ADVANCEMENTS IN PHYSICAL/CHEMICAL TREATMENT

NTNU - Norwegian University of Science and TechnologyDep. Hydraulic and Environmental Engineering

Prof. Hallvard Ødegaard

NTNU/XUAT Postgraduate course 21.05.02-31.05.02: Wastewater as a resource

ADVANCEMENTS IN PHYSICAL/CHEMICAL TREATMENT

Hallvard Ødegaard



CHALLENGES IN THE USE OFCOAGULATION OF WASTEWATER

• MINIMISATION OF SLUDGE PRODUCTION

• MINIMISATION OF SPACE REQUIREMENT• Flocculation• Floc separation

• REMOVAL OF SOLUBLE (ORGANIC) MATTER

• PRODUCTION OF CARBON SOURCE IF NITROGENREMOVAL IS TO BE ACHIEVED



DOWNSIDE OF TRADITIONAL PRIMARY PRECIPITATION

LARGE SLUDGE PRODUCTION

SP = SSin - SSout + Kprec * D

SP = sludge production (g SS/m3)Kprec = sludge production coeff. (g SS/g Me)(Fe~4, Al~6)D = dose ofmetal coagulant (g Me/m3)



EVALUATION OF SLUDGE PRODUCTION

SP = SSin - SSout + Kprec.* D

SP SSprod Kprec.= = 1 + * D

SSin-SSout SSrem SSrem

When D 0

SSprod.1

SSrem



COMPARISON AT DIFFERENT DOSAGE SCENARIOSa. FeCl3 (high dose) only b. FeCl3 (high dose) only

c. Cationic polymer only d. FeCl3 (low dose) + cationic polymer

0,0

0,5

1,0

1,5

2,0

2,5

0 1 2 3

5,5 mg Fe + mg DC 242/244/l

SSpr

od/S

Srem

0

20

40

60

80

100

SS-r

emov

al (%

)

SSp/ SSr

R

0,0

0,5

1,0

1,5

2,0

2,5

0 20 40 60

mg Fe/l

SSpr

od/S

Srem

0

20

40

60

80

100

SS-r

emov

al (%

)

SSp/ SSr

R

0,0

0,5

1,0

1,5

2,0

2,5

0 2 4 6

mg DC 242/244/l

SSpr

od/S

Srem

0

20

40

60

80

100

SS-r

emov

al (%

)

SSp/ SSr

R

0

50

100

150

200

250

300

0 20 40 60

mg Fe/l

SP-S

Srem

(mg

SS/l)



FLOCCULATION - KEY FACTOR

a) Orthokinetic flocculation* Turbulent velocity gradient (G) G = (W/µ)1/2

* Residence time (T) T = V/Q* Residence time distribution (m) m~number of

reactors in series* Floc volume fraction Φ = f(Me,dose)

b) Chemical flocculation (polymeric flocculants) by anionic polymer addition

* Polymer charge (anionic, cationic, non-ionic) * Polymer type (polyacrylamide, polyDadmac, polyamin)* Polymer dose * Polymer characteristic (MW, Charge density)



ORTHOKINETIC FLOCCULATIONRelationship between flocculation performance and flocculation variables



CHEMICAL FLOCCULATION

INFLUENCE OF ANIONIC POLYMER ADDITION ON CHEMICAL FLOC SETTLING RATE

1. Anionic polymer addition leads to larger flocs dueto the bridging mechanism

2. Low dosage needed (0,1 - 1,0 mg/l)

3. Polymer flocculant addition leads to higher acceptableturbulent velocity gradient and consequently to lower acceptable residence time



Organic flocculants and coagulants

Charge density cationic

PEI/Fennofix 30

MW

5-5anionic

10 000 000

1 000 000

100 000

10 000

1000

P-epiamine/

FennoFix 50/57P-DADMAC /

Fennofix 40

PAM/Fennopol

PEO/FRA

Mannich/FennoFloc

Flocculants

Org. Coagulants

Fennopol K 990

FennoFix 2X0



FLOC SETTLING RATE (vs) VERSUS CHEMICAL DOSAGES(Ce - turbidity of settled effluent)



THE IMPORTANCE OF ORTHOKINETIC FLOCCULATION EVEN IN PRIMARY TREATMENT

a: No chemicals

Slow mixing time (min)0 5 10 15 20 25 30

Sus

pend

ed s

olid

s (m

g/l)

020406080

100120140160180200220240260280300

No pipe flocc., 15 min. settlingPipe flocc., 15 min settlingPipe flocc., 30 min settling

No flocculation (15 min. settling)



COMPARISON AT DIFFERENT DOSAGE SCENARIOSb: Cationic polymer addition


Sus

pend

ed s

olid

s (m

g/l)

020406080

100120140160180200220240260280300

a: No chemicals


Sus

pend

ed s

olid

s (m

g/l)

020406080

100120140160180200220240260280300

No pipe flocc., 15 min. settlingPipe flocc., 15 min settlingPipe flocc., 30 min settling



c: Low dose FeCl3 + cat. polym


Sus

pend

ed s

olid

s (m

g/l)

020406080

100120140160180200


d: High dose FeCl3 addition


Sus

pend

ed s

olid

s (m

g/l)

020406080

100120140160180200


4 mg/l Sepco DC 242

0.1mmol Fe/l + 4 mg/l Sepco DC 242 0.7 mmol Fe/l



THE BIOPOLYMER CHITOSAN AS REPLACEMENTFOR METAL CATION IN PRIMARY COAGULATION

40

50

60

70

80

90

100

0 2 4 6

mg Chitosan/l

SS-r

emov

al (%

)

7,8 mg Al/l

13,2 mg Al/l

200220240260280300320340360380

0 2 4 6mg Chitosan/l

Slud

ge p

rodu

ctio

n (m

g/l) 7,8 mg Al/l

13,2 mg Al/l



DEEP SETTLING TANK WITH INTERNAL FLOCCULATION



DEEP SETTLING TANK WITH PIPW FLOCCULATION ANDCOARSE FILTRATION/LAMELLA SEPARATION







ACTIFLOMICROSAND SEPARATION



LAMELLA SETTLING



FLOTATION



LAMELLA FLOTATION



THE DYNASAND FILTER



ZENON ULTRAFILTRATION



DEVELOPMENT OF FLOTATION



ADVANTAGES AND DISADVANTAGES OF FLOTATION IN COMPARISON WITH

SEDIMENTATION

ADVANTAGES

• Less space required, vf = 5-15 m/h against 1-2 m/h

• Better separation efficiency

• Higher sludge concentration

DISADVANTAGES

• Higher costs ?

• Less known technology

• More skilled operatorsneeded ?



FLOCCULATION/FLOTATION EXPERIMENTSØdegaard(1995) Wat.Sci.Tech. Vol. 31, No 3.-4. Pp 73-82



FLOCCULATION /FLOTATION EFFICIENCY VSG-VALUE AT VARIOUS RESIDENCE TIMES (T)



REMOVAL (%) VERSUS G AT VARIOUS TPP – particulate phosphate N - turbidity



FLOCCULATION/FLOTATION EFFICIENCYVERSUS T AT VARIOUS G



FLOCCULATION AHEAD OF FLOTATIONØdegaard, Wat.Sci.Tech. Vol 31, No3-4, 1995

1. The theor.mean residence time at design flow should be 25 - 30 min.

2. The flocculator should be designed to give a residence timedistribution as plug flow like as possible. If stirred tanks are used, the flocculator should be divided into at least two chambers

3. The G-value should be the same in each of the flocculator chambers and in the order of 60 - 80 sec-1.

4. The flotation unit should be designed for a hydraulic surface load of 5 - 6 m3/m2⋅h at design flow allowing for variations up to 10 m3/m2⋅h at maximum design flow. If the variation in the flow is small, a load of 8 m3/m2⋅h could be recommended at design flow.

5. The amount of pressurized water should be 10-20 % of design flow when the pressure is 0.5 MPa.



THE MUSLINGEN FLOTATION PLANT





Plant Overflow

rate (m/h) Tot P

In (mg/l) Tot P

Out (mg/l) Tot P

% A 1.9 (4,0) 5,9 (9,3) 0.12 (0,42) 98.0 B 4.2 (8.7) 4,6 (7,3) 0.21 (0.59) 95.4 C 1.9 (6.9) 4.4 (7.6) 0.10 (0.34) 97.7 D 4.6 (7.3) 4.6 (7.3) 0.38 (1.63) 91.7 E 4.4 (6.6) 1.9 (2,7) 0.06 (0.07) 96.8

Plant Overflow rate (m/h)

COD (TOC) In (mg/l)

COD (TOC) Out (mg/l)

COD (TOC) %

A 1.9 (4,0) 337 (710) 62 (120) 81.6 B 4.2 (8.7) 109 (190) 8.9 (15.3) 91.8 C 1.9 (6.9) 343 (643) 97 (151) 71.7 D 4.6 (7.3) 93 (180) 28 (58) 69.9 E 4.4 (6.6) 119 (167) 30 (30) 74.8

TREATMENT RESULTS MUSLINGEN



Dutch experiments (Mels et al, 2000)

Chain scraper

Sludgecollectiontrough

Air saturated water

Return flow

Saturator

cationicpolyelectrolyte

InletInfluent

Effluent

Stat ic mixer

Flocculat ionCoagu-lation

Pilot system



DAF Pilot results: COD removal

050

100150200250300350400

0.0 2.0 4.0 6.0 8.0 10.0mg PE/g CODinfluent

CODparticulate

CODdissolved



y = 2.6 x - 11.5R2 = 0.88

0

50

100

150

200

250

300350

400

0 50 100 150 200

EffluentTurbidity (NTU)Influent

0

20

40

60

80

100

0.0 5.0 10.0 15.0 20.0

mg pe/100 NTU

8 Mg/mol 4 Mg/mol

0

20

40

60

80

100

Setpoint

Discussion: Determining flocculation/flotation efficiency with turbidity measurements

Evaluation of two PE’s by plotting particulate COD as a

function of PE-NTUinfluent-ratio

Linear relation turbidityand particulate COD



PROPOSED SECONDARY TREATMENT PROCESS

• Particulate organic matter is coagulated and separated as in a conventionalchemical plant

• Easily biodegradable matter is removed in a highly loaded biofilm reactor at such a high load that only easily biodegradable organic matter is degraded (no hydrolysis)

• Good biomass separation of incoming particles as well as produced biomass

Flocseparation

Coagulant



THE PRINCIPLE OF THE MOVING BED REACTOR

Anaerobic/anoxic reactorAerobic reactor



THE KALDNES MOVING BED BIOFILM PROCESS

Carrier under waterAerated tank for nitrification



CHARACTERISTICS OF THE BIOFILM CARRIERS

Biofilm carrier :Material : Polyethylene (density 0,95 g/cm3)Size : K1 - Diam./Length = 10mm/7mm

K2 - Diam./Length = 15mm/15mm

K1

K2Surface area K1 K2

Per carrier (mm2) Total Effective for biofilm growth

670490

23001530

Specific area (m2/m3) Total at 70 % carrier filling Effective for biofilm growth

490350

330220



SOLUBLE COD REMOVAL RATE VERSUS SOLUBLE COD LOADING RATE

0

5

10

15

20

25

30

35

40

0 20 40 60 80 100

Filtered COD loading rate [g SCOD/m2*d]

Filte

rd C

OD

rem

oval

rate

[g S

CO

D/m

2 *d]

100%

Period 1 and 2 Period 3

0

5

10

15

20

0 20 40 60 80Filtered COD loading rate [g SCOD/m2*d]

Filte

red

CO

D re

mov

al ra

te[g

SC

OD

/m2 *d

]

HRT=380 min

HRT=52 min

HRT=27 min

HRT=18 min



“OBTAINABLE” COD REMOVAL RATE VERSUSTOTAL COD LOADING RATE

”Obtainable" COD removal rate : (CODinfluent-SCODeffluent)*Q/A

0

25

50

75

100

125

150

0 50 100 150 200

Total COD loading rate [g COD/m2*d]

Obt

aina

ble

rem

oval

rate

[g C

OD

/m2 *d

]

100%

Period 1 and 2 Period 3

0

25

50

75

100

125

150

0 50 100 150 200

Total COD loading rate [g COD/m2*d]

Obt

aina

ble

rem

oval

rate

[g C

OD

/m2 *d

]

HRT=380 minHRT=52 minHRT=27 minHRT=18 min

100%



RESULTS SETTLING EXPERIMENTS

0 %

20 %

40 %

60 %

80 %

100 %

0 10 20 30Bioreactor loading [g COD/m2*d]

SS

-rem

oval

in s

ettli

ng ta

nk

v=0.05 m/hv=0.16 m/hv=0.16 m/h w/polymerv=0.35 m/h

Influence of polymer addition on settleability

Medium charge, high MW cationic polymer

0 %

20 %

40 %

60 %

80 %

100 %

0 20 40 60Bioreactor loading [g COD/m2*d]

SS

-rem

oval

in s

ettli

ng ta

nk

v=0.05 m/hv=0.35 m/hv=0.65 m/h

Influence of organic loading rate in bioreactor on settleability



RETROFITTING EXISTING PRIMARY PRECIPITATION PLANTSBY THE HIGH RATE MOVING BED PROCESS

T = 20-40 min

Fe

Fe (evt +cat. pol.)

Alt. dosong point (or anionic polymer)

T=10-20 T=10-20

Air



THE HIGH RATE PROCESS IN A NEW PLANT(total residence time < 1 time)

Coagulant

Pre treatmentfine sieve

MBBRHRT: ~30 min

FlocculationHRT: 10 - 15 min

FlotationHRT: 15 - 30 min



TURBULENTFLOTATION



QUESTIONS TO BE ANSWERED

ON COAGULATION/FLOCCULATION• Where to dose the coagulant?• What coagulant?• How much coagulant?

ON THE BIOREACTOR• What happens to the soluble COD?• What happens to the particulate COD?• How to design the MBBR

ON THE FLOTATION REACTOR• Performance of turbulent flotation• Design of turbulent flotation



COD DEGRADATION/TRANSFORMATIONTotal COD in wastewater - 100%

1 µm

SCOD PCOD

“True solution” “Particulate fraction” (colloids & SS)

Degradable in MBBR

Coagulation Flocculation

ChemicalsMBBRWe want:

ChemicalsMBBR

We don’t want:

0.1 µm

Total COD in wastewater - 100%

1 µm

SCOD PCOD

“True solution” “Particulate fraction” (colloids & SS)

Degradable in MBBR

Coagulation Flocculation

ChemicalsMBBRWe want:

ChemicalsMBBR

We don’t want:

0.1 µm



POLYMERS INVESTIGATED

02468

10121416

0 1 2 3 4 5 6 7

Charge density, (meq/g)

MW

, (10

^6 g

/mol

)

Design region, D4&D5 Design region, D8 C587 C591

C595 Ffix 40 Ffix 210 Ffix 220

Ffix 230 Ffix 240 K194 K211

K504 K506 K508 K594

K1333 K1351 K1370 K1384

K1390 K1488 K1912 K3297

K3450 K4650 K5060



-30.0-20.0-10.0

0.010.020.030.040.050.060.070.080.0

<0.1

micron

0.1-1

micron

1-11 m

icron

11-41

micr

on41

-160 m

icron

totCOD

COD-fraction

COD i

n - C

OD o

ut, (

mg

COD/

l)

MBBR 1MBBR 3

Net change in COD fractions through the MBBRPositive value: net removal, negative value: net production



EFFECT OF POLYMER AND IRON DOSAGE ON SS REMOVAL

PolyacrylamidePolyamine

0

20

40

60

80

100

0 1 2 3 4

Polymer dosage (mg/l)

SS re

mov

al (%

)

a

0

20

40

60

80

100

0 1 2 3 4

Polymer dosage (mg/l)SS

rem

oval

(%)

b



DETERMINATION OF OPTIMAL Fe/Polymer-DOSE

PAM01_pls1_MIS_…, PC: 2, Y-var: SSe, (X-var = value): CD = 2.1939, MW = 4.6231, SCODi = 67.6315, pHi = 7.7063

Response Surface

3.0

2.5

2.0

1.5

1.0

0.5 00.05

0.100.15

0.20P

ol

M e

33.774 38.611 43.448 48.285 53.122 57.959



0

20

40

60

80

100

0 1 2 3 4


CO

D re

mov

al (%

)a

0

20

40

60

80

100

0 1 2 3 4


CO

D re

mov

al (%

)

b

Polyamine Polyacrylamide

0

20

40

60

80

100

0 1 2 3 4


SCO

D re

mov

al (%

)

a

0

20

40

60

80

100

0 1 2 3 4


SCO

D re

mov

al (%

)b

EFFECT OF POLYMER

AND IRON

DOSAGE ON COD

REMOVAL



EFFECT OF POLYMER PROPERTIES

0

20

40

60

80

100

0 5 10 15

Molecular weight (106 g/mol)

SS re

mov

al (%

)

b

0

20

40

60

80

100

0 5 10 15

Molecular weight (106 g/mol)

SS re

mov

al (%

)

a

0

20

40

60

80

100

0 2 4 6 8Charge density of the polymer (meq/g)

SS re

mov

al (%

)b

0

20

40

60

80

100

0 2 4 6 8Charge density of the polymer (meq/g)

SS re

mov

al (%

)

a

Results Model predictions

Molecular weigth

Charge density



PARTICULATE COD FRACTIONS IN RAW WATER AND FLOTATED WATER WITH DIFFERENT

POLYDADMAC DOSAGES AND 0.2 MMOL FE/L IRON.

0.0

20.0

40.0

60.0

80.0

100.0

120.0

>11 µm 1-11 µm 0.1-1 µm <0.1 µm

CO

D (m

g/l)

Raw waterP = 0.58 mg/lP = 1 mg/lP = 2 mg/lP = 3 mg/lP = 3.4 mg/l



FLOTATION FOR FINAL SEPARATION



VOSS WASTEWATER TREATMENT PLANT



0

100

200

300

400

500

600

0 20 40 60

Week no, 1999

mg

CO

D/l

Inlet

Outlet

70

75

80

85

90

95

100

0 20 40 60

Week no. 1999

% r

emov

al

COD

TotP

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

0 20 40 60

Week no. 1999

mg

Tot P

/l

InletOutlet

DATA VOSS TREATMENT PLANT

Overflow rate: 3 – 9 m/h

Effluent COD concentration : 19.6 + 8.7 mg/l

COD-removal efficiency : 91.4 + 5.2

Effluent Tot P concentration: 0.07 + 0.04 mg/l

Tot P removal efficiency : 97.1 + 1.6

Secci-depth in effluent : 2.0 – 3.75 m



GARDERMOEN WWTP



OPERATIONAL EXPERIENCES NORDRE FOLLO

Inlet and outlet tot P conc.

0

1

2

3

4

5

6

7

8

1 12 23 34 45 56 67 78 89 100

111

122

Number of routine samples taken weekly

mg

P/l

Outlet

Inlet

0

10

20

30

40

50

60

0 10 20 30

Dispersion ratio (Qr/Q)

Susp

ende

d so

lids

out,

mg/

l

Effluent SS versus Qr/Q



SUMMARY• A very good particle removal and hence organic matter

removal can be obtained by the use of pre-coagulation

• If advanced phosphate removal is not the objective,sludge production can be minimised by replacing part of the metal cation for coagulant by a organic polymer cation

• The addition of an anionic organic polymer as flocculantcan improve the settleability of flocs dramatically with corresponding reduction in plant space requirement

• The combination of a high-rate moving bed process andcoagulation/flotation can result in an extremely compact and efficient secondary treatment process

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ADVANCEMENTS IN PHYSICAL/CHEMICAL TREATMENT