequently separated

in the decanting centrifuge and discharged.

Today the Kellogg Company has 25,000 employees in

19 countries who make more than 50 different cereal

products in 19 countries.

At the Manchester site, considerable quantities of flush-

ing water and waste water with different constituents

(corn components, cocoa, sugar etc.) result from the pro-

duction of muesli. Up to 2003, the waste water was only

treated by a curved screen to separate the solid matter.

The main reason for the planning of an efficient waste

water treatment plant in 2003 construction was the con-

tinuously increasing waste water fees. It was put into

operation in 2004.

For expansion of the waste water treatment plant, a pro-

cess was to be chosen which had a low demand for space

and was able to cope with highly variable pollution loads

and water quantities. Moreover, it should be expandable

with the ability to recycle the treated waste water. Figure

3-43 shows the flow sheet of the waste water treatment

plant.

230

Start-up

Objectives


Modules


Pretreatment

Benefit

2004

Compliance with the requirements for indirect discharge and reduction of the costs for waste water treatment

5 x 216 m2

Tube modules

60 – 80 m3/h

Rotary screen and decanting centrifuge

Reduction of the effluent charge, expandable waste water treatment plant with low space requirement


UF3.6.1.1


and the energy costs for activated sludge separation by

the cross-flow ultrafiltration membranes. On top of that

there are the costs for membrane replacement (membrane

exchange every four years is prognosticated) and the costs

for the application of membrane cleaning agents (chemi-

cal cleaning every 6 – 8 weeks, according to empirical

values from other installations).

The energy consumption of the biological stage depends

on the incoming COD load. The energy uptake of the ex-

ternal cross-flow ultrafiltration is a function of the

specific filtrate capacity. The possibility to connect indi-

vidual ultrafiltration lines depending on the waste water

quantity and an automatic control of the aeration devices

allows for an energy-saving operation mode of the waste

water treatment plant.

The investment for the membrane installation was

930,000 Euro. The operating costs for the external cross-

flow ultrafiltration system amount to 0.36 s/m3 of perme-

ate, for the biological stage they are 0.38 s/m3.

The costs for waste water treatment mainly consist of the

energy costs for aeration of the biological treatment stage

231

buffer tankactivated sludgetank

storage tankdecanter

decanter

liquid phase

solids

solids

rotary screen

turbidi-metry

ultrafiltration

feed

recirculation

receivingwater

Figure 3-43

Flow sheet of the waste water treatment plant at the Kellogg Company in Manchester


Figure 3-44

Cross-flow ultrafiltration at the Kellog Company in

Manchester [photo: WEHRLE UMWELT GMBH 2004]


Primary Starch Production at Raisio Chemicals, Belgium

At the site Veurne/Belgium, the Finnish company Raisio

Chemicals, which was taken over in March 2004 by Ciba

Spezialitätenchemie, makes primary starch products from

starch for the food industry, photographic industry and

the pharmaceutical industry.

The processing of the primary starch products requires

large amounts of fresh-water, so that a closed water circuit

would be useful for both economic and ecological reasons.

A waste water treatment plant suited for the site Veurne

had to be not only efficient but also compact due to re-

stricted space. Figure 3-45 shows the flow sheet of the

membrane bioreactor.

232

Start-up

Objectives


Modules


Pretreatment

Benefit

2004

Efficient and compact waste water treatment

1,188 m2

Immersed rotating plate membranes

Max. 12 m3/h

No mechanical pretreatment

Reduction of the fresh-water demand and of the waste water, reduction of costs


waste water

blowerinstallation

membrane system

waste watercollector

production

permeatetank

Figure 3-45

Flow sheet of the membrane bioreactor at Raisio Chemicals [according to HUBER AG 2004]

Figure 3-46

Huber VRM® process (rotating modules)

[photos: HUBER AG 2004]

UF3.6.1.2

UF3.6.1.3

process is the rotating plate membranes immersed in the

waste water. By the rotating membrane plates, combined

with air input, optimized covering layer removal can be

attained. The membrane installation can be expanded

with up to two additional plate membrane modules of

the type VRM® 20/252.The treated waste water is fed into

the production process via a permeate storage tank.


The process technology for the installation, which was

commissioned in 2004, consists of a mixing and com-

pensating tank, the membrane bioreactor and a permeate

storage tank. The waste water from the production is

homogenized and fed into the activated sludge stage

(V = 1,800 m3) in which two plate membrane modules of

the type VRM® 20/198 from the company Huber are

immersed (Figure 3-46). A special feature of the VRM®

Dairygold Food Products is one of the biggest and lead-

ing dairies in Europe, with its headquarters in Michels-

town, Ireland. Dairygold Food Products produces milk

powder, cheese and butter and runs a meat and sausage

factory. At the site in Michelstwon, 5,000 m3 of waste

water are produced per day which is treated by a conven-

tional activated sludge plant. During the milk season

from March to November the waste water volume increa-

ses to 7,000 m3/d, due to whey processing. The increase

of the waste water volume and of the COD load exceeded

the treatment capacity of the existing activated sludge

plant so that in the milk season the biological treatment

stage was overloaded, which resulted in an exceedance of

the effluent limits. This situation was the reason to study

the technical and economic efficiency of separate treat-

ment of the waste water from whey treatment (approx.

2,000 m3/d) by a membrane bioreactor. In 2000, a new

installation according to the BIOMEMBRAT® process

from the company Wehrle Umwelt GmbH was built.

The concept provides the operation of the membrane

installation during the summer months with higher

loads and its shutting-down in winter. During winter

time, the membrane modules are preserved and stored.

The required short start-up phase in the beginning of the

season is of special importance. Especially in times with

peak loads, the membrane installation contributes to a

considerable improvement in the effluent concentrations

of the whole waste water treatment plant. Figure 3-47

shows the flow sheet of the waste water treatment plant.

233

Dairygold Food Products, Ireland

Start-up

Objectives


Modules


Benefit

2000

Compliance with the demands on the effluent quality during the milk season

648 m2

Tube modules

80 - 90 m3/h

Relief of the existing activated sludge plant, compliance with the effluent standards



The membrane bioreactor consists of an upstream deni-

trification tank (V = 400 m3), a nitrification tank (V =

2,000 m3) and four lines of ultrafiltration, which are oper-

ated in cross-flow mode and serve to separate the biomass.

Each of the four ultrafiltration lines has a membrane

surface area of 162 m2. They can be connected or discon-

nected individually depending on the waste water quan-

tity. The membranes are tube modules with an inner dia-

meter of the tubes of 8 mm. The mean transmembrane

pressure difference in operation is 0.8 bar. The individual

ultrafiltration lines have to be cleaned chemically in inter-

vals of approx. 4 – 6 weeks to ensure a constant filtration

capacity. During the last four years the membranes have

not been replaced. A service life of 5 – 6 years is expected.

The COD inflow concentration of up to 3,600 mg/L

(2,600 mg/L on average) is reduced to 50 mg/L in the

effluent. The effluent requirements of BOD5 < 12 mg/L,

TKN < 15 mg/L and Ptot < 10 mg/l are reliably fulfilled.

234

denitrification andnitrification tank

clarifier

feed membrane stage

seasonalactivity

recirculation

sludge

recirculation

recirculation

denitrification andnitrification tank

receivingwater

Figure 3-47

Flow sheet of the waste water treatment plant at Dairygold Food Products, Ireland


Figure 3-48

Complete plant at Dairygold Food Products with

the membrane installation in the foreground

[WEHRLE UMWELT GMBH 2004]

UF3.6.1.4


From 2000 to 2003, the specific energy consumption was

approx. 5kWh/m3 on average, approx. 2.8kWh/m3 of which

was used for ventilation and recirculation and 2.2 kWh/m3

for membrane filtration. The energy consumption of the

biological treatment stage mainly depends on the COD

and notrogen loads.

The energy demand of the ultrafiltration and the mem-

brane replacement costs make up approx. 23 % of the

total operating costs. The specific operating costs of the

overall membrane bioreactor are approx. 0.90 Euro per m3

of permeate. However, it must be taken into account that

the membrane installation only works about 7 months

per year. The investment for the membrane installation

was approx. 700,000 Euro.

235

Dairy Crest Limited, Great Britain

Start-up

Objectives


Modules


Pretreatment

Benefit

2003

Expansion of the capacity of the waste water treatment plant

486 m2

Tube modules

~ 50 m3/h

Flotation

Increase of the production capacity at the same site


The company Dairy Crest, one of the leading dairies in

England, has increased its production capacity in the

Davidstow Creamery at the site Camelford. This resulted

in an increase in the waste water volume and load. Since

the Dairy Crest waste water treatment plant had no cor-

responding reserve capacities, it had to be expanded. The

waste water treatment process concept used at Dairygold,

Ireland, has also been implemented at the site of the

company Dairy Crest.

The existing conventional activated sludge plant had two

lines. During expansion, one of these lines was replaced

with a BIOMEMBRAT® installation (Figure 3-49). In addi-

tion, a flotation process was arranged upstream of the

biological stage to separate grease and suspended matter

and thus relieve the downstream treatment stages.

After flotation, the waste water flow is divided. The daily

waste water flow is approx. 2,000 m3/d, 1,200 m3/d of

which are fed into the new membrane stage and 800 m3/d

into the existing conventional plant. The effluents of

both installations, operated in parallel, are then com-

bined and discharged into the receiving water. The three-

line membrane installation is equipped with tube mod-

ules with a membrane surface area of 162 m2 per line. It

is possible to expand the installation by a fourth line.

The BIOMEMBRAT® installation in the Davidstow Cream-

ery at the site Camelford is able to reduce the influent

COD load by approx. 98 %, and the Ntot and Ptot loads by

approx. 90 % each. The demands on the effluent of BOD5

< 10 mg/L and NH4-N < 6 mg/l are met with reliability.

The investment for the membrane installation was

550,000 Euro.

UF3.6.1.5


236

recirculation

denitrification and nitrification tank

sludge

clarifier

receivingwater

membrane stage

buffer flotationprocess

feed

denitrification and nitrification tank

recirculation

Figure 3-49

Flow sheet of the waste water treatment at Dairy Crest, Great Britain


Malthouse Sobelgra n. v., Belgium

Start-up

Objectives


Modules


Pretreatment

Benefit

2004

Compact, space-saving and efficient waste water treatment plant, pretreatment upstream of a planned

reverse osmosis installation

8,000 m2

Immersed capillary membrane modules

80 – 100 m3/h

Curved screen

Expansion of the waste water treatment capacity without extensive site construction. In future,

part of the treated waste water will be reused.



The Belgian malthouse Sobelgra is situated in the Antwer-

pen harbour and belongs to the multinational Boortmalt

group. Sobelgra produces malt for breweries and is at pre-

sent increasing its production capacity from 110,000 to

250,000 t/a. This means that the works will become the

biggest independent malthouse in Belgium.

Within the scope of production increase, the capacity of

the existing company-owned waste water treatment plant

had also to be doubled. Due to limited space at the facto-

ry site (Figure 3-50), it was impossible to expand the plant

according to the conventional activated sludge process.

The reasons to install the membrane bioreactor process

were its compact size and the high volume-specific degra-

dation capacity.

The company-owned waste water treatment plant treats

the waste water from barley processing by a combination

of mechanical presieving, biological stage and membrane

filtration (Figure 3-51).

After removal of coarse impurities by two curved screens

(mesh size: 1.0 mm), the waste water flows into the acti-

vated sludge stage, which consists of two tanks for deni-

trification and nitrification connected in series. The

membrane stage serving for separation of the biomass is

arranged downstream of the activated sludge stage. The

16 membrane modules from the company PURON AG

(Figure 3-52) have been installed in two separate cham-

bers. A third chamber is available for future expansion of

the plant (represented as dotted line in Figure 3-51). The

chambers are fed from below so that the waste water flows

upward through the membranes modules. The permeate

is withdrawn from the membrane modules by means of

negative pressure. The concentrated activated sludge is

recycled into the activated sludge tanks. The membrane

surface area in the immersed modules is 8,000 m3, it is

able to treat the entire waste water of the company. With

this, the installation has a capacity of more than 2,000m3/d.

To maintain the filtration capacity of the membrane mod-

ules, backwashing with filtrate takes place in regular

intervals, combined with air rinsing of the membrane

modules. The chambers can be emptied independently of

each other for cleaning and maintenance purposes.

About 80 % of the treated waste water will be reused in

the production process after installation of the planned

reverse osmosis installation.

237

Figure 3-50

Aerial photograph of the malthouse Sobelgra in

the Antwerpen harbour [photo: PURON AG]

feed

recirculation

blowerinstallation

sieve bend 1.0 mmbiological reactor

membrane stage

recycling

sieve bend 1.0 mm

Figure 3-51

Flow sheet of the company-owned waste water treatment plant of the company Sobelgra

[according to PURON AG]


238

Figure 3-52

Schematic representation of the membrane bioreactor (left) and membrane modules (right)

[photo: PURON AG]

RO3.6.2


Laundry Massop, The Netherlands

The waste water passes an (integrated) two-stage filter

(fluff screen), before it flows into the reverse osmosis in-

stallation, which is equipped with spiral-wound modules

from polyethylene membranes. With a membrane surface

area of 250 m2 and at an operating pressure of 10 bar, the

permeate flow is approx. 8 m3 per hour. The permeate is

reused as washing water. The brine is discharged into the


The membranes are backwashed once a day and cleaned

with commercial chemicals every third month. Practical

operation has shown that under these circumstances the

service life of the membranes is two years.

The following example illustrates the employment of

membrane technology for the treatment of waste water

from laundries. The installation described is used in a

laundry in The Netherlands and is similar to two installa-

tions which will be commissioned in the near future in a

laundry at Lemgo and another one at Olsberg. The reali-

zation of these projects is supported by funds from a

development program6) of the Ministry for Environment

and Nature Conservation, Agriculture and Consumer Pro-

tection (MUNLV) of the Land North-Rhine Westphalia.

The company Massop at Kerkrade cleans laundry from

hospitals and hotels. The waste water from washing is

loaded with contaminants, surfactants, bacteria and salts,

so that it has to treated.

The reason for the employment of a membrane installa-

tion was the possibility to save water and energy. When

planning the installation, it was especially important to

consider the close interaction between the membrane

and the detergent applied. For parallel development of

the reverse osmosis (Figure 3-53) and the suitable deter-

gent, the company Henkel-Ecolab GmbH & Co. OHG

(production of detergents and washing agents) coopera-

ted with the company Wientjens, NL. The installation

has operated successfully since 1998 and treats the water

to a sufficient quality for reuse in the washing process.

239

Start-up

Objectives


Modules


Pretreatment

Benefit

1998

Conservation of water and energy

approx. 250 m2


8 m3/h

Integrated two-stage filter (fluff screen)

Saving of freshwater, energy and chemicals


6) Development program for production-integrated environmental protection: “Action group for ecological and sustainable water management NRW”

Figure 3-53

Reverse osmosis installation at the laundry Massop,

Kerkrade [ROTH 2001]

MF3.6.3


The employment of reverse osmosis for waste water treat-

ment and the reutilization of the treated water as process

water offer ecological and economic advantages. Besides

reduced detergent consumption, water (80%), energy (50%)

and softening chemicals (80 %) are also saved. The instal-

lation at Kerkrade is leased, which is profitable for the

operator. The amortization period of such an installation

may vary depending on the location and the general con-

ditions, thus it has to be determined for each single case.

With approx. 13,000 employees all over the world, the

company Sandoz (formerly company Biochemie) works

in the fields of development and production of pharma-

ceutical, biopharmaceutical and industrial products. In

Barcelona, the company Sandoz makes penicillin for the

production of medicine.

Up to now, the waste water generated from the produc-

tion process at the site in Barcelona was treated by con-

ventional processes. The quality of the treated waste

water strongly varied. Moreover, an increase in the pro-

duction volume at Barcelona was planned which requir-

ed an expansion of the company-owned waste water

treatment plant. Since an expansion with conventional

process engineering was impossible because of limited

space, it was decided to build a membrane bioreactor.

The installation was commissioned in February 2003.

Within the scope of pilot tests at the site Kundl of the

company Sandoz, the membrane bioreactor process using

immersed plate membranes from the company Kubota

was compared to other membrane systems at the site of

the company Sandoz (formerly company Biochemie) and

implemented as a large-scale installation already in 1999.

The waste water treatment plant at Kundl was expanded

in 2002 to a membrane surface area of 1,440 m2.

Based on the experience acquired at Kundl and on account

of the comparable boundary conditions, the membrane

bioreactor at Barcelona was equipped with a membrane

surface area of 1,440 m2 without further pilot tests. Figure

3-54 shows the flow sheet of the membrane bioreactor at

the site Barcelona.

The development and employment of membrane proces-

ses for the treatment of laundry waste water is currently

being pursued intensely. Besides the described process,

there are other membrane solutions for the treatment of

laundry waste water that are being developed. In plann-

ing, it is critical to consider the interaction between the

membrane and the detergent applied, so that cooperation

between installation- or membrane manufacturer and the

detergent producer is imperative.

240

Pharmaceutical Industry,

Penicillin Production at the Company Sandoz/Biochemistry, Spain

Start-up

Objectives


Modules


Pretreatment

Benefit

2003

Expansion of the waste water treatment capacity at the site of the company-owned WWTP

1,440 m2

Immersed plate membranes

~ 400 m3/d

Protection of the site when increasing the production volume



After treatment in the existing high-load biological stage

with 3 reactors of 500 m3 each, the waste water volume

of approx. 400 m3/d flows into the membrane separation

stage. For operation of the membrane installation, the TS

content in the activated sludge tanks was increased from

approx. 6 g/L to 12 – 16 g/L. With this, the biological de-

gradation capacity of the waste water treatment plant is

approximately doubled. The two-line membrane instal-

lation consists of 6 plate membrane packages from the

company Kubota of the type EK 300. Filtering takes place

at a constant transmembrane pressure of 0.05 – 0.15 bar.

Chemical in-situ cleaning is done automatically twice a

year. The permeate is discharged into a municipal waste

water treatment plant for further treatment.

241

membrane stage

feed

biological reactor

1

2

3

recirculation

blowerinstallation

blowerinstallation

receivingwater

Figure 3-54

Flow sheet of the membrane bioreactor in Barcelona [according to AGGERWASSER GMBH 2004]

Figure 3-55

Membrane bioreactor and membrane modules under construction at the company Sandoz in Spain

[photos: AGGERWASSER GMBH 2004]


3.6.4

Miscellaneous

Animal Carcass Disposal Plant of SARIA

Bio-Industries, France

The company SARIA Bio-Industries operates in Bayet, in

Central France, an aminal carcass disposal plant. Up to

240,000 t of slaughterhouse waste and perished animals

are processed per year at this site. About 1,100 m3 of pro-

duction waste water with a mean COD concentration of

16,000 mg/L are produced per day. Due to increasing de-

mands on the effluent quality and increasing operational

capacity, the waste water treatment plant at the site of

the animal carcass disposal plant at the site Bayet had to

be adapted to the state of the art.

The decision-maker of the animal carcass disposal plant

chose in 2000 to convert the existing waste water treat-

ment plant to a membrane bioreactor. After successful

two-year operation, the installation was expanded already

in 2002.

The individual waste water flows from the animal carcass

plant are pretreated in part by flotation, treated mechani-

cally by a fine screen and homogenized in a mixing and

storage tank. The pretreated waste water is pumped into

an activated sludge tank (V = 4,000 m3) where the orga-

nic substances are degraded (Figure 3-56). The activated

sludge flows through a curved screen with a mesh size of

750 µm to protect the membranes from coarse matter

before it is fed in free overflow into the membrane stage.

The membrane stage is realized with four lines (Figure

3-57). Each line is integrated in a filtration container and

contains capillary membrane modules from the company

ZENON (Figure 3-58). At present approx. 1,800 m3 of mem-

brane surface area are installed. The first membrane line

consists of four immersed modules of the type 500a, the

second line has two immersed modules of the type 500c.

By treatment of the waste water in the membrane biore-

actor it is possible to attain COD effluent concentrations

of < 300 mg/L. Thus, the COD load in the installation is

reduced by 98 %.

242

Start-up

Objectives


Modules


Pretreatment

Benefit

2000, expansion in 2002

Compliance with increasing effluent standards and adaptation to capacity enlargement

1,800 m2

Immersed capillary membrane modules

~ 40 - 50 m3/h

Fine screen

Economic expansion and adaptation of the waste water treatment plant to the state of the art


UF3.6.4.1


243

feed

biological reactor4.000 m3

fine sieve750 µm

recirculation

blowerinstallation

membrane stage

blowerinstallation

receivingwater

Figure 3-56

Flow sheet of the membrane bioreactor at SARIA Bio-Industries in Bayet

[according to ZENON GMBH 2004]

Figure 3-57

General view of the membrane bioreactor of the

animal carcass disposal plant in Bayet

[photo: ZENON GMBH 2004]

Figure 3-58

Container with fitted modules at SARIA Bio-Indus-

tries in Bayet [photo: ZENON GMBH 2004]

membrane containers


3.6.4.2

Mechanical-Biological Waste Treatment Plant

Mechanical-biological waste treatment has become es-

tablished in Europe as a concept for the treatment of

municipal waste. Biological conversion can take place in

composting plants (aerobically) or in fermentation plants

(anaerobically). Biological conversion in mechanical-bio-

logical waste treatment plants aims at biodegradation of

the organic constituents to reduce the waste volume and

to get a stabilized final product. From biodegradation

and dewatering results complex, high-loaded waste water.

Depending on the treatment process, approximately half

of the treated solid waste results as waste water which

needs treatment. The composition of the waste water

mainly depends on the raw solid waste (water content,

organic part) and on the fermentation process (wet, dry).

The concentrations of the individual parameters may

strongly vary. In principle, intensive conversion during

fermentation means higher pollutant concentrations in

the process waste water.

244

Waste Disposal at the Company TIRME, Spain

Start-up

Objectives


Modules


Pretreatment

Benefit

2004

Closed production water circuit

100 m2

Tube modules

5 – 6 m3/h

Fine screen

Savings of freshwater and waste water


Besides a waste incineration plant, the company TIRME

also runs a plant for material separation and mechanical-

biological waste treatment at Mallorca. At this site, approx.

45,000 m3 of high-strength waste water are produced an-

nually which mainly comes from the mechanical-biologi-

cal waste treatment plant. Additional waste water result

from the cleaning of yards and vehicles and from the treat-

ment of waste air. The complex waste water composition

requires a combination of treatment processes. At first

the solids have to be removed from the waste water.

For mechanical-biological waste treatment, nitrogen-free

process water is required. The new waste water treatment

plant installed by the company Wehrle Umwelt GmbH

treats the waste water to such an extent that part of it can

be used after treatment for this purpose. The installation

consists of a mechanical pretreatment stage, an activated

sludge stage and an ultrafiltration installation (Figure 3-59).

The plant is designed for a throughput of approx.

45,000 m3/a or 140 m3/d of waste water with a COD con-

centration of 7,300 mg/L and a NH4-N concentration of

2,500 mg/L. The effluent COD concentration has to be

below 1,500 mg/L, which corresponds to a reduction of

approx. 80 %. Ammonium is completely degraded in

order to reuse the treated waste water as process water in

the mechanical-biological waste treatment plant.

UF3.6.4.2.1


Mechanical pretreatment of the waste water takes place

by settling with subsequent filtration by a fine sieve with

a separation size of 200 µm. After mechanical treatment,

the waste water flows into the activated sludge stage

which consists of upstream denitrification with following

nitrification (Figure 3-60). The activated sludge is separat-

ed in the downstream two-line ultrafiltration stage

(Figure 3-60). The filtration lines consist of four tube

modules each which can be operated and cleaned inde-

pendently of each other. The membranes are operated in

cross-flow mode with a mean transmembrane pressure of

approx. 4 bar and a flow velocity of 5 m/s. The total mem-

brane surface area is approx. 100 m2. The excess sludge is

discharged via the biological stage of the mechanical-bio-

logical waste treatment plant.

245

feed

recirculation

ultrafiltration

fine screen200 µm

nitri-fication

denitri-fication


ultrafiltration

to mechanical-biological waste watertreatment

excesssludge

receivingwater

Figure 3-59

Flow sheet of the waste water treatment plant at the company TIRME, Spain


Figure 3-60

Waste water treatment plant at the company TIRME [photos: WEHRLE UMWELT GMBH 2004],

left: membrane installation, right: bioreactors


246

Instructions and Standards

in Membrane Technology

4

Instructions and Standards in Membrane Technology4

As shown in the preceding chapters, the fields of applica-

tion of membrane technology for waste water treatment

and the objectives pursued are manifold (see chapter 3.2).

The utilisation of a membrane installation has to be exa-

mined for each single case and must be adapted to the

specific task. This explains the lack of DIN standards and

the small number of existing instructions. There are no

standard solutions for the use of membrane technology

and for the design of a membrane installation. However,

for some applications it is possible to fall back on the

experience acquired to-date.

The demands on the construction of membrane installa-

tions are defined in the instructions for plant construc-

tion. The design of installations with a certain capacity

and the demands on the membrane depend on the defi-

ned aim and on the boundary conditions.

The primary aim in waste water treatment consists of the

compliance with limit values which are defined in the

conditions for discharge into water bodies [ABWV 2002]

and into the public sewer system (Ordinances on Indirect

Discharge of the federal states and stipulations in the

articles of associations). They are based on § 7a of the

Federal Water Act [WHG 1996]. To be able to comply

with these limit values, advisory leaflets give recommen-

dations for the treatment of the characteristic emissions

of single industrial branches. In some advisory leaflets,

the utilization of membrane processes is also mentioned,

e. g. for the treatment of emissions from the metal-wor-

king industry [ATV-DVWK 2000b]. However, they con-

tain no design instructions.

DWA has established two expert committees concerning

the subject “membrane technology in waste water treat-

ment“: the Expert Committee KA-7 „Membrane biore-

actor process“ and the Working Group IG-5.5 “Membrane

technology“.

The expert committee mentioned first has already pub-

lished two work reports “Membrane bioreactor process“

[ATV-DVWK 2000a; DWA 2005]. The reports deal with

the basics of the membrane bioreactor process, design

approaches and necessary pretreatment measures. The

design approaches are not related to the design of the

membrane used, but to the change in dimensioning the

activated sludge tank compared to the conventional acti-

vated sludge process. The change results from the possibly

higher dry matter content. It mainly consists of another

calculation approach for the excess sludge production

and the oxygen consumption as well as in the definition

of a minimum sludge age and a minimum excess sludge

production.

The DWA Working Group IG 5.5 „Membrane technology“

has elaborated a work report with the title “Treatment of

industrial waste water and process water by the membrane

bioreactor process“ [ATV-DVWK 2002]. This work report

consists of two parts. Part 1 deals with the membrane

process for the separation of undissolved, colloidal or dis-

solved substances. Part 2 addresses the membrane bioreac-

tor process. It indicates in particular the differences which

result from the application of the membrane bioreactor

process for the treatment of industrial waste water com-

pared to municipal waste water. Due to the great variety

of application cases and the differences between the

waste waters, these work reports cannot contain design

instructions. But they give information on suitable or

unsuitable applications and list examples.

Additional instructions dealing with the utilization of

membrane technology in water and waste water treat-

ment are described briefly described in the following.

The Verband Deutscher Maschinen- und Anlagenbau e. V.

(Association of the German Mechanical Engineering and

Plant Construction) has published a standard sheet con-

cerning the application of membrane technology in the

treatment of landfill leachate [VDMA 1994]. This standard

sheet is to be seen as a provisional instruction which can

be used during consultations on the standardization or

preciseness of European standards. It contains qualitative

information on the design of membrane installations.

Not only the parameters to be determined are mentioned

(necessary membrane surface area, quantitative evaluation

of the volume flows for permeate and brine/concentrate),

but also the necessary planning steps (laboratory tests,

pilot installation and on-site tests in technical scale, see

also chapter 3.3). It is emphasized in particular that values

known from practice or determined by tests should be

used to determine the operating parameters (e. g. operating

pressure, overflow velocity, process temperature, specific

248

Instructions and Standards in Membrane Technology 4

permeate flow), examining thoroughly the boundary con-

ditions under which these values have been determined

[VDMA 1994]. This procedure for the planning of mem-

brane installations can be transferred to all other fields of

application.

In addition, the working group „Membrane technology“

of the Bundesvereinigung der Firmen im Gas und Wasser-

fach e. V. (FIGAWA) (Federal Association of the Companies

of the Gas and Water Branch) has published some advi-

sory leaflets and Technical Information on membrane

technology in water and waste water treatment. In differ-

ent releases, electrochemical desalination [FIGAWA 1999],

reverse osmosis [FIGAWA 1996a; FIGAWA 1996b; FIGAWA

1985], cross-flow microfiltration [FIGAWA 1992], electro-

dialysis and diffusion dialysis [FIGAWA 1991] and mem-

brane processes (RO, UF, elektrodialysis) in freshwater and

waste water treatment [MARQUARDT 1988] are explained.

Besides the mode of functioning of the respective process,

the Technical Information and advisory leaflets also men-

tion the fields of application. However, concrete design

instructions are not given.

249

1) FIGAWA: independent technical-scientific expert association, established in 1926. Its main task is the promotion of technology and science in the field

of gas and water. The working group „Membrane technology“ was founded in 1975 within the specialist group „Water treatment“. It accompanies the

development of rules and standards in this field as well as the technical development of the corresponding plants and equipment [FIGAWA 1999].

Instructions and Standards in Membrane Technology4

250

Summary and Outlook 5

Summary and Outlook5

Membrane technology currently represents a proven alter-

native to classical processes for many applications in

municipal and industrial waste water treatment and may

contribute to reduce the costs for water supply and waste

water disposal, production costs and environmental pol-

lution. This publication gives an introduction to mem-

brane technology and its application in municipal and

industrial waste water treatment in Germany according to

the state of the art. Applicability and capacity of membrane

installations are illustrated with examples of large-scale

installation realized on a municipal and industrial level.

The share of membrane installations used on a municipal

level worldwide is still small due to economic aspects,

concerning especially membrane replacement and energy

demand. Under some boundary conditions, the use of

membrane processes in municipal waste water treatment

may turn out to be economical, e. g. in the case of more

stringent or additional demands on the effluent quality,

limitations in space for new construction or expansion of

plants and possible reuse of the treated waste water.

The utilisation of low-pressure processes has shown that

waste water treatment by membrane technology with high

biomass concentration in the activated sludge tank may

be technically feasible and profitable. The investment for

a modern conventional plant and the investment for a

membrane bioreactor currently are of the same order of

magnitude. However, the operating costs of a membrane

installation are a little higher. To reduce these costs,

which also make a membrane bioreactor compete with a

conventional plant under economic aspects, research and

development have to focus on the increase of the permea-

te flow, the reduction of the specific energy consumption

and the prolongation of the service life of membranes.

In contrast to the municipal field of application, the use

of membrane technology in industry is common and pro-

ven by a large number of references. In industrial waste

water treatment, the use of membrane technology is often

associated with production-integrated environmental pro-

tection (PIUS). Since water is the solvent used most, PIUS

aims at avoiding the partly dissolved substances or, if this

is impossible, to separate them from the water and thus

to make a closed water circuit possible. Even if the water

circuit cannot be completely closed, the waste water

quantity may be reduced significantly by skillful multiple

use of the water.

Besides the examples presented in this publication, there

are other fields of application for membrane technology.

Thanks to the availability of different membranes and

modules, it is possible to find for nearly each task a tech-

nically suited system, which then has to be examined

under economical and ecological aspects. An exact inven-

tory of the existing boundary conditions and an econo-

mic analysis in comparison to alternative processes

should precede the choice, independent of the field of

application of a membrane process. However, it must be

emphasized that in most cases no standard solution

exists, so that in each case detailed planning and pilot

tests by experts, considering the existing boundary condi-

tions, are necessary for successful operation of a membrane

installation. Tests in laboratory and semi-technical scale

contribute to plan a safe and practical system. Special

attention should be paid to the demand for energy and

cleaning chemicals as well as to the service life of the

membranes. Increasing water and waste water costs and

decreasing membrane prices lead to continuous improve-

ment of the economic situation of membrane processes

compared to other waste water treatment processes.

The development of membrane technology in the field of

water and waste water treatment has not yet ended. In

future, a still broader range of applications can be expect-

ed. By continuous development of membrane materials

and module constructions as well as process design and

process engineering, it will be possible to solve problems

for which, in the past, membrane processes were not suit-

ed due to the characteristic of the liquid to be treated.

Therefore it is important to always observe and examine

new developments, besides the assessment of working

plants. There is still need for research in the field of plant

design, operating parameters and in the control of fouling

effects.

252

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WVER (2004): personal information from Mr. Rolfs,

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ZENON (2002): several information from the company

ZENON, Hilden.

ZENON GmbH (2004): several information from the

company ZENON GmbH, Hilden.

ZKR – Zentralkommission für die Rheinschiff-

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262

Annex A

AnnexA

A.1

Addresses (mentioned in the concrete examples)

A.1.1

Locations of the membrane systems in Germany

Municipal waste water treatment

WWTP Büchel

WWTP Seelscheid

WWTP Kaarst

WWTP Rödingen

WWTP Glessen

WWTP Knautnaundorf

WWTP Markranstädt

WWTP Simmerath

WWTP Konzen

WWTP Rurberg-Woffelsbach

WWTP Geiselbullach

WWTP Monheim

Aggerverband

Postfach 340240

51624 Gummersbach

Mr. Dr. Scheuer

www.aggerverband.de

Erftverband

Paffendorfer Weg 42

50126 Bergheim

Mr. N. Engelhardt

Ms. K. Drensla

www.erftverband.de

KW Leipzig GmbH

Johannisgasse 7

04103 Leipzig

Ms. S. Stein

www.wasser-leipzig.de

Wasserverband Eifel Rur

Eisenbahnstraße 5

52325 Düren

Mr. T. Rolfs

www.wver.de

Amperverband

Verwaltung Eichenau

Bahnhofstraße 7

82223 Eichenau

Mr. T. Kopmann

www.amperverband.de

Stadt Monheim

Marktplatz 23

86653 Monheim

Mr. Wild

www.monheim.de

WWTP Schramberg-

Waldmössingen

WWTP Xanten-Vynen

WWTP Eitorf

WWTP Kohlfurth

WWTP Merklingen

WWTP Richtheim

Stadtwerke Schramberg

GmbH & Co. KG

Am Hammergraben 8

78713 Schramberg

Mr. Rosenbohm

www.stadtwerke-schramberg.de

Linksniederrheinische Entwässe-

rungs-Genossenschaft (LINEG)

Friedrich-Heinrich-Allee 64

47475 Kamp-Lintfort

Mr. Dr. Kühn

www.lineg.de

Gemeindewerke Eitorf

Ver- und Entsorgungsbetriebe

Auf dem Erlenberg 3

53783 Eitorf

Mr. Neulen

www.eitorf.de

Wupperverband

Untere Lichtenplatz Straße 100

42289 Wuppertal

Mr. Dr. Erbe

www.wupperverband.de

Gemeinde Merklingen

Hauptstraße 31

89188 Merklingen

Gemeinde Ursensollen

Rathausstraße 1

92289 Ursensollen

www.ursensollen.de

264

Annex A

265

Municipal waste water treatment (Continuation)

WWTP Hailfingen

WWTP Dormagen

WWTP Piene

Abwasserzweckverband

Bondorf-Hailfingen

Rathaus

Marktplatz 18

72108 Rottenburg am Neckar

Stadt Dormagen

Stadtentwässerung

Tiefbauamt

Mathias-Giesen-Straße 11

41540 Dormagen

Stadtwerke Gummersbach

Rathausplatz 1

51643 Gummersbach

Mr. Bock

WWTP Golf Course St. Wendel

German Armed Forces

Stadt St. Wendel

Rathaus IV, Abwasserwerk

Marienstraße 1

66606 St. Wendel

Mr. Schmidt

Bundesamt für Wehrtechnik

und Beschaffung

Ferdinand-Sauerbruch-Straße 1

56073 Koblenz

www.bwb.org


Food industry

Malthouse

Potato starch production

Emsland Stärke GmbH

Emslandstr. 58, 49824 Emlichheim

Mr. Dr. M. Lotz

www.emsland-staerke.de

“Deutsche See” GmbH & Co. KG

BEECK Feinkost GmbH & Co. KG

Albert-Schweitzer-Ring 35

22045 Hamburg

Mr. L. Diederichs

www.beeck-feinkost.de

Mälzerei Heinrich Durst

Malzfabriken GmbH & Co. KG,

Betrieb Gernsheim

Mainzer Staße 15 – 16

64579 Gernsheim

Mr. M. Filip

www.durst-malz.de

Branch CompanyBranch Company

Printing industry

Paper mills

Fibre industry

Grafische Handelsvertretung

Peter Leis

Mühlweg 32

35606 Solms

Mr. P. Leis

Papierfabrik Palm

Werk Eltmann

Industriestraße 23

97483 Eltmann

Mr. R. Schirm

www.wellenwunder.de/

palm-gruppe/main.htm

Vulkanfiber Ernst Krüger

GmbH & Co. KG

Postfach 1262, 47592 Geldern

Nordwall 39, 47608 Geldern

Mr. Dr. M. Joseph

www.hornex.de

AnnexA

266

Industrial waste water treatment (Continuation)

Textile industry

Plastics industry

Laundry

Gerhard van Clewe

GmbH & Co. KG

Loikumer Straße 10

46499 Hamminkeln-Dingden

Mr. A. van Clewe

www.van-clewe.de/vanclewe.html

Drews Meerane GmbH

Äußere Crimmitschauer Straße 80,

08393 Meerane

Mr. Ellmer

www.drews-meerane.de

Pongs Textil GmbH

Boschstraße 2

48703 Stadtlohn

Mr. Wening

www.pongs.de

HT Troplast AG

TROSIFOL

Mülheimer Straße 26

53840 Troisdorf

Mr. U. Offermann

www.ht-troplast.de

Rentex Fortex B. V.

Locatie Massop

Grisenstraat 5

NL-6465 CE Kerkrade

Mr. P. Massop

www.fortex.nl

ALSCO Berufskleidungs-Service

GmbH

Niederlassung Kaiserslautern

Otto-Hahn-Straße 1

67661 Kaiserslautern

Mr. Winter

www.alsco.de


Laundry (Continuation)

Metal-working industry

Paint processing

Textilservice MEWA GmbH

Hermann-Gebauer-Straße 1

15831 Groß Kienitz

Mr. Lehmann

www.mewa.de

Rasselstein GmbH

Koblenzer Straße 141

56626 Andernach

Ms. Dr. S. Arnold

www.rasselstein-hoesch.de/

deutsch/index.htm

Faurecia Autositze

GmbH & Co. KG

Werk Stadthagen

Industriestraße 3

31655 Stadthagen Ort

Mr. K. Kasten

www.faurecia.com

Wieland Werke AG

Werk Langenberg

Ziegeleiweg 20

42555 Velbert

Mr. H.-U. Koböcken

www.wieland.de

Galvanik Rudolf Jatzke

Edisonstraße 7

33689 Bielefeld

Mr. K. Wickbold

DaimlerChrysler AG

Werk Düsseldorf

Ratherstraße 51

40467 Düsseldorf

Mr. T. Bergmann

www.daimlerchrysler.com

Annex A

267

Industrial waste water treatment (Continuation)


Paint processing (Continuation)

Pharmaceutical industry

Power stations

Landfill leachate

Deoiling of bilge water

Ford-Werke GmbH

Henry-Ford-Straße 1

50725 Köln

Mr. S. Baumeister

www.ford.de

Schering AG

Ernst-Schering-Straße 14

59192 Bergkamen

Mr. Dr. Neuhaus

DREWAG

Gas- und Dampfturbinen

Heizkraftwerk Dresden

Rosenstraße 32

01065 Dresden

www.drewag.de

Abfallwirtschaft Kreis und Stadt

Aachen (AWA) GmbH

Deponie Alsdorf-Warden

Postfach 1459

52243 Eschweiler

Mr. R. Koch

www.awa-gmbh.de

Bilgenentölungsgesellschaft mbH

August-Hirsch-Straße 3

47119 Duisburg

Mr. R. Deutsch

www.bilgenentoelung.de

Swimming pools

Fish hatchery

Aquana Freizeitbad

GmbH & Co. KG

Willy-Brandt-Ring 100

52146 Würselen

Mr. M. Dovermann

www.aquana.de

Hertener Stadtwerke GmbH

Schwimmbad COPA CA BACKUM

Herner Straße 21

45699 Herten

Mr. H. Kuhlmann

www.freizeitbad.de/deutschland/

copacabackum.html

Freizeitbad Bergische Sonne

GmbH & Co.

Lichtscheider Straße 90

42285 Wuppertal

Mr. G. Geier

www.bergische-sonne.de

Umweltbundesamt

Fachgebiet III 3.5

Postfach 33 00 22

14191 Berlin

Mr. Dr. Pluta

www.umweltbundesamt.de

AnnexA

A.1.2

Planners and manufacturers of installations,

membrane manufacturers, Consulting Engineers

A large number of planners and manufacturers of installa-

tions, membrane manufacturers and consulting engineers

are working in the field of membrane technology. Even for

Germany, it is hardly impossible to draw up a complete

list, partly due to high fluctuations in this branch. There-

fore, in the following only the addresses of those com-

panies and offices are listed which have been specially

mentioned in the previous chapters and have contributed

information, e. g. for the concrete examples. Thus, this

selection does not claim to be complete. Additional

sources of information and important institutions in

connection with the subject membrane technology are

compiled subsequently.

268

A3-Abfall-Abwasser-

Anlagentechnik GmbH

Aggerwasser GmbH

ACO Passavant GmbH

Altenburger Elektronic GmbH

amafilter Deutschland GmbH

ATEC Automatisierungstechnik

GmbH

atech innovations GmbH

Magdeburger Straße 16 b

45881 Gelsenkirchen

Mr. U. Brüss

www.3a-gmbh.de

AV Aggerwasser GmbH

Sonnenstraße 40

51645 Gummersbach

www.aggerwasser.de

Ulsterstraße 3

D-36269 Phillipsthal

www.aco-passavant.de

Schlossweg 2 – 5

77960 Seelbach

Mr. Dr. S. Siegfried

www.altenburger.de/index.html

Am Pferdemarkt 11

30853 Langenhagen

Mr. Dr. G. Baumgarten

www.amafilter.com

Emmi-Noether-Straße 6

89231 Neu-Ulm

Mr. G. Enderle

www.atec-nu.de

Am Wiesenbusch 26

45966 Gladbeck

Mr. P. Bolduan

www.atech.daw.com

ATEMIS GmbH

Atotech Deutschland GmbH

Berghof Filtrations- und

Anlagentechnik GmbH & Co. KG

BKT Burggräf GmbH

BUSSE GmbH

CSM Filtrationssysteme

GmbH & Co. KG

degebran GmbH Anlagenbau

Dennewartstraße 25 – 27

52068 Aachen

www.atemis.net

Industriestraße 69, 90537 Feucht

Postfach 12 40, 90532 Feucht

Mr. Dr. R. Schmidt

www.atotech.com

Harretstraße 1

72800 Eningen

Mr. H.-U. Roth

www.berghof.com

Zum alten Zollhaus 20 – 22

42281 Wuppertal

Mr. H. Burggräf

Zaucheweg 6

047316 Leipzig

Mr. R.-P. Busse, Mr. C. Belz

www.busse-gmbh.de

Gewerbestraße 32

75015 Bretten-Gölshausen

Mr. R. Verschaeve

www.guthgroup.de

Resser Straße 65

44653 Herne

Mr. K. Paulus, Mr. H.- J. Krein

www.degebran.de

Annex A

269

DHV Water BV

Dr. Dahlem –

Beratende Ingenieure

Earth-Tech GmbH

Eisenmann Lacktechnik KG

EnviCare

ENVIRO-CHEMIE

Abwassertechnik GmbH

Erftverband

Fraunhofer IGB

Henkel-Ecolab GmbH & Co. OHG

Hese Umwelt GmbH/A3 GmbH

Postbus 484

3800 AL Amersfort

Mr. H. F. van der Roest

www.dhv.nl

Bonsiepen 7

45136 Essen

www.drdahlem.de

Forumstraße 24

41468 Neuss

www.axeljohnson.de

Heinrich-Hertz-Straße 8

74351 Besigheim-Ottmarsheim

Mr. E. Neubauer

www.eisenmann.de

Wittekeweg 9

A-8010 Graz

www.envicare.at

In den Leppsteinswiesen 9

64380 Roßdorf

Mr. J. Quaiser

www.enviro-chemie.de

Paffendorfer Weg 42

50126 Bergheim

www.erftverband.de

Nobelstraße 12

70569 Stuttgart

Henkel-Ecolab Deutschland

Reisholzer Werftstraße 38 – 42

40554 Düsseldorf

Mr. R. Krack

www.ecolab.de

Magdeburger Straße 16 a

45881 Gelsenkirchen

www.hese-umwelt.de

Hans Huber AG

Hydro-Ingenieure GmbH

HST-Systemtechnik

iat-Ingenieurberatung für

Abwassertechnik GmbH

inge AG

Ingenieurbüro Dr. Resch

imb + frings water systems gmbh

I-T-G GmbH, Ingenieurgemein-

schaft für Umwelttechnologie

ItN Nanovation

Keppel Seghers Belgium NV

Maschinen- und Anlagenbau

Maria-Hilf-Straße 3 – 5

92334 Berching

Mr. Dr. O. Christ

www.huber.de

Stockkampstraße 10

40477 Düsseldorf

www.hydro-ingenieure.de

Sophienweg 3

59872 Meschede

www.systemtechnik.net

Taubenheimstraße 69

70372 Stuttgart

www.iat-stuttgart.de

Flurstraße 17

86926 Greifenberg

Mr. M. Hank

www.inge-ag.de

Lehenwiesenweg 31

91781 Weißenburg

Mr. Dr. H. Resch

Horbeller Straße 15

50858 Köln

Mr. Dr. J. Lindemann

www.imbfrings.de

Buchenstraße 24

72810 Gomaringen

Ms. J. Knödler

www.itg-gmbh.de

Untertürkheimer Straße 25

66117 Saarbrücken

www.itn-nanovation.de

Hoofd 1

B-2830 Willebroek

www.segherskeppel.com

AnnexA

270

Klapp-Müller GmbH,

Ingenieurbüro für Umwelt-

und Bautechnik

KOCH-GLITSCH GmbH

KOCH Membrane Systems

GmbH

Krüger-Wabag

(see Veolia Water)

Kubota

L. V. H. T.

Mall GmbH

Martin Systems AG

Rehwinkel 15

51580 Reichshof

Mr. Dr. S. Schilling

www.klapp-mueller.de

Membrane Systems Divisions

Neusser Straße 33

40219 Düsseldorf

Mr. J. Hadler

www.kochmembrane.com

Krantzstraße 7, Eingang D

52070 Aachen

Mr. Dr. S. Schäfer

www.puron.de

Baumeisterallee 13 – 15

04442 Zwenkau

Standort Ratingen

Lise-Meitner-Straße 4a

40878 Ratingen

www.wabag.com

Under licence Aggerwasser GmbH

Lehr- und Versuchsgesellschaft für

innovative Hygiene-Technik mbH

Am Zehnthof 191a

45307 Essen

Mr. Dr. D. Pacik

www.lvht.de

Hüfingerstraße 39– 45

78166 Donaueschingen

Mr. S. Klemens

www.mallbeton.de

Ackerstaße 40

96515 Sonnenberg

Mr. M. Grigo

www.martin-systems.de

Memcor Australia

(see Siemens AG)

Memtec

Membrain

MDS Prozesstechnik GmbH

MFT

MICRODYN-NADIR

Filtration GmbH

NERAtec AG

NORIT N. V.

OSMONICS

40 Blackman Crescent

South Windsor, NSW 2576

Mergenthalerallee 45 – 47

65760 Eschborn

Mr. Baur

Contact: ZENON GmbH

Bahnhofstraße 315

47447 Moers

Mr. Dr. D. Böttger

www.mds-prozesstechnik.com

Membran-Filtrations-Technik GmbH

Eupener Straße 150

50933 Köln

Mr. H.-U. Hübbel

www.mft-koeln.de

Kalle Albert Industriepark

Rheingaustraße 190

65174 Wiesbaden

Mr. W. Ruppricht

www.microdyn-nadir.de

Max-Planck-Straße 7b

52249 Eschweiler

Mr. U. Kolbe

www.neratec.de

P. O. Box 89

7620 AB Borne

The Netherlands

www.norit.com

230, rue Robert Schumann

Z. A. des Uselles

B. P. 85

F-77350 Le Mee sur Seine

France

www.osmonics.com

Annex A

271

Pall GmbH

PURON AG

Dr.-Ing. Peters Consulting

(CMU)

ROCHEM UF-Systeme GmbH

Rhodia

RWW Wassertechnologie GmbH

Schwander GmbH

Siemens AG Water Technologies

TAMI Deutschland GmbH

Pall GmbH

Philipp-Reis-Straße 6,

63303 Dreieich

Mr. Dr. H. Eipper, Mr. C. Maurer

www.pall.com

refer to KOCH Membrane Systems

GmbH

www.puron.de

Dr.-Ing. Peters Consulting für

Membrantechnologie und

Umwelttechnik

Broichstraße 91

41462 Neuss

Mr. Dr. T. A. Peters

Stadthausbrücke 1 – 3

Fleethof

20355 Hamburg

www.rochemuf.com

Stadelstraße 10

60595 Frankfurt

Mr. Hoffmann, Mr. Linz

www.rhodia.com

Heinrich-Haanenstraße 6

41334 Nettetal-Lobberich

Mr. B. Lang

www.rww-wt.de

Theodor-Heuss-Straße 38

61118 Bad Vilbel

Mr. Dr. T. Jäger

www.schwander.de

Nonnendammallee 101

13569 Berlin

www.siemens.com/water

Heinrich-Hertz-Strasse 2/4

07629 Hermsdorf

Mr. B. Ruschel

www.tami-industries.com

Toray Deutschland GmbH

Tuttahs & Meyer

Ingenieurgesellschaft

US-FilterMEMCOR Products

(see Siemens AG)

VA TECH WABAG AG

Veolia Water Deutschland GmbH

WEHRLE-WERK AG

Weise Water Systems

GmbH & Co. KG

Wientjens b. v.

X-Flow B. V.

(see NORIT N. V.)

ZENON GmbH

Hugenottenallee 175

63263 Neu-Isenburg

Bismarckstrasse 2 – 8

52066 Aachen

www.tuttahs-meyer.de

441 Main Streel

Sturbridge, MA 01566

www.usfilter.com

VA TECH WABAG

Siemensstraße 89

1210 Vienna

www.vatechwabag.com

Unter den Linden 21

10117 Berlin

www.veoliawater.de

Bismarckstraße 1 – 11

79312 Emmendingen

Mr. G. Streif

www.wehrle-werk.de

Steinbruchstraße 6b

35428 Langgöns

www.weise-water-systems.com

Im Sprokkelveld 9

NL-6596 DH Milsbeek

www.wientjens.com

Bedrijvenpark Twente 289

NL-7602 KK Almelo

Mr. B. Brocades Zaalberg

www.xflow.nl

Nikolaus-Otto-Straße 4

40721 Hilden

Mr. H. Möslang

www.zenonenv.com

MUNLV

(Ministry for Environment and

Nature Conservation, Agriculture

and Consumer Protection of the

state North-Rhine Westphalia)

LUA NRW

(Environmental Office of the

state North-Rhine Westphalia)

EFA NRW

(Efficiency Agency North-Rhine

Westphalia)

BEW

(Training centre for waste water

and waste disposal and water

management)

DGMT

(German Association for

Membrane Technology)

Forschungsinstitut für Wasser-

und Abfallwirtschaft an der

RWTH Aachen (FiW) e. V.

(Research Institute for Water

and Waste Management at the

RWTH Aachen University)

Ministerium für Umwelt und

Naturschutz, Landwirtschaft und

Verbraucherschutz des Landes

Nordrhein-Westfalen

40190 Düsseldorf

www.munlv.nrw.de

Landesumweltamt

Nordrhein-Westfalen

Wallneyer Staße 6

45133 Essen

www.lua.nrw.de



47057 Duisburg

www.efanrw.de

Bildungszentrum für die

Entsorgungs- und Wasser-

wirtschaft GmbH

Bildungsstätte Essen

Wimberstraße 1

45239 Essen

www.bew.de

Deutsche Gesellschaft für

Membrantechnik e. V.

Eupener Straße 150

50933 Köln

www.dgmt.org


52056 Aachen

Ms. M. Lange

Mr. Dr. F.-W. Bolle

Mr. J. Schunicht

www.fiw.rwth-aachen.de

Institut für Siedlungswasserwirt-

schaft der RWTH Aachen (ISA)

(Institute of Environmental

Engineering of the RWTH

Aachen University)

Experts, consultants


52056 Aachen

Mr. S. Baumgarten

Mr. Dr. S. Köster

Univ. Prof. Dr.-Ing. J. Pinnekamp

www.isa.rwth-aachen.de

Prof. Dr.- Ing. P. Cornel

(Head of the work group IG-5.5

“Membrane technology“ of ATV-

DVWK or DWA respectively)

Technische Universität Darmstadt

Institut WAR

Petersenstraße 13

64287 Darmstadt

www.iwar.bauing.tu-darmstadt.de

Mr. Prof. Dr.-Ing. F.-B. Frechen

(in place of the Committee of Ex-

perts KA-7 “Membrane bioreactor

process“ of ATV-DVWK or DWA

respectively)

Universität Kassel

FG Siedlungswasserwirtschaft

Kurt-Wolters-Straße 3

34125 Kassel

www.uni-kassel.de

Mr. Dr. Firk


Eisenbahnstraße 5

52353 Düren

www.wver.de

Mr. Dr. J. Oles

Mr U. Voss

Oswald Schulze GmbH & Co. KG

Krusenkamp 22 – 24

45964 Gladbeck

www.oswald-schulze.de

AnnexA

272

A.1.3

Scientific assistance for the realization of this publication

Annex A

273

Members of the work group

Membrane Book

Mr. Dr. T. A. Peters

Dr.-Ing. Peters Consulting für

Membrantechnologie und

Umwelttechnik

Broichstraße 91

41462 Neuss

Mr. Dr. V. Mertsch

Ministerium für Umwelt,

Naturschutz, Landwirtschaft und

Verbraucherschutz des Landes

Nordrhein-Westfalen (MUNLV)

40190 Düsseldorf

www.munlv.nrw.de

Ms. K. Drensla

Erftverband

Abteilung Abwassertechnik

(Division waste water engineering)

Forschung und Entwicklung

(Research and development)

Paffendorfer Weg 42

50126 Bergheim

www.erftverband.de

Ms. A. Kaste

Ms. C. Wiedenhöft

Ms. Dr. K. Dreher

Landesumweltamt

Nordrhein-Westfalen (LUA)

Wallneyer Straße 6

45133 Essen

www.lua.nrw.de

Mr. RBD A. Schmidt

Bezirksregierung Köln

(District Government Cologne)

Zeughausstraße 2 – 10

50667 Köln

www.bezreg-koeln.nrw.de

Prof. Dr. rer. nat. W. Schmidt

Fachbereich Versorgungs- und Ent-

sorgungstechnik (Department of

Water Supply, Waste and Waste

Water Disposal Engineering)

Fachhochschule Gelsenkirchen

(Gelsenkirchen University of

Applied Sciences)

45877 Gelsenkirchen

www.fh-gelsenkirchen.de/

fb03/ent/enthf.html

Ms. Dr. J. R. Tschesche

Ms. I. Dierschke

Effizienz-Agentur NRW (EFA NRW)


47057 Duisburg

www.efanrw.de

Mr. T. Wozniak

Aggerverband

Sonnenstraße 40

51645 Gummersbach

www.aggerverband.de

Mr. S. Tenkamp

Staatliches Umweltamt Krefeld

(StUA Krefeld)

(State Environmental Office)

St. Töniser Straße 60

47803 Krefeld

www.stua-kr.nrw.de

AnnexA

274

A.1.4

Other institutions and persons having contributed to the contents

BMU

(Federal Ministry of the Environ-

ment, Nature Conservation and

Nuclear Safety)

DBU

(German Federal Foundation

Environment)

DECHEMA e. V.

(Society for Chemical

Engineering and Biotechnology)

FIGAWA

(Federal Association of

Companies in the Field of Gas

and Water)

PIA e. V.

(Testing and Development

Institute for Waste Water

Engineering at the RWTH

Aachen University)

Ms. E. Brands

Prof. Dr. rer. nat. J. Marzinkowski

Prof. Dr.-Ing. habil. N. Räbiger

Tuttahs & Meyer

Universität Wuppertal

Bergische Universität,

Gesamthochschule Wuppertal

(comprehensive university)

Fachbereich 14, Sicherheitstechnik

(Department of safety engineering)

Gaußstraße 20

42097 Wuppertal

Prof. Dr. rer. nat. J. Marzinkowski

www.uni-wuppertal.de/FB14

Universität Bremen

Institut für Umweltverfahrens-

technik (Institute for Environ-

mental Process Engineering)

Postfach 330440

28334 Bremen

www.fb4.uni-bremen.de

Tuttahs & Meyer Ingenieur-

gesellschaft mbH

Bismarckstraße 2 – 8

52066 Aachen

www.tuttahs-meyer.de

Fachgebiet Sicherheitstechnik/

Umweltschutz der Bergischen

Universität Wuppertal (Department

of Safety Engineering/Pollution

Control)

Campus Freudenberg, Gebäude FF

Rainer-Gruenter-Straße 21

42097 Wuppertal

Frau D. Kunz

www.uws.uni-wuppertal.de

Bundesministerium für Umwelt,

Naturschutz und Reaktorsicherheit

Alexanderplatz 6

10178 Berlin

www.bmu.de

Deutsche Bundesstiftung Umwelt

Postfach 1705

49007 Osnabrück

www.dbu.de

Gesellschaft für Chemische

Technik und Biotechnologie e. V.

Theodor-Heuss-Allee 25

60486 Frankfurt am Main

Mr. Dr. L. Nick

www.dechema.de

FIGAWA Bundesvereinigung

der Firmen im Gas- und

Wasserfach e. V.

Marienburger Straße 15

50968 Köln

www.figawa.de

Prüf- und Entwicklungsinstitut

für Abwassertechnik an der

RWTH Aachen (PIA) e. V.

Mies-van-der-Rohe Straße 1

52074 Aachen

www.pia.rwth-aachen.de


Eisenbahnstraße 5

52352 Düren

www.wver.de

Annex A

275

A.1.5

Other information sources in the field of membrane technology

• DWA-Branchenführer Wasserwirtschaft Abwasser-Abfall 2005

(Trade directory water economy waste water – solid waste)

Edited by

Gesellschaft zur Förderung der Abwassertechnik e. V.

Theodor-Heuss-Allee 17

53773 Hennef

www.gfa-ka.de

• ENVITEC- Internationale Fachmesse

für Ver- und Entsorgung mit Fachkongress (International special fair for

water supply, waste water and solid waste disposal with specialist

conference)

www.envitec.de

• IFAT

Internationale Fachmesse für Wasser – Abwasser – Abfall – Recycling

(International special fair for water – waste water – waste recycling)

www.ifat.de

Conferences on membrane technology:

• AMK – Aachener Membran Kolloquium

(Institut für Verfahrenstechnik (IVT) an der RWTH Aachen)

(Aachen Membrane Colloquium, organized by the Institute for Process

Engineering of the RWTH Aachen University)

• ATSV – Aachener Tagung Siedlungswasserwirtschaft und Verfahrens-

technik (Institut für Verfahrenstechnik (IVT) und Institut für Siedlungs-

wasserwirtschaft (ISA) an der RWTH Aachen)

(Aachen Conference on Environmental Engineering and Process Engi-

neering, organized by the Institute for Process Engineering and Institute

of Environmental Engineering of RWTH Aachen University)

• Bremer Colloquium „Produktionsintegrierte Wasser-/Abwassertechnik“

(IUV – Institut für Umweltverfahrenstechnik, Universität Bremen und

GVC – VDI-Gesellschaft Verfahrenstechnik, Düsseldorf)

(Bremen Colloquium “Production-integrated Water and Waste Water

Technology”, organized by the Institute for Environmental Process

Engineering of the Bremen University and GVC-VDI Society Process

Engineering, Düsseldorf)

Information on the Internet

The Internet portal www.pius-info.de is a cooperation project of the

federal states North-Rhine Westphalia, Rhineland-Palatinate and

Schleswig-Holstein. It offers, among other things, information on the

projects realized, literature, software and possibilities for promotion. It is

continuously updated, extended and supported with contents from other

partners.

In January 2002 it received the Umwelt-Online-Award (Environment-On-

line Award) in silver, the seal of quality for modern environmental com-

munication.

Office of the PIUS-Internet-Portal:

c/o Die Effizienz-Agentur NRW


47057 Duisburg

Mr. H. H. Sittel, Ms. A. Schmitt

www.pius-info.de

AnnexA

A.2

Possibilities for promotion

Planning and implementation of measures contributing

to pollution control, such as the utilization of a membrane

system for waste water treatment, may be promoted and

funded in different ways. Comprehensive development

programs of the federal states, the Federal Government

and the EU promote consultancy and give financial sup-

port for innovations and investments, e. g. in the form of

cost sharing, loans, grants. In order to find the adequate

development program and to make the decision easier,

some development programs in the field of “waste water

avoidance, closed process water circuit” are compiled in

the following. The institutions and contact persons men-

tioned give additional information and advice (for the

most part free of charge) concerning the choice of an

adequate development program for each individual case.

276

Development programs of the Federal Government

KfW-Umweltprogramm (environmental program)

ERP – Umwelt- und Energiesparprogramm

(environmental and energy-savings program)

DtA – Umweltprogramm (environmental program)

BMU – Programm zur Förderung von Demonstrationsvorhaben

(program for the promotion of demonstration projects)

Different fields of promotion of DBU

(German Federal Foundation Environment)

Contact

Kreditanstalt für Wiederaufbau

Palmengartenstraße 5 – 9

60325 Frankfurt am Main

Information centre:

0 18 01/33 55 77 (at local rates)

www.kfw.de

Deutsche Ausgleichsbank

Ludwig-Erhard-Platz 1 – 3

53179 Bonn

Information line:

0 18 01/24 24 00 (at local rates)

www.dta.de

DBU – Deutsche Bundesstiftung Umwelt

Postfach 1705

49007 Osnabrück

An der Bornau 2

49090 Osnabrück

Tel.: 05 41/96 33-0

Fax: 05 41/96 33-190

A.2.1

Development programs and advisory service of the Federal Government

Annex A

The use of the promotion data base is only the first step.

The various advisory services of the Chambers of Industry

and Commerce, associations, of management consultancy,

tax advisers and banks help to clarify all questions con-

cerning concepts, taxes or legislation.

A.2.2

Development programs of the federal states

The institutions to be contacted for the development

programs of the federal states are the environmental

ministries or environmental offices of the respective

federal state. Their addresses are compiled in Table A-1.

In addition, a selection of well-known development pro-

grams concerning the subject “waste water avoidance,

closed process water circuit“ is listed together with the

institutions and persons to be contacted.

For the state North-Rhine Westphalia, the Effizienz-

Agentur NRW (EFA) (Efficiency Agency) must be men-

tioned in particular. It is an action group of the Ministry

for Environment and Nature Conservation, Agriculture

and Consumer Protection. Since the end of 1998, it has

been the first institution to contact for all questions con-

cerning production-integrated environmental protection

(PIUS).

The EFA gives advice and supports small and medium-

sized businesses with the introduction of integrated pol-

lution control measures. It establishes contacts to experts

and shows new ways and possibilities for future-oriented

economic structures. The first analysis of the production

by engineers of EFA shows potentials; the following con-

sultation in cooperation with external experts helps the

enterprises to use them (PIUS ®-Check) . The aim is reduc-

ing both the production costs and environmental pollu-

tion by increasing the efficiency of the raw material used.

277

Advisory service of the Federal Ministry of

Economics and Labour (BMWA)

In the information office, founders of businesses and small

and medium-sized businesses seeking advice get quickly

and unbureaucratically information on the development

programs of the Federal Government, the federal states

and the EU, including information on the procedures to be

followed for receiving development funds, on contact in-

stitutions and conditions of the development programs.

Founders of businesses and investors may also fix a date

for a personal conversation in order to get free-of-charge

information about promotion possibilities.

Promotion data base of the Federal Ministry of

Economics and Labour

The promotion data base of the Federal Ministry of Eco-

nomics and Labour is available as central information

source to private individuals, founders of businesses, enter-

prises and consultants. It addresses users without previ-

ous knowledge as well as experts in economic promotion

and allows the search for development funds and ade-

quate promotion programs.

The promotion data base of the Federal Government pro-

vides a complete and topical overview of the development

programs of the Federal Government, the federal states

and the European Union. The promotion activities are

summarized according to uniform criteria, independent

of the promotion level or the funding institution, and

represented consistently. The connections between the

individual programs are also explained, this is important

for the efficient use of government promotion.

The comprehensive cross-linkage on the Internet allows

to get more detailed information on the different pro-

viders of promotion information.

Advisory service of BMWA

Tel.: +49 (0)30/20 14-800

Fax: +49 (0)30/20 14-70 33


Promotion data base of the

Federal Ministry of Economics and Labour

www.bmwa.bund.de

1) PIUS® is a registered trademark of the Effizienz-Agentur NRW

AnnexA

In addition, the EFA informs about topical possibilities for

the promotion of small and medium-sized businesses and

helps in searching the adequate development program for

financing of projects in the field of production-integrated

environmental protection. The headquarters of the EFA is

the House of Economic Promotion in Duisburg. Since the

beginning of the year, four regional offices at Aachen, Biele-

feld, Münster and Siegen have ensured direct contact in

the different economic regions of North-Rhine Westphalia.

In addition, the publication “Förderprogramme für den

Produktionsintegrierten Umweltschutz“ (Development

programs for production-integrated environmental pro-

tection) gives an overview of the different promotion

278

EFA – Die Effizienz-Agentur NRW: “Förderprogramme für den Produk-

tionsintegrierten Umweltschutz“. Zielgerichtet planen. Effizient

umsetzen. Umfassend profitieren. (“Development programs for pro-

duction-integrated environmental protection”. Calculated planning.

Efficient implementation. Comprehensive profit.) As of 06/2000.

Baden-Württemberg

Bavaria

Berlin

Landesanstalt für Umweltschutz (LfU)

Baden-Württemberg

Griesbachstraße 1

76185 Karlsruhe

Postfach 21 07 52

76157 Karlsruhe

Tel.: +49 (0)7 21/9 83-0

Fax: +49 (0)7 21/9 83-14 56

www.lfu.baden-wuerttemberg.de

Bayerisches Staatsministerium für

Landesentwicklung und Umweltfragen

Rosenkavalierplatz 2

81925 München

Tel.: +49 (0)89 / 92 14-00

Fax: +49 (0)89 / 92 14-22 66

www.umweltministerium.bayern.de

Senatsverwaltung für Stadtentwicklung

Brückenstraße 6

10179 Berlin

Tel.: +49 (0)30/90 25-0

Fax: +49 (0)30/90 25-29 20

www.stadtentwicklung.berlin.de/umwelt

Development program for pollution control and

energy saving measures

Contact:

L-Bank; Wirtschaftsförderung II

Friedrichstraße 24

70174 Stuttgart

Telephone hotline: +49 (0)7 11/1 22-23 45

Fax call for information on the conditions:

+49 (0)7 11/1 22-26 74

www.l-bank.de

Additional program of LfA-Umweltschutz

Contact:

LfA Förderbank Bayern

Königinstraße 17

80539 München

Tel.: +49 (0)1 8 01/21 24 24 (at local rates)

www.lfa.de

Das Umweltentlastungsprogramm – UEP

(program for pollution reduction)

Contact: Beratungs- und Servicegesellschaft

Umwelt mbH (B & SU)

Hohenzollerndamm 44

10713 Berlin

Tel: +49 (0)30/3 90 42-84

www.uep-berlin.de

Table A-1

Contacts for development programs of the federal states and selected development programs concerning

“waste water avoidance, closed process water circuits“

Federal state Contact Development programs

possibilities. Besides much additional information on

production-integrated environmental protection, the

Internet portal www.pius-info.de offers information on

promotion possibilities. The Internet portal is a joint pro-

ject of the federal states North-Rhine Westphalia, Rhine-

land-Palatinate and Schleswig-Holstein, it is continuously

updated and extended.

Annex A

279

Brandenburg

Bremen

Hamburg

Hesse

Mecklenburg-Vorpommern

Ministerium für Landwirtschaft, Umweltschutz

und Raumordnung des Landes Brandenburg

Heinrich-Mann-Allee 103

14473 Potsdam

Tel.: +49 (0)3 31/8 66-0

Fax: +49 (0)3 31/8 66-70 68, -70 69, -70 71

www.brandenburg.de/land/mlur

Der Senator für Bau und Umwelt

Hanseatenhof 5

28195 Bremen

Tel.: +49 (0)4 21/3 61-21 36

Fax: +49 (0)4 21/3 61-60 13

www.umwelt.bremen.de

Freie und Hansestadt Hamburg

Behörde für Umwelt und Gesundheit

Fachamt für Energie und Immissionsschutz (I1)

Billstaße 84

20539 Hamburg

Tel.: +49 (0)40/4 28 45-0

www.hamburg.de/Behoerden/Umweltbehoerde

Hessisches Ministerium für Umwelt,

Landwirtschaft und Forsten

Bereich Umwelt und Energie

Mainzer Straße 80

65189 Wiesbaden

Tel.: +49 (0)6 11/8 15-0

Fax: +49 (0)6 11/8 15-19 41

www.mulf.hessen.de

Umweltministerium Mecklenburg-Vorpommern

Allgemeine Information und Koordinierung

der Förderprogramme

Schlossstraße 6 – 8

19053 Schwerin

Tel.: +49 (0)3 85/5 88-0, -8 20

Fax: +49 (0)3 85/5 88-87 17

www.um.mv-regierung.de

Development program for environmental technology

Contact:

see left

Freie und Hansestadt Hamburg

Behörde für Umwelt und Gesundheit

Innovation Foundation Hamburg

Alter Steinweg 4

20459 Hamburg

Tel.: +49 (0)40/4 28 41-17 59

www.hamburg.de/Behoerden/Umweltbehoerde

Table A-1 (Continuation)




AnnexA

280

Lower Saxony

North-Rhine Westphalia

Rhineland-Palatinate

Niedersächsisches Umweltministerium

Postfach 4107

30041 Hannover

Tel.: +49 (0)5 11/1 20-0

Fax: +49 (0)5 11/1 20-33 99

www.mu.niedersachsen.de

Ministerium für Umwelt und Naturschutz,

Landwirtschaft und Verbraucherschutz des

Landes Nordrhein-Westfalen

Schwannstraße 3

40 476 Düsseldorf

Tel.: +49 (0)2 11/45 66-0

Fax: +49 (0)2 11/45 66-3 88

www.munlv.nrw.de

Landesumweltamt NRW

Wallneyer Straße 6

45133 Essen

Tel.: +49 (0)2 01/79 95-0

Fax: +49 (0)2 01/79 95-14 48

www.lua.nrw.de



47057 Duisburg

Tel.: +49 (0)2 03/3 78 79-58

Fax: +49 (0)2 03/3 78 79-44

www.efanrw.de

Ministerium für Umwelt und Forsten

Kaiser-Friedrich-Straße 1

55116 Mainz

Tel.: +49 (0)61 31/16-0

Fax: +49 (0)61 31/16 46 46

www.muf.rlp.de

“Action group Ecological and Sustainable Water

Management in North-Rhine Westphalia NRW“

Development area 1: Innovative or proved

production-integrated environmental protection

Contact:

see left, and in addition:

INVESTITIONS-BANK NRW

Zentralbereich der WestLB

Friedrichstraße 56

40217 Düsseldorf

Tel.: +49 (0)2 11/8 26-09

Fax: +49 (0)2 11/8 26-84 59

IISB loans for small and medium-sized businesses

within the scope of pollution control

Contact:

Investitions- und Strukturbank Rheinland-Pfalz

(ISB) GmbH

Holzhofstraße 4

55116 Mainz

Tel.: +49 (0)61 31/9 85-3 50

www.isb.rlp.de





Annex A

281

Saarland

Saxony

Saxony-Anhalt

Schleswig-Holstein

Thuringia

Ministerium für Umwelt

Keplerstraße 18

66117 Saarbrücken

Tel.: 06 81/5 01-00

Fax: 06 81/5 01-45 21

www.umwelt.saarland.de

Sächsisches Staatsministerium für Umwelt und

Landwirtschaft

Archivstraße 1

01097 Dresden

Tel.: 03 51/5 64-0

Fax: 03 51/5 64-22 09

www.smul.sachsen.de

Ministerium für Landwirtschaft

und Umwelt des Landes Sachsen-Anhalt

Olvenstedter Straße 4

39108 Magdeburg

Tel.: 03 91/5 67-01

Fax: 03 91/5 67-17 27

www.mrlu.sachsen-anhalt.de

Landesamt für Natur und Umwelt des Landes

Schleswig-Holstein (LANU)

Hamburger Chaussee 25

24220 Flintbek

Tel.: 0 43 47/7 04-0

Tel.: 0 43 47/7 04-12

www.umwelt.schleswig-holstein.de

Thüringer Ministerium für Landwirtschaft,

Naturschutz und Umwelt

Beethovenplatz 3

99096 Erfurt

Tel.: 03 61/37-9 00

Fax: 03 61/37-9 99 50

www.thueringen.de/de/tmlnu

Compilation of topical development programs in

the field of energy and pollution control

Contact:

Investitionsbank Schleswig-Holstein

Fleethörn 29-31

24103 Kiel

Tel.: 0431 / 900 3651

www.lanu.landsh.de





AnnexA

A.2.3

Development programs of the EU in the field of

pollution control and water management

Structural and regional promotion

Structural and regional promotion by the European

Union is based on the four European Structural Funds:

European Regional Development Funds (ERDF), European

Social Funds (ESF), The European Agricultural Guidance

and Guarantee Fund (EAGGF) and the Financial Instru-

ment for Fisheries Guidance (FIFG). Concerning measures

in the field of pollution control, the ERDF is the most

important Structural Funds of the EU.

• Structural Funds

The aim of European Regional Development Funds

(ERDF) is to promote economic and social cohesion by

correcting the main regional imbalances and partici-

pating in the development and conversion of the various

regions. The ERDF funds are provided for certain less-

favoured regions and mainly used to finance improvement

of the infrastructure, productive investments, local

development and protection of the environment.

For promotion, it is distinguished between Objective 1

and Objective 2 regions.

Objective 1 supports the development and structural

adaptation of underdeveloped regions. Among them are

those regions with a per capita gross domestic product

(GDP) lower than 75% of the Community average.

Five main actions are provided:

• Promotion of the competitiveness of the industry and

small and medium-sized businesses

• Development of the infrastructure

• Protection of the environment

• Development of the manpower potential

• Development of rural areas

Objective 2 supports the economic and social conversion

of areas experiencing structural difficulties. During the

period 2000-2006, it is distinguished between four types

of areas with structural difficulties:

• Industrial areas

• Rural areas

• Urban areas

• Areas depending on fishery

The measures within the scope of the Objectives 1 and 2

are co-financed. The maximal part of the EU for Germany

and Objective 1 is 75 %, for Objective 2 maximally 50.

Development programs in the field of environmental

protection

The main objectives of the development programs descri-

bed in the following are the protection of the environment

and the development of the environmental policy of the

Community.

LIFE III Program

The general objective of LIFE is to contribute to the im-

plementation, updating and development of Community

policy and legislation relating to the environment, in

particular, with regard to the integration of the environ-

ment into other policies, as well as to sustainable devel-

opment in the Community.

LIFE offers financial support for environmental measures

in the Community and certain third countries (Mediter-

ranean countries or littoral states of the Baltic Sea,

countries of Central and East Europe which have signed

association agreements with the European Union).

The following areas are promoted by LIFE:

• European Community, Central and East European

countries: nature conservation, promotion of

sustainable development in industrial activities, inte-

gration of environmental aspects in regional planning

policy, waste management, atmospheric pollution and

water management;

• other Third Countries: technical assistance in the

establishment of administrative structures, maintenance

and rehabilitation of habitats of endangered species,

promotion of sustainable development.

282

Annex A

The eligibility for promotion mainly depends on the

following points:

• The measures in the European Community have to be

of Community interest, they must be innovative,

reliable and feasible.

• The measures outside the Community must be techni-

cally and financially feasible and contribute to sustain-

able development and cooperation.

Die Aktion wird in den betreffenden fünf Jahren (2000 –

2004) auf drei wichtige Bereiche konzentriert:

Over the respective five years (2000 – 2004), the action

will focus on three important fields:

• Nature conservation (LIFE-Nature): actions aimed at

conservation of natural habitats and the wild fauna

and flora of European Union interest They support

implementation of the nature conservation policy and

the Natura 2000 Network of the European Union.

• Environment (LIFE-Environment): actions which aim

to implement the Community policy and legislation

on the environment in the European Union and candi-

date countries. This approach enables demonstration

and development of new methods for the protection

and the enhancement of the environment.

• Third countries (LIFE-Third Countries): actions con-

cerning technical assistance activities for establishing

administrative structures in the field of environmental

protection, actions for nature conservation and

demonstration measures for promoting sustainable

development in some Mediterranean countries and

littoral states of the Baltic Sea.

For actions financed by the LIFE program, a subsidy of

50 % of the total costs is given. Within the scope of LIFE-

Environment, demonstration projects are funded which,

however, must not be research, studies or investments in

infrastructure. The proposals must have for subject pilot

actions or actions concerning technical assistance which

are suited to improve the environmental conditions in a

quantifiable way and which can be reproducible at other

locations of the European Union.

In Germany, eight projects are being promoted by LIFE-

Environment in 2004, one of it in the field of waste

water with the subject “Nutrient removal by membrane

bioreactors“. This project called ENREM will run until

December 2006. It is realized by Kompetenzzentrum

Wasser Berlin GmbH.

EU contact:

General Direction Environment

LIFE-Program

Bruno Julien

General Direction Environment D. 1

BU 2/01

Rue de la Loi 200

B-1049 Brüssel

[email protected]

Instrument for structural policies for pre-accession

(ISPA)

This development program aims at preparing the countries

Estonia, Latvia, Lithuania, Poland, The Czech Republic,

Slovakia, Hungary, Slovenia, Romania, Bulgaria) for acces-

sion. Investment projects in the field of national trans-

port and environment are funded.

Community assistance under the ISPA is granted for the

period 2000-06. The total budget is 7 billion s . The rate

of assistance may be up to 75 % of the total costs in the

form of non-repayable subsidies for public administra-

tions and public enterprises.

Further information:

http://www.europa.eu.int/comm/regional_policy/

index_en.htm

EU contact:

General Direction Regional Policy

Rue de la Loi

B-1049 Bruxelles


283

AnnexA

284

Definition of the objective

Expansion/Upgrade of activated sludge stages

New construction

Upgrade in order to comply with more stringent demands

...

A.3

Short check lists for Figure 2-1

1 Reason and objective

Technical boundary conditions

Demands on the effluent (minimum requirements/more far-reaching requirements)

Capacity of an existing waste water treatment plant

Drainage system

Inflow features

Conversion/possible addition of membranes into existing tanks

...

Economic conditions

Investments, in particular specific membrane costs

Subsidies for investments

Operating costs (membrane replacement costs, cleaning, energy consumption)

Waste water charge

...

2 Analysis of the current situation

Utilization of existing tanks

New construction of tanks and membrane stage

Selection and arrangement of the membrane modules

Necessary pretreatment measures

Design and realization of membrane cleaning

3 Study of variations

Design

Sludge age, sludge loading, excess sludge production

Solid matter content in the activated sludge tank

Minimum retention time, mixing and compensating tank

Distribution of denitrification, nitrification and variable zone

Oxygen carry-over by recirculation

Necessary membrane surface area for constantly stable flow rates

Influence of the temperature on the permeability

Membrane surface area available in the case of cleanings

Module ventilation according to the manufacturer’s specification

Oxygen input depending on the solid matter content

Phosphorus removal

Sludge treatment: dewatering and digestibility

…

4 Planning, design and construction

Design of the construction

Pretreatment quality (screen, separator for light-density material)

Buffer tank in the inflow or the installation

Realization of two or more lines

Hydraulic decoupling of several lines

Short membrane replacement and delivery times

Devices for membrane cleaning

Power supply

…

4 Design of the construction (continuation)

Operating stability

Training/instruction of the staff

Guarantee of the filtration capacity

Control of the membrane state (sticking of fibrous material etc.) and permeability

Regular membrane cleaning (intermediate, intensive cleanings)

Operating costs

Energy consumption of tank and module aeration

Service life of the membranes

Costs of cleaning agents

Regular membrane cleaning (intermediate, intensive cleanings)

…

Safety at work

Handling of cleaning agents

…

5 Operation and control

Annex A

285

AnnexA

286

Compliance with the demands

Cost reduction

Saving of water

Saving of chemicals

Saving of energy

Recovery of valuable substances

Reduction of discharge costs

Reduction of the transport costs

Reduction of waste water charges

…

A.4

Short check lists for Figure 3-1

1 Reason and objective

Data recording

Production process

Input and output of resource flows

Determination of the material flows and place of their production

Waste water flows

Waste water volume, chemical and physical quality

Valuable and undesired substances in the flow to be treated

Processes limiting the process, and other restrictions

Costs for the current situation, i. e. without recovery and recycling under monetary and environmental-engineering aspects

…

Suggestions for improvements / potentials

Possibilities for avoidance in the production process

Treatment of residual matter

Is it possible to recover valuable resources from the material flow?

Utilization / whereabouts of the valuable material recovered

…

2 Analysis of the current situation

Definition of the objective

Possible separation processes

Is it necessary or possible to modify the production process?

Effectiveness of the processes?

Is it possible to attain the required objectives by this process?

Comparison of the economic efficiency

Laboratory tests, pilot tests

3 Selection of the process

Annex A

287

Comparison of the economic efficiency

Existing process, no change

Costs of water supply

Energy costs

Costs of chemicals

Costs of raw material

Discharge costs for liquid waste

Disposal costs for solid waste

Laboratory costs

…

Membrane process installed

Investments for new installation

Membrane replacement costs

Investments for peripheral installations, pumps, equalization tank …

Separated valuable material

Possibilities for promotion

…

3 Selection of the process (Continuation)

Tests on different levels

Preliminary tests

Laboratory tests

Choice of membranes

Pilot tests


…

Operator model or owner-operated

e. g. ”BOO Build-Own-Operate“

…

Contract regulation

Duration of the contract

Guarantee period, service life of the membranes

Price regulation

…

5 Operation and control

4 Planning and pilot phase

AnnexA

A.5

Work report of the ATV-DVWK working group

IG-5.5 “Membrane Technology”: Treatment of indus-

trial waste water and process water by membrane

processes and membrane bioreactor processes

This work report has been established by the ATV-DVWK

working group IG-5.5 “Membrane Technology” of the

ATV-DVWK Committee of Experts IG-5 “Industrial Waste

Water Treatment”. The report consists of several parts.

Part 1 deals with the membrane treatment process itself,

i. e. with its use for the separation of undissolved, colloidal

or dissolved substances.

Part 2 looks into the membrane bioreactor process. It

focuses on the process unit consisting of biological de-

gradation in the aeration tank and separation of the bio-

mass by membranes. It deals in particular with the requi-

rements and specific features of the membrane bioreactor

process compared to the conventional activated sludge

process. A third part is planned in which concrete exam-

ples, operating experience and design instructions will be

summarized.

The ATV-DVWK working group included the following

members:

Dr.-Ing. Goetz Baumgarten, Langenhagen

Dr.-Ing. Martin Brockmann, Hilden

Dipl.-Biol. Ulrich Brüß, Herten

Prof. Dr.-Ing. Peter Cornel, Darmstadt (speaker)

Dr.-Ing. Oliver Debus, Hamburg

Dipl.-Ing. Michael Kiefer, Stuttgart

Dr.-Ing. Angelika Kraft, Essen

Prof. Dr. Peter M. Kunz, Mannheim

Dr.-Ing. Otto Neuhaus, Bergkamen

Dr.-Ing. Thomas Peters, Neuss

Prof. Dr.-Ing. Karl-Heinz Rosenwinkel, Hannover

(deputy speaker)

Prof. Dr.-Ing. em. Carl Seyfried, Hannover (chairman)

Dr.-Ing. Jianming Shang, Hamm

Prof. Dr.-Ing. Ulf Theilen, Gießen

Dr.-Ing. Frieder Wagner, Heuweiler

With the cooperation of:

Dipl.-Biol. Annette Achtabowski, Bergkamen

Dipl.-Ing. Stefan Krause, Darmstadt

Prof. Dr. Winfried Schmidt, Gelsenkirchen

Dipl.-Ing. Jens Wagner, Hannover

Part I

Membrane processes

A.5.1

Introduction

Membrane processes are pure physical processes for

material separation, by which the waste water or the pro-

cess water to be treated is separated into purified water

(filtrate or permeate) and a concentrated phase (concen-

trate) (Figure A-1). The driving force for these separation

processes is the transmembrane pressure difference. These

pressure-driven processes differ in the extent of the pres-

sure difference. Membrane processes based on other

driving forces, such as an electrical field or a concentra-

tion difference, will not be discussed here because of

their insignificant practical importance in waste water

treatment. In contrast to conventional filtration techno-

logies, pressure-driven membrane processes allow for

separation up to the molecular range.

Two features are of special importance for the success of

a membrane process:

• the selectivity of the membranes, i. e. their capacity to

distinguish between the components of a mixture (e. g.

between oil and water or between ions and water). The

membrane hinders the transport of various components

in different ways.

• the performance of the membrane (often called mem-

brane flux), i. e. the permeate or filtrate (usually given

in L/(m2 �h) to be obtained under certain operating

conditions.

288

Annex A

Figure A-2 shows the classification of the membrane pro-

cesses as function of the particle or molecular size and

the pressure difference.

With membrane processes it is possible to separate waste

water constituents, such as:

• solids

• dissolved matter

• colloids and

• liquids of a second phase

289

waste water(feed)100 %

membrane process treated waste water(permeate/filtrate)e. g. 90 %

concentrated waste wateror reusable matter(concentrate)e. g. 10 %

Figure A-1

Schematic representation of the basic principle of a membrane process

1

0,1

0,0001

particle or molecular size [µm]

pre

ssur

e d

iffe

ren

ce [

bar

]

0,001 0,01 0,1 1 10 100

10

100

200

reverse osmosis

nanofiltration

ultrafiltration

microfiltration

filtration

common salts

metal salts

virus bacteria

coloured pigments

Figure A-2

Classification of membrane and filtration processes

AnnexA

Independent of the process or the separation goal, various

treatment objectives can be pursued which are of economic

interest, for example:

1.water purification e. g. for

• compliance with the discharge standards

• reuse

2.concentration of water constituents, e. g. for

• recovery of reusable material

• reduction of discharge costs

To understand the selectivity of membranes, models have

been developed which can be condensed, for a coarse

overview, into two borderline cases. One distinguishes

the so-called solution-diffusion membranes (reverse

osmosis, nanofiltration) and the pore membranes (micro-

and ultrafiltration).

• The solution-diffusion membranes have a homogeneous

interlayer, comparable to a gel. To pass the membrane,

the substance must dilute in the membrane material.

Consequently, the selectivity is based on the varying

solubility and the varying passage velocity of the sub-

stances to be separated through the membrane material.

Material transport through the membrane takes place

according to the principles of diffusion (Fick principle).

The driving force for the dissolved substances in all

diffusion-controlled membrane processes is the dif-

ference in the chemical or electrochemical potential

at both sides of the membrane, while the driving force

for the solvent, i. e. the water, is the pressure difference.

This model describes the separation effect of reverse

osmosis membranes. To describe the separation features

of nanofiltration membranes, electrochemical inter

actions with the membrane surface, which as a rule is

negatively charged, must also be considered.

• The pore membranes have a porous structure with

channels. The selectivity is based on a screening effect

which is determined by the pore size distribution of

the membranes. Material transport takes place in a

pure convective way according to the principles of the

laminar capillary tube flow (Hagen-Poisseulle principle)

as a result of the pressure difference between both sides

of the membrane. This model describes theoretically

the separation effect of micro- and ultrafiltration mem

branes. In practice, however, these processes are as a

rule controlled by a covering layer. This covering layer

(“secondary membrane”) develops from the substances

concentrated on the membrane surface.

Due to the concentration of the water constituents taking

place at the raw-water side of the membrane, the follo-

wing effects may occur on the membrane surface as well

as on components of the membrane elements or the

membrane modules which have negative effects on the

performance of a membrane installation:

scaling

deposition of inorganic water constituents after precipi-

tation by supersaturation, crystal formation

fouling

formation of a covering layer by organic water constituents

biofouling

formation of a biofilm by microorganisms

These effects can be avoided or at least minimized by cor-

responding measures. It is for example possible to avoid

the precipitation of inorganic components such as CaSO4

or CaCO3 by shifting the pH value (and, with this, the

solubility limit) and/or dosing of anti-scaling agents

(complexing agents, e. g. phosphonic acid, polycarboxylic

acid). The formation of a biofilm can be avoided or mini-

mized by corresponding pretreatment of the raw water

as well as backwashing and cleaning of the membranes

adapted to the special case.

290

Annex A

291

A.5.2

Choice of a membrane process

When choosing a membrane process, at first four impor-

tant decisions have to be made:

• determination of the necessary molecular separation

size of the membrane to be chosen

• determination of the membrane material

• decision on the module type

• decision of the process

The criteria for this choice are described in the following.

A.5.2.1

Determination of the necessary molecular

separation size

The type of the components to be separated from a waste

water or a process water, i. e. the necessary selectivity,

determines the type of the membrane to be used. Some

examples in Table A-2 illustrate the classification of the

separation of water constituents with the membrane

types. For the pore membranes, the pore size, utilized by

majority in practice, is indicated. The units and separa-

tion sizes used in the Table correspond to the terms ap-

plied normally by the membrane manufacturers. The

unit (g/mol) for the molecular weight corresponds to the

unit Dalton which is used in other publications.

A.5.2.2

Determination of the membrane material

Today nearly the whole membrane technology in the field

of water and waste water treatment is based on synthetic

polymer membranes, briefly described in the following.

In spite of high investment costs, ceramic membranes

recently have become established in special fields of ap-

plication (high temperatures, aggressive media, solvents).

From the general material transport principles (convection,

diffusion) it is known that the permeate flow [L/(m2 � h)]

is inversely proportional to the length of the transport way.

For this reason, the membrane manufacturers have tried

to make available rather thin separating layers. Yet the

mechanical strength of the membrane has to be ensured.

While in microfiltration, as a rule, symmetric membranes

are used, asymmetric membranes have gained acceptance

in ultra- and nanofiltration as well as in reverse osmosis.

In this case, one distinguishes between phase-inversion

and composite membranes, depending on the production

process. Active layer and substructure of the phase inver-

Abtrennbare Trenngrenze Verfahren Betriebsdruck

Wasserinhaltsstoffe (Porengröße) [Membran-Typ] kPa (bar)

Table A-2

Membrane processes and their fields of application

Partikel > 0.1 µm 0.1 – 1 µm Microfiltration (MF) 50 – 300 kPa

emulgierte Stoffe (pore membranes) (0.5 – 3 bar)

Kolloide, Makromoleküle 2,000 – 200,000 g/mol Ultrafiltration (UF) 50 – 1,000 kPa

Molmasse > 2,000 g/mol (0.004 – 0.1 µm) (pore membranes) (0.5 – 10 bar)

emulgierte Stoffe

Organische Moleküle > 200 g/mol Rückhaltung Nanofiltration (NF) 500 – 4,000 kPa

mehrwertige, anorganische Ionen MgSO4 > 90 % (solution-diffusion (5 – 40 bar)

(0.001 – 0.005 µm) membranes with integrated

ionogenic groups)

Organische Moleküle und alle Ionen < 200 g/mol Rückhaltung Reverse osmosis (RO) 500 – 7,000 kPa

für NaCl > 95 % High-pressure reverse osmosis (5 – 70 bar)

(solution-diffusion membranes) up to 12,000 kPa

(up to 120 bar)

AnnexA

sion membrane are made from the same material, while

composite membranes have a thin, homogeneous poly-

meric layer cast on a support back-up structure which

enables separate optimization of the layers. The Figures

A-3 and A-4 show the general structure of phase-inver-

sion and composite membranes.

The membranes produced from cellulose derivates often

applied in the past have been replaced to a great extent

by membranes from completely synthetic polymers (poly-

sulphone, polyether sulphone, polyamide, polypropylene,

polyacrylonitrile etc.). These membranes offer the particular

advantage of being more resistant to the various media.

Table A-3 gives an overview of the most current membrane

materials used for the different membrane processes.

292

Figure A-3

Cross-section of a phase-inversion membrane,

example: UF hollow-fibre membrane

microporous backing materialup to a thickness of 50 µm

porous polyester networkup to a thickness of 125 µm

active layer up to 2500 Å= 1/4000mm thickness barrier layer

2500 Å

Figure A-4

Composite membrane, left: general structure of a composite membrane, right: cross-section of a composite

membrane

Annex A

293

A.5.2.3

Determination of the membrane module

The main element of each membrane installation is the

module in which the membrane surface area is arranged

as an engineered system. The ideal module ensures the

following aspects:

• good and constant flow over the membranes without

dead-water zones

• low pressure losses

• high packing density

• low-cost production

• easy cleaning

• easy replacement of the membranes

• low disposition for clogging

Since no module is capable of meeting all these contra-

dictory requirements in an optimal way, various module

types have been developed, including some designs for

Microfiltration polypropylene (PP)

polyvinylidene fluoride (PVDF)

polysulphone (PSU)

�-aluminium oxide

high-grade steel, titanium dioxide

zirconium oxide

Ultrafiltration polysulphone (PSU)

reg. cellulose

polyacrylonitrile (PAN)

polyether sulphone (PES)

titanium oxide, zirconium oxide

polyvinylidene fluoride (PVDF)

Nanofiltration polyamide (PA)

(zirconium oxide), PES

cellulose acetate (CA)

Reverse osmosis polyamide (95 %)

cellulose acetate (5 %)

Table A-3

Overview of the most current membrane materials for the different membrane processes

Process Active layer

specific applications. Disregarding constructive details,

the modules can be subdivided into two groups:

modules with tubular membranes

• tube module

• capillary module

• hollow-fibre module

modules with flat membranes

• plate module

• spiral-wound module

• cushion module

• rotating module

AnnexA

The size and investment and operating costs of a mem-

brane installation are closely related to the specific per-

meate performance and the membrane surface area to be

installed. It has to be arranged as favourably, i. e. as com-

pact as possible, without endangering the operational

safety.

In waste water engineering, this means that the type and

concentration of the solid matter fed to a membrane

installation and the solid matter formed in the course of

the process decisively influence the module system to be

chosen. Table A-4 gives an overview of the features and

fields of application of the different module types.

The structure of the different modules is represented in

Figures A-5 – A-7.

294

Type (examples) Packing density [m2/m3] Specific costs per m2 Covering layer control Fields of application

Table A-4

Features and fields of application of different module types

Rotating module 10 – 50 – – – + + + MF and UF

Tube module 20 – 90 – – + + MF, UF, NF, RO

Plate and cushion module 100 – 250 – + + MF, UF, NF, RO

Capillary module 600 – 1,200 0 + MF, UF, NF

Spiral-wound module 700 – 1,000 + – RO, NF, UF

Hollow-fibre module > 1,000 ++ – – RO, UF

– negative 0 average + positive

Figure A-5

Front view of a tube module with 5.5 mm tubular

membranes [photo: X-FLOW]

Figure A-6

View of a cushion module (type ROCHEM FM)

permeate collecting tube(central tube)

tube water

permeate outlet afterpassage through themembrane concentrate

membrane

permeate spacer

feed spacer

feed

wrap

permeate

permeatespacer

membrane

Figure A-7

Principle of a spiral-wound module

A.5.2.4

Determination of the operating mode of

membrane installations

Like the choice of the module, the operating mode of a

membrane process is determined by the load or the con-

centration of the dissolved and/or the undissolved

constituents of the respective waste water or process

water. The specific energy demand of the operating mode

influences the economic efficiency and, with this, the

feasibility of the individual applications.

As a rule, membrane processes are operated in cross-flow

mode, also called tangential flow. Tangential flow to the

brine or concentrate side of the membrane attempts to

limit the development of a covering layer on the mem-

brane and to maintain a constant permeate flow at the

highest possible level.

Annex A

295

The dead-end operation stands in contrast to the cross-

flow mode. Like in classical cake-forming, static filtration,

the filtration capacity decreases with increasing thickness

of the covering layer. Combined with an effective back-

washing technique, this operating mode is used success-

fully in microfiltration and ultrafiltration applications.

The combination of both operating modes is called semi-

crossflow mode.

Both operating modes, dead- end and cross-flow, differ

considerably in their energy demand. Pure cross-flow

processes need between 2 kWh/m3 and 10 kWh/m3 (for

MF and UF) or between 0.5 and 5 kWh/m3 (for NF and

RO), while pure dead-end processes operate with an ener-

gy consumption of between 0.1 and 0.3 kWh/m3.

AnnexA

A.5.3

Examples for the use of membrane processes

Pressure-driven membrane processes have proved their

suitability in many fields. The following list does not

claim to be complete.

• filtration of pickling acids (MF, UF)

• treatment of waste water from a CP plant in

electroplating (RO)

• treatment of landfill leachate (NF, RO)

• extension of the service life of degreasing baths

(MF, RO)

• recovery of reusable material from dyeing waste

water (UF)

• treatment of waste water from flexographic

printing (MF)

• treatment of waste water from spark erosion (MF)

• treatment of waste water from slide grinding (MF)

• treatment of grey water on ships (RO)

• water recycling from solid matter-containing waste

water from the production of semiconductor

elements (CMP, grinding, sawing) (UF)

• reutilization in the semiconductor industry (RO)

• oil separation from compressor condensates (MF)

• concentration of cutting oils (UF)

• treatment of lyes (MF, UF, NF)

• reutilization in the food industry (RO)

• treatment of rinsing water from degreasing in the

metal-processing industry (RO)

• treatment of recirculation water in non-metal

processing (UF)

• separation of biologically hardly degradable organic

components (NF)

• treatment of waste water from flue gas cleaning (MF)

• treatment of acids (NF)

• treatment of sludge water (filter backwash water) (UF)

• treatment of sludge water in swimming-pools (RO)

• concentration before thermal treatment (RO)

• pretreatment of waste water for further treatment by

reverse osmosis (MF, UF)

• closing of water cycles (UF, NF, RO)

• recovery of reusable material from water-based paint

(UF)

• reduction of germs in the effluents of waste water

treatment plants (MF, UF), see Part 2 of the work report

• retention of sludge in membrane bioreactors

(MF, UF), see Part 2 of the work report

A.5.4

Planning of membrane installations

A.5.4.1

Acquisition of basic data

As a basis for the planning of a membrane installation,

all relevant data on the waste water or process water to

be treated has to be collected for the longest possible

period and documented in an adequate way. This data con-

cerns volume flow or batch quantity, chemical/physical

parameters and other process-specific dissolved and undis-

solved water constituents (see chapter A.5.6 “Questionnaire

for the acquisition of process data”).

Besides the waste water situation of the present-day oper-

ating state, the water balance of the whole enterprise

also has to be determined in order to get the basis for the

specification of the objective and a rough assessment of

the effects of a new process concept on the operation.

The assessment of the potential for savings and the results

expected should be completed by examinations of partial

flows and of changes concerning upstream process steps.

A.5.4.2

Planning and design

When the acquisition of basic data has shown that a certain

membrane process can be used, the procedure described

below should be followed because it has proved successful

in planning such installations. As a rule, successful opera-

tion can only be ensured by the procedure described.

A.5.4.2.1

Preliminary laboratory tests

The preliminary tests serve for first orientation and are

usually carried out with reference to the following aspects:

• selection of membranes and modules with determina-

tion of the general suitability of a medium to be

treated by the membrane process chosen

296

Annex A

• preselection of potentially necessary pretreatment

measures, assessing at the same time the scaling,

fouling and biofouling potential, and preliminary tests

on membrane cleaning

• approximate determination of the most important

process parameters such as pressure, temperature,

overflow velocity and attainable output

A.5.4.2.2

On-site pilot tests

The pilot tests to be outlined on the basis of the laboratory

tests serve to establish the specific design basis, the purifi-

cation strategies and other process-engineering and installa-

tion-specific conditions. The pilot installation has to be

planned in such a way that the hydraulic conditions (over-

flow conditions of the membrane, module connection)

of the membrane elements, i. e. of the modules, can be

transferred to the large-scale installation. Only in this way

will up-scaling be possible without problems. The pilot tests

should be carried out with the following considerations:

• on-site operation of a semi-technical pilot plant in con-

tinuous operation under practical conditions, taking

down all data relevant for calculation including pre-

treatment

• determination of the permeate efficiency as function of

the process section and the time

• of the membranes: determination of the cleaning

intervals, optimization of the cleaning processes, deter-

mination of the demand for chemicals

Optimal chemical cleaning of the membranes is impor-

tant for their continuous functioning. Depending on the

type of contamination, different chemicals have to be

used. A cleaning strategy has to be developed for each

single case, but in principle the following chemicals are

used for the different types of contamination:

membrane contamination by scaling: cleaning by

acids, e. g. citric acid, hydrochloric acid; if necessary,

complexing agents

membrane contamination by fouling: cleaning by

oxidizing agents, e. g. hydrogen peroxide, peracetic acid,

sodium hypochlorite

membrane contamination by biofouling: cleaning by

oxidizing agents or by lyes, e. g. caustic-soda solution

Between the individual cleaning steps, the installation

has to be rinsed with water to avoid interactions between

the chemicals used.

The following cleaning strategy is described by way of

example:

1. displacement of the process water from the installation

2. cleaning by citric acid/hydrochloric acid at pH 3 to

detach inorganic layers, duration about 1 – 4 hours at

slightly increased temperature

3. intermediate rinsing with water, i. e. displacement of

the cleaning solution used in step 2

4. treatment by NaOCl/NaOH at pH 11 to oxidize

bacterial depositions, duration about 5 – 8 hours at

slightly increased temperature

5. final rinsing with water for complete displacement of

all chemicals from the system

6. the installation is again put into operation with

process water

The duration of the individual steps may vary depending

on the degree of contamination. It may also be necessary

to repeat one of these steps several time.

A.5.4.2.3


The installation is now planned based on the results of

the pilot phase. The working steps are as follows:

• analysis of the test data, determination of the perme-

ability [in L/(m2 �h�bar)] at the end of the expected

membrane service life at each point in the membrane

process, as the most important design parameter

• design of the installation considering the real operating

conditions of the membranes and modules used

• integration of the membrane process into the complete

process

297

AnnexA

A.5.5

Assessment criteria for the choice of a membrane

installation

After having followed the working steps described above,

the selection procedures carried out should be assessed

again before the installation is realized. The following

sections will serve the future operator as check list for his

own work and for the assessment of offers.

A.5.5.1

Technical assessment of a membrane process

concerning employment and completeness

A.5.5.1.1

Definition of the terms of reference

• Have the waste water constituents been sufficiently

specified and documented?

• Have the variations in quality and quantity of the

waste water been defined?

• Have rare or cyclically appearing conditions in the

production process been considered in the specification

of the waste water data?

A.5.5.1.2

Material and mass fluxes during operation

of a membrane installation

• Are the mass fluxes logical, i. e. is the total balance

exact? (sum influents = sum effluents! Figure A-8)

• Are the measuring devices available which are necessary

for balancing the operation of the installation?

• Is it possible to bridge periods of chemical cleanings by

internal measures or buffering tanks?

• Is the installation sized in such a way that it can cope

in adequate time with the additional amount of waste

water resulting from these cleanings?

• Are there problems with waste disposal (replaced

membranes, prefilters?)

• If yes, how high is the expense?

298

membrane installationwaste water inflow

treated water (permeate or filtrate)

concentrate

chemicals for operating

chemicals for chemical cleaning

resources (electric power, compressed air)

other consumables (filter substitute etc.)

waste water from chemical cleaning

waste water from backwashing

Figure A-8

Material and mass fluxes during operation of a membrane installation

Annex A

A.5.5.1.3

Utilization or discharge of the resulting products

• Does the treated water (permeate or filtrate) comply

with the standards for discharge into the sewer system

or the receiving water, or the standards for reuse?

• Is the quality concerning this aspect continuously

controlled?

• Can the concentrate stream be used internally, or does

it comply with the standards for discharge into the

sewer system or a receiving water?

• Does the recycling of waste water have effects on the

existing waste water discharge or on the existing waste

water installation (increase of the concentration)?

• Which method is used for the discharge of the waste

water from chemical cleaning of the installation?

A.5.5.1.4

Pretreatment

• Do the membrane modules/the membranes need a

pretreatment?

• Does this pretreatment consider the required

technology and costs?

• What happens if pretreatment breaks down

(emergency measures to protect the membranes)?

• Have precautions (measuring methods, safety filters)

been taken in case of insufficient pretreatment?

A.5.5.1.5

Technical realization

• How high is the degree of automation of the installation?

• Is it sufficient for operation?

• Is the installation offered capable of reacting to varying

quantities and compositions of the waste water to be

expected?

A.5.5.1.6

Redundancies

• What are the consequences to the operation of a break-

down of the complete installation for some hours/some

days? (discharge costs/discharge safety/production los-

ses/follow-up costs)

• Are the considered redundancies sufficient in light of

the costs arising from a breakdown of the installation?

A.5.5.1.7

References/similar applications

• Have examples already been realized which are similar

to this case?

• Does the offering company have references for the

membrane technology chosen, perhaps for similar

applications?

A.5.5.2

Operating costs

A.5.5.2.1

Equipment

• How high is the input power/the power consumption?

• How high is the consumption/the cost of compressed

air?

• How high is the consumption of additional water

(e. g. for chemical cleaning, backwashing)?

• Is the water available for these measures sufficient in

quantity and quality?

• Which chemicals are necessary for normal operation?

• Are these chemicals available in the company?

• Is the amount of chemical consumption known?

• How high are the annual costs for analyses?

A.5.5.2.2

Auxiliaries

• Service life/annual costs for possible prefilters (offer for

wearing parts available)

A.5.5.2.4

Service life and replacement of membranes

• How long is the service life of the membranes used?

Expected/guaranteed service life (guaranteed value at least

two thirds of the expected value?)

• Is a longterm offer for spare membranes available?

• Does it include the costs for the amount of work involved

in the replacement of the membranes?

299

AnnexA

300

A.5.5.3

Change of the conditions during operation of the

installation

A membrane process has not only to be assessed concern-

ing completeness, costs and process safety, but some

boundary parameters have also to be considered during

operation. Neglecting them may partly give rise to pro-

blems or damages. With existing installations, the follow-

ing observations have been made:

• corrosion of some components due to the change of

cleaning chemicals

• change of the composition of cleaning chemicals, e. g.

by change of the supply source

• change of the succession of cleaning steps

• change of the temperature during the cleaning process

• hydraulic changes in the inflow or inside the

installation, e. g. by decreasing pumping performance

• change of the inflow quality, e. g. by change of the load

or by additional constituents (use of process chemicals

from other suppliers or change of the production

process)

• change of the membranes (change of the membrane

supplier)

• insufficient maintenance of the measuring or analytical

instrumentation (e. g. pH electrodes)

This list of operating problems observed in the past

clearly shows that maintenance of a membrane installa-

tion is of high importance. Of course, changes to the

inflow quality cannot always be avoided because changes

in the production process are always possible. Slight

changes normally will not influence the treatment instal-

lation. Nevertheless, it is recommended to keep close con-

tact with the manufacturer of the membrane installation,

since important changes to the water inflow can often be

managed by slight modifications to the installation. Pre-

requisite is that the operator is informed immediately

about these changes by internal measures.

The pages 315 – 316 contain the bibliography of Annex A.5.

A.5.5.4

Other items

A.5.5.4.1

Failures

• Are spare membranes or modules available at short

notice in the required quantity, if necessary?

• Is this time acceptable for operation (possible break-

down of the installation for this period)?

A.5.5.4.2

Preliminary tests

• Have preliminary tests been carried out for this case or

application?

• If yes, are the indications of the offer in accordance

with the data from the preliminary tests?

A.5.6

Questionnaire for the acquisition of process data

A.5.6.1

Description of the separation problem to be

solved with the help of a membrane process

• What type of waste water will be treated? Origin?

Composition? Results from physical and chemical

analysis (among others temperature, pH value, electric

conductivity, disposition for fouling, solid matter

content, type of solid matter)

• Which components have to be removed from the

medium?

• What requirements are there for permeate quality?

• Does the medium contain substances which may

damage the membrane? (see list in the annex) If yes,

which substances?

• Is the medium microbiologically conspicuous?

Annex A

A.5.6.2

Concerning the assessment or the integration

of a membrane process into an overall treatment

concept

• Is there a possibility to reuse the permeate/filtrate and

the concentrate (e. g. reuse in operation, recovery of

reusable material)

• Which possibilities exist for the treatment of the con-

centrate, if necessary? Assessment of discharge paths

and costs?

• How important are the cost savings which possibly

result from the use of a membrane process? (chemicals,

water and waste water levies etc.)

• Which processes competing with the membrane

process have to be considered?

A.5.6.3

Sizing of the installation

• What waste water quantity is to be expected? How is it

produced? Are there mixing and equalizing possibilities,

if necessary? Future development? (graphs of quantities

and concentrations of the constituents, given in

m2/h, m2/d and m2/a)

• What is the minimum permeate output (= % related to

the treated water quantity) that should be obtained?

• Are there possibilities to influence the process

temperature?

A.5.6.4

Requirements for the construction of the

membrane installation

• What demands are made of the material to be used?

Are there materials which cannot or must not be used?

• What other demands are made of the membrane

installation? (e. g. flame protection, sanitary execution,

operation under food conditions, CIP capacity)

• Are there instructions for the degree of automation of

the installation or for the type of control device?

• How much space is available for a possible membrane

installation?

Annex

Depending on concentration and operating mode, the

following substances may have negative effects on the

performance of the system and have to be examined in

a more detailed way:

oxidizing agents [e. g. chlorine, peroxide, chromium(VI)],

cationic detergents, flocculants, defoamers, polymers,

silicones, organic solvents, silicates, calcium, barium,

strontium, iron/manganese, tin, acids/lyes (pH value),

gypsum, lime, abrasives.

Part II

Aerobic membrane bioreactor processes

A.5.7

General information

This work report addresses operators, planners and plant

manufacturers who deal with industrial waste water treat-

ment. It is the second part of the work report “Treatment

of industrial waste water and process water by membrane

processes and membrane bioreactor processes”, based on

the work report “Membrane bioreactor processes” for

municipal plants which presents the most important

basics and definitions.

In membrane bioreactor installations, the final clarifica-

tion stage is replaced by microfiltration or ultrafiltration.

From this result two important advantages:

• the effluent is free of solid matter,

• the biomass concentration is independent of the

sedimentation behaviour.

Therefore, membrane bioreactors are capable of reaching

much higher TS concentrations than conventional acti-

vated sludge plants. Tank volume can be saved to the

same extent, if the same design principles are applied.

Figure A-9 shows the flow sheet of a membrane bioreactor

compared to a conventional activated sludge plant.

301

AnnexA

This work report is divided into the description of the

construction of membrane bioreactors (chapter A.5.8),

and the quality requirements for the effluent (chapter

A.5.9). In chapter A.5.10, instructions for design are given,

and chapter A.5.11 deals with some special features of

membrane bioreactors compared to conventional activated

sludge processes. Chapter A.5.12 contains information on

the economic efficiency of membrane bioreactors. A list

of exemplary installations in the field of industrial waste

water treatment in Europe completes the report.

A.5.8

Construction

Membrane bioreactors consist of an aeration tank in

which the waste water is biologically treated with the

help of activated sludge and a filtration unit which serves

to retain the activated sludge by means of membranes

integrated into modules, so that the effluent is free of

solid matter.

A.5.8.1

Arrangement

The membranes and membrane modules available on the

market differ with regard to the module construction, the

molecular separation size (micro- or ultrafiltration mem-

brane), the membrane structure (flat, tubular and capillary

membranes), the filtering sense (inside-out or reverse),

the place of installation (dry-arranged or immersed

systems) and the operating mode. Because of the high

solid matter content of the activated sludge process, the

filtration unit of a membrane bioreactor is generally ope-

rated in cross-flow mode, i. e. the mixed liquor is fed

tangentially across the membrane surface; a partial flow

passes through the membrane and is withdrawn as filtrate.

The development of a covering layer can be influenced by

varying the overflow conditions. Compared to membrane

modules in a dry arrangement, immersed systems have a

lower specific energy demand for the generation of the

cross-flow, but larger membrane surfaces are necessary

because the flow rate [L/(m2 �h)] is also lower.

A.5.8.1.1

Immersed membrane modules

Immersed membrane modules are installed in the aerobic

part of the aeration tank or in a separate “filtration tank”

(Figures A-10 and A-11). The necessary cross-flow is gene-

rated by coarse-bubble aeration arranged below the mem-

branes and/or mechanical movement. The filtrate is with-

drawn by means of a vacuum of approx. 0.05 - 0.6 bar (as

low as possible).

A.5.8.1.2

Dry-arranged membrane modules

In dry arrangement of the membrane modules, the mixed

liquor is taken from the aeration tank and pumped

through the module. The cross-flow is generated by a

pump. Due to high pressure loss in the common modules,

the energy demand is higher than that of immersed sys-

tems. However, the covering layer control is very effective

so that a higher specific flow is obtained. Figure A-12

shows a diagram of this arrangement.

302

BB = activated sludge tank

NK = secondary settling tank

effluent

ÜSS = excess sludge

BBeffluent

ÜSS

inflow inflowBB NK

Figure A-9

Schematic comparison of the conventional activated sludge process with the membrane bioreactor process

Annex A

A.5.8.2

Control of the covering layer

A.5.8.2.1

Control of the covering layer in immersed systems

Immersed systems are installed directly in the aeration

tank or in an external filtration tank (cf. Figure A-10 and

Figure A-11). The covering layer is controlled by coarse

bubble aeration at the bottom of the modules. The rising

air bubbles generate innumerable small turbulences. By

pressure differences in these turbulences, particles attached

to the membrane surface are detached.

In hollow-fibre membranes, extensive movements of the

hollow fibres are generated by the large number of turbu-

lences. These movements can be supported by intermittent

aeration; the resulting pumping effect induces a cross-flow

inside the fibre bundle. This improved covering layer con-

trol has the additional advantage of minimizing the energy

consumption for air intake.

Concerning flat membranes, it is possible to generate a

forced air flow along the membrane by means of a fitting

(the membrane is cased in a box) or a mechanical move-

ment. With some systems, e. g. plate membranes, the re-

sulting air lift pumps the activated sludge in an effective

way only if a free up-flow channel is arranged below the

membrane to accelerate the air-sludge mixture.

A.5.8.2.2

Covering layer control in dry-arranged systems

In dry-arranged systems, filtration by the membrane

bioreactor process is carried out in cross-flow mode. By

tangential flow across the membrane surface on the side

of the solid matter, the development of a covering layer

is limited by deposition of filtered particles to obtain a

constant, high-level filtrate flow. The more permeable,

i. e. the thinner the filtering cover layer of the membrane,

the higher is the flow rate. To control the covering layer

as effectively as possible, several times the flow (feed) is

recycled. The typical velocity in cross-flow filtration is

approx. 1 – 4 m/s, depending on the module construction.

303

Figure A-12

Membrane modules in dry arrangement

Figure A-10

Arrangement of the immersed membrane modules

in the aerobic section of the activated sludge tank

Figure A-11

Arrangement of the immersed membrane modules

in an external filtration tank

AnnexA

A.5.8.2.3

General facts

The generation of the cross-flow is the main contributor

to the specific energy demand of membrane filtration.

The objective of a large number of process developments

is the reduction of energy consumption by minimizing

the cross-flow, while maintaining the same high flow

rate. Therefore, the membrane surfaces required, and

thus the investments and costs for membrane replace-

ment, are reduced.

Figure A-13 presents the theoretical relationship between

membrane surface area, energy demand and flow for the

membrane bioreactor processes.

A.5.8.3

Cleaning strategies

Cleaning of the membranes is necessary to take precau-

tions against a reduction of the flow [more exactly: of the

permeability, expressed in L/(m2 �h�bar) or to increase

the permeability in case of reduced throughput.

Permeability losses may have the following causes:

• deposition of (colloidal) organic and inorganic particles

• deposition and precipitation of salts (see scaling)

• deposition of organic macromolecules

• biofouling, i. e. penetration and growth of micro-orga-

nisms and/or their excretions such as enzymes, EPS

(extracellular polymer substances) in and at the

membrane

According to the diversity of causes, the cleaning strate-

gies have to be adapted to the waste water composition,

to the operating mode of the activated sludge stage and

to the membranes and membrane modules used.

One distinguishes between process-controlled integrated

backwashing, periodic in-situ maintenance cleanings, e. g.

by backwashing using chemicals, and irregular, disconti-

nuous main cleanings with chemicals for which the fil-

tration unit has to be shut down.

All cleaning processes proceed more quickly at higher

temperatures. Moreover, the same effect is obtained with

a lower chemical concentration, i. e. the cleaning process

is more gentle. Experience from large-scale testing of orga-

nic membranes has been acquired at cleaning temperatures

of 35 – 40 °C.

Since cleaning processes strongly depend on the type of

membrane and module and new cleaning processes are

continuously being developed, it is only possible to pro-

vide general information on membrane cleaning practices.

Rinsing/backwashing

Backwashing refers to a periodic reversal of flow in the

membranes to detach the particles adsorbed during the

filtration process (covering layer). In principle, the filtrate

is used for backwashing.

A typical operating regime for a commercially available

hollow-fibre module is a filtering duration of 5–8 minutes,

followed by a backwashing interval of approx. 30 – 40 sec.

[Remark: With this operating mode, one has to distinguish

between cross flow (flow during the filtration phase) and

net flow (i. e. the flow obtained from a complete sequence

of filtration and backwashing, taking into account the

backwashing volume)].

304

spec

ific

mem

bran

e su

rfac

e [m

2 /(m

3 ·h)

]

flow

[l/

(m2 ·

h)]

energy demand (kWh/m3)

surface

flow

immersedmembrane modules

dry-arrangedmembrane modules

Figure A-13

Qualitative relationship between necessary mem-

brane surface area, energy demand and flow

Annex A

Rinsing refers to shortterm operation with clear water

without flow reversal in order to wash away and to dis-

charge the covering layer. This procedure is used for dry-

arranged membrane modules.

Maintenance cleaning (chemical enhanced backwash)

For this (intermediate) cleaning, chemicals such as citric

acid or oxidizing chemicals (e. g. hypochlorite) are added

to the rinsing or backwash water. Cleaning is done in situ,

i. e. the membrane remains in contact with the mixed

liquor (the mixed liquor can also be drained off). The inter-

val between two rinsing cycles and the type of chemicals

and their concentration depends on the respective appli-

cation.

Typical intervals for maintenance cleanings, e. g. with

sodium hypochlorite (NaOCl) or acid, are from a few days

up to several weeks.

Rinsing is done with a very low backwash flow rate (often

in a cycle of short rinsing – leaving on – rinsing, which is

repeated several times) to minimize the introduction of

chemicals and undesired formation of pollutants (AOX).

Intensive cleaning

Depending on the application, an intensive cleaning may

be necessary from between once a month up to twice a

year. For an intensive cleaning the membrane modules are

put into a separate cleaning tank or the mixed liquor is

withdrawn and substituted by cleaning solutions.

The type of cleaning chemicals used depends on the appli-

cation. The cleanings should be carried with hot water. A

typical cleaning sequence may comprise the following

steps:

• rinsing of the membranes with water

• treatment by acids, e. g. citric acid (250 – 2,000 ppm)

with addition of hydrochloric acid or sulphuric acid to

adjust the pH value to 2 – 3, in order to detach/remove

inorganic depositions

• intermediate rinsing (neutralisation) to avoid salt depo-

sitions and heat development in the membrane (neutra-

lisation heat), if the following cleaning step takes place

at alkaline pH values

• cleaning by oxidizing chemicals to oxidize organic and

bacterial depositions, e. g. by a solution of 0.05 %

(weight percent) (= 500 ppm (500 mg/L) related to active

chlorine), i. e. a NaOCl solution of approx. 0.4 %

(= 4,000 ppm NaOCl) at pH 11 for an exposure time of

5 – 20 h; if necessary, at high temperature.

• final rinsing with water to wash out the caustic soda

solution (NaOH). This reduces the scaling potential and

the risk of saponification (reaction of NaOH with grease

and oil to glycerol and Na salts of the fatty acids, which

might lead to undesired foam development).

In general, the cleaning solution should be purged from

the system, depending on the degree of contamination of

the membranes.

Cleaning – instructions and experiences

Given the large number of membrane applications and the

variety of membranes and membrane modules, it must be

stated that cleaning concepts and experiences cannot be

transferred from one case to another. However, the follow-

ing general instructions should be considered:

• Cleaning chemicals, especially when concentrated, may

affect membranes, back-up tissue of the membranes,

components of the membrane modules, and tank walls

and instruments.

– This is especially true for low and high pH values. It

has to be considered that due to chemical reactions,

higher pH values may locally occur than measured/

calculated in the reactor (example: increase of the

pH due to the oxidation of organic matter by sodium

hypochlorite).

• Oxidizing chemicals attack organic membranes and

lead to accelerated aging. The more aggressive the che-

micals, the higher the concentration, and the longer

the expo-sure time, the more acute is the damage to

the membrane. Some membrane manufacturers give

chemical-specific maximum values for the product of

chemical concentra-tion and exposure time. Example:

250,000 ppmh of free chlorine mean 500 h with a solu-

tion concentration of 500 ppm, or 100 h with a solu-

tion concentration of 2,500 ppm.

305

AnnexA

• Due to chemical reactions, cleaning chemicals themselves

may give rise to disturbances or may form harmful

substances. Examples:

– saponification, by reaction of NaOH with greases and

oils " intense foam development. Measure: sufficient

rinsing with water

– salt deposition in the membrane by neutralisation

reactions. Measure: sufficient intermediate rinsing

with water

– AOX formation by reaction of OCl– with organic

constituents. Measures: utilization of drinking water

(instead of filtrate) to prepare the cleaning solution;

utilization of halogen-free oxidants such as H2O2,

peracetic acid (the cleaning effect has to be examined!)

• Cleaning solutions have to be duly stored; if necessary,

they can be processed and reused several times. All safety

regulations concerning the handling of chemicals have

to be observed.

• The cleaning solutions have to be duly discharged.

(In principle, they can be fed into the activated sludge

stage – to be examined!)

• During planning it has to be assessed whether the

necessary intensive cleanings shall take place in situ or

in an external tank. This has consequences for the costs,

for the material choice (e. g. tank coatings, fittings) as

well as for the logistics of removal and transport of the

membrane, feasibility of cleaning at higher temperature,

flexibility in the choice of chemicals, etc.

• The concentrations of cleaning solutions should be

indicated as exactly as possible. Especially when using

hypochlorite, it must be indicated whether the concen-

tration value is related to NaOCl, HOCl, OCl–, the

calculated Cl content or the free (active) chlorine. For

the conversion from litres into kg, weight percent or

ppm, it is necessary to consider the density of the

commercial NaOCl solution (chlorine bleaching lye)

of � = 1.2 kg/L. The solution contains maximally

12 – 13 % of effective (free, active) chlorine.

• It is useful to coordinate the details of the cleaning

processes with the membrane supplier (manufacturer)

and to record the results of each cleaning. Membrane

guarantees should include agreement about cleaning

concepts, intervals and parameters to be recorded.

A.5.9

Requirements for the influent

A.5.9.1

General information

Before feeding waste water to a membrane bioreactor, it

is necessary to remove undesired material such as long

fibres and filamentous or strongly abrasive, sharp-edged

substances because they may clog the modules or mecha-

nically destroy the membranes.

In addition, it must be considered that dissolved waste

water constituents may also damage the membranes. If

necessary, membrane-typical specifications (limit values)

have to be taken into account. This concerns not only

the organic (non-degradable) solvents contained in the

waste water, but also substances which are added in waste

water treatment, e. g. defoaming agents (have to be free

of silicone!) and organic polymers. For the specific appli-

cation, the experiences of manufacturers and suppliers

should be used.

A.5.9.2


Screens

Fibrous, sharp-edged and agglomerating material has to

be prevented from entering from membrane bioreactors.

The composition of the waste water from different indus-

trial branches may vary considerably as to the content of

those substances. Large quantities of fibres, as present in

municipal waste water, only occur in the waste water of

few branches. Screens with an aperture size of 0.5–2 mm

or slot sieves with a slot size of 0.5 –1 mm are normally

sufficient. If a pretreatment stage is arranged upstream, a

screen mainly has a protecting task.

Separator for grease and light-density material

Undissolved, hardly degradable greases and oils have to

be removed from the waste water before it is fed into the

membrane bioreactor because they may have a negative

effect on the filtrate performance. Well degradable greases

and oils do not give rise to problems.

306

Annex A

Primary treatment

Primary treatment should be planned in the case of high

solid matter contents in order to maintain a sufficient frac-

tion of active biomass in the activated sludge, so that the

biological treatment capacity is not negatively influenced.

A.5.9.3

Mixing and equalizing tank

With membrane bioreactors, hydraulic compensation is

of importance. The membrane surface area has to be de-

signed, proportionately to the secondary treatment, for

the maximum water quantity. Since large membrane sur-

faces are very expensive and an increase in the through-

put rate in the case of larger waste water volumes is pos-

sible only to a rather limited extent, it is useful to equal-

ize the waste water flow. For this purpose, volume-equal-

izing tanks are suited, independent of considerations

concerning the equalization of concentrations.

If the waste water volume varies only slightly, the necessary

storage volume can be made available in the tank itself,

since impoundment is also possible in the aeration tank

to a limited extent.

A.5.9.4

Calcium concentration

Increased Ca2+ concentrations (> 200 mg/L), either from

the use of calcium in the production process, from up-

stream precipitation processes, or from neutralisation of

acid waste water by lime milk, may be problematic for the

membranes. Due to the high air intake which provides

turbulent flow for immersed membranes, a large part of

the CO2 formed in the aeration tank is stripped out. As a

result, the pH value rises (keyword: lime-carbon dioxide

balance, solubility product), which may lead to a reduc-

tion in the filtration capacity. Consequently, the mem-

branes have to be cleaned more frequently.

A.5.9.5

Iron and aluminium content

Partial flows of various industrial branches may contain

iron and aluminium salts. They are frequently used as

precipitants to support primary treatment, and they may

also be present in the process waste water flow itself.

Oxidized forms and particular compounds have no in-

fluence on the membrane and the filtration characteris-

tics. Dissolved compounds, which under aerobic condi-

tions are oxidized in an activated sludge stage, may give

rise to depositions. Oxidation partly takes place directly

on the membrane so that the undissolved precipitation

product sticks to the surface. The resulting visible colora-

tion can be removed, if necessary, by acid cleaning.

A.5.10

Instructions for the design of membrane bioreactors

A.5.10.1

General information

The biological degradation of organic matter in membrane

bioreactors does not differ fundamentally from the pro-

cess in conventional installations, i. e. these substances

oxidize to CO2 and are used for cell growth. The biomass

developed accumulates as excess sludge together with the

input of non-degradable and insoluble particulate sub-

stances (chapter A.5.11.1.3).

However, membrane bioreactors differ from conventional

installations in particular by the high TS content in the

aeration tank (usually 10 – 20 g/L, conventional instal-

lations: 3 – 5 g/L) and the resulting change in the sludge

characteristics. While aeration tank volumes are calculated

according to the load to be degraded, the membrane sur-

face area is determined, correspondingly to the secondary

settlement tank, according to the hydraulic throughput.

Because of higher expense for the filtration unit, hydrau-

lic design has to be performed with the utmost care

(cf. chapter A.5.12).

307

AnnexA

Comparisons of operating results of membrane bioreac-

tors by theoretical models have shown that the sludge

yield can be assessed rather well, especially by detailed

models such as the Activated Sludge Model of the Inter-

national Water Association, but also with simpler ap-

proaches, provided that the specific boundary conditions

of the respective industrial waste water are sufficiently

considered. With high sludge ages, it is recommended to

perform the calculation on the basis of the maintenance

metabolism [WICHERN AND ROSENWINKEL 2002].

The references available show that the current engineering

design based on semi-technical preliminary tests is the

basis for a large number of well-functioning installations.

A.5.10.2

Space requirements

In industrial waste water treatment, the space requirement

of an installation is often a decisive criterion. For new

industrial settlements, space requirement for waste water

treatment can often be alloted. However, for industrial

enterprises which have grown for decades it is often im-

possible to integrate waste water treatment on their fac-

tory sites.

Compared to a conventional activated sludge plant, the

required aeration tank volume can be reduced to approx.

one half or even one quarter; moreover, secondary treat-

ment is no longer necessary. Therefore, the space require-

ment for the waste water treatment plant is significantly

reduced. This is often a decisive advantage for industrial

enterprises and enables them to treat their waste water

on their facilities.

A.5.10.3

Elimination rates

An operating mode with low excess sludge production

requires attention to the considerably higher oxygen re-

quirement, the effluent quality, and the possible accumu-

lation of harmful and inhibitory substances in the acti-

vated sludge.

The specific oxygen requirement increases with decreas-

ing sludge loading, i. e. with decreasing specific excess

sludge production. This is because in this operating mode,

the organic matter has to be oxidized to CO2 to a greater

extent [CORNEL 2000].

The increased operating TS concentration in a membrane

bioreactor results in one of two design scenarios relative

to conventional activated sludge treatment:

• smaller aeration tank volumes with equal sludge

loading and equal excess sludge production, or

• equal aeration tank volumes and lower sludge loading

with less excess sludge, but higher energy costs.

It is not possible to realize all “positive” features – low

energy demand, reduced excess sludge production and

smaller aeration tank volumes – in the same installation,

because these features, in part, are mutually exclusive.

The impact of an operating mode with low excess sludge

production, i. e. low sludge loading rate, on the effluent

quality (“refractory substances”) has to be determined for

each case. The extent of removal of refractory compounds

depends on the waste water constituents and the operating

conditions (sludge age). Ultra- and microfiltration mem-

branes do not reject low-molecular weight substances.

However, increased degradation of slowly degradable sub-

stances is possible at high sludge ages along with possible

retention of macromolecules by the covering layer. Con-

stituents attached to particles, e. g. adsorbed AOX com-

pounds, are rejected by the membrane installation.

Compared to conventional activated sludge plants, load-

peaks have a stronger effect on the effluent quality. This

is due to reduced dilution because of the smaller aeration

tank volume. In general, it is true that loadpeaks are

more difficultly to manage at very low sludge loading

rates [F/M < 0.03 kg BOD5/(kg TS �d)], due to the lower

biomass activity.

Inhibited degradation due to the accumulation of heavy

metals in the activated sludge is observed in some indus-

trial branches. In cases where there exists increased heavy

metal concentrations in the waste water, the sludge age

in membrane bioreactors has to be carefully controlled

especially.

308

Annex A

Phosphorus elimination in membrane bioreactors can be

realized very easily by simultaneous precipitation with

iron salts. Since ultrafiltration is able to absolutely reject

very small particles, better effluent quality can be obtained.

In this case, the molar ratio can be set more favourably.

By adaptation of the cleaning strategies and the cleaning

agents, it is possible to counteract the adsorption of pre-

cipitant residues on the membrane surface. Membrane

filtration itself is not normally influenced by regular pre-

cipitant dosing. If the installation is correspondingly de-

signed, biological phosphorus removal is also possible

when the sludge age is designed in the appropriate range.

Membrane filtration produces solidsfree water which is

disinfected to a great extent. With conventional mecha-

nical-biological processes it is not possible to reach

comparable effluent quality, even if a conventional filtra-

tion process, e. g. sand filter, is arranged downstream.

A.5.10.4

Aeration

The mass transfer of oxygen from the gas phase into the

liquid phase is influenced by, among others, the parameters

salt concentration, viscosity of the medium, surface-active

substances, surface tension, solid matter content, aeration

system, turbulence, and pressure (water depth). A general

guide value of oxygen input and �-values cannot be

given for industrial (membrane) bioreactors. In industrial

waste water treatment plants with conventional biological

processes, �-values of > 1 may also occur due to various

waste water constituents, and, above all, because of high

salt concentrations (> 5 g/l). These have positive effects

on the oxygen transfer due to their coalescence-reducing

effect. However, the oxygen input also depends on the

dynamic viscosity which itself is strongly dependent on

the sludge concentration. Therefore, lower �-values than

in conventional activated sludge plants have to be expected

with high TS concentrations. Relatively high �-values

compared to municipal applications can be expected

with higher salt concentrations.

The transfer of air or pure oxygen is also possible by

means of injector systems. In the case of waste water

which tends to deposits, it should be taken into account

that the pH value will increase in intensely aerated zones.

This is due to stripping of CO2, which on the contrary,

may enrich during aeration with pure oxygen and conse-

quently resulting in reduced CO2 discharge.

When transferring the results of oxygen transfer measure-

ments in semi-technical or laboratory scale to large-scale

installations, it has to be considered that the fluid-dynamic

parameters can be represented and transferred only to a

limited extent. Oxygen transfer measurements should be

carried out at test installations with the waste water to be

treated, the design sludge concentration, and the design

liquid depth.

A.5.10.5

Hydraulics

A.5.10.5.1

Flexibility

The modular construction of membrane installations allows

adaptation to flow variations by switching on or off single

modules. In low flow events, it is more energy-efficient

to switch off single modules than treating the entire flow

through the complete membrane system. If the waste water

volume is consistently higher than designed, the modular

construction facilitates easy upgrading and adaptation to

the new requirements. In planning as well as during oper-

ation, great importance has to be attached to distribute

the flow as uniformly as possible to both modules.

A.5.10.5.2

Recirculation

The activated sludge concentrates on the membrane due

to filtrate withdrawal. If immersed membranes are

directly installed in the aeration tank, concentration distri-

bution by a mixing device is a sufficient compensating

measure.

If the membranes are installed in separated tanks or

arranged dry, sufficient recirculation has to be ensured.

In general the recirculation rate should be four or five

times the filtrate quantity which is being discharged. In

filtration tanks with immersed modules, the mixed liquor

feed and recirculation discharge should be at opposite

ends of the tank in order to avoid short-circuit flows.

309

AnnexA

In the case of immersed membranes, the recirculation flow

is oxygenated. This has to be taken into account if this flow

is to be recycled directly into the denitrification reactor.

A.5.10.6

Influence of the temperature

As a result of biological degradation in waste water treat-

ment, the bulk liquid temperature rises by approx. 2–3 °C

per gram of COD degraded per litre. This rise in tempera-

ture has to be taken into account, if necessary, in the

treatment of high-strength industrial waste water. How-

ever, with low organic loads this does not give rise to

problems. For dry-arranged systems, a rise in temperature

in the aeration stage may also be expected due to the

energy input of the mechanical equipment, e. g. the

pumps for cross-flow generation.

Concerning the flow characteristics, higher temperatures

are quite favourable for the use of membranes. For acti-

vated sludge plants the temperature has to be limited to

37 – 39 °C.

A.5.11

Specific features of membrane bioreactors

A.5.11.1

Sludge features

A.5.11.1.1

Characterization of the sludge

Due to an increased solid matter content, the sludge fea-

tures differ considerably from those of activated sludge

from conventional plants. The strong shear forces occur-

ring in cross-flow installations are responsible for an in-

crease in the abundance of single bacteria in microscopic

analysis. According to the biotic community, which de-

pends on the waste water quality, the sludge can be vis-

cous or thick, but may also have the consistency of a gel.

With high solid matter content, inclusion of oxygen bub-

bles may occur. As a rule, the viscosity is higher com-

pared to conventional activated sludge. The solid matter

contents are

• with immersed modules:

10 – 15 g TS/L and

• with dry-arranged modules:

up to 30 g TS/L

The dry matter content cannot be correlated directly

with the viscosity and the filterability. However, within

an installation it can be used as indicator.

A.5.11.1.2

Rheological properties

Activated sludge shows a more or less distinct shear thin-

ning, i. e. the viscosity decreases with increasing shear

load. The viscosity of the activated sludge which devel-

ops in the membrane bioreactor depends on many fac-

tors, including the size and structure of the sludge flocs,

composition of the waste water, the TS concentration as

well as the organic part of the TS concentration, and the

physiological properties of the biology [e. g. formation of

extracellular polymeric substances (EPS) under certain

operating conditions], e. g. floc stress due to forced circu-

lation. Therefore, simple correlation between viscosity

and TS concentration of activated sludges from different

installations is not possible.

If the relationship between the viscosity and the TS con-

centration of the biology shall be used as an auxiliary

parameter for the description of mass transfer (i. e. of the

oxygen intake), it has to be determined individually for

each installation/each waste water and, if necessary, also

for each sludge loading. Moreover, due to the more or

less distinct shear thinning properties of the activated

sludge, the viscosity in the settling tank is not homoge-

neous, but appears dependent on the local shear stress

condition. Thus, each statement on “the” viscosity of an

activated sludge is useful only if the respective shear load

(shear rate D in s-1) is defined.

Consistency, number of free bacteria, floc structure, inert

fraction etc. have a great influence on the filterability of

the activated sludge. Although the filterability within one

installation may possibly correlate with the TS concentra-

tion, this parameter is too inexact for the design of the

required membrane surface area. For this purpose tests

have to be carried out.

310

Annex A

The survey of rheological properties by continuous

measurement of the viscosity at a certain shear load or

the measurement of flow curves, may represent for mem-

brane bioreactors – combined with TS determination and

the regular assessment of the biocenosis by microscopic

analyses – a useful completion of the process parameters

for the control of the installation (cf. GÜNDER 1999;

KRAUSE ET AL. 2001).

A.5.11.1.3

Excess sludge production

Sludge production results from the growth of heterotrophic

and autotrophic biomass as well as from the biologically

inert fraction of the solid matter inflow and the inert

material resulting from the death of the biomass. While

the organic part at infinitely high sludge age may be nearly

completely biodegraded (at least in theory), the insoluble,

particulate, mineral part remains in the aeration tank and

has to be withdrawn as excess sludge. Since with usual

system settings the growth rates are higher than the death

rates, the excess sludge contains an organic part.

The same principles as for all activated sludge processes

are valid, i. e. the sludge output decreases with

• decreasing sludge load, i. e. increased sludge age

• decreasing solid matter input and

• rising temperature

Industrial waste water often has high temperatures and

low solid matter contents. For this reason the excess

sludge production rate, related to the treated load, is

often lower in the treatment of industrial waste waters

than in municipal applications. This tendency is reinforced

by the use of a low-loaded membrane bioreactor design.

For the activated sludge process, the excess sludge with-

drawn represents an accumulation medium for non-

degradable, but sorbable substances. If this withdrawal

does not take place, the substances are either found in

the filtrate or they accumulate – as far as they cannot

pass through the membrane – in the system. Several non-

degradable substances have a biologically inhibiting

effect or are toxic for bacteria when they exceed certain

threshold concentrations. For this reason regular excess

sludge withdrawal should be integrated into the design.

A.5.11.1.4

Sludge treatment

In principle, all systems available on the market can be

used for sludge dewatering. Optimal mixing of the poly-

mers, due to the increased viscosity of the excess sludge

at high TS concentrations, has to be considered in the

design.

According to the waste water situation, it may be useful

not to treat the excess sludge separately, but to dewater it

in a mixture together with the primary sludge. In this

manner the consumption of conditioning agents may be

reduced. It could be observed that the addition of e. g.

used activated carbon, which has to be discharged any-

how, may have positive effects on the dewatering beha-

viour. This is possibly also true for other structure-for-

ming additive substances.

In each case, attention should be paid to using membrane-

compatible polymers for sludge dewatering. They should

be tested on laboratory and technical scale.

A.5.11.1.5

Foam development

The pressure differences necessary for dry-arranged mem-

branes as well as the flow conditions may lead to consid-

erable stress on the biocenose and, with this, to increased

EPS development. In combination with intensive aeration,

this may result in considerable foam development.

Construction measures to control foam are, for example,

flat tanks with a large surface area (more advantageous

compared to slim tanks), and mechanical or physical

destruction of the foam. When using defoaming agents,

their membrane compatibility has to be ensured.

311

AnnexA

A.5.12

Economic efficiency

A.5.12.1

Definition of economic efficiency

Although the term “economic efficiency” is always used

in technology and economy, there is no general definition

that can be applied. It is necessary to define economic

efficiency for each single case. However, membrane bio-

reactors will be applied in all probability in the case of

corresponding demands on the effluent quality. Therefore,

a reference value related to other waste water treatment

processes can be defined: “The membrane bioreactor pro-

cess is more profitable than a conventional process if the

cash value (or capital value) of the discounted expense

after X years is similar to or higher than the cash value of

the alternative processes at comparable treatment results.”

ATV-DVWK recommends calculating the cash value; in

industrial practice, calculation of the capital value is more

frequent. However, both methods only differ in the fact that

in the first case one considers the time of commencement

and in the other case the end of the respective period.

Calculation of the cash value requires knowledge of the

expense for financing the investment (interest and amor-

tization) as well as the operating costs for one year and the

following years. The type of financing of the acquisition

and the expected service life (of installations, machines and

spare parts) have an effect on the part of fixed costs. The

operating costs mainly comprise energy and cleaning costs,

costs for membrane replacement as well as for manpower,

auxiliaries, etc. The costs avoided may possibly be included

into the assessment (e. g. for saved space, further treatment

steps, improved effluent quality, etc.). The process engi-

neering determines not only the amount of fixed costs,

since type and size of the installation determine the invest-

ment volume and thus the size of annual charges, but also

the variable costs. The membrane surface area chosen, the

number of modules (and the reserve supply), and the re-

sulting reactor volume required determine the amount of

investments. The operating mode determines the energy

consumption, personnel and cleaning costs. The follow-

ing aspects have an effect on the costs:

A.5.12.2

Investment/capital costs

The working life and the depreciation time of the indivi-

dual components have an important impact on the capital

costs of membrane bioreactor processes. The planner has

to elaborate suggestions according to the information from

the membrane manufacturer; the client has to make the

decisions.

The greatest influence on the capital costs include the

tank volumes, and the membrane surface area. The mem-

brane surface area required (and the surface area kept in

reserve) is determined by the choice of the process. In

general, the choice of a smaller separating surface area

leads to higher energy and cleaning costs (see also Figure

A-13). With immersed modules, larger membrane surface

area is necessary than with dry-arranged ones, since the

specific flow rate [L/(m2 �h)] is lower.

While the specific costs of aeration and final sedimentation

tanks rise only in a degressive way with increasing plant

size, the costs for the filtration unit of the membrane

process increase nearly in a linear way (costs per module).

The space requirement is often a decisive criterion for the

use of a membrane installation. Reduction of the necessary

aeration tank volume to approx. half or a quarter compared

to a conventional activated sludge plant, and due to the

fact that final sedimentation becomes unnecessary, the

space requirement, and thus the capital costs, are consider-

ably minimized. In spite of space reduction for activation,

one must not neglect that in some cases space is required

for mixing and compensation tanks, and possibly also for

cleaning tanks.

312

Annex A

313

A.5.12.3

Operating costs

Energy costs

The generation of a flow across the membrane is the main

contributor to the specific energy demand of membrane

filtration plants. The objective of numerous process de-

velopments is the minimization of the energy consumption

by reducing the amount of energy necessary for control

of the covering layer (flow across the membrane), while

maintaining high specific flow rates to minimize the ne-

cessary membrane surface area (examples: rotating modu-

les, oscillating modules etc.).

Compared to dry-arranged membrane modules, the gene-

ration of a cross-flow with immersed systems requires less

energy; about 0.5 – 1.5 kWh/m3 are required for covering

layer control of immersed modules and 1 – 4 kWh/m3 are

needed for dry-arranged systems.

Cleaning costs

The type of cleaning and the cleaning intervals strongly

depend on the waste water quality, but also on the type

of membranes and modules. Therefore, no generalized

specific costs can be given. Besides the chemicals required,

inclusive of their storage, the personnel costs, the energy

costs for heating of the cleaning solutions and, if neces-

sary, the discharge costs have to be taken into account.

According to the type of cleaning, additional investments

for separate cleaning tanks, including the necessary lifting

and transport facilities, or special chemical-resistant coat-

ings of the filtration tanks may become necessary.

Membrane replacement and membrane disposal

costs

The service life of membranes depends on different factors,

such as:

• type of the waste water

• type and frequency of cleaning

General service lives or disposal costs cannot be indicated.

However, membrane replacement and membrane dispo-

sal costs have to be taken into account.

AnnexA

314

Branch/application Total number Number of Number of dry- Flow rate m3/d

immersed installations arranged installations

Table A-5

Membrane installations in West European industry

Solid waste treatment ≥ 1 ≥ 1 – 140

Car industry ≥ 1 ≥ 1 – 230

Chemistry ≥ 15 ≥ 7 ≥ 8 50 - 1,400

Landfill for municipal waste ≥ 48 ≥ 9 ≥ 39 10 - 900

Print shops ≥ 1 – ≥ 1 25

Groundwater rehabilitation ≥ 1 – ≥ 1 20

Cosmetics industry ≥ 3 ≥ 3 - 120 - 700

Laboratory water ≥ 1 – ≥ 1 10

Food industry ≥ 9 ≥ 4 ≥ 5 100 - 480

Leather production/tanneries ≥ 5 ≥ 3 ≥ 2 30 - 820

Malthouse ≥ 1 ≥ 1 ≥ 1 100

Pharmaceutical industry ≥ 15 ≥ 14 ≥ 1 50 - 1,500

Ships’ waste water ≥ 15 ≥ 5 ≥ 10 4 - 740

Tank cleaning ≥ 1 ≥ 1 – 200

Textile industry ≥ 5 ≥ 3 ≥ 2 100 - 1,500

Animal waste processing ≥ 4 ≥ 3 ≥ 1 427 - 960

Laundries ≥ 5 ≥ 1 ≥ 4 30 - 820

A.5.12.4

Comparison of cost-relevant factors

The following factors improve the economic efficiency

compared to conventional plants:

• high influent concentrations

• low concentration of substances causing scaling

and/or fouling

• high costs for the building site

• constant hydraulic load

• high demands on the effluent quality

• reutilization of the treated waste water

Compared to conventional activated sludge plants, mem-

brane bioreactors may be more cost-effective if the influent

concentration is high, and the volume flow is small and,

in particular, very constant.

A membrane bioreactor process will always be considered

if the demands on the effluent are high or if the water

shall be reused, e. g. as process water.

If the filtrate can be reused, saved waste water charges

– for indirect dischargers: saved effluent charges –

according to the waste water statutes and saved freshwater

costs have to be included in the economic analysis.

Annex A

315

A.5.13

Examples in the field of industrial waste water

(Europe)

Without claiming to be complete, Table A-5 summarizes

exemplary applications of membrane bioreactors in

Western Europe. The examples come from the reference

lists of the manufacturers and plant contractors, complet-

ed by the knowledge of the work group members. Test

installations have been or are being operated in a large

number of other branches.

Pages 315 – 316 contain the bibliography of Annex A.5.

A.5.14

Literature

Baumgarten, G. (1998): Behandlung von Deponiesicker-

wasser mit Membranverfahren – Umkehrosmose, Nano-

filtration – Veröffentlichungen des Institutes für Sied-

lungswasserwirtschaft und Abfalltechnik der Universität

Hannover, Heft 99.

Brockmann, M. (1998): Beitrag zur membranunterstützten

biologischen Abwasserreinigung. Veröffentlichungen des

Institutes für Siedlungswasserwirtschaft und Abfalltechnik,

Universität Hannover, Heft 98.

Cornel, P. (2000): Membranbelebung: biologische Ab-

wasserreinigung ohne Anfall von Überschussschlamm?

61. Darmstädter Seminar Abwassertechnik, Schriftenreihe

WAR, Bd. 128.

Diverse Autoren (1997, 1998, 2000, 2001): Membran-

technik in der Wasseraufbereitung und Abwasserbehand-

lung Begleitbücher zur 1. bis 4. Aachener Tagung Sied-

lungswasserwirtschaft und Verfahrenstechnik, IVT der

RWTH Aachen.

Diverse Autoren: Preprints zum 1. bis 8. Aachener Mem-

bran Kolloquium, GVT, VDI-GVC Düsseldorf und IVT,

Aachen.

Flemming, H.- C. (1995): Biofouling bei Membran-

prozessen, Springer-Verlag Berlin, Heidelberg.

Gröschel, A. (1991): Umkehrosmose organisch/wässriger

Systeme – Stofftransport in Membranen und Verfahrens-

entwicklung; Dissertation RWTH Aachen.

Günder, B. (1999): Das Membranbelebungsverfahren in

der kommunalen Abwasserreinigung, Stuttgarter Berichte

zur Siedlungswasserwirtschaft, Band 153.

Henze et al. (1987): Activated Sludge Model No. 1,

Scientific and technical report No. 1, IAWPRC (jetzt IWA),

London.

AnnexA

316

Rautenbach, R.; Melin, T.; Dohmann, M. (1997): Mög-

lichkeiten und Perspektiven der Membrantechnik bei der

kommunalen Abwasserbehandlung und Trinkwasserauf-

bereitung, Begleitbuch zur 1. Aachener Tagung Siedlungs-

wasserwirtschaft und Verfahrenstechnik.

Rautenbach, R.; Melin, T.; Dohmann, M. (1998): Mem-

brantechnik in der öffentlichen Wasseraufbereitung und

Abwasserbehandlung – Bemessung, Umsetzung, Kosten,

Begleitbuch zur 2. Aachener Tagung Siedlungswasserwirt-

schaft und Verfahrenstechnik.

Rautenbach, R.; Melin, T.; Dohmann, M. (2000): Mem-

brantechnik in der Wasseraufbereitung und Abwasserbe-

handlung, Begleitbuch zur 3. Aachener Tagung Siedlungs-

wasserwirtschaft und Verfahrenstechnik.

Rautenbach, R. (1997): Membranverfahren – Grundlagen

der Modul- und Anlagenauslegung, Springer-Verlag Berlin,

Heidelberg.

Wagner, J.; Rosenwinkel, K.-H. (1999): Sludge production

in membrane bioreactors under different conditions, In-

ternational Specialized Conference on Membrane Techno-

logy in Environment Management, Tokyo, 1. – 4., Novem-

ber 1999.

Wichern, M.; Rosenwinkel, K.-H. (2002): Bemessung

von Sauerstoffbedarf und Überschussschlammanfall für

die Membranbelebung auf Basis des ATV-DVWK-A 131

(2000); KA (49) Nr. 5, Mai 2002.

Irmler, H. W. (2001): Dynamische Filtration mit kerami-

schen Membranen, Vulkan-Verlag Essen.

Kiefer, M. (1995): Prozessnahe Aufbereitung von Abwasser

aus der Chemie und Halbleiterindustrie und Rückgewin-

nung von Einsatzchemikalien mit Ionenaustausch und

Membrantechnik. Handbuch Fachveranstaltung „Aufbe-

reitung und Entsorgung von Industrieabwässern und Pro-

zesswässern mit Kombinationsverfahren“, VDI Bildungs-

werk, 25./26.10.1995, Düsseldorf.

Kraft, A. (2000): Abwasserbehandlungskonzepte in der

chemischen und pharmazeutischen Industrie unter Einbe-

ziehung der Membranbioreaktoren – Technik – Beispiele,

6. VDMA-Abwassertagung in der chemischen und phar-

mazeutischen Industrie.

Krause, S.; Cornel, P.; Wagner, M. (2001): Grundsätzliche

Überlegungen zur Messung des Sauerstoffeintrags in

Membranbelebungsanlagen; 64. Darmstädter Seminar

Abwassertechnik, Schriftenreihe WAR, Bd. 134.

Lonsdale, H. K. (1972): Theory and practice of reverse

osmosis and ultrafiltration; in: R. E. Lacey, S. Lacey (Hrsg.):

Industrial processing with membranes, Wiley-Interscience,

New York, S. 123-178.

Melin, T.; Dohmann, M. (2001): Membrantechnik in

der Wasseraufbereitung und Abwasserbehandlung – Pers-

pektiven, Neuentwicklungen und Betriebserfahrungen im

In- und Ausland, Begleitbuch zur 4. Aachener Tagung

Siedlungswasserwirtschaft und Verfahrenstechnik.

Peters, Th. (1998): Wasseraufbereitung mit Membranfil-

trations-Verfahren. Umwelt Bd. 28, Nr. 4, S. 34 – 39.

Peters, Th. (2001): Möglichkeiten und Grenzen der Mem-

branverfahren aufgezeigt an internationalen Beispielen.

Handbuch Fachveranstaltung „Membranverfahren in der

industriellen und kommunalen Abwassertechnik“, Haus

der Technik, 22. – 23. November, Berlin.

Annex A

317

A.6

2nd Work report of the DWA Committee of

Experts KA-7 “Membrane bioreactor process“

from 19th January 2005

This second working report has been prepared by the

DWA Committee of Experts KA-7 “Membrane bioreactor

process“. The committee includes the following people:

Dipl.-Ing. Eberhard Back, Ulm

Dipl.-Biol. Evelyn Brands, Düren

Dr.-Ing. Elmar Dorgeloh, Aachen

Dipl.-Ing. Kinga Drensla, Bergheim

Prof. Dr.-Ing. Franz-Bernd Frechen, Kassel (chairman)

Dr.-Ing. Werner Fuchs, Tulln

Dipl.-Ing. Regina Gnirß, Berlin

Dipl.-Ing. Karl-Heinz Greil, Kundl

Prof. Dr.-Ing. Karl-Heinz Rosenwinkel, Hannover

Dr.-Ing. Wernfried Schier, Kassel

Prof. Dr. rer. nat. Dirk Schoenen, Bonn

Dipl.-Chem. Simone Stein, Leipzig

Prof. Dr.-Ing. Ulf Theilen, Gießen

Dipl.-Ing. Helle van der Roest, Amersfort

Dr.-Ing. Klaus Voßenkaul, Aachen

Dipl.-Ing. Detlef Wedi, Braunschweig

Dipl.-Ing. Thomas Wozniak, Gummersbach

Dipl.-Ing. Petra Zastrow, Merseburg

and guests.

A.6.1

Introduction

Since the publication of the 1st working report on the

membrane bioreactor process [ATV-DVWK 2000b], the

knowledge of this technology has increased due to further

operating experience with large-scale installations and

research projects. This 2nd working report takes the con-

tents of the first report, completes them and describes

the findings from the operation of large-scale installations.

It is now possible to specify design parameters such as

oxygen input with the help of data from large-scale ap-

plications. The following subjects are covered:

• pretreatment of the raw waste water,

• chemical cleaning,

• sludge treatment,

• energy consumption,

• commissioning,

• membrane bioreactor process for the upgrading of

waste water treatment plants and

• reference information on the costs of membrane

bioreactors.

It must be noted that at present membrane technology is

developing at a high speed, in particular in the field of

municipal waste water treatment. This is reflected not

least by the high frequency of meetings of the Committee

of Experts. Therefore the content of this second work

report, too, will certainly soon be supplemented by new

findings.

The next document of the Committee of Experts will be

an advisory leaflet which will probably be published in

2006.

AnnexA

318

A.6.2

Description of the membrane bioreactor process

Principle

The combination of an activated sludge tank and mem-

brane filtration for the separation of the activated sludge

is called the membrane bioreactor process. The membrane

filtration takes over the separation of the activated sludge

in place of the conventional final clarification. While in

secondary settling tanks only the part of the activated

sludge that is settleable is separated, i. e. forms setlleable

flocs, during membrane filtration all parts of the activated

sludge are separated which are larger than the molecular

separation size of the membrane. Thus, the separation of

the activated sludge from the treated waste water becomes

independent of the settling characteristics of the activated

sludge and depends only on the membrane applied.

To separate the activated sludge with its micro-organisms

and particles from the treated waste water, microfiltration

membranes with a molecular separation size of maximally

0.4 µm are used for the membrane bioreactor process.

Concerning the arrangement of the modules, two varia-

tions can be distinguished for the membrane bioreactor

process.

• Membrane bioreactor process with dry-arranged

membrane filtration

Membrane filtration takes place downstream of the acti-

vated sludge tank in an external, closed filtration unit.

The modules (e. g. tube modules) are set up in a dry ar-

rangement (see Figure A-14). The activated sludge is

pumped through the modules, which results in higher

pressures (more than 1 bar) with this process.

Up to now, this external membrane filtration is not found

at municipal plants and therefore not a subject of this

work report. Information is available in the work report

IG 5.5 Part 2 [ATV-DVWK 2002].

feed permeate


excesssludgeconcentrate (return sludge)

membrane filtrationin dry arrangement

Figure A-14

Membrane filtration in dry arrangement

Annex A

319

• Membrane bioreactor process with immersed

membrane filtration

In this variation, the membrane modules are placed in the

mixed liquor. The membrane modules can be installed

either in the activated sludge tank or in a separate filtra-

tion tank. Figure A-15 shows both configurations.

For proper functioning of the membrane bioreactor pro-

cess, the following basic requirements have to be fulfilled:

• Oxygen supply to the activated sludge,

• circulation and thorough mixing of the activated sludge

tank,

• transmembrane pressure difference as a driving force

for the filtration process,

• control of the development of a covering layer.

With immersed arrangement, the overflow necessary for

covering layer control is typically generated by coarse-

bubble aeration. For this purpose, a blower with air inlets

under the immersed membrane modules and a suited flow

control to generate the overflow are necessary. Separate

aeration in the activated sludge tank is required besides

module aeration.

The transmembrane pressure difference can be generated

by a permeate pump or hydrostatically. In principle, the

lowest possible transmembrane pressure is favourable in

operation.

feed permeate


excesssludge

cross-flowaeration

membrane filtration

feed permeate


filtrationtank

cross-flowaeration

membrane filtration

excess sludge

concentrate(return sludge)

A) immersed membrane filtrationin the activated sludge tank

B) immersed membrane filtrationin a separate filtration tank

Figure A-15

Ways of configuring an immersed membrane filtration

AnnexA

320

Constructional forms and operating modes

Up to now, the following membranes have been used in

large-scale applications of the membrane bioreactor

process:

• plate membranes and

• hollow-fibre membranes

Membranes are used as modules in different construc-

tional forms.

Plate modules are assembled from membrane plates

which are arranged in parallel. They consist of a support-

ing plate with a drainage device. The plate membrane is

fitted for the most part on each side of the membrane.

The flat membranes are overflown by the mixed liquor

and filtration takes place from outside to inside.

The permeate is withdrawn from the inside of the plate

by a suction duct.

Hollow-fibre modules consist of membrane hollow fibres

which may be reinforced by an in-side supporting tissue.

Filtration takes place from outside to inside. For module

assembling, a larger number of fibres are combined to form

a bundle, and are potted with resin at one or both ends.

A permeate collecting tube connects all of the individual

fibres. Depending on the manufacturer, the hollow-fibre

membranes are installed horizontally or vertically into

the module.

The module aeration device is for the most part integrated

into the module. Other module constructions are in dif-

ferent testing stages.

permeate

module aeration

A) Plate module

flat membrane onsupporting plate

module aeration

flexible hollow-fibremembrane

lower fittingwith resin

upper fittingwith resin

(depends onprovider)

permeate permeatelateral fittingswith resin

vertically arranged horizontally arranged

B) Hollow-fibre module

Figure A-16

Schematic representation of different module constructions

Annex A

321

Membrane modules are operated discontinuously. Depen-

ding on the module construction, periodic filtration pau-

ses or backwashing with permeate are performed to mini-

mize the covering layer. Therefore, it is necessary to dis-

tinguish gross and net permeate flow (see Figure A-17).

Additional chemical cleaning is required for further re-

generation of the modules and to remove the membrane

fouling (see chapter A.6.5).

To adapt the filtration capacity to the volume of inflow,

two operating modes are possible:

• The permeate flow of all modules is changed equally.

• Certain modules are disconnected such that the remain-

ing modules work with the flow permissible for conti-

nuous operation. A constant operating time of the in-

dividual modules has to be respected. Moreover, this

operating mode ensures that sufficient recovery phases

(phases without operation) for the individual modules

are kept. As a rule, this operating mode is more energy-

efficient than the first mentioned.

pause

per

mea

te v

olu

me

time

net fl

ux

filtration

cycle

gros

s flu

x

backwashing

per

mea

te v

olu

me

time

net fl

ux

filtration

cycle

gros

s flu

x

Figure A-17

Typical operating modes of the membrane modules

AnnexA

322

Capacity of the membrane bioreactor process

The advantages of the membrane bioreactor process result

from the possible higher MLSS contents in the activated

sludge tank and complete separation of all solid matter

by the membranes. From this results an improved elimi-

nation of nutrients and micro-organisms. Therefore, nitro-

gen, phosphorus and carbon in the effluent of membrane

bioreactors are reduced by the fraction which in conven-

tional plants results from solid matter in the effluent.

Membrane filters are able to retain micro-organisms to

a very large extent. The permeate complies with the

hygienic requirements of the EU Directive on Bathing

Waters 76/160/EWG [COUNCIL OF EC 1976] concerning

the microbiological parameters total number of Bacteria

coli, faecal coliforms and streptococci. Studies at the Rödingen

and Markranstädt waste water treatment plants during the

first months of operation (in 2000) have shown that the

concentrations of all micro-organisms mentioned in the

EU Directive on Bathing Waters were reduced to values

close to the detection limit, independent of the weather

conditions (dry weather, storm, continuous rain). The

limit values and guide values of the EU Directive on

Bathing Waters were met in all cases. Studies at the Rödin-

gen waste water treatment plant carried out after several

years of operation (in 2002 and 2003) have shown that

the germ reduction continues to be at a high level, but

indicate that with increasing operating time, the removal

rate may possibly decrease. This aspect has to be studied

in more detail.

Even virus, the smallest pathogenic organisms which theo-

retically may pass through the membrane pores, are re-

tained by the membrane bioreactor process. The viruses

typically accumulate with particles and micro-organisms

so that they are removed from the waste water by the

elimination of larger particles. During the studies men-

tioned above, it was possible to significantly reduce the

concentrations of intestinal viruses. However, safe com-

pliance with the limit values of the EU Directive on Bathing

Waters cannot be ensured.

Prerequisite for the high removal of pathogenic micro-

organisms in the membrane bioreactor process is that no

short-circuits between treated and non-treated waste water

exist and that membranes and connections are always

secure. This requirement seems to be trivial. In practice,

however, appropriate controls are necessary.

The elimination of micro-pollutants, e. g. residues from

drugs and substances with endocrine effect, requires bio-

logical processes or adsorption on at the sludge because

the membranes used with the membrane bioreactor pro-

cess do not retain dissolved substances.

A.6.3

Instructions for planning and design

Pretreatment of the raw waste water

Sufficient pretreatment of the waste water is an essential

prerequisite for the operation of membrane bioreactors.

Especially hair and grease may accumulate and stick to

the modules and thus cause considerable operating pro-

blems. In principle, a grit and grease trap is necessary.

Coarse matter can be removed by single-stage or two-stage

devices. Screens with spacings used up to now are not

sufficient as the only measure for the removal of coarse

matter. Therefore, screens have to be combined with sieves

or with primary treatment.

Sieves should have a mesh size of ≤3 mm and should be

preferably configured with flow reversal. The mesh size

of sieves should be chosen considering the following

boundary conditions:

• of drainage system (combined or separate system,

emptying and cleaning of stormwater tanks, etc.),

• sensitivity of the membrane module construction

concerning fibrous matter,

• other pretreatment installations, especially the spacing

of the screen, if existing.

Therefore, sieve mesh sizes of ≤1 mm may be required.

If primary treatment is used in place of a sieve, special

measures are necessary to avoid the passage of floating

matter into the activated sludge stage. Experience has

shown that primary treatment realized as so-called coarse

desludging is not sufficient to effectively retain undesired

substances.

Annex A

323

To protect the membrane effectively against coarse matter,

it is strongly recommended to install redundant screens

and sieves and not to equip the mechanical treatment

stages with an emergency circuit.

Design and construction

The design data for biological treatment in a membrane

bioreactor have to be determined according to the proce-

dure for conventional waste water treatment plants laid

down in the standard A 198 [ATV-DVWK 2003]. In general,

the loads, the inflows and the waste water temperatures

have to be determined for the design load period.

The size of the activated sludge tanks can be calculated

according to the ATV-DVWK standard A 131 [ATV-DVWK

2000a]. For determination of the volumes, a higher solids

content has to be considered which in current practice is

not chosen higher than 12 g/L. Possibly existing filtration

tanks can be added to the volume VBB minus the volume

displaced by the built-in components. For the load cases

to be fully assessed, it is necessary to consider the down-

times of filtration tanks.

Compared to conventional activated sludge plants (acti-

vated sludge tank, secondary settling tank), the total

volume of membrane bioreactors is significantly smaller

which in the case of peak loads, this results in increased

peak concentrations in the effluent for hydraulic reasons.

Experience acquired up to now with the operation of test

plants and large-scale installations suggests that non-de-

graded waste water components give rise to fouling of

the membranes and thus accelerate the reduction of the

permeability. Therefore it is recommended to bring the

waste water to the membrane only after a time which is

sufficient for biodegradation of the waste water consti-

tuents. This can be realized by adequate hydraulic design

of the tank volumes (cascading, plug-flow). Short-circuit

flows of the waste water to the membrane modules have

to be avoided at any rate.

The separate installation of the membrane stage in a fil-

tration tank is normally also advantageous for cleaning

and maintenance.

To avoid that the activated sludge in separate filtration

tanks is overconcentrated, it is required to maintain a

sufficient return sludge flow from the filtration tank back

into the activated sludge tank. Depending on the system,

the maximum solid matter content at the membrane may

be up to 18 g/L. The necessary return sludge flow is cal-

culated from the solid matter content in the activated

sludge tank and in the completely mixed filtration tank.

Attention must be paid to constant mixing of the filtration

tank to avoid deposits and to ensure optimal membrane

functioning.

The waste water flowing into the waste water treatment

plant has to be filterable at any time by the available

membrane surface area. Therefore, the design basis for

the membrane surface area is the combined water flow

QM at the lowest temperature over the course of the year

because the permeate flow depends on the temperature.

In contrast to the standard A 198 [ATV-DVWK 2003],

mean daily values of the waste water temperature are

essential.

The net permeate flow of designed installations (design

flow in constant operation) as a quotient of the combined

water flow QM and the membrane surface area AM in-

stalled is between approx. 8 L/(m2 �h) and 30 L/(m2 �h)

depending on the module type. The design has to con-

sider necessary shut-downs because of chemical cleaning,

failures, module replacement, etc. During such shut-

downs, the remaining membrane surface has to be able

to filter the maximum waste water volume QM. Depen-

ding on the membrane system, it is possible to attain, for

a limited period, significantly higher permeate flows.

To manage hydraulic peaks, a buffer volume in the form

of upstream tanks, storage capacities or as variable level

in the activated sludge tank may be useful instead of

keeping membrane surface area in reserve.

AnnexA

324

Membrane material PVDF, mod. PVC,

PES, PAN or PE1)

pH resistance 2 - 11

Filter surface area per module m2 240 - max. 2,880

Net permeate flow (QM/AM) L/(m2 �h) 8 - 30

Permeability L/(m2�h�bar) 100 - 400

Maximal working pressure mbar 300 - 400

Mean working pressure mbar 20 - 200

“Footprint“ (modules in fitted state) m2/m2 70 - 165

(filter surface area per tank floor area)

Package density (modules in fitted state) m2/m3 40 - 100

(Filter surface area per module volume)

Injection depth module aeration m 1.5 - 5.5

Energy demand module aeration2) kWh/m3INFLOW 0.25 - 0.80

Energy demand permeate pump kWh/m3INFLOW 0.06 - 0.07

Reference data on membrane systems from information

of manufacturers and operating results available up to now

are compiled in Table A-6 [WEDI 2002a]. Together with

the progress of knowledge and module development,

these data are also subject to changes.

Typical cycle times are in the range of minutes. But there

are also installations with continuous filtration during

several hours.

Information on the service life (years until the membranes

have to be replaced) cannot yet be given.

Oxygen input

With membrane bioreactors, we distinguish between the

coarse-bubble aeration of the modules and the typical

fine-bubble aeration in the activated sludge tanks necessary

for the biological processes. For the design of the activa-

ted sludge tanks, it has to be considered that the �-value

to be assessed for the air input into the activated sludge

tank must be significantly lower because of the higher TS

content of the sludge.

The tendency of the reduction of the �-value as a result

of increased solids concentrations is consistent in all

studies.

Table A-6

Characteristic data of designed membrane bioreactors [WEDI 2002a]

Nominal pore size mm < 0,1 – 0,4

1) PVDF: polyvinylidene fluoride; PVC: polyvinylidene chloride; PES: polyethersulfone; PAN: polyacrylonitrile; PE: polyethylene

2) depending on the operating mode of the modules

Annex A

325

The �-value also depends on other variables. In addition

to the aeration system, other factors include the measure-

ment method (measurements with or without waste water

inflow), the salt content, the surfactant concentration, and

the specific air flow or the flow in the tank. Measurements

at the Rödingen waste water treatment plant suggest that

the characteristics of the activated sludge or substances

of biogenic origin which are retained in the process have

effects on the oxygen input in the membrane bioreactor

process (e. g. EPS).

It is recommended to use a reduced �-value of 0.5 for the

design of fine-bubble aeration systems in membrane bio-

reactor applications. This �-value is based on a typical

solids concentration of 10 – 12 g/L. If there are specific

findings about further �-value reduction at lower TS con-

centrations, a reduction should be made.

If the cross-flow aeration of the membranes is considered

in the design to cover the biological oxygen demand, the

designer has to prove this separately, taking into consid-

eration the specific situation and the load cases. According

to the arrangement of the membranes in the system, this

oxygen input can be assessed to reduce the operating costs.

For the installation of the membranes in the nitrification

tanks, KRAUSE/CORNEL [2003] quote mean energy savings

of 15 %. If the membranes are arranged in separate filtra-

tion chambers, the energy savings are lower. However,

the instructions in section A.6.3 concerning the reactor

form and the retention time behaviour have to be ob-

served in any case.

1,00

0,75

0,50

0,25

0

alp

ha

201510 25

TS in g/L

5

Beverwijk

1st work report KA-7, only pilot plants (2000)

Markranstädt/Cornel et al. (2001)Rödingen/Cornel et al. (2001)

Rödingen/Wagner, Krause (2003)

Figure A-18

Influence of the solids concentrations on the �-value for fine-bubble pressure aeration installations

AnnexA

326

Nitrogen removal

Nitrogen removal is designed according to the ATV-DVWK

standard A 131 [ATV-DVWK 2000a].

As a result of module aeration, a considerable quantity of

oxygen is entrained with the mixed liquor recycled from

the separate filtration tank or from the filtration zone, in

particular in the case of combined water flow. This has to

be considered in the design of the process.

Phosphorus removal

With the membrane bioreactor process, phosphorus elimi-

nation can take place by pre-precipitation in the primary

treatment stage or by simultaneous precipitation in the

activated sludge stage.

For pre-precipitation, all common precipitants can be used.

There is no difference compared to the conventional acti-

vated sludge process. A disadvantage of pre-precipitation

is significantly higher sludge production in the primary

treatment stage which has to be considered in the design

of the sludge treatment facilities.

In the activated sludge stage, phosphorus removal can take

place by means of simultaneous chemical precipitation

or increased biological phosphorus removal, in principle

combined with simultaneous precipitation. With the mem-

brane bioreactor process, lower total phosphorus concen-

trations in the effluent can be attained than with a con-

ventional activated sludge process because

• the particulate phosphorus compounds can be

separated completely, and

• orthophosphate cannot be redissolved in a secondary

settling tank.

The cleaning agents used for membrane cleaning have to

be adapted according to the use of precipitants. Up to now,

no signs of increased cleaning expenditure for the mem-

branes by the use of precipitants have been observed. A

spatial distance between the dosing point and the mem-

brane modules is recommended. Additives into the waste

water treatment plants, including precipitants, generally

have to be approved by the membrane manufacturers.

Up to now, increased biological phosphorus removal in the

membrane bioreactor process has been only used within

the scope of research and development [GNIRß 2003],

[DICHTL ET AL. 2004].

Excess sludge production

The design of a membrane bioreactor typically considers

a sludge age in the range that for of simultaneous aerobic

sludge stabilization. Therefore, in principle it must be as-

sumed that the biological metabolic rates in membrane

bioreactors do not differ significantly from those in con-

ventional activated sludge plants [among others ROSEN-

WINKEL/WAGNER 2000]. Concerning the treatment of

municipal waste water, no significant reduction of the

excess sludge production can be expected compared to

conventional systems.

According to GÜNDER [1999], the excess sludge produc-

tion can be reduced by operating with an extremely high

sludge age. However, the BOD5 sludge loadings of less

than 0.01 kg/(kg d) required to achieve this are, as a rule,

are not economic.

The excess sludge production can be determined follow-

ing the ATV-DVWK standard A 131 and the ASM models

[HENZE ET AL. 1987; HENZE ET AL. 1999; GUJER ET AL.

1999].

A.6.4

Sludge treatment

General facts

The excess sludge from the large-scale membrane bio-

reactors at Rödingen, Markranstädt and Monheim are

stored in a stacking container. They are either transported

periodically to a collecting place at a central waste water

treatment plant for joint treatment with sludge from

conventional plants or they are still used for agricultural

purposes. Therefore, in Germany there is up to now no

experience with the operation of large-scale sludge treat-

ment plants.

Annex A

327

The sludge from the large-scale plants, particularly from

the Rödingen waste water treatment plant, have been sub-

ject to extensive studies which are described in the follow-

ing section.

Dewaterability

As a rule, sludge from membrane bioreactors has a small

floc size (about 50 µm, in part only 10 µm). Despite the

increased specific floc surface area of the small flocs, no

deterioration of the dewaterability has been observed.

Table A-7 shows characteristic values of large-scale studies.

In a large-scale test with a high-performance centrifuge, a

dried solid content of nearly 30 % was attained with the

sludge from the Rödingen waste water treatment plant.

Laboratory tests proved this dewaterability with results of

27 % on annual average and maximum values up to 31 %

at an organic content of the sludge (ignition loss) of

61 – 48 %. With lower organic content, the sludge showed

an improved dewaterability. The polymer demand of

2.9 gWS/kg dried solid content on average was signifi-

cantly below the polymer demand of 5.9 gWS/kg dried

solid content from 15 different conventional activated

sludge plants with aerobic stabilization.

The studies to-date show that the demand for flocculation

agents is comparable to that of conventional plants or even

lower.

The experience acquired up to now indicates that no

additional expenditure for sludge dewatering compared

to conventional sludge has to be expected. Screening in

mechanical pretreatment removes structural substances

that may affect the dewaterability.

A special solution was chosen for the waste water treat-

ment plant on the Säntigs peak (Switzerland) [MÖRGELI

2001]. The excess sludge is filled into special bags. The

water drains off and the sludge compacts. Then the sludge

is ready for dispatch by the cableway. By means of this

method, a dried solid content of approx. 20 % is attained.

This system has also been installed also at the Schwägalp

waste water treatment plant.

Digestibility

Despite the typically low sludge loading rate, which is

similar to or less than that of a simultaneous aerobic sta-

bilization plant, the organic total solids content of the

excess sludge from large-scale installations and from pilot

plants varies between 46 % and 69 %. This high organic

content was the reason for an examination of the digesti-

bility or the residual gas potential respectively according

to DIN 38 414 S8 [N. N. 1999].

Another reason to examine the digestibility is that the

membrane bioreactor process is also a possible variation

for the upgrading of existing plants with aerobic sludge

stabilization.

In literature, 200 to 300 standard litres of gas produced

per kg of organic dry solids (Nl/kg oTS) are given for the

digestion of excess sludge [BAHRS ETAL. 1994]. During the

Device/method Installation Dried solid content of the excess sludge Dried solid content after dewatering

Ignition loss of the excess sludge

Table A-7

Studies on the dewaterability of excess sludge on a large-scale centrifuge

centrifuge Markranstädt 2.4 % dried solid content

65 % ignition loss 24.5 %

Rödingen 3.8 % dried solid content

46 % ignition loss 29.9 %

Monheim 1.0 % dried solid content

54 % ignition loss 28 %

AnnexA

328

study, the excess sludge from membrane bioreactors

attained this value reported in literature.

The results show that the sludge from membrane bioreac-

tors has a (residual) gas production comparable to sludge

from conventional plants.

A.6.5

Chemical cleaning of the membrane modules

To maintain and increase the permeability and to disinfect

the permeate tubes, chemical cleaning of the membranes

is required from time to time. There is no uniform recom-

mendation for cleaning. Optimization takes place conti-

nuously based on experiences from large-scale operation.

Oxidizing chemicals serve to remove organic deposits. To

avoid AOX formation, chlorine-free chemicals should be

used, if possible, e. g. hydrogen dioxide. However, the

best cleaning results up to now have been attained with

sodium hypochlorite solution as oxidizing agent, inde-

pendent of the membrane.

Depending on the requirement and particularly to remove

inorganic deposits, more cleaning steps are added. The

following chemicals can be used: citric acid, organic per-

oxide compounds, oxalic acid, acetic acid, mineral acids,

surfactants, detergents and manufacturer-specific combi-

nation products.

As a rule, two-step cleaning by means of an oxidizing agent

and an organic acid is used.

The load on membranes from cleaning should be as low

as possible. This has to be considered in the choice and

dosage of the cleaning chemicals. The cleaning method

has to be approved by the manufacturer.

At present, the following cleaning processes are used:

• in-situ cleaning (in fitted state)

– in the activated sludge

During chemical cleaning, the membrane modules

remain immersed in the activated sludge. The chemi-

cals are added from the permeate side. The quantity

of the cleaning solution passing into the activated

sludge depends to a high degree on the concept of

the cleaning process.

– in the cleaning solution

The activated sludge is pumped off from the tank.

The tank is then filled with cleaning chemicals until

the modules are submerged.

– in the air

As a rule, the level of the activated sludge is lowered

to the bottom edge of the modules. The membrane

modules suspend freely in the air. The chemicals are

added from the permeate side. The contact time is

5 – 10 minutes.

• external cleaning

The membrane modules are withdrawn from the

membrane bioreactor tank and put into an external

“cleaning cell“.

In-situ cleaning in a cleaning solution or in the air are

particularly suited for installations with separate filtra-

tion tanks.

Up to now, we distinguish between intensive cleaning

and intermediate cleaning, depending on the chemical

concentration and the cleaning interval.

As a rule, intensive cleaning is required at least once a year

to significantly increase the permeability. It can be real-

ized, for example, with high concentrations of oxidizing

agents (e. g. NaOCl – 1,000 mg/l Cl or H2O2 – 2,000 mg/l),

followed by acid cleaning (e. g. by citric acid). The clean-

ing cycles should preferably be timed in such a way that

the maximum hydraulic performance is reached in the

beginning of the cold season.

Intermediate cleaning, typically by means of low oxidant

concentration (e. g. NaOCl – 150 mg/L Cl), serves to pro-

long the interval between intensive cleaning events. It is

carried out in intervals of 2 – 7 days. In order to realize

longterm successful intermediate cleaning, it is necessary

to apply this cleaning method during the first operating

period with a relatively contaminant-free membrane.

Annex A

329

Intermediate cleaning is not used for all module construc-

tion types.

In-situ cleaning can be used for intensive cleaning or inter-

mediate cleaning. External cleaning is used exclusively for

intensive cleaning.

The operational expenditure of external cleaning is very

high. Therefore, it has been replaced in some installations

by the in-situ cleaning method described above.

If cleaning takes place directly in the cleaning solution,

the effect at the membrane surface is far better because

the solution is not diluted by the activated sludge. More-

over, it is possible to increase the temperature of the clean-

ing water to 30 – 35 °C. To improve the mixing of the

chemicals applied in the cleaning tank, the membrane is

aerated during cleaning.

The operator of a membrane bioreactor process should

demand a detailed instruction for proper membrane clean-

ing and the necessary cleaning intervals from the plant

manufacturer or the membrane manufacturer, respectively.

In the planning of membrane bioreactors, adequate stock-

rooms, dosing devices, adequate materials for tanks and

tubes as well as safety have to be considered (Wedi, 2002b).

Since cleaning processes are being continuously developed

and may be optimized for an individual case, as many

options as possible should be kept open for the chemical

stock-room and the dosing devices in compliance with the

relevant safety requirements. In Germany, besides the in-

structions according to the Federal Water Act, also aspects

of work safety, fire protection and emission control have

to be observed depending on the combination of chemi-

cals. The following instructions can or have to be applied

in particular:

• Technical Regulations for Hazardous Substances

(TRGS), in particular TRGS 515,

• instructions and advisory leaflets of the Statutory

Accident Insurance Institutions,

• Ordinance on the Workplace (ArbStättV),

• plant identifications according to the Ordinance on

Hazardous Substances (GSV),

• if necessary, Ordinance on Flammable Liquids (VbF),

• if necessary, VCI concept for joint storage of chemicals,

predefinition of the dangerous groups for storage,

• if necessary, Ordinance on the Retention of Fire-

fighting Water (LöRüRL),

• if necessary, leak detection according to DVGW,

• if necessary, other ordinances specific to the individual

federal state.

Planning and approval of the installations should be car-

ried out in coordination with authorities and specialized

institutions such as industrial inspection boards, TÜV or

occupational health services.

A.6.6

Energy demand

The operating cost of a membrane bioreactor system is

influenced significantly by the energy demand for cross-

flow aeration in addition to the energy demand for oxy-

gen input for biological waste water treatment.

The aeration energy depends on the specific aeration de-

mand of the membrane used and the immersion depth

of the corresponding aeration devices. For the membrane

modules currently applied, these values vary in a wide

range for the specific air demand from 0.2 Nm3/(m2 �h)

to 0.45 Nm3/(m2 �h) and immersion depths of 2 metres

to 5 metres.

Current experience with large-scale operation shows a

specific energy demand for cross-flow aeration of approx.

0,25 kWh/m3INFLOW to 0.8 kWh/m3

INFLOW (mean annual

value).

Thus, the potential energy savings are to be found main-

ly in the reduction of the specific air demand and in the

increase of the filtration capacity of the membrane system

(e. g. connection or disconnection of individual modules

depending on the inflow).

AnnexA

330

If the permeate is withdrawn by pumps, a specific energy

demand of 50 W/m3 to 70 W/m3 can be assumed. Depend-

ing on the system configuration, recirculation of the

concentrated activated sludge from separate filtration

chambers has to be considered with approx. 15 W/m3 to

20 W/m3. As a result of the lower �-value, also the energy

consumption for fine-bubble aeration devices increases

by the factor �konv./�Membran.

Concrete data on the energy demand and its distribution

exists for the membrane bioreactors at Markranstädt and

Monheim. Both installations are equipped with hollow-

fibre membranes. From the figures below it can be seen

that as the waste water throughput approaches maxi-

mum capacity, the specific energy demand decreases.

The specific energy demand normalized to the mean

inflow (approx. 43 % or 35 % of Qmax) is in the range of

0.8 kWh/m3 to 0.9 kWh/m3 for both installations. Com-

pared to conventional activated sludge plants with an

average specific energy consumption of 0.3 kWh/m3 to

0.5 kWh/m3 and additional expansions for e. g. space

filtration and radiation plants with approx. 0.15 kWh/m3

to 0.25 kWh/m3 altogether, the energy demand of mem-

brane bioreactors is still high. For this comparison it has

to be taken into account that the capacity of the mem-

brane bioreactor is greater, in particular concerning the

hygiene-relevant parameters.

2.0

1.5

1.0

0.5

spec

ific

en

erg

y co

nsu

mp

tio

n [

kWh

/m3 ]

0

inflow [m3/d]

5,0001,000 2,000 3,000 4,000

microfiltration 500 Awithout air-cycling(Jun – Jul 2001)

microfiltration 500 Awithout air-cycling(Jan – Nov 2002)

microfiltration 500 Cwith air-cycling(Jan – Jun 2003)

Figure A-19

Specific energy consumption of the Markranstädt WWTP [STEIN, KERKLIES 2003]

Annex A

331

A.6.7

Upgrading of existing municipal waste water

treatment plants

In future, the main focus of necessary investments in

waste water treatment will move from new constructions

of waste water treatment plants to rehabilitation and up-

grading measures combined with expansion projects. For

these tasks, too, the membrane bioreactor process may be

a technically and financially viable solution [SCHIER 2003].

Favourable conditions for MBR treatment arise when in

the course of plant upgrades large new tank volumes would

have to be built, where problems exist as a result of in-

sufficient capacity of the secondary settling tanks, but

especially in those cases where both problems have to be

addressed. Prerequisite is that the structural condition of

the existing activated sludge tanks and secondary settling

tanks allows further utilization.

For the conversion of phase separation from settling to

membrane filtration, the utilization of the existing secon-

dary settling tank volume as additional activated sludge

tank volume is possible. In this way it is not only unne-

cessary to build new activated sludge tanks but a TSBB

concentration results which is below the TSBB concentra-

tion typical with membrane bioreactor processes. De-

pending on the degree of undercapacity of the existing

plant, the guarantee of the aerobic sludge age has to be

considered in the design of the TSBB concentration be-

sides the available activation volume. TSBB concentrations

of 4 g/l – 7 g/l usually result [FRECHEN, SCHIER, WETT

2001 and 2003]. If it were possible to realize such a con-

cept, the usual disadvantages of membrane bioreactors

(sensitivity to peak loads, unfavourable �-value) could be

largely compensated.

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

spec

ific

po

wer

co

nsu

mp

tio

n [

kWh

/m3 ]

inflow [m3/d]

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000

future median of the inflow, 35 % of Qmax

start-up, non-optimized operation in July/August 2003

min. consumption filtration

Figure A-20

Specific energy consumption of the KA Monheim WWTP [WEDI 2003]

AnnexA

332

Besides the higher effluent quality of the permeate, more

process- and expansionspecific advantages of this upgrad-

ing concept have to mentioned:

• significant biological reserve capacities in the case of

future demand for expansion,

• economical handling of space resources.

Up to now this upgrading concept has not yet been im-

plemented on an industrial scale. In a first research pro-

ject, different membrane systems have been examined for

operating and design parameters by semi-technical tests

[UNI KASSEL 2004]. Besides the general technical feasibility

and technical suitability of the membrane bioreactor pro-

cess for upgrading of the waste water treatment plants

studied, it was stated that concerning the hydraulic capa-

city, the hollow-fibre systems studied attained flow rates

which were in the range of or even slightly above the

operating or design flow rates of large-scale plants. Thus we

cannot start from a reduced hydraulic capacity for the

operation of a membrane bioreactor with process-specific

low TSBB concentrations. If a higher capacity is desired, it

is recommended to carry out preliminary tests. The studies

concerning this are still ongoing (Kassel University).

A further process solution is to upgrade existing plants

with partial flow treatment with the membrane bioreac-

tor process.

A.6.8

Instructions for start-up

Principles

For the start-up of a membrane bioreactor, the principles

concerning the biological characteristics and the treatment

capacities are similar to those of conventional plants. In

the following section some specific aspects of the start-up

of a membrane bioreactor are discussed.

Performance test

Membrane bioreactors are complex technical installations,

for which functional capability and the concurrence of

the individual components are particularly important in

order to ensure long-term processstable operation.

Extensive performance tests of the individual components

and the complete process- and electric measurement and

control equipment are indispensable. The programs used

for the control of the membrane installation are sized to

the specific system of the respective project.

The functional capability of the membrane-specific pro-

cess components such as mechanical pretreatment stage

and chemical treatment is of special importance.

Leak detection

To detect defects of the membranes and their installations

due to their production or which may result from the con-

struction of the plant, it is necessary to carry out a per-

formance test to examine for leaks. The following measu-

res are possible for this purpose:

• air pressure holding test on the filtrate side

(low pressure) with an empty tank,

• air pressure holding test on the filtrate side (over-

pressure) with constant clean water level or with a

clean water level which rises during measurement.

The pressure applied for the leak test has to be adjusted

to the respective membrane system (capacity for back-

washing, e. g. with plate modules).

Start-up operation

After successful performance and leak testing, the instal-

lation is filled with activated sludge. If no adapted sludge

from a municipal membrane bioreactor is available, it is

possible to use return sludge from a conventional plant.

It is necessary to remove fibrous material from this acti-

vated sludge (e. g. by sieving).

During start-up of the installation, the TS content increases

to the level of the design values (cf. chapter A.6.3). From

this may result a change in the floc structure. At TS con-

tents of approx. 8 g/l – 10 g/l, strong foaming may occur

which can be treated for example by defoamers. When

this process is finished, the tendency for foaming decreases.

Experience has shown that the development of a foam

layer in the range of < 10 cm can be expected.

Annex A

333

A.6.9

Costs

General facts

Cost comparisons have to consider the annual costs re-

sulting from operation and capital costs. In general, cost

estimates and comparisons for a rather new process tech-

nology have the disadvantage that they typically become

inaccurate after a short time, because developments in

process optimization and free-market regularities influence

the costs to such an extent that new processes increasingly

gain competitiveness. Such estimates and comparative

calculations indicate that membrane technology may

become economically interesting, depending on the respec-

tive boundary conditions [RAUTENBACH ET AL. 2000].

For purposes of evaluating the costs of membrane biore-

actors, the increased capacity for germ reduction of waste

water compared to “conventional” processes must be

considered. For this reason, too, a simple comparison of

membrane bioreactors with activated sludge plants accord-

ing to ATV-DVWK-A 131 without germ reduction is use-

ful only to a limited extent and should be left to special

cases. As a rule, membrane installations are at present

still more expensive compared to conventional activated

sludge plants.

Since membrane bioreactors only consist of a few struc-

tures, they are advantageous under special boundary con-

ditions, e. g. sites with restricted space, complicated sub-

soil conditions or in the case of special architectural de-

mands. This is increased in particular for demands on

germ reduction in waste water due to special conditions

of the receiving water.

On account of the higher total solids content in the acti-

vated sludge, it is useful to examine for the membrane bio-

reactor process the possibility of simultaneous aerobic

sludge stabilization. From this result significant liberties

in planning. The size of the activated sludge tanks is con-

siderably reduced, settling devices and possibly necessary

filtration units can be spared as well as downstream germ

reduction installations. Depending on the possibility, sepa-

rate sludge stabilization processes and primary treatment

may be dropped.

However, the effects of increased pollution loads flowing

into the activated sludge stage and of possibly no diges-

ter gas production have to be considered in the overall

energy balance.

Investments

Additional expenses arise from the purchase of the mem-

brane installation, including the necessary mechanical

pretreatment (cf. chapter A.6.3), which has to be equip-

ped very carefully, high-performance aeration equipment,

the chemical storage room and the dosing stations as

well as the electrical and control technology.

In the case of a new construction, the additional invest-

ments for a single-stage sieving or screening installation

are limited in spite of significantly increased requirements

concerning screenings removal, redundancy and process

stability. They are in the range of 2 – 4 % related to the

construction costs of a new membrane bioreactor. A two-

stage screening/sieving installation including the enclosed

volume results in additional construction costs.

Compared to a conventional plant, smaller activated sludge

tank volume has to be kept in reserve. The reduced costs

are not as high as the pure volume comparison would

lead one to believe, especially if filtration tanks are built.

Figure A-21 shows a distribution of the investments in

the case of a new construction of a membrane bioreactor

(Monheim WWTP) for a maximum flow of approx.

300 m3/h. Concerning the mechanical equipment, the

membrane installation is clearly dominant with approx.

34 %. The expenditure for sieving installations and acti-

vated sludge tanks are of less importance.

The orienting guide values represented in Figure A-22

take into account costs for plate and hollow-fibre module

systems available on the market in Germany from 1999

to 2002, which were designed for comparable flows for

“typical“ conditions (municipal waste water, temperatures

of 8 – 12 °C) of approx. 22 L/(m2 �h) to 30 L/(m2 �h)

[WEDI 2003].

AnnexA

334

If the costs of the ready-for-use membrane installation

are normalized by the maximum inflow of the installa-

tion, the inflow-specific system price of the membrane

installation only results. This normalized cost allows mem-

brane systems with different specific filtration capacities

to be compared.

In these specifications, the ready-for-use filtration unit

with pumps, blowers, connecting tubes, dosing installa-

tions for chemicals and the necessary controls are con-

sidered. Costs for equipment engineering, start-up and,

as a rule, a five-year guarantee on the membranes are

also included. With increasing size of the installation, the

relative fraction of these services decreases significantly.

Structural parts of a waste water treatment plant or equip-

ment for mechanical pretreatment are not included.

construction engineering39 %

all data related to the total building costs

mechanical equipment44 %

electric equipment13 %

ventilation/sanitation3 %

others1 %

(filtration chamber: 4 %)(activated sludge tank: 5 %)

(total membrane filtration installation incl. electric,measure and control equipment: 34 %)

(2 compact installations sieving/grit chamber: 5 %)

Figure A-21

Example for the distribution of construction costs of a membrane bioreactor

for approximately 300 m3/h [WEDI 2003]

Annex A

335

The share for the membranes only is approx. 50% to 65%

and rises with increasing size of the installation or with

increasing maximum inflow. Currently the surface-speci-

fic prices for membranes used for large-scale applications

in Germany vary between 60 euro/m2 and 100 euro/m2

(initial investment). But membranes with lower specific

filtration capacities and correspondingly lower prices are

available on the market.

The investments resulting from Figure A-21 and those

for mechanical pretreatment have to be considered

against the savings for plant components which may no

longer be necessary, such as secondary settling tanks,

sand filtration, UV disinfection, possibly primary settling

or separate sludge stabilization facilities as well as the

site-specific cost advantages. Since the tank construction

costs are low at the moment, there are limited possibili-

ties for cost savings concerning the activated sludge

tanks, in particular in the case of systems with filtration

tanks. The additional expenses for special installations,

coatings or additional mechanical equipment are often

comparable with the cost for larger activated sludge tanks.

Due to the worldwide demand for membrane installa-

tions, additional reduction in the specific costs is expect-

ed during the next years. Also, technical simplifications

are expected in the field of mechanical equipment.

spec

ific

co

sts

[o/(

m3 /

h)]

design inflow [m3/h]

300 600 900 1,200 1,500 1,800 2,100 2,400

as of 1999 –200210,000

9,000

8,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

Figure A-22

Orienting net cost guide values for the ready-for-use membrane filtration installation without structural

part [WEDI 2003]

AnnexA

336

A.6.10

Annual costs

A.6.10.1

Loan servicing and membrane replacement

In principle, the cost structure for a waste water treatment

plant changes if a membrane bioreactor process is instal-

led. While with new conventional activated sludge plants

the structural equipment clearly dominates the machinery

in terms of investment cost (in a ratio of 2:1 approxima-

tely), this ratio at least reverses for membrane bioreactors,

due to the elimination of the secondary settling tank and

the smaller activated sludge tank as well as the increased

expense for machinery. This ratio may move further still

if it is not a matter of a new plant building, but of a plant

upgrading for which existing tank volumes are used (see

chapter A.6.7).

The investments for the membrane stage have to be

divided into those parts which are subject to the usual

depreciation periods for machinery, and the membrane

itself which is replaced after the end of its service life.

The membrane replacement costs have to be covered by

the loan service. For definition of a depreciation period,

the service life of the membrane has to be estimated, which

is normally shorter than the depreciation period of the

machinery.

Table A-8 underlines the influence of the membrane replace-

ment on the annual costs of membrane bioreactors. From

this, it is clear that internal measures aiming at extending

the service life of the membranes are of importance.

A.6.10.2

Operating costs

Compared to conventional activated sludge plants, mem-

brane bioreactors have higher operating costs due to the

energy- and chemical demand. An essential cost factor is

the energy demand for cross-flow aeration.

The demand for chemicals of the various membrane sys-

tems may differ significantly. Depending on the necessary

intervals of intermediate and main cleanings as well as

the chemicals to be applied, specific costs of approx.

0.2 euro/(m2 � a) to 1.1 euro/(m2 � a) have been deter-

mined. This wide range indicates that there is still need

for optimization in membrane cleaning.

A.6.11

Final remark

A comparison of cost-effectiveness has to be made exclu-

sively on the basis of the annual costs (sum of loan service

and operation costs). A comparison based only on the in-

vestment is not serious.

Costs [Ct/m3] Field1)

Table A-8

Membrane-specific annual cost shares

Cross-flow aeration 0.20 – 0.75 kWh/m3 2.0 – 7.5 B

Permeate/recirculation 0.08 – 0.10 kWh/m3 0.8 – 1.0 B

Additional demand for aeration 0.08 – 0.10 kWh/m3 0.8 – 1.0 B

Chemicals 0.20 – 1.10 euro/m2 a 0.3 – 1.8 B

Membrane replacement 10 – 5 a 13.3 – 26.6 K

1) B = operating costs; K = loan service

electric current: 10 Ct/kWh; waste water production 90 m3/(PE �a), specific membrane surface area: 1.5 m2/PE,

current chemical costs for H2O2, acids and alkalis, membrane costs: 80 euro/m2

Annex A

337

A.6.12

Advantages and risks of the membrane bioreactor

process

A.6.12.1

General facts

From the comments above it is clear that the membrane

bioreactor process has important advantages compared to

the conventional activated sludge process. However, this

process also has several risks and disadvantages. For the

individual case, an assessment of advantages and dis-

advantages has to be carried out in order to make a con-

scientious decision on the optimum process. Therefore,

the most important arguments are given again in the

following section.

Advantages

The special advantages of the membrane bioreactor process

can be summarized as follows:

• less space required because the higher TS content

allows smaller activated sludge tank volumes and

secondary settling can be eliminated,

• it is easier to enclose the waste water treatment plant,

thus higher acceptance in densely populated areas,

• the process produces hygienically perfect effluent

quality because no filterable solids are found in the

effluent, and therefore the number of germs is signifi-

cantly reduced,

• improvement in the operational reliability by avoidance

of negative effects on the effluent quality by bulking or

floating sludge or sludge carry-over,

• reduction in the residual organic pollution.

Risks and disadvantages

For each case, the risks and disadvantages that may be

relevant for the installation of a membrane bioreactor

must be assessed. In the following section, critical issues

that should be examined, depending on the existing bound-

ary conditions, are summarized:

• increased sensitivity to peak loads as a result of

reduced tank volumes,

• increased total energy demand, in particular for

module aeration,

• membrane modules may silt up or clog in the filtra-

tion zone by fibrous material, too high biomass con-

centration or poor intermixing; for this reason correct

functioning of the module aeration is critical,

• membrane damaging waste water constituents, which

may get into the waste water treatment plant e. g. as a

result of failures, may lead to considerable and irrever-

sible reduction of the filtration capacity,

• increased technical expense and additional demands

on the process control,

• input/production of pollutants by cleaning chemicals

(e. g. AOX by chlorine-containing oxidizing agents),

• building of adequate chemical stock-rooms.

A.6.13

Glossary

The terms which are of special importance for the mem-

brane bioreactor process are briefly defined in the follow-

ing section.

AnnexA

338

Backwashing

Short-term reversal of the flow direction through the mem-

brane in intervals to remove the “particles“ accumulated

during the filtration process (covering layer), usually with

permeate.

Biofouling

Development of a biofilm on the membrane surface or in

the membrane due to the growth of micro-organisms; bio-

fouling causes a reduction of the performance or the per-

meability (see also fouling and scaling).

Concentrate

Partial flow of the material mixture in which the activated

sludge retained by the membrane is concentrated. It is

usually recycled as return sludge into the activated sludge

tank (see Figure A-15).

Covering layer

Accumulation of the components retained by the mem-

brane surface.

Cross flow

The term cross flow comes from the configuration of the

dry-arranged membrane systems operated in a pressure

vessel. During this process, the membranes are overflown

(transverse flow = cross-flow) in order to limit the devel-

opment of a covering layer on the membrane surface. In

membrane bioreactors with submerged membrane filtra-

tion, a transverse flow develops at the membrane surface

by the air injected (usually coarse bubbles), which is also

called cross flow and serves to control the covering layer.

As a result of the two-phase flow, the effective mechanisms

clearly differ from the principle of classical cross-flow

operation of pressure tube systems with inside flow.

Cycle

Temporal sum of filtration phase and following back-

washing phase or shut-down phase (see Figure A-17)

Filtrate

Part of the material mixture which passes the membrane

in micro- and ultrafiltration (see also permeate).

Flow

Volume per time unit

Flux (or permeate flux)

specific filtrate volume flow per unit surface area- and

time unit (per m2 of membrane surface area, per hour),

unit [L/(m2�h)]

with: VF = permeate flux (L/(m2�h)

QF = permeate volume flow (L/h)

AM = membrane surface area (m2)

With stationary conditions, the permeate flux is calculated

from the permeate volume flow (QF) related to the mem-

brane surface area (AM). With variable conditions, only

a mean permeate flux can be given. It is determined by

choosing a sufficient time interval (∆ t) and the accompa-

nying permeate volume (∆VF).

Fouling

In general: deposition of material on the membrane, at

or in the pores. According to the material which causes

fouling, we distinguish organic fouling, inorganic fouling

and biofouling. Fouling always results in a reduction of

the performance or the permeability of the membrane

(see also biofouling and scaling).

Gross permeate flux

Current permeate flux during the filtration phase of a

cycle (see Figure A-17 and net permeate flux).

Membrane

Barrier which causes the retention of particles in mem-

brane bioreactors.

�F =QF

AM

=1

AM

�∆VF

∆ t

L

m2 � h[ ]

Annex A

339

Membrane surface area AM

The membrane surface available for the filtration process:

systems with internal flow: inner surface, for tube-

shaped systems defined by the inner diameter

systems with external flow: external surface, for tube-

shaped systems defined by the external diameter

Module

Plant component ready for connection and operation,

consisting of

• membranes or membrane elements,

• internal piping,

• module aeration,

• fittings and valves, joints,

• other holding devices

Net permeate flux

The specific permeate flux that is actually attainable in

continuous operation and which is achieved in one cycle

of the membrane installation [L/(m2�h]; the following

points have to be considered:

• filtration pauses,

• backwashing times, switching times and

• the permeate volume required for backwshing.

Operating pauses required for cleaning as well as permeate

volumes have to be considered in conceptual planning.

Operating pressure

The operating pressure is necessary to attain filtration.

The operating pressure consists of:

• transmembrane pressure and

• feeder losses.

The operating pressure is usually described as the pressure

difference between the suction side of the pump/control

instrument and the ambient pressure considering the

water level situation (see also transmembrane pressure).

Permeability

Parameter for the description of the hydraulic perfor-

mance of a membrane. Quotient from the gross permeate

flux and the transmembrane pressure; unit:

[L/(m2�h � bar)]. The permeability should be corrected to

a reference temperature in order to allow accurate com-

parison of values.

with: VP = gross permeate flux [L/(m2�h)]

∆pTM

= transmembrane pressure (bar)

Permeate

Part of the material mixture which passes the membrane

in nanofiltration and reverse osmosis (see also filtrate).

Lp =Vp

∆pTM

L

m2 � h � bar[ ]

Net permeate flux =L

m2 � h[ ]Permeate volume during one cycle [L] – backwashing losses [L]

time of the cycle [h] � membrane surface area [m2]

AnnexA

340

Remark: Although the membrane bioreactor process in

municipal waste water treatment is micro- or ultrafiltra-

tion, according to the membrane pore diameteres used,

the term permeate has become established – contrary to

the formal definition – in practice, in literature and in

the specialist discussions. This will not be changed in this

2nd work report.

Pore diameter

As a rule, the pores of pore membranes are not uniform,

i. e. they show a more or less strong pore size distribution.

The pore diameter with a maximum in pore size distribu-

tion is called nominal pore diameter (unit as a rule [µm])

(according to RAUTENBACH, “Membranverfahren“,

Springer-Verlag). The maximum pore diameter can be

determined with the help of the bubble point method

according to DIN 58 355, part 2, which is used to deter-

mine what pressure is required to press the first air bub-

bles through the membrane. The maximum pore diameter

is then calculated by means of a formula.

Scaling

Accumulation of inorganic water constituents at the

membrane after precipitation (see also fouling and bio-

fouling).

Transmembrane pressure ∆pTM

Pressure difference or pressure loss by the membrane

(between outside and inside of the membrane); abbrevia-

tion: TMP (see also operating pressure)

Annex A

341

A.6.14

Literature

ATV-DVWK (2000a): Arbeitsblatt A 131, Bemessung von

einstufigen Belebungsanlagen, GFA, Hennef

ATV-DVWK (2000b): Membranbelebungsverfahren,

1. Arbeitsbericht des ATV-DVWK-Fachausschusses KA-7,

Korrespondenz Abwasser, Nr. 10

ATV-DVWK (2002): Arbeitsbericht der AG IG-5.4 :

Endokrin wirksame Substanzen in Kläranlagen – Vorkom-

men, Verbleib und Wirkung. Deutsche Vereinigung für

Wasserwirtschaft, Abwasser und Abfall e. V., Hennef,

ISBN 3-936514-18-6

ATV-DVWK (2003): Arbeitsblatt A198, Vereinheitlichung

und Herleitung von Bemessungswerten für Abwasseran-

lagen, GFA, Hennef

Bahrs, et al. (1994): Stabilisierungskennwerte für bio-

logische Stabilisierungsverfahren; Arbeitsbericht der

ATV/BDE/VKS-Arbeitsgruppe 3.1.1, Korrespondenz

Abwasser, 41. Jg., Heft 3

Böhnke, B.; Bischofsberger, W.; Seyfried, C. F.

(Herausgeber), (1993): Anaerobtechnik, Handbuch der

anaeroben Behandlung von Abwasser und Schlamm;

Springer-Verlag, Berlin und Heidelberg, 1993,

ISBN 3-540-56410-1

Churchhouse, S; Wildgoose, D. (2000): Membrane Bio-

reactors Hit the Bid Time – From Lab to Fulls Scale Appli-

cations, 3. Aachener Tagung Siedlungswasserwirtschaft

und Verfahrenstechnik, B12, ISBN 3-921955-24-6,

Aachen

Cornel, P.; Wagner, M.; Krause, S. (2001): Sauerstoffein-

trag in Membranbelebungsanlagen; 4. Aachener Tagung

Siedlungswasserwirtschaft und Verfahrenstechnik,

ISBN 3-921955-25-4, Aachen

Dichtl, N.; Kopp, J. (1999)

Entwässerungsverhalten von Klärschlämmen aus Anlagen

mit Membranfiltration, WAP, Nr. 1

Engelhardt, E., Rothe, J. (2001): Sind großtechnische

Membrankläranlagen wirtschaftlich? Erkenntnisse aus

Anlagenbetrieb und Planung, 4. Aachener Tagung Sied-

lungswasserwirtschaft und Verfahrenstechnik, Ü3,

ISBN 3-921955-25-4, Aachen

Erftverband (2001): Weitergehende Optimierung einer

Belebungsanlage mit Membranfiltration; Zwischenbericht

über das Pilotprojekt an das MUNLV

Frechen, F.-B.; Schier, W.; Wett, M. (2001): Membran-

filtration zur Ertüchtigung von Kläranlagen in Hessen;

Begleitbuch zur 4. Aachener Tagung Siedlungswasserwirt-

schaft und Verfahrenstechnik, A3, ISBN 3-921955-25-4,

Aachen

Frechen, F.-B.; Schier, W.; Wett, M. (2003): Ertüchtigung

kommunaler Kläranlagen durch den Einsatz der Mem-

branfiltration; 5. Aachener Tagung Siedlungswasserwirt-

schaft und Verfahrenstechnik, A2, ISBN 3-921955-28-9,

Aachen

Universität Kassel, Fachgebiet Siedlungswasserwirt-

schaft (2004): Membranfiltration in Hessen, Teil 1;

Schriftenreihe des Fachgebietes Siedlungswasserwirtschaft

der Universität Kassel, Band 23 (in Druck)

Gnirß, R.; Lesjean B.; Buisson H.; Adam C.; Kraume M.

(2003): Enhanced biological phosphorus removal with

postdenitrification in membrane bioreactor. Proceedings

of the Membrane Technology Conference of the AWWA

in Atlanta, 3 – 5. March, 2003.

Gnirß, R.; Lesjean B.; Buisson H.; Zühlke S.; Dünnbier U.

(2003): Kosteneffektive Abwasserreinigung mit dem

Membranbelebungsverfahren für dezentrale Standorte.

Proceedings für Wasser Berlin 2003, Veranstaltung KWB

– ”Forschung für die Zukunft“

Gujer, W.; Henze, M.; Takahashi M.; van Loosdrecht, M.

(1999): Activated sludge model No.3., IWA Scientific and

Technical Report No. 1, IWA Task Group on Mathematical

Modelling for Design and Operation of Biological Waste-

water Treatment, Water Science and Technology, Vol.39 (1),

pp 183 – 193.

AnnexA

342

Hegemann W.; Busch K.; Spengler P. und Metzger J. W.

(2002): Einfluss der Verfahrenstechnik auf die Eliminie-

rung ausgewählter Estrogene und Xenoestrogenen in

Kläranlagen – ein BMBF Verbundprojekt; GWF Wasser

Abwasser 143 Nr. 5

Henze, M.; Grady, C.P.L.; Gujer, W.; Marais, G.v.R.;

Matsuo, T. (1987): Activated sludge model No. 1,

IAWPRC Scientific and Technical Report No.1, IAWPRC

Task Group on Mathematical Modelling for Design and

Operation of Biological Wastewater Treatment

Henze, M.; Gujer, W.; Mino, T.; Matsuo, T.; Wentzel, M.C.;

Marais, G. v. R.; van Loosdrecht, M. (1999): Activated

sludge model No. 2d, Water Science and Technology,

Vol. 39 (1), pp 165 – 182

Mörgeli, B. (2001): Die Sensation ist perfekt; 4. Aachener

Tagung Siedlungswasserwirtschaft und Verfahrenstechnik,

A7, ISBN 3-921955-25-4, Aachen

N. N. (1999): Deutsche Einheitsverfahren zur Wasser-,

Abwasser- und Schlammuntersuchung; Herausgeber:

Fachgruppe Wasserchemie der Gesellschaft Deutscher

Chemiker, Normenausschuß Wasserwesen (NAW) Deut-

sches Institut für Normung e. V., 45. Lieferung 1999,

Verlag VCH, Weinheim

ÖWAV (2002): Informationen zum Membranbelebungs-

verfahren, ÖWAV-Arbeitsbehelf Nr. 30

Arbeitsbehelfe des Österreichischen Wasser- und

Abfallwirtschaftsverbands, Wien

Rat der Europäischen Gemeinschaft (1976): EG-Richt-

linie 76/160/EWG über die Qualität der Badegewässer vom

08. Dezember 1975

Rautenbach, R.; Voßenkaul, K.; Melin, T.; Ohle, P.

(2000): Perspektiven der Membrantechnik bei der Abwas-

serbehandlung; Begleitbuch zur 3. Aachener Tagung Sied-

lungswasserwirtschaft und Verfahrenstechnik, A25,

ISBN 3-921955-24-6, Aachen

Rosenwinkel, K.-H.; Wichern, M. (2002): Bemessung

von Sauerstoff- und Überschussschlammanfall für die

Membranbelebung auf Basis des ATV-DVWK-A 131

(2000); Wasserwirtschaft · Abwasser · Abfall 05/2002,

S. 640 – 647

Schier, W. (2003): Ein exemplarischer Ansatz zur Einbin-

dung neuer Bemessungswege und neuer Reinigungstech-

nologien bei der Ertüchtigung von Kläranlagen; Schrif-

tenreihe des Fachgebietes Siedlungswasserwirtschaft der

Universität Kassel, Band 22

Stein, S.; Kerklies, G. (2003): Betriebserfahrungen mit

unterschiedlichen Membrantechniken ZeeWeed® und

VRM®; 5. Aachener Tagung Siedlungswasserwirtschaft

und Verfahrenstechnik, A6, ISBN 3-921955-28-9, Aachen

Wagner, J.; Rosenwinkel, K.-H. (2001): Einfluss gelöster

Stoffe auf den Sauerstoffeintrag in Membranbelebungsan-

lagen, 4. Aachener Tagung Siedlungswasserwirtschaft und

Verfahrenstechnik, A15, ISBN 3-921955-25-4, Aachen

Wedi, D. (2002a): Pilotprojekt Abwasserentsorgung Gai-

lachtal, Technisch-wissenschaftliche Begleitung der Mem-

branfiltration Kläranlage Monheim, 3. Zwischenbericht,

Bay. Landesamt für Wasserwirtschaft, unveröffentlicht

Wedi, D. (2002b): Membrananlagen zur kommunalen

Abwasserreinigung, Verfahren, Auslegungen und Kosten,

13. Magdeburger Abwassertage, 10./11. Oktober 2002,

Verlag Mainz, ISBN 3-89653-978-7

Wedi, D. (2003): Wirtschaftlichkeit des Membranbele-

bungsverfahrens, ATV-DVWK Membrantage, 1./2. Juli

2003 in Bonn

Annex A

343

Location Capacity m3/h Raw water Start-up Manufacturer Membrane process

A.7

Large-scale membrane installations for drinking water treatment in Germany

Neckarburg 70 Karst spring 9’1998 Aqua-source UF

Hermeskeil 140 Spring and Prims dam 2’1999 X-Flow UF

Sundern 250 Sorpe dam 3’2001 X-Flow UF

Marmagen 45 Karst spring 3’2001 Zenon UF

Denkingen 15 Karst spring 6’2001 X-Flow UF

Neustadt, Saale 70 River 7’2001 X-Flow UF

Olpe, Elspetal 80 Creek/spring 8’2001 X-Flow UF

Calw, Hirsau 50 Spring 3’2001 X-Flow UF

Jachenhausen 72 Karst spring 8’2002 Inge UF

Partenstein 35 Karst spring 11’2002 Inge UF

Olef 750 Olef dam 1’2003 X-Flow UF

Regnitzlosau 27 Well 1’2003 Zenon UF

Bad Herrenalb 36 Spring 2’2003 X-Flow UF

Kandern 50 Spring 3’2003 X-Flow UF

Lauterhofen 90 Well 5’2003 X-Flow UF

Miltenberg 80 Well 6’2003 Zenon UF

Waldberg 210 Spring 6’2003 Zenon UF

Burglauer 30 Well 7’2003 Inge UF

Bad Kissingen 120 Well 11’2003 Inge UF

Heinrichsthal 13 Well 11’2003 Inge UF

Sulzbach-Lauf. 36 Spring 12’2003 X-Flow UF

Bad Ditzenbach 22 Spring 12’2003 X-Flow UF

Günterstal 60 Spring 1’2004 PALL UF

Fellen 18 Spring 1’2004 Inge UF

Gaggenau 15 Spring 4’2004 Inge UF

Bad Herrenalb 18 Spring 4’2004 X-Flow UF

Roetgen 6,000 Dam under construction X-Flow UF

AnnexA

344

Key word Explanation

A.8

Glossary

Backwashing Short-term reversal of the flow direction in intervals to remove the particles accumulated during the filtration

process (covering layer), normally with filtrate.

Brine/concentrate Partial flow of the substance mixture which is retained by the membrane.

Capacity Surface-specific permeate flow rate of a membrane under defined operating conditions.

Concentrate Partial flow of the substance mixture which is retained by the membrane, i. e. separated from the feed respectively.

Covering layer Accumulation of the components retained by the membrane at the feed side of the membrane surface area.

Cross-flow filtration/ Operating mode: the feed flows in parallel of the membrane surface area.

dynamic filtration

Dalton [D] Unit for the molecular weight.

Dead-end filtration/ Operating mode: the membrane surface area is supplied orthogonally with the feed.

static filtration

Dynamic filtration See cross-flow filtration.

End-of-pipe measures Measures for the reduction of emissions at the end of a process chain.

Feed Material mixture to be treated in the influent (raw solution in the case of liquid substance mixtures).

Feed-and-bleed structure Variation in the connection of modules:

The concentrate of the upstream module is used as feed of the downstream module.

Filtrate, permeate Part of the substance mixture that passes the membrane.

Filtration controlled Height and thickness of the covering layer can be influenced by the pressure applied and the overflow velocity so

by the covering layer that the filtering characteristics of the covering layer can be used in a calculated way.

Fir-tree structure Variation in module connection: The modules within the blocks connected in series are connected in parallel. The

concentrate volume flow is continuously concentrated from one block to the other, i. e. minimized, the permeate

yield is increased accordingly. The permeate is discharged from each block so that the volume flow to be treated is

reduced from one block to the other.

Flow (surface-specific) or flux Filtrate or permeate volume flow related to the membrane surface area. Throughput through the membrane.

Unit [L/(m2 � h)].

Flushing Short-term operation with clear water without reversal of the permeation direction.

Fouling Development of a covering layer on the membrane by organic components which leads to a reduction of

the filtration capacity.

Intermediate cleaning Chemicals such as citric acid or oxidizing chemicals (e. g. hypochlorite) are added to the backwashing or

flushing water.

Irreversible fouling Fouling which can no longer be removed by backwashing or flushing and chemical cleanings.

Membrane Selective barrier between two phases of different concentration [RAUTENBACH 1997].

Module Connectable, operable plant component consisting of membrane or membrane elements, pressure reservoir and

module-specific apparatus parts [MARQUARDT 1998].

Molecular separation size The separation size of a membrane is indicated by the so-called cut-off molecular weight. This is the specific mass

of a macromolecule which is retained by 95 % by the respective membrane.

Nominal pore diameter Pore size which occurs as maximum in the pore size distribution (of a membrane).

Nutrient removal Degradation or elimination of nitrogen and phosphorus compounds.

Parallel connection Module connection: the feed is distributed to two or more modules.

Permeability Parameter for the description of the permeability of a membrane.

Quotient of the surface-specific flow and the transmembrane pressure. Unit: [L/(m2 � h � bar].

Permeate, filtrate Part of the substance mixture that passes the membrane.

Annex A

345

Key word Explanation

Pore membranes Separation of these membranes is based on a screening effect which can be improved by the development of a

covering layer, microfiltration and ultrafiltration membranes.

Recirculation Recycling of the concentrate or part of it into the feed.

Scaling Layer on the membrane formed by inorganic precipitations (crystallization).

Selectivity Capability of a membrane to differentiate between the components of a substance mixture to be separated.

Semi-cross-flow or Combination of dead-end and cross-flow process, e. g. by dead-end filtration with discontinuous flow in parallel

semi-dead-end process tothe membrane.

Series connection, Module connection: the concentrate of one module serves as feed of the following module. The permeate of the

cascade connection individual modules is combined.

Solution-diffusion membranes Membranes which use the different solubility and diffusivity of the substance components for separation, reverse

osmosis and nanofiltration membranes.

Stage (pressure stage) Unit of a membrane installation functioning in itself, consisting of modules, pumps, valves etc.

Static filtration See dead-end filtration.

Tertiary waste water treatment Originally: treatment steps which go beyond the separation of settleable substances and carbon elimination.

Today this term often summarizes measures which go beyond nutrient removal, zusammengefasst (e. g. sand

filtration, disinfection, material separation and treatment by membrane technology).

Transmembrane Pressure difference or pressure loss across the membrane (from the feed or concentrate side to the

pressure difference permeateside).

Waste-water-free operation Closure of the circuit so that means that no waste water emissions develop. This means in the case of membrane

processes that permeate as well as concentrate can be reused.

Yield, output Ratio of permeate (filtrate) and raw water quantity fed.

AnnexA

346

Abbreviation Sense

A.9

List of abbrevations

VBB volume of the bioreactor

BOD5 biochemical oxygen demand within five days

COD chemical oxygen demand

PE population equivalent

MF microfiltration

NF nanofiltration

Ptot totality of phosphorus compounds (unit: mg/L)

Qd daily waste water inflow at dry weather

Qt maximum waste water inflow as 2 h mean value at dry weather

RO reverse osmosis

TS Trockensubstanz: der TS-Gehalt entspricht der Biomassekonzentration (Einheit: g/L)

UF ultrafiltration

WHG Wasserhaushaltsgesetz

VN volume of the nitrification tank

VDN volume of the denitrification tank

Vvario volume of the variable zone

MW combined water flow

WWTP waste water treatment plant

ISBN 3-939377-01-5

ISBN 978-3-939377-01-6

Documents

Membrane Technology for Waste Water Treatment 4 Preface Membrane technology for the treatment of water and waste water shows impressively how innovative, future-orientated, and economically