Question

Name the two different categories of microbes naturally occurring in sewage water. Explain their role in cleaning sewage water into usable water.

Answer 1

The two categories of naturally occurring microbes present in sewage are bacteria and fungi. The bacteria along with the fungal filaments form flocs which are utilized during the secondary treatment of sewage. The primary effluent after separation of the grit and debris is taken to the secondary treatment. Here, the effluent is passed to an aeration tank where it is constantly agitated and the air is pumped into it. This leads to the vigorous growth of bacteria and formation of flocs, the bacteria in these flocs consume the organic matter; thus decreasing the BOD of the sewage.