2. Contact digestion
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◂ Anaerobic contact digestion (ACD) is a type of anaerobic digestion that
uses a series of reactors to separate the biomass from the effluent.
◂ This allows for a high concentration of biomass to be maintained in the
reactor, which improves the efficiency of the digestion process.
◂ ACD systems typically consist of two reactors: an digestion reactor and
a clarifier. The digester is where the digestion process takes place. The
effluent from the digester flows into the clarifier, where the biomass is
separated and returned to the digester.
3. Advantages
•High efficiency: ACD systems can achieve high conversion rates of
organic matter to biogas.
•Low energy requirements: ACD systems require less energy to
operate than other types of anaerobic digestion systems.
•Stability: ACD systems are less susceptible to upsets than other
types of anaerobic digestion systems.
ACD systems are used to treat a variety of organic wastes, including:
•Agricultural wastewater, Industrial wastewater, Municipal
wastewater sludge, Food waste and Animal manure
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4. ACD systems can be used to produce biogas, which can be used to generate
electricity or heat. The digestate produced by ACD systems can also be used as
fertilizer.
COMPONENTS
1. Digester
2.Clarifier
3.Biogas
4.Effluent
5.Returned biomass
6. Filter digestion
◂ Anaerobic filter digestion (AFD) is a type of anaerobic digestion that uses a
fixed-bed of filter media to support the growth of anaerobic microorganisms.
The filter media provides a large surface area for the microorganisms to
attach to and grow on.
◂ AFD systems are typically upflow reactors, meaning that the wastewater
flows from the bottom of the filter to the top.
◂ As the wastewater flows through the filter, the anaerobic microorganisms
break down the organic matter into methane, carbon dioxide, and other
gases.
◂ The biogas is collected at the top of the filter and can be used to generate
electricity or heat.
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7. Advantages
•AFD systems can achieve high conversion rates of organic
matter to biogas.
•AFD systems require less energy to operate than other types
of anaerobic digestion systems.
• AFD systems are less susceptible to upsets than other types
of anaerobic digestion systems.
•AFD systems are relatively simple to construct and operate.
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9. Process
◂ Wastewater enters the AFD system at the bottom and flows
up through the filter media.
◂ As the wastewater flows through the filter, the anaerobic
microorganisms break down the organic matter into
methane, carbon dioxide, and other gases.
◂ The biogas rises to the top of the filter and is collected.
◂ The effluent flows out of the AFD system at the top.
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10. Sample – Olive mill waste
Microbe - Aspergillus niger
Inlet – 30 g/L
HRT – 15 days
The anaerobic filter reactor
remained more stable than the
anaerobic contact
