Describe the role of microbes in Sewage treatment plant.

Explanation

After the primary treatment in the plant effluent is taken for secondary treatinent biological treatment effluent is constantly agitated mechanically, airpumped into it. It allows Vigorous growth of aerobic microbes into flocs.
Microbes use `O_(2)` to reduce organic matter. To reduce BOD, effluent passed into setting tank where bacterial flocs allowed to sediment which is called activated sludge. Small part of activated sludge pumped back into aeration tank to serve as inoculums and the remaining part is pumped into large tanks called as 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.