Question

Choose the correct options with regard to activated sludge process.

• A. The activated sludge process is an aerobic process
• B. The entire settled sludge is sent back to the aeration tank
• C. The entire effluent from the final settling tank is sent back to the aeration tank
• D. In aeration tanks, sewage is aerated and agitated for a few hours

Hint:

In the activated sludge process, aerobic conditions are maintained in aeration tanks, where microorganisms decompose organic matter.

Answer 1

The Correct Option is A, D

The activated sludge process is a well-known method used for wastewater treatment, where microorganisms break down organic matter in the sewage. Let's analyze the options:
- (A) Correct: The activated sludge process is an aerobic process, meaning it requires oxygen to help microorganisms break down pollutants in the water.
- (B) Incorrect: Not all settled sludge is returned to the aeration tank. Only a portion of the sludge (known as excess sludge) is removed, while the remaining is returned for further treatment.
- (C) Incorrect: The entire effluent from the final settling tank is not sent back to the aeration tank. Only the treated water is removed from the aeration tank, while the sludge is returned.
- (D) Correct: In the aeration tank, sewage is aerated and agitated for several hours to facilitate the breakdown of organic pollutants by microorganisms.
Thus, the correct options are (A) and (D).
Final Answer: (A) The activated sludge process is an aerobic process, (D) In aeration tanks, sewage is aerated and agitated for a few hours