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a. How is activated sludge produced during sewage treatment?b. Explain how this sludge is used in biogas production. |
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Answer» a. Once the BOD of sewage or waste water is reduced significantly, the effluent is passed into a settling tank where the bacterial flocs undergo sedimentation and the sediment is thus called activated sludge. b. A small part of the activated sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part of the activated sludge is pumped into large tanks called anaerobic sludge digesters. The anaerobic bacteria digest the bacteria and fungi in the sludge and produce mixture of gases like methane, hydrogen sulphide and CO2 which constitute biogas. |
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