Besides promoting mixing of the bacterial population with the fecal waste material, what is the purpose of aeration system as used in a biological sewage treatment plant?

Correct Answer: Option D — The air provides an oxygen source for the aerobic bacteria required for metabolism, and it helps prevent settling in the aeration chamber.

Aeration provides the essential oxygen required for aerobic bacteria to metabolize organic waste. Furthermore, the constant agitation from the air supply prevents the formation of stagnant zones and keeps the biomass in suspension, ensuring uniform contact between the bacteria and the waste material for efficient treatment within the chamber.