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“Microbes play a dual role when used for sewage treatment as they not only help to retrieve usable water but also generate fuel”. Explain. |
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Answer» • Microbes naturally present in the sewage are employed in the secondary treatment of the sewage. • The effluent from the primary treatment is passed into large aeration tanks. • This allows the rapid growth of aerobic microbes into flocs which consume the organic matter of the sewage and reduces the BOD. • Then the effluent is passed into a settling tank, where the flocs are allowed to sediment forming the activated sludge. • Major parts of this activated sludge is pumped into anaerobic sludge digesters, where the anaerobic bacteria digest microbes in the activated sludge. • During this digestion bacteria produce a mixture of gases like methane, hydrogen sulphide and carbon dioxide, which form the biogas and can be used as a source of energy. The effluent is generally released into rivers and streams. |
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