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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