ENVE 424. Anaerobic Treatment. Associate Professor, PhD., Eng.

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1 ENVE 424 Anaerobic Treatment Barış ÇALLI Associate Professor, PhD., Eng. Marmara University, Department of Environmental Engineering Kadıköy, Istanbul, Turkey Chapter 1 Introduction to Anaerobic Digestion 1

2 Anaerobic Digestion (AD) Anaerobic digestion (AD) is a process in which complex organic materials are converted to finally CH4 and CO2 in the absence of O2 via activity of several groups of anaerobic microorganisms linked trophically to each other. Anaerobic Digestion (AD) CH4 formation does not or hardly occur in medium where nitrate or sulfate is readily available as electron acceptor. Swamps, soil, river sediments, lakes, seas and digestive tracks of ruminant animals are natural environments of CH4 production. 2

Composition of Biogas Component Methane (CH 4 ) Carbondioxide (CO 2 ) Nitrogen (N 2 ) Hydrogen (H 2 ) Oxygen (O 2 ) Hydrogen sulfide (H 2 S) Percentage (%) 50-80 20-40 0-5 <1 <0.4 0.

3 Composition of Biogas Component Methane (CH 4 ) Carbondioxide (CO 2 ) Nitrogen (N 2 ) Hydrogen (H 2 ) Oxygen (O 2 ) Hydrogen sulfide (H 2 S) Percentage (%) <1 < History John Dalton ( ), collecting marsh gas with youngsters nearby Manchester, UK In 17th century, Jan Baptita Van Helmont found that decaying organic material produced flammable gases In 1776, Alessandro Volta resolved that there was a relationship between the amount of decaying organic matter and the amount of flammable gas produced. 3

The technology then moved to England in 1895, when biogas was recovered from a sewage system and used to fuel street lamps.

4 History, cont. In 1808, Sir Humphrey Davy determined that CH 4 was present in the gases produced by cattle manure First AD was built in Bombay, India in The technology then moved to England in 1895, when biogas was recovered from a sewage system and used to fuel street lamps. Biogas street lamp History, cont. In the 1930 s, developments in microbiology identified the anaerobic bacteria and the conditions needed to promote CH 4 production In 1970s, the energy crisis renewed interest in AD Anaerobic sludge digesters In 1970s - 80s, the lack of understanding and overconfidence resulted in numerous failures in ADs 4

5 Currently Hundreds of farm-based digesters operating in Europe plus several centralized AD systems Danish systems co-digest manure, organic industrial wastes and municipal solid waste Large numbers of family-sized, low technology digesters in developing world provide biogas for cooking and lighting Renewed interest in U.S. because of high oil & natural gas prices. Environmental Benefits Reduces odor from land application Protects water resources Reduces pathogens Weed seed reduction Fly control after digestion Greenhouse gas reduction 5

Suitable Wastes Industrial wastewaters Bakeries Beverage production Breweries and Wineries Chemical plants Dairies Food processing plants Meat and poultry

Green waste Sewage sludges Carbon and Energy Balance Aerobic treatment Anaerobic treatment COD (100%) CO 2 (40-50%) COD (100%) Biogas (70-90%) Aerobic

6 Suitable Wastes Industrial wastewaters Bakeries Beverage production Breweries and Wineries Chemical plants Dairies Food processing plants Meat and poultry processing Pharmaceutical plants Pulp and paper mills Rendering plants Textile mills Biosolids Household food waste Animal manure Farm wastes Waste paper Green waste Sewage sludges Carbon and Energy Balance Aerobic treatment Anaerobic treatment COD (100%) CO 2 (40-50%) COD (100%) Biogas (70-90%) Aerobic bioreactor Effluent (5-10%) Anaerobic bioreactor Effluent (10-20%) Sludge (50-60%) Heating Sludge (5-15%) 100 kwh consumed for O kwh produced from CH 4 6

7 Advantages: Anaerobic vs Aerobic Less energy required Less biological sludge production Fewer nutrients required CH 4 production, a potential energy source Smaller reactor volume required Elimination of off-gas air pollution Rapid response to substrate addition after long periods w/o feeding Disadvantages: Anaerobic vs Aerobic Longer start-up time May require alkalinity addition May require further treatment with an aerobic process to meet discharge requirements Biological N and P removal is not possible Much more sensitive to the adverse effect of lower temperatures on reaction rates May be more susceptible to upsets due to toxic substances Potential for production of odor and corrosive gasses 7

8 Materials flow in AD Waste Stream 6-12% solids ANAEROBIC DIGESTER Liquid Liquid 5% solids Solids separator Biogas Engine/ Generator Stream Discharge Secondary treatment Animal Consumption Lagoon/ Liquid storage Crop Application 30-35% solids Composting Compost Electricity Electricity Company Owner Usage Recaptured Heat Hot water 8

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