application of anaerobic bioreactor and membrane...

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Application of anaerobic bioreactor and membrane technology sewage treatment for generating energy

Talk by:Dr. V. Kalyanraman

Divisional Manager & Head Centre of Excellence (Biotechnology) &

Water and Wastewater Technology Research, Technology and Innovation Centre

Thermax Limited, Pune - 411018


Application of anaerobic bioreactor and membrane technology sewage treatment for generating energy

Dr. R. R. Sonde, Dr. V. Kalyanraman and Mr. Janardhan Bornare

R. D. Aga Research, Technology and Innovation Centre, Thermax Ltd. Pune

Abstract:

• An anaerobic bioreactor coupled with membrane unit is phrased as the AnaerobicMembrane Bioreactor (AnMBR). Unlike the conventional single stage anaerobicreactor, a membrane coupled systems facilitates independent control of hydraulic andsolid retention within reactor. Such system can withstand at higher organic loading rateand operating biomass concentration. AnMBR, although to date is in infancy stagecompared to aerobic MBR for sewage treatment, it is a prospective system forsimultaneous energy recovery in terms of biogas, good treated water output and lesssludge production.

• This paper endeavors to summarize the investigations made around the world onapplications of anaerobic MBR. Special emphasis is given on rate of organic removal,biogas yield and biomass concentration while treating sewage.

• This paper also highlights the efforts made at our laboratory on sewage treatment usingan AnMBR system. The AnMBR was performed well for COD and BOD removal fromthe low strength wastewater such as sewage, demonstrating the effectiveness of thissystem for sewage treatment with COD and BOD removal efficiency of over 90%.The results also show generation of more than 0.4 m3 biogas/kg of COD removed.The critical challenges persist on membrane fouling abatement and flux maintenance.

Key words: AnMBR, Membrane, COD/BOD, Flux, Fouling, Biomass, Biogas


Sewage generation scenario in India

Source: CPCB report, 2009


Sewage treatment scenario in India

Class I Cities Class II Towns

Source: CPCB report, 2009


Major Technologies on Sewage Treatment

De-centralized – Community based sewage

treatment plant ( mostly aerobic)

Activated sludge process ( ASP)

Rotating biological contractor ( RBC)

Sequencing batch reactor ( SBR)

Fluidized /moving Bed Bioreactor ( MBBR)

Submerged fixed film Bioreactor ( SAFF)

Membrane Bioreactor (MBR)

Centralized – municipal sewage treatment plant

Activated sludge process ( ASP)

Sequencing batch reactor ( SBR)

Fluidized /moving Bed Bioreactor ( MBBR)

Membrane Bioreactor (MBR)

Upflow anaerobic sludge blanket ( UASB)

SBR technological

innovation

Membrane bioreactor technology

Newly introduced

Newly introduced

Newly introduced

Newly introduced

Newly introduced

Newly introduced

Except the UASB all the above technologies are energy intensive. However considering the nature of waste aerobic technologies are most acceptable. UASB failed under lean sewage conditions


Oxidation ponds

ASPs / Anaerobic

SAFF/ RBC/UASB

FAB/SBR/HA

MBR

1860 1910 1950 1980 2000

Bio -Technological advances in wastewater treatment


Paradigm shift in recent past

In the past, wastewater was considered as “problem”. Now, it is realized as a “resource”

Example:

– “Newater” scheme in Singapore

– Treated domestic wastewater for Industrial use

– “Zero Discharge” norm for major industries

– “Recycled water” for domestic use

– Treated wastewater for groundwater recharge & irrigation

Zero Discharge


For SustainabilityPromote Anaerobic treatment technologies for sewage treatment leading to energy generation and to produce recyclable quality of treated water Less energy intensive Can generate alternate energy Minimal sludge handling However: So far not very successful for lean wastewater eg., sewage Cannot achieve recyclable treated water quality – further

treatment is required UASB based systems are failed due to operational difficulties


Anaerobic Wastewater treatment

High Strength wastewaterEnergy Carrier Biogas

Low Strength wastewater

Aerobic Wastewater treatment

Treatment cost due to aeration

system is becoming higher

Treatment of Low strength wastewater

with anaerobic system suffers poor biomass retention

Comparison


Why Anaerobic system failed for sewage treatment

Anaerobic system like UASB is able to bring down BOD to 70-100 mg/l hence required further aerobic treatment

Though theoretical methane yield is 0.35 m3/kg COD removed, the actual yield is recovered only 0.08 m3/Kg COD removed. Remaining goes as dissolved.

UASB suffer poor solid retention in the reactor due to hydraulics load and leads to frequent solid washout


New Potential Option for sewage treatment

Application of Membrane for retention of Biomass within anaerobic system for sewage treatment

Anaerobic Membrane Bioreactor - AnMBR

Biogas

Low to medium strength wastewater

Waste to Energy Solution


Conventional Anaerobic System Vs AnMBR


Development of Anaerobic Membrane Bioreactor ( AnMBR)

The basic objective is to Develop Anaerobic Membrane

Bioreactor (AnMBR) technology for generation of energy

and recyclable water from sewage

Assessing performance of Anaerobic system and Integration of Anaerobic system with membrane

Process optimization and Performance evaluation in pilot scale for sewage

Bacterial Kinetics, Bacterial Characterization to get high biogas yield and maximum organic degradation

Membrane studies, fouling pattern, flux,fouling abatement studies


Schematics

Different Configurations of AnMBR


Lab and Pilot plant Setup


Performance Monitoring

Data Acquisition program– Pressure– Temperature– Influent Flow– Flux– Biogas Production– pH

Chemical Assay– COD– BOD– Alkalinity– Volatile Fatty Acid– Methane Content ( GC)– Mixed Liquor Suspended Solids


Wastewater Characteristics

Inlet Characteristics

S. No

Parameters Concentration

1 pH 6.5 – 7.0

2 COD, mg/l 450 – 600

3 BOD, mg/l 260 - 320

4 TDS, mg/l 400 - 600

5 TSS, mg/l 120-140

#Sewage wastewater equivalent

MonoMono-- ethylene Glycol as substrateethylene Glycol as substrate

Outlet Characteristics

S. No

Parameters Concentration

1 pH 7.0 – 7.3

2 COD, mg/l 30 – 40

3 BOD, mg/l 8-10

4 TDS, mg/l 400-600

5 TSS, mg/l ND

Low strength wastewater#


Optimization of HRT at low strength wastewater

Output Quality water < 40 mg/l at 12 hrs HRT


Performance of AnMBR at lower organic Inputs

Performance at low strength wastewater

treated water quality - < 40 mg/l


Membrane Fouling pattern

0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30 35 40

Days of Operation

Flu

x (L

MH

)

FLUX

Constant flux

Flux drops and chemical cleaning required


Biogas Generation at Lower organic load

Biogas generation - Theoretical Vs Actual

0 . 0 0

2 . 0 0

4 . 0 0

6 . 0 0

8 . 0 0

10 . 0 0

12 . 0 0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 26 2 7 2 8 2 9 3 0 3 1 3 2

Days

Bio

gas g

en

eratio

n (

Lit

)

Theor e t i c a l b i oga s ge ne r a t i on

Act ua l B i oga s pr oduc t i on

Biogas generation - 25% lower

than the theoretical


Anaerobic MBR lab scale unit installed at Thermax

Controls

Bioreactor


Challenges:

Validation of the performance in actual sewage

Prolong filterability and reduce fouling phenomena

Improve the biogas yield and reduce the solubility of biogasin treated effluent

Scalability issues and membrane configuration

In-situ membrane cleaning

Acceptable/affordable capital cost of the technology inIndian context

Development and Indigenization of suitable membrane


Conclusion

Anaerobic Membrane Bioreactor could be a betteralternative technology to treat low strength municipalsewage wastewater without producing high sludge

A useful renewable source of energy ( biogas) can beproduced

Membrane separation of sludge from the treated watercan produce consistent and better quality of effluent

Finally the advantages of the AnMBR can be summarized as below:

Complete solid-liquid separation Energy conservation High loading rates Long SRT and low sludge production Small footprint High quality effluent

Considering trappable sewage source of 38000 MLD theoretical

energy generation could be

approx.16000 MW


Acknowledgement

Thermax would like to acknowledge the grant provided by Department of Biotechnology ( DBT, GOI) under BIPP program to support the research work.


Thank You

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