Effluent from the primary settling tank passed into aeration tank, agitated mechanically and air is pumped into it, vigorous growth of aerobic microbes into flocs, microbes consume major part of the organic matter in effluent.
Detailed Answer:
The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into flocs. While growing, these microbes (flocs). decompose The major part of the organic matter in the effluent. This decreases the biological oxygen demand (BOD) of the effluent. Sewage is treated till the BOD is significantly reduced.
