characteristics of nutrient removal in vertical membrane ......1 the 2nd mbr workshop at hokkaido...

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The 2nd MBR workshop at Hokkaido University

Characteristics of Nutrient Removalin Vertical Membrane Bioreactors

Prof. Hang-Sik Shin

Dept. of Civil and Environmental EngineeringDept. of Civil and Environmental EngineeringKKorea orea AAdvanced dvanced IInstitute of nstitute of SScience and cience and TTechnologyechnology

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Content

Research Background

Operating factors for vertical MBR

Nutrient removal in vertical MBR

Remediation of fouling in vertical MBR

Conclusions

3

Mechanisms of membrane bioreactors

Water

NH4-N NO3-N

Organic

NO3 T-P

N2 gas Ortho P

Mem-brane

Anoxic reactor

Ortho P

A I R

Oxic reactor

Organic

Water

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Research Objectives and Scope

Novel MBR(Anoxic/Oxic vertical)

Membrane fouling

• Characterization• Dynamic membrane• Remediation

Membrane foulingMembrane fouling

•• CharacterizationCharacterization•• Dynamic membraneDynamic membrane•• RemediationRemediation

Operating factors

• Hydraulic retention time• Internal recycle rate• C/N ratio

Operating factorsOperating factors

•• Hydraulic retention timeHydraulic retention time•• Internal recycle rateInternal recycle rate•• C/N ratioC/N ratio

Modelling

• Kinetic study• Sludge production • EPS accumulation

ModellingModelling

•• Kinetic studyKinetic study•• Sludge production Sludge production •• EPS accumulationEPS accumulation

Nutrient removal

• Various carbon source• EBPR activity• Population dynamics

Nutrient removalNutrient removal

•• Various carbon sourceVarious carbon source•• EBPR activityEBPR activity•• Population dynamicsPopulation dynamics

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Operating factors in vertical MBR

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Objective and Scope

Aerobic tank

Settling tank

Anoxic tank

-Denitrification-Phosphorus release

-Nitrification-Organic oxidation-Phosphorus uptake

-Liquid/solid separation

Distribution devicesDistribution devices

High MLSS conc. High MLSS conc. anoxic zoneanoxic zone

Internal recycleInternal recycle

Aerobic zoneAerobic zone

Aeration Aeration devicesdevices

EffluentEffluent

P

InfluentInfluent

PP

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Test phases

[Q is the influent flow rate]

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Characteristics of the membrane used

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I.R. (3Q 4Q 5Q): T-N= 68 83%, T-P= 51 80%

C/N ratio (4 10): T-N= 55 80%, T-P= 38 76%: Phosphorus removal is more dependent on the content of

organics than nitrogen

HRT (12 6 hrs): at least 8 hrs HRT was needed

Desirable operating conditions; internal recycle rate = 4Q, HRT > 8 hrs

Sludge production = 1 - 6% of the CASP

Summary of Results

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Nutrient removal in vertical MBR

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4242Objective and Scope

GlucoseMBR3

Propionic acidMBR2Sodium acetateMBR1Laboratory

Ax (12L) +Ox (20L)

SubstrateReactorScale

Nutrient removal

EBPR activity

Municipal wastewater

PilotAx (500L) +Ox (833L)

SubstrateScale

[EBPR= Enhanced Biological Phosphorus Removal]

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Materials and Methods

Characteristics of laboratory-scale MBRs

400%Internal

recycle rate

96 L/dayCapacity

2012Volume (L)

+257-147ORP (mV)

2.25.7MLSS (g/L)

53HRT (hr)

30SRT(d)

OxAxItem

[MLSS= mixed liquor suspended solid]

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Characteristics of synthetic wastewater

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Experimental conditions for lab-scale MBRs

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Characteristics of a pilot-scale MBR

2.3m

1m

400%Internal

recycle rate

4 m3/dayCapacity

833500Volume (L)

+274-153ORP (mV)

4.218.68MLSS (g/L)

53HRT (hr)

60SRT(d)

OxAxItem

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Experimental conditions for a pilot-scale MBR

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Characteristics of municipal wastewater

Total COD/Total N = 5.5 insufficient for nutrient removal

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Characteristics of external carbon source

Food waste Fermenter(100 - 120 oC, 12 hr)

Condensate of food waste(CFW)

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Time (min)

0 15 30 45 60

Nitr

ate-

N c

once

ntra

tion

(mg/

l)

0

5

10

15

20

25

30

35

CO

D concentration (m

g/l)

0

50

100

150

200

250

300

Nitrate-N COD

COD source: CFWMLVSS: 4.1 g/l

Nitrogen removal potential of the CFW

20

21

Phosphorus release potential of the CFW

Time (min)

0 15 30 45 60

Orth

o-P

con

cent

ratio

n (m

g/l)

0

10

20

30

40

50

CO

D concentration (m

g/l)

0

50

100

150

200

250

300

NO

3-N

con

cent

ratio

n (m

g/l)

0.0

0.2

0.4

0.6

0.8

1.0

Ortho-PCODNitrate-N

COD source: CFWMLVSS: 4.1 g/l

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Results and Discussion

Time (day)

0 50 100 150 200 250 300 350 400 450

CO

D c

once

ntra

tion

(mg/

l)

0

10

20

30

40

50

T-N concentration (m

g/l)

0

5

10

15

20

T-P concentration (m

g/l)

0

2

4

6

8

10

COD T-N T-P

Phase 1 Phase 2 Phase 3

C/N=10 C/N=5 C/N=5 + 5

Effluent quality of lab-scale MBR fed with sodium acetate

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Stage

In Anoxic Oxic Out

CO

D c

once

ntra

tion

(mg/

l)

0

50

100

150

200

250

300

350

Phase 1Phase 2Phase 3

Stage

In Anoxic Oxic Out

pH

7.0

7.2

7.4

7.6

7.8

8.0

Phase 1Phase 2 Phase 3

Behaviors of pH and pollutants in the reactor

Stage

In Anoxic Oxic Out

NH

3-N

con

cent

ratio

n (m

g/l)

0

5

10

15

20

25

30

35

NO

3 -N concentration (m

g/l)

0.0

2.5

5.0

7.5

10.0

12.5

15.0

Phase 1Phase 2Phase 3

Stage

In Anoxic Oxic Out

Orth

o-P

con

cent

ratio

n (m

g/l)

0

5

10

15

20

Phase 1Phase 2Phase 3

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Removal efficiencies of organics and nutrients

Sodium acetate

Propionic acid

Glucose

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Characteristics of EBPR activity with various substrates

Experimental conditions for assessment of EBPR activity

C/N=10C/N=10

C/N=5C/N=5

C/N=5+C/N=5+55

C/N=5+C/N=5+55

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Results of the assessment of EBPR activity with various substrates

1316171116154

7111579133

2362352

57104681

GlucosePropionic acidAcetateGlucosePropionic

acidAcetate

P uptake (mg P/g VSS)P release (mg P/g VSS)Batch test

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Removal efficiencies of nutrients

HRT

10 hr10 hr8 hr6 hr4 hr

8 hr +CFW 0.43%8 hr +CFW 0.86%

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Behaviors of nitrogen and phosphorus in the pilot-scale reactor

Stage

In Anoxic Oxic Out

Am

mon

ia-N

con

cent

ratio

n (m

g/l)

0

5

10

15

20

25

30

35

Nitrate-N

concentration (mg/l)

0

2

4

6

8

10

12

Phase 1APhase 2Phase 6

Stage

In Anoxic Oxic Out

Orth

o-P

con

cent

ratio

n (m

g/l)

0

1

2

3

4

5

6

Phase 1APhase 2Phase 6

- Phase 1A = 10 hr HRT w/o internal barrier- Phase 2 = 8 hr HRT- Phase 6 = 8 hr HRT + CFW 0.86%

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Removal efficiencies of nutrients at various temperatures

-- HRT=8 hrsHRT=8 hrs

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Photographs of the formation of dynamic membranes

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The role of dynamic membrane in removal of pollutants

Experimental conditionsExperimental conditions

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Schematic diagram of dynamic membranes

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Reuse potential of the effluent in the pilot-scale vertical MBR

34[Source: The STOWA, 2002]

Normal effluent quality(N=10, P=1 mg/L)

Stringent effluent quality(N=2.2, P=0.15 mg/L + disinfection)

100%

Civil

Mechanical

Electrical

Membrane

CASP MBR CASP

For a 2,500 m3/d treatment plant

Comparison of capital costs

135%125%

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Condensate of food waste (CFW) great potential as a carbon source for nutrient removal !

In the lab-scale vertical MBRs (acetate, propionic acid, glucose),- Average removal efficiency of nitrogen was about 80%- Removal efficiencies of phosphorus decreased in order of acetate (87%), propionic acid (83%), and glucose (78%) at C/N = 10

- Addition of the CFW (50% of COD) improved nitrogen and phosphorus removal efficiencies by 2 - 4% and 4 - 11%, respectively.

Assessment of EBPR activity (batch test)- P release/uptake activity; acetate > propionic acid > glucose

several kinds of PHAs were detected inside the cells

Summary of Results

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In the pilot-scale MBR treating municipal wastewater, - Average removal efficiency of total COD, T-N, and T-P

96%, 74%, and 78%, respectively at 8 hr HRT and C/N = 5.5- As the CFW was supplemented (0.86%), T-N and T-P removal

efficiencies increased to 81% and 91%, respectively.- At differing temperature (13 - 25 °C),

Nitrification efficiency = 79 - 81% Phosphorus removal efficiency = 77 - 81%

- Additional removal by the formation of dynamic membranesOrganics (8%), nitrification (5%) and denitrification (4%)

- The effluent quality could satisfy the current drinking water standards except for ammonia-N.

Analysis of population dynamics- As C/N ratio decreased, the number of microbial species decreased- Species of the beta subclass or Proteobacteria are considered toplay an important role in EBPR.

- When the CFW was added, Geothrix fermentans appeared.

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Remediation of membrane foulingin a vertical MBR

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Objective and Scope

Characteristics of membrane fouling

Membraneresistance

Physical factorsPhysical factors

Chemical factorsChemical factors

Biological factorsBiological factors

`̀Ax/Ox vertical MBR Ax/Ox series MBRLab-scale (glucose)

Ax/Ox vertical MBRPilot-scale (sewage)

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Ax/Ox series MBR

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Operating conditions: lab-scale MBRs

- Organic source = glucose- COD : N : P = 160 : 40 : 6

Operating conditions: pilot-scale vertical MBR

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Results and Discussion

Time (day)

0 10 20 30 40 50 60 70 80 90 100

Per

mea

te fl

ux (L

/m2 /h

)

0

2

4

6

8

10

Transmem

brane pressure (kPa)

0

10

20

30

40

50

Permeate fluxTMP

Variations of flux and TMP in the series MBR

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Variations of flux and TMP in the vertical MBR

Time (day)

0 10 20 30 40 50 60 70 80 90 100

Per

mea

te fl

ux (L

/m2 /h

)

0

2

4

6

8

10

Transmem

brane pressure (kPa)

0

10

20

30

40

50

Permeate fluxTMP

43Time (day)

0 10 20 30 40 50 60 70

Perm

eate

flux

(L/m

2 /h)

0

2

4

6

8

10

Transmem

brane pressure (kPa)

0

10

20

30

40

50

Flux at HRT of 8 hrsTMP at HRT of 8 hrs

Variations of flux and TMP in the pilot-scale vertical MBR

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Effect of EPS concentration on fouling at various HRTs

Total EPS concentration (mg/g VSS)

0 25 50 75 100 125 150 175 200

Ra

+ R

p (x

1012

m-1

)

0

10

20

30

40

50R

c (x 1012 m

-1)

0

10

20

30

40

50

Rt (x 10

12 m-1)

0

10

20

30

40

50

Adsorption + Pore blockingCake layerTotal resistance

R2= 0.997Rt = 12.38 -0.2197X + 2162X2

10hrs 4hrsHRTs

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Effect of particle size on fouling at various HRTs

Nominal particle size (µm)

0 20 40 60 80 100 120 140

0

10

20

30

40

50

0

10

20

30

40

50

0

10

20

30

40

50

Adsorption + Pore blockingCake layerTotal resistance

Ra

+ R

p ( x

1012

m-1

) Rc ( x 10 12 m

-1)HRT

Y = -22.88 + 0.55X (R2=0.999)

Rt ( x 10 12 m

-1)

10 hrs 4 hrs

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Schematic diagrams of fouling remediation techniques

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Fouling remediation by outside air supply

Time (day)

0 10 20 30 40 50 60 70

Perm

eate

flux

(L/m

2 /h)

0

5

10

15

20

Transmem

brane pressure (kPa)

0

10

20

30

40

Permeate fluxTMP

Designed permeate flux = 18.6 L/m2/h

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Fouling remediation by inside air supply

Time (day)

0 10 20 30 40 50 60 70

Per

mea

te fl

ux (L

/m2 /h

)

0

10

20

30

Transmem

brane pressure (kPa)

0

10

20

30

Permeate fluxTMP

18.6 LMH 27.9 LMH40 40

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1. Series MBR vs. Vertical MBR (SRT = 30 days)- Vertical-type MBR; relatively low MLSS concentration

(EPS and viscosity) reduce membrane fouling !- Cake layer resistance was about 60-70% of the total resistance

2. Lab-scale vs. Pilot-scale vertical MBR- PPilot-scale showed relatively higher values of EPS and viscosity,

smaller particle size severe fouling !- In pilot-scale MBR (HRT=10 8 6 4 hrs);

EPS content and particle size increasedCake layer resistance appeared to be the controlling factor of the total resistance

3. Fouling remediation- The inside air supply was more efficient than the outside air supply

Summary of Results

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Final Conclusions

High MLSS conc. High MLSS conc. anoxic zoneanoxic zone

Internal recycleInternal recycle EffluentEffluentP

P Stable and desirable effluent quality

Aerobic zoneAerobic zone Low sludge productionLow membrane fouling

Bulking problem ignore!

High nutrient removal efficiencyP

InfluentInfluentDistribution devicesDistribution devices

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52

Enhanced Biological Phosphorus Removal (EBPR)

Anaerobicenvironment

Organics

SCFAs

Glucose SCFAs PHAs

Poly-P

ortho-P

Gly

PAOs

Gly

PHAsPoly-P

ortho-P

Aerobicenvironment

[Source: Smolders et al., 1995]