Describe the role of Microbes in sewage treatment plant.

Explanation

After the primary treatment in the plant, effluentis taken for secondary treatment or biological treatment. Effluent is constantly agitated mechanically, air pumped into it. It allows vigorous growth of aerobic microbes into flocs.
Microbes use organic matter to reduce BOD.
Effluent passed into settling tank where bacterial flocs allowed to sediment which is called activated sludge. 1 Small part of activated sludge pumped back into aeration tank to serve as inoculum and the remaining part is pumped into large tanks called anaerobic sludge digester.
Other kinds of anaerobically grown bacteria, digest the bacteria and the fungi in sludge. Bacteria produce mixture of gases, methane, hydrogen sulphide and carbon dioxide.