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 systems supply oxygen to aerobic bacteria, which are essential for breaking down organic matter in sewage. Simultaneously, the air agitation prevents the solids from settling prematurely in the aeration chamber, ensuring the bacteria remain in constant contact with the waste material for efficient and thorough biological decomposition.