Answers

Mahesh
Jul 29, 2020

Bacteria and fungi are the two categories of naturally occurring microbes in sewage. The bacteria along with the fungal mycelia form the floes. These floes are utilised  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 air is pumped into it. This leads to vigorous growth of bacteria and floe formation. The  bacteria in these floes consume organic matter, thus decreasing the BOD of the sewage.