Membrane Fouling Studies in Suspended and Attached …faculty.ait.ac.th/visu/public/uploads/Data/AIT-Thesis/Doctoral... · Membrane Fouling Studies in Suspended and Attached Growth

Asian Institute of TechnologySchool of Environment, Resources & Development

Environmental Engineering & Management

Membrane Fouling Studies in Suspended and Attached Growth Membrane Bioreactor Systems

Examination Committee:

Prof. C. Visvanathan (Chairman)

Prof. Sudip K Rakshit

Prof. Ajit P. Annachhatre

Dr. Oleg V. Shipin

Prof. Jy S. Wu

Kwannate (Manoonpong) Sombatsompop

K. Sombatsompop-May 2007 1/361/36

K. Sombatsompop-May 2007

Sludge storage

Clarifier

Aeration tankSludge return

Treated water

Excess sludge

Influent

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Membrane Membrane BioreactorBioreactor SystemSystem

Limitation of MBR : Limitation of MBR : FoulingFouling

•A reduction of the membrane performance•A decrease of flux•An increase in filtration resistance•Membrane cleaning requirement

High effluent qualitySmall sizeFlexible in the operationLow sludge productionRemoval of infectious pathogens

immerged MBR Membrane module

PermeateAir

WastewaterWastewater

Biological Biological reactorreactor

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Advantages and disadvantages of Advantages and disadvantages of membrane bioreactormembrane bioreactor

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Advantage for attached growth bioreactor

Better oxygen transfer

High organic removal ability

Relatively short HRT

Being more compact

(Tavares et al, 1994; Ødegaard et al,1994;Ødegaard 2000 )

Effluent

Screen

Air

Carrier

Influent

Attached growth reactor

Biomass growth on small carrier materials that move along with the water in the reactor


Attached growth bioreactorAttached growth bioreactor

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Objectives of the studyObjectives of the study

To examine suitable test conditions and to select suitable media for attached growth reactor

To investigate effects of operating conditions, such as HRT and MLSS on membrane performance, fouling characteristics, EPS production and sludge properties

To compare membrane fouling behavior of attached and suspended growth MBRs

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Scope of the studyScope of the study

• Synthetic wastewater with a constant COD value of 500 mg/L

• Five different types of media polyethylene bead (PB), polyethylene granule (PG), polyethylene sheet (PS), cylindrical polypropylene (CP) and polyethylene sponge (S)

• Effect of operating conditions;1. HRT was varied at 2, 4, 6 and 8 h.2. MLSS was altered at 6, 10 and 15 g/L.

• Sludge characteristics, EPS production, fouling rate, cake resistance and microscope observation

• Removal efficiency of COD, and nitrogen compounds

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Preliminary studyPreliminary study

To examine suitable test conditions and to select suitable media for attached growth reactor

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Research methodologyResearch methodology

Batch reactorBatch reactor EPS Extraction analysisEPS Extraction analysis

Preliminary StudyPreliminary Study

Variation ofmedia

Variation ofmedia

Removal efficiencyRemoval efficiencyEPS productionEPS production

Variation of re-suspended solution

Variation of re-suspended solution

Variation of centrifugation speed

Variation of centrifugation speed

Variation of centrifugation time

Variation of centrifugation time

Attached growth reactorAttached growth reactorSuspended growth reactorSuspended growth reactor

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Media typesMedia types

Cylindrical Cylindrical polypropylene (CP)polypropylene (CP)

Sponge(S)Sponge(S)PolyethylenePolyethylenebeads (PB)beads (PB)

PolyethylenePolyethylenesheet (PS)sheet (PS)

PolyethylenePolyethylenegranule (PG)granule (PG)

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Experimental setExperimental set--upup and operationand operation

Timer

Air

Air diffuser

Motor

PB PG CP SPSControl (no media)

Suspended growth reactor

Attached growth reactors

Conditions: Conditions: pH 7pH 7--8 8 DO 2DO 2--4 mg/L4 mg/LCOD 500 mg/L COD 500 mg/L HRT 6 h. HRT 6 h. SRT 10 d.SRT 10 d. MLSS 4000 mg/LMLSS 4000 mg/LF/M 0.1 F/M 0.1 kgCOD/kgMLSS.dkgCOD/kgMLSS.d

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Question and RecommendationQuestion and Recommendation


Table 4.1 Removal efficiency of COD and TKN in batch reactors

S

CP

PS

PG

PB

Control (no media)

Batch reactor

8359425EffluentAttached growth





7969523EffluentSuspended growth

-30-460Influent-

% removalmg/L% removalmg/L

TKNCODSampling

point

System

A. A. Selection of Media Type for Attached Growth ReactorSelection of Media Type for Attached Growth Reactor

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Figure 4.2 EPS compositions in different media types

0

5

10

15

20

25

Control PB PG PS CP S

Media types

EPS

com

posi

tions

(mg/

gVSS

)

Protein Carbohydrate Ratio of Protein/Carbohydrate

A. A. Selection of Media Type for Attached Growth ReactorSelection of Media Type for Attached Growth Reactor

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1

10

100

1000

10000

PS PG PB CP S

Media types

EPS

(mg/

m2 o

f med

ia su

rfac

e)

A. A. Selection of Media Type for an Attached Growth ReactorSelection of Media Type for an Attached Growth Reactor

Figure 4.4 EPS content in terms of media surface at different media types

Cylindrical polypropylene was selected due to; floating, well mixing, high surface media and non biodegradable nature.

(CP)

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Conclusions for Preliminary studyConclusions for Preliminary study

• No significant difference in COD removal efficiency was found between the suspended and the attached growth systems.

• The average TKN removal efficiency in the attached growth system was in the range of 83 to 90%.

• There was no significant difference in EPS production in the suspended and the attached growth systems.

• The productions of EPS and biofilm formation were affected by shape and size characteristics of media used. Cylindrical polypropylene (CP) was most suitable.

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LaboratoryLaboratory--scale MBR studyscale MBR study

To investigate effects of operating conditions, such as HRT and MLSS on membrane performance, fouling characteristics, EPS production and sludge properties

To compare membrane fouling behavior of attached and suspended growth MBRs

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LaboratoryLaboratory--scale MBR studyscale MBR study

Operational conditions

Operational systems

Operational analysis

Suspended growth MBRSuspended growth MBR Attached growth MBRAttached growth MBR

Laboratory-scale MBR study Laboratory-scale MBR study

Removal efficiencyRemoval efficiency

Fixed mediaFixed mediaMoving mediaMoving media

Variation of MLSSVariation of MLSS Variation of HRTVariation of HRT

Fouling characteristics

Fouling characteristics

Sludge characteristics

Sludge characteristics

Microscopeobservation

Microscopeobservation

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Experimental setExperimental set--upup of MBRof MBR

Storagetank

Timer

Air line

SG-MBR

Air flow meter

Control tank

Pressure gauge 3

1

2

Levelcontrol

Air diffuser

AG-MBRMoving media

AG-MBRFixed media Manometer

Effluent

Pump

Solenoid valve

Baffle

Hollow fiber membrane

Note: SG: Suspended growthAG: Attached growth

Mitsubishi RayonPore size - 0.1 µm

Surface area- 0.42 m2

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Table 4.6 COD removal in the MBRs with varying HRT

25 (94)

23 (96)

15 (97)

19(96)

Effluent of attached growth MBR with fixed media

10 (98)

16 (97)

10(98)

13 (97)

Effluent of attached growth MBR with moving media

15(97)

19(96)

12(98)

16(97)

Effluent of suspended growth MBR

435522507504Influent

HRT 2 hHRT 4 hHRT 6 hHRT 8 h

COD (mg/L)(%Removal efficiency)

Item

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Results and DiscussionsResults and Discussions

Effect of Hydraulic Retention Time (HRT) Effect of Hydraulic Retention Time (HRT)



Effect of HRT Effect of HRT

Table 4.7 TKN removal in the MBRs with varying HRT

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3.4(92)

2.1 (95)

1.9 (97)

3.3 (94)

Effluent of attached growth MBR with fixed media

2.5(94)

1.7 (96)

1.3 (98)

2.9 (95)

Effluent of attached growth MBR with moving media

2.8 (94)

1.7(96)

1.3 (98)

2.8 (95)Effluent of suspended growth MBR

44.845.456.857.5Influent

HRT 2 h

HRT 4 h

HRT 6 h

HRT 8 h

TKN (mg/L)(%Removal efficiency)

Item



B. EPS Compositions


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0

30

60

90

120

150

8 6 4 2HRT (hours)

Bou

nd E

PS (m

g/gV

SS)

Suspended growth MBRAttached growth MBR with moving mediaAttached growth MBR with fixed media

Figure 4.16 Bound EPS concentration in the MBR

with varying HRT

0

30

60

90

120

150

8 6 4 2HRT (hours)

Solu

ble

EPS

(mg/

L)

Suspended growth MBR

Attached growth MBR with moving media

Attached growth MBR with fixed media

Figure 4.17 Soluble EPS concentration in the MBR with varying HRT



Table 4.10 Dewatering properties of sludge (CST-sec.) in the MBR for different HRTs

30.220.617.910.0Attached growth MBR with fixed media

101.386.078.350.0Attached growth MBR with moving media

52.832.718.19.6Suspended growth MBR

2468

HRT (hours)Reactor

Sludge in the moving media reactor was more difficult to dewatering than that in the other reactors.

Sludge dewatering property was found to increase with decreasing HRT.


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Table 4.11 Floc morphologies in MBR system

Compact, large and round floc with some filamentous embedded within floc and some protozoa

2Attached growth MBR with fixed media

Dense and matrix floc, irregular shape floc and small floc size

1Attached growth MBR with moving media

Compact, round floc with some filamentous and some type of protozoa

2Suspended growth MBR

Description of floc morphologyFISample

(a) Suspended growth MBR (b) Attached growth MBR with moving media (c) Attached growth MBR with fixed media

Figure 4.26 Sludge particle observed under optical microscope


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Conclusions: Effect of HRT

1. COD removal efficiency was greater than 90% with a short HRT.

2. The removal efficiencies of TKN and ammonia were greater than 90% and 94%, respectively at HRT of 2 h.

3. There was no significant difference in bound EPS for all HRT while the soluble EPS was high at short HRT (2 and 4 h).

4. CST value in the attached growth MBR with moving media was higher than that in the suspended growth MBR, and attached growth MBR with fixed media.

5. Sludge morphologies of the three reactors were different in terms of floc shape, floc size and type of microorganism.

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Effect of Mixed Liquor Suspended Solid (MLSS) Effect of Mixed Liquor Suspended Solid (MLSS)

Results and DiscussionsResults and Discussions

MLSS was varied at 6, 10 and 15 g/L

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0

20

40

60

80

100

120

0 5 10 15 20 25 30

Time (Days)

Tran

smem

bran

e pr

essu

re (k

Pa)



Chemical cleaning

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80

Time (Days)

Tran

smem

bran

e pr

essu

re (k

Pa)


Attached growth MBR with moving mediaChemical cleaning

0

20

40

60

80

100

120

0 5 10 15 20 25

Time (Days)

Tran

smem

bran

e pr

essu

re (k

Pa)

Suspended growth reactor

Attached growth reactorChemical cleaning

Figure 4.27 TMP changes with time at MLSS of 6 g/L Figure 4.28 TMP changes with time at MLSS of 10 g/L

Figure 4.29 TMP changes with time at MLSS of 15 g/L

B. Membrane Fouling Behavior

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8.8616.7615

2.6710.3810

1.735.836

Attached growth MBRSuspended growth MBR

Total cake formation (g/m2)*MLSS(g/L)

Table 4.13 Total cake formation on membrane surface for varying MLSS concentration

*(weight of the cake / membrane surface area)


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Table 4.14 Resistance values for suspended and attached growth reactors at 6, 10 and 15 g/L MLSS

0.320.330.84

0.620.650.58

0.821.062.09

0.660.8414.0

2.092.5516.7

61015

Attached growth MBR

0.950.970.97

0.630.630.54

0.980.461.18

33.142.449.7

34.743.551.4

61015


Rc/RtRm(*1012 m-1)

Rf(*1012 m-1)

Rc(*1012 m-1)

Rt(*1012 m-1)

MLSS(g/L)

Reactor

0

4

8

12

16

20

0.01 0.1 1 10 100 1000

Particle diameter (mm)

% In

tens

ity

6 gMLSS/L of Suspended growth MBR10 gMLSS/L of Suspended growth MBR15 gMLSS/L of Suspended growth MBR6 gMLSS/L of Attached growth MBR with moving media10 gMLSS/L of Attached growth MBR with moving media15 gMLSS/L of Attached growth MBR with moving media

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.01 0.1 1 10Particle diameter (mm)

% In

tens

ity

6 gMLSS/L of Suspended growth MBR



6 gMLSS/L of Attached growth MBR with moving media





Figure 4.32 Relationship between particle size

and MLSS concentration

Particle size Particle size distributiondistribution

Enlarge scale

Normal scale

Attached growth reactor


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(µ(µm)m)

(µ(µm)m)



Sludge viscositySludge viscosity

Suspended growth reactor: (242, 970 and 1387mPa.s.)

Attached growth reactor: (277 and 705 and 900 mPa.s)

Sludge viscosity increased with increasing MLSS

concentration.Figure 4.33 Relationship between sludge viscosity and MLSS concentration

0

300

600

900

1200

1500

1800

6 10 15

MLSS (g/L)

Slud

ge V

isco

sity

(mPa

.s)

Suspended growth MBRAttached growth MBR with moving media

C. Sludge Characteristics

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CSTCST

Small floc in attached growth led to a decrease in dewatering property.

1

100

10000

6 10 15

MLSS (g/L)

CST

(sec

)



Figure 4.34 Relationship between CST and MLSS concentration

C. Sludge Characteristics

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Bound EPS compositionsBound EPS compositions

0

30

60

90

120

150

180

6 10 15

MLSS (g/L)

EPS

com

pone

nt (m

g/gV

SS) Bound Protein

Bound CarbohydrateTotal Bound EPS

Figure 4.35 Bound EPS components in Figure 4.35 Bound EPS components in suspended growthsuspended growthMBR at varying MLSS concentrationMBR at varying MLSS concentration

0

30

60

90

120

150

180

6 10 15

MLSS (g/L)

EPS

com

pone

nt (m

g/L)

Bound ProteinBound CarbohydrateTotal Bound EPS

Figure 4.36 Bound EPS components in Figure 4.36 Bound EPS components in attached growthattached growthMBR at varying MLSS concentrationMBR at varying MLSS concentration

D. Bound and Soluble EPS Compositions

0

30

60

90

120

150

180

6 10 15

MLSS (g/L)

EPS

com

pone

nt (m

g/L)

Soluble ProteinSoluble CarbohydrateTotal Soluble EPS

Figure 4.37 Soluble EPS components in Figure 4.37 Soluble EPS components in suspendedsuspendedgrowth MBR at varying MLSS concentrationgrowth MBR at varying MLSS concentration

0

30

60

90

120

150

180

6 10 15MLSS (g/L)

EPS

com

pone

nt (m

g/L)

Soluble ProteinSoluble CarbohydrateTotal Soluble EPS

Figure 4.38 Soluble EPS components in Figure 4.38 Soluble EPS components in attached attached growth growth MBR at varying MLSS concentrationMBR at varying MLSS concentration

Soluble EPS compositionsSoluble EPS compositions

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1. As the MLSS was increased from 6, 10 and 15 g/L, the TMP values were found to increase due to clogging of the membrane. More membrane fouling in the suspended growth MBR was greater than that in the attached growth MBR.

2. More cake formation was observed on membrane surface in the suspended growth as compared with the attached growth reactors for all MLSS concentrations.

3. The total resistance (Rt) in the suspended growth reactor was higher than that in the attached growth reactor. The majority ofthe membrane fouling in suspended growth reactor was caused by the cake resistance (Rc).

4. Membrane fouling increased with increasing MLSS concentration. The cake resistance (Rc) increased with the MLSS concentration. The fouling on the membrane was found to be affected by the design of operating system.

Conclusions: Effect of MLSS

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5. The attached growth reactor with moving media was found to have lower fouling and prolong filtration as compared to the suspended growth reactor.

6. The bound EPS contents in the suspended growth and attached growth reactors was similar. The amount of soluble EPS at 15 g/L MLSS was higher than that at 6 and 10 g/L MLSS. The EPS was not the main factor to cause fouling.

7. The particle size of the biomass influenced by the movement of the media had a significant effect on the formation of cake layers on the membrane.

Conclusions: Effect of MLSS

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1. Conduct pilot scale to verify the laboratory-scale results.

2. Comparing removal efficiency and fouling performance between moving bed MBR and anaerobic MBR in the condition of high organic loading.

3. Considering bio-mechanisms of microbial activity and bio-kinetics in the moving bed MBR in more detail and identifying microbial species and their quantification through microbial techniques (FISH, PCR and DGGE).

Recommendations for Further Study

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Originality and novelty of this workOriginality and novelty of this work

Experimental technique: The operating system and design of MBR are novel and quite different from the other researches. That is, the media is moving during the operation. The moving media was coupled with the membrane bioreactor into a single unit.

Experimental explanation: The proposed explanation is based on the movement of media which produced small particles in the attached growth system leading to high cake porosity, small cake thickness and low cake resistance in the attached growth MBR.

Outcome and contribution: The performance and lifetime of the membrane used in MBR could be improved by the use of attached growth system with the presence of moving media. Attached growth system can withstand high organic loading and consequently require small footprint making it feasible for domestic and industrial wastewater treatment.

Conclusion: The attached growth MBR exhibited less fouling than the suspended growth MBR.

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Publication for this studyPublication for this study

Sombatsompop, K., Visvanathan, C. and Ben, Aim, R. 2006. Evaluation of biofouling phenomenon in suspended and attached growth membrane bioreactor systems. Desalination, 201, 138-149.

Sombatsompop, K. M. and Visvanathan, C. 2005. Evaluation of biofoulingphenomenon in suspended and attached growth membrane bioreactor systems. Proceedings of 3rd Regional Symposium on Membrane Science & Technology: Membrane Technology for Industry and EnvironmentalProtection Institute Teknologi Bandung, Indonesia, 26-27 April.

Manoonpong, K. and Visvanathan, C. 2004. Fouling behavior in attached and suspended growth membrane bioreactor. AIT-KIST International Joint Symposium, Asian Institute of Technology, Pathumthani, Thailand, 20-21 May.

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Thank you very much for Thank you very much for your attentionyour attention

Acknowledgements

Prof. C. Visvanathan Prof. Ajit P. AnnachhatreProf. Sudip K Rakshit Prof. Jy S. Wu Dr. Oleg V. Shipin

Prof. R. Ben AimProf. R. Ben Aim Prof. Chris A. BuckleyProf. Chris A. Buckley

Dr. Nguyen Dr. Nguyen PhuocPhuoc DanDan Dr. Dr. BoonchaiBoonchai WichitsathianWichitsathian, , Mr. Mr. SherSher Jamal Khan Jamal Khan Ms. Ms. NimaradeeNimaradee BoonapatcharoenBoonapatcharoenMy lab colleagues and all Environmental Engineering Laboratory sMy lab colleagues and all Environmental Engineering Laboratory staff taff

King King MongkutMongkut’’ss Institute of Technology North Bangkok (KMITNB)Institute of Technology North Bangkok (KMITNB)

Prof. Dr. Prof. Dr. NarongritNarongrit SombatsompopSombatsompop, daughters, daughters((AchirayaAchiraya and and PawitchayaPawitchaya SombatsompopSombatsompop) and my ) and my parentsparents

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Membrane Fouling Studies in Suspended and Attached …faculty.ait.ac.th/visu/public/uploads/Data/AIT-Thesis/Doctoral... · Membrane Fouling Studies in Suspended and Attached Growth