Sludge recirculation is done in Activated Sludge Process to
- Amaintain the flow rate
- Bincrease the bacterial countCorrect
- Cincrease the flow velocity
- Ddecrease the retention time
Solution
Concept
Return activated sludge
Step-by-step solution
1. Returned sludge carries active micro-organisms back to the aeration tank. 2. This keeps a high microbial concentration (MLSS) for treatment.
Explanation
Recirculation seeds the aeration tank.
Why the other options are wrong
It does not change flow rate, velocity or retention time.
Shortcut
Return sludge = seed.
Correct answer: B) increase the bacterial count