During secondary treatment of primary effluents, vigorous growth of useful aerobic microbes into flocs occur when it is agitated mechanically and air is pumped into it in a large aeration tank. These microbes while growing consume major part of the organic matter in the effluent. This significantly reduces BOD.
• Useful aerobic microbes grow rapidly and form flocs.
• Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
• The growing microbes consume organic matter and thus reduce the biochemical oxygen demand (BOD).
