Energy Efficient MBR Design: Rabigh Refinery, Saudi Arabia · MBR Aeration Power Consumption • Aeration power consumption elevated in MBR due to depressed alpha value associated

Energy Efficient MBR Design:Rabigh Refinery, Saudi ArabiaEnergy Efficient MBR Design:

Rabigh Refinery, Saudi Arabia

Water Arabia

Wednesday, February 2, 2011

Dr. Dirk HeroldKoch Membrane Systems

© 2010, Koch Membrane Systems, Inc. All rights reserved. 2

Power Consumption MBRPower Consumption MBR

• Aeration

• RAS Pumping

• Air Scour

• Permeate

• Other

• Lighting


Relevant Aspects for MBR Energy ConsumptionRelevant Aspects for MBR Energy Consumption

• Matching membrane area with design flowsReduce peak flowsAdequate flux rate to reduce membrane areaMBR membrane train layout

• Efficient return activated sludge (RAS) pumping designPump feed versus gravity feedVariable speed control

• Minimize air scour requirementsModule designMBR membrane train layout

• Maximize aeration tank alpha valueMixed liquor suspended solids (MLSS) selected based on

loading/process


MBR Aeration Power ConsumptionMBR Aeration Power Consumption

• Aeration power consumption elevated in MBR due to depressed alpha value associated with increased MLSS concentration of MBR process.

• α-factor indirectly proportional to power required to supply air for adequate oxygen transfer.

• α-factor: ratio of oxygen mass transfer coefficient (Kla) in wastewater to the same coefficient in clean water.

MLSS

Alpha (α)

Power


Offgas Alpha Testing Fine Bubble Diffusers

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000 50,000MLSS (mg/l)

Alph

a

Site #1Site #2 Site #3Site #4German Research - (Gunder)German Research - (Krampe & Krauth)

Alpha as a Function of MLSSAlpha as a Function of MLSS

German Research – (Cornel & Wagner)

Design range







loading/process


MBR RAS Pumping PowerMBR RAS Pumping Power

• RAS pumping in MBR typically 4x influent flow rate.

• MBR RAS important to balance MLSS between membrane tank and bioreactor.

3 mm PT

DN N

1Q 1Q

5Q

4Q


MBR RAS Gradient MBR RAS Gradient

MLSSm = MLSSb * (R+1)/R

MLSSm : MLSS membrane

MLSSb : MLSS bioreactor

R : Recirculation factor

Selection of bioreactor MLSS impacts:

1.Alpha value2.Recycle rate


Pumped Feed and Gravity ReturnPumped Feed and Gravity Return• Better control over MLSS distribution • Pumping additional Q compared to gravity feed but usually at lower pumping head







loading/process


Influencing Factors on Permeate FluxesInfluencing Factors on Permeate Fluxes

Membrane Module

permeateflux

membranematerial

membranefouling

biologydesign

moduledesign

module operation

membraneage

moduleclogging

membranecleaning


Optimizing Membrane AreaOptimizing Membrane Area

AVERAGE Q

PEAK Q

20%80%

Buffer peak flows

Multiple train design


Optimizing Membrane EnergyOptimizing Membrane Energy

• How do we fine tune membrane operation to conserve energy?

Number of trains in operationFlux

TRAINS

1 4

2 3

FLUX

offopt

max

Max Day

Avg Day

QMin Flow

Max Day

Avg Day

No. of Trains

N trains

Min Flow N-X


Flux & Membrane Train OperationFlux & Membrane Train Operation

0

50

80 96Bioreactor Level [%]

MS1

Foff

Fopt

Flow[m³/h]

MS 5

Fmax

88 92

MS 3 MS 2L H 1 H 2100

Tank Level


MBR Train DesignMBR Train Design

• Multiple train design allowsEnergy friendlyRedundancyCyclical air supplyStand-by of membranes under low flow conditions







loading/process


Membrane Air ScouringMembrane Air Scouring

• Major power consumer with regard to membrane operation

• Critical to membrane operation/permeability

• Efficient design allows intermittent air supply and variable air delivery rate without compromising membrane permeability

• Air scour systems vary with manufacturers


How to Optimize the Membrane Aeration?How to Optimize the Membrane Aeration?

• Membrane module design• Plant design

Design aspects:Design aspects:

Both aspects have to be optimized


PURON® Air Scour ConceptPURON® Air Scour Concept

Membrane Bundle


Specific Instantaneous Air FlowSpecific Instantaneous Air Flow

2004 2008

Spe

cific

Inst

anta

neou

s Ai

r Flo

w[N

m3 /

hm2 ]

0.70.8

0.53


General Operation ModesMembrane Module AerationGeneral Operation ModesMembrane Module Aeration

2 Trains: 50 % Aeration3 Trains: 33 % Aeration4 Trains: 25 % Aeration

at average flow treatment


4 Train SystemAlternating Membrane Aeration4 Train SystemAlternating Membrane Aeration

• At average hydraulic capacity, only 1 blower is operated

• Air is switched alternating between the four filtration lines

• Only at peak hydraulic capacity, 2 blowers are operated parallel

• Air is switched alternating between 2 x 2 filtration lines

• Air supply is realized depending on hydraulic capacity

Membranes1

Membranes2

Membranes3

Membranes4

Duty

Assist

Standby

25 % Aeration management during average flow conditions for a 4 train membrane filtration systems


Advantages of Intermittent Air Scour Advantages of Intermittent Air Scour

Specific aeration rate 0.53 Nm³/m²h

Specific aeration rate (@ 50 % aeration) 0.27 Nm³/m²h

Specific aeration rate (@ 25 % aeration) 0.14 Nm³/m²h

Aeration pressure for operation 300 mbar

Overall energy consumption 0.15 – 0.09 kWh/m³

Highly energy efficientIntermittent aeration management


Example Project (4 trains): Total Energy Consumption of Membrane Filtration Example Project (4 trains): Total Energy Consumption of Membrane Filtration

• Sludge circulation => 0,025 kWh/m³

Energy consumed by:Energy consumed by:

Total Membrane filtration:≤ 0,20 kWh/m³ treated effluent

• Membrane aeration => 0,128 kWh/m³

• Permeate & Backwash pumps => 0,046 kWh/m³

© 2010, Koch Membrane Systems, Inc. All rights reserved.

Rabigh Design BasisRabigh Design Basis

MBR plant realized by:Parkson ME in cooperation with Al-Busaili

MBR plant realized by:Parkson ME in cooperation with Al-Busaili


Rabigh LayoutRabigh Layout

Pre-treatment

Equalization

Denitrification

Nitrification

Membrane tanks

Design MLSS Nitrification: 8.5 g/L

Multiple train layout

Equalization (~ 7 h buffer

capacity)Energy efficiency


Rabigh LayoutRabigh Layout

Start of commissioning: December 2010

Adaptation of biologyIncrease of influent flows


SummarySummary

• Minimize membrane area to optimize power consumption• Effective management of solids• Flexible membrane operation• Effective air scour device• Multiple trains allow intermittent air scour• Bioreactor operation


Questions & CommentsQuestions & Comments

Thank youfor your attention!

Documents

Energy Efficient MBR Design: Rabigh Refinery, Saudi Arabia · MBR Aeration Power Consumption • Aeration power consumption elevated in MBR due to depressed alpha value associated