Seccondary treatment of the sewage is also called Biological treatment Justify this statement and explain the process.

Explanation

It is called biological treatment because it involves living organisms such as aerobic or anaerobic bacteria and fungi to digest organic waste. The primary effluent is passed into an aeration tank where vigorous growth of aerobic microbes (flocs) takes place as a result of which BOD gets reduced. The effluent is passed to a settling tank where flocs sediment to produce activated sludge. The sludge is pumped to an anaerobic sludge digester to digest the bacteria and fungi.