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Anaerobic Digestion of Wastewater

Global Methane Initiative – Wastewater Task Force Meeting

November 11, 2010, Thursday, 15:30 – 16:00

Lettinga Associates Foundation LeAF

Delft University of Technology

Contents

• Basics Anaerobic Digestion • Reactors • State of Practice • Developments

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Basics Anaerobic Digestion

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Comparison Aerobic - Anaerobic

ANAEROBIC

Biogas 40-45 m3 (70% CH4)

Effluent, 10-20 kg COD

Influent

100 kg COD

AEROBIC

Heat loss

Sludge, 30-60 kg

Effluent, 2-10 kg COD

Influent +

Aeration (100 kWh)

100 kg COD

Sludge, 5 kg

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tan tan tan

Basic setup of aerobic treatment

primary activated secondary grit sedimentation sludge sedimentation

screens chamber

Raw sewage Treated effluent

Sludge

sludge digestion dewatering

k k k

sludge

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Basic setup of anaerobic treatment

high-rate effluent grit anaerobic polishing

screens chamber treatment pond

Raw sewage Effluent

Sludge

sludge drying beds

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Methanogenesi

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CH4 / CO2

Methanogenesis Methanogens

Acetogenesis Syntrophic acetogenic bacteria

Mono- and oligomers amino acids, sugars, fatty acids

Organic Polymers proteins carbohydrates lipids

Hydrolysis Hydrolytic enzymes

Acidogenesis Fermentative bacteria

s

Volatile Fatty Acids Lactate Ethanol

Acetate H2 / CO2

Anaerobic Digestion

Homoacetogenic bacteria

Fermentation

Hydrolysis Organic Polymers

proteins carbohydrates lipids

Mono- and oligomers amino acids, sugars, fatty acids

Volatile Fatty Acids Lactate Ethanol

H2 / CO2 Acetate Homoacetogenic bacteria

CH4 / CO2

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Hydrolysis: Surface related

Rate increases

Particle breakdown or “lysis”

More enzymes “attack” the substrate

From: Wendy Sanders

� Hydrolysis as a surface-related process

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Acidogenesis Organic Polymers

proteins carbohydrates lipids

Mono- and oligomers amino acids, sugars, fatty acids

Volatile Fatty Acids Lactate Ethanol

H2 / CO2 Acetate

CH4 / CO2

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Acetogenesis Organic Polymers

proteins carbohydrates lipids

Mono- and oligomers amino acids, sugars, fatty acids

Volatile Fatty Acids Lactate Ethanol

H2 / CO2 Acetate

CH4 / CO2

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_______________________________________________________________________________________________

Acetogenesis (Acetate formation)

• Conversion of fermentation products into acetic acid, CO2, and H2

• Mainly from propionic acid, butyric acid and ethanol

-propionate- + 3H2O → acetate- + HCO3 + H+ + 3H2 Δ G0’ = + 76.1 kJ/mole

butyrate- + 2H2O → 2 acetate- + H+ + 2H2 Δ G0’ = + 48.1 kJ/mole

ethanol + 2H2O → acetate- + H+ + 2H2 Δ G0’ = + 9.6 kJ/mole

4 H2 + CO2 → CH4 + 2H2O Δ G0’ = -138.9 kJ/mole

Need for syntrophic associations !!!

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Methanogenesis Organic Polymers

proteins carbohydrates lipids

Mono- and oligomers amino acids, sugars, fatty acids

Volatile Fatty Acids Lactate Ethanol

H2 / CO2 Acetate

CH4 / CO2

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Acidogenesis: Acidification

Methane Poor

Exceeded Capacity Buffering

Capacity

Methanogenic Toxicity VFA Increasing increases

pH Unionized VFA increasing decreases

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Maximum Production of Biogas

[Nm

³/kg

]

1,40

1,20

1,00

0,80

0,60

0,40

0,20

0,00 Lipids Carbohydrates Proteins

0,86

0,40 0,50

production of biogas production of methane

(ATV-DVWK M 363)

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Basics Anaerobic Treatment: Summary

• Nett energy production • No fossil fuel required • Low sludge production • Higher effluent COD • No nitrogen and phosphorus removal • High loading rates • Small footprint • Sewage: Hydrolysis limiting step • Sewage: Limited biogas production

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Reactors

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Fixed Dome Domestic Digester

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Digester: SchematicDigester with rubber membrane cover > 50 %

of all digesters

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Biogas Plant in the UK

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Completely mixed

(Bio)gas

influent effluent

Relative capacity: 1

Physical retention

Relative capacity: 5

Immobilisedbiomass

Relative capacity: 25

Enhanced contact

Relative capacity: 75

Development of “high-rate” anaerobic treatment systems

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UASB and EGSB

Auto immobilization / granulation

UASB

EGSB

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Reactor Technologies for Liquids

influent

influent influentinfluent

influent

influent

effluent

effluent

effluent

effluent

effluenteffluent

gas

gasgas

gas gasgas

UASB-Reactor

Fluidized bed Reactor Fixed bed Reactor Anaerobic Contact Reactor

Biobed-Reactor IC-Reactor

second stage

first stage

sludge bed

reci

rcul

atio

n

reci

rcul

atio

n

reci

rcul

atio

n

(loop

)

(loop

)

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UASB: Sewage

Bucaramanga, Colombia, 12000 m3/d

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UASB Reactor: SewageMirzapur, India, 14 m3/d plant

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UASB: Sewage

Accra, Ghana

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UASB: Industrial

Palsana, India

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Anaerobic Industrial Wastewater TreatmentAnaerobic UASB-Reactor CSM

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(Kraul & Wilkening u. Stelling)

IC-Reactor: Distillery Hanover

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Cumulative BIOPAQ® references N=580

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Reactors: Summary

• Sludges and slurries: Digester – CSTR, no biomass retention

• Liquids (<~2% solids): High rate reactor – Biomass retention

• Sewage: UASB reactors – Flocculent biomass

• Industrial wastewater: UASB, EGSB and IC reactors– Granular biomass

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State of Practice

LeAF

Europe37%

North & Central America16%

Australia 1%

Africa 3%

South America11%

Asia32%

(1981 – 2007, N= 2266, Mainly industrial)

Geographic Distribution of Anaerobic Plants

LeAF

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

1972

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

*

Year

Ref

eren

ces

Anaerobic Industrial Wastewater Reactors, census 2007over 2200 registered high-rate reactors+ ≈ 500 (?) non registered (“home made”)

Data collected by Yolanda Yspeert (2007)

Worldwide cumulative anaerobic references

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Types of industries

LeAF

Others17%

Biothane(now Veolia)20%

Biotim+EnviroAsia+GWE12%

ADI Systems5%

Local suppliers6%

Paques26%

Waterleau+Biotim+Ecovation3%

Degremont 5%

Kurita 3%

Envirochemie 1%

Grontmij 2%

Major Technology Suppliers (1981 – 2007, N= 2266)

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Country City pe Year °C m3 HRT (h) COD BOD TSS

Colombia Bucaramanga 35 5-19Colombia Cali 1000 25.2 64 6-8 267 95 215Brazil Sumare City 1410 1992 16-23 67.5 7 402 515 379Brazil 1987 18-28 120 5.15 188-459 104-255 67-236Brazil Sao Paulo 120 4Brazil Pedegral 160 6 799Italy 7-27 336 12-42 205-326 55-153 100-250Brazil 477 13 600 303Brazil Mangueira 18000 30 810 9.4 549 ± 150 196 ± 100India Kanpur 1989 20-30 1200 6 563 214 418Egypt Fayoum 105000 2007 2304Colombia Bucaramanga 1990 24 3360 5 380 160 240India Yamunanagar 55000 2002 17.3 3500 8.4 939 318 374India Panipat 69000 1999 18.6 3500 8.4 985 411Brazil Minas Gerais - Laboreauz 70000 2007 4840 8India Mirzapur 100000 1994 18-32 6000 8 404 205 362Ghana Accra 2000 6500 10 150-16550 1500 500-22000Colombia Bucaramanga 160000 1990 6600 5.2 380India Faridabad 110000 1998 22.5 7000 8.4 1194

Large Municipal Anaerobic WWTPs

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Country City pe Year °C m3 HRT (h) COD BOD TSS

India Yamunanagar 130000 2000 18.4 9000 8.4 702 250 372India Agra 570000 2004 18.8 10000 9.3 762 264 514India Sonepat 200000 1999 18.5 11000 8.4 481 160 189India Gurgaon 150000 1998 18.6 11000 8.4 870 318 435India 18-32 12000 8 1183 484 1000India Panipat 240000 2000 23.8 13000 8.4 487 196 320India Karnal 270000 2000 19.7 14000 8.4 443 141 236India Noida 190000 2000 20.0 14000 10.9 674 247 558India Faridabad 250000 1998 23.8 16000 8.4 1055 318 920Brazil Campinas 25 16464 14.3 522 ± 80 257±30 266±70UAE Ajman 490000 2008 17600 8.6India Faridabad 270000 1999 23.7 18000 8.4 1113 365 593India Ghaziabad 350000 2002 21.7 20000 10.7 418 185India Ghaziabad 430000 2002 21.2 26000 10.7 829 293 458India Saharanpur 310000 2000 21.6 28000 10.4 363 169Brazil Piracicamirim 92000 1998 18-32Brazil Minas Gerais - Onca 1000000 2006 53088 8

Large Municipal Anaerobic WWTPs (con’d)

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Gas Utilization

-49 (43)Middle East

+43 (53)India

-120 (60)India

-30 (17)Brazil

--38 (22)Brazil

-48 (25)Brazil

--70 (41)Brazil

--90 (69)Brazil

-100 (43)Brazil

-164 (95)Brazil

Gas UtilisationCapacity (actual)Plant

Biothane-Veolia, 2010

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Issues

• Lower COD/BOD removal than expected• Biogas yield lower than expected (0.1-0.2 Nm3 instead of

0.35 Nm3 per kgCOD removed)• Sludge production higher than anticipated (0.3-0.4 kgTSS

per kg COD applied, instead of 0.15)• Significant operator attendance required

Survey Biothane-Veolia 2010

10 Large scale (>10 ML/d) UASB STPs

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Current Projects: Summary

• Industry: many reactors• Large (>10 ML/d) municipal UASB STPs

– India 45

– Brazil 15

– Ghana, Egypt, UAE

• Large scale: lower performance than early pilot and full scale• Many small UASB STPs

– Brazil, India, China, ...

• Large number of small systems mostly without biogas capture• Decentralized sanitation (less/no dilution, no sewer):

– Domestic biogas plants: India, China, Nepal, ...

– New reactor concepts: Germany, Sweden, Netherlands

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Developments

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Anaerobic treatment of sewage in colder climates

• Challenge: treat municipal sewage to achieve net energy production while meeting effluent standards

• Two approaches: – enhanced pre-sedimentation– direct anaerobic treatment

Anaerobic treatment of domestic solids

• Decentralized sanitation (less/no dilution, no sewer):– Domestic biogas plants: India, China, Nepal, ... – New reactor concepts: Germany, Sweden, Netherlands

Developments

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Anaerobic Sewage Treatment

Conventional

Enhanced pre-sedimentation

Anaerobic pre-treatment

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Methane Production Net Energy Production

Perry L. McCarty, 2010

Aerobic/Anaerobic Comparison

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The Energy Factory

Scenarios based on 100 000 p.e.

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Basic scenario

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Plus scenario

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Super scenario

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700 m3/d

Influent

Water

700 m3/d

Air

1.2 m

95% Methane Removal

Energy Requirement:

0.01 kWh/m3

Air

plus

Methane

Oxygenated

Treated

Water

Liqui-Cel Membrane Contactor for Air Stripping of Methane

50% of Methane lost via Effluent!

Perry L. McCarty, 2010

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Developments: Summary

• Anaerobic sewage treatment in colder climates• The Energy Factory• Anaerobic sewage treatment: 50% loss of methane• Decentralized sanitation