Activated sludge is the
- Aaerated sludge in the aeration tank
- Bsludge settled in the humus tank
- Csludge in the secondary tank after aeration and rich in microbial massCorrect
- Dsludge in the secondary tank after aeration and rich in nutrients
Solution
Concept
Definition and properties of activated sludge
Formula
NONE
Step-by-step solution
1. The activated sludge process utilizes biological oxidation to treat wastewater. 2. The biological solids settle in the secondary settling tank after aeration. 3. This settled sludge, containing active microorganisms capable of further decomposing organic matter, is known as activated sludge. Answer: C
Explanation
In the activated sludge process, wastewater undergoes aeration where microorganisms decompose organic matter into biological flocs. This active biological mass settles out in the secondary settling tank, yielding sludge that is rich in live microbial mass and recirculated to maintain process efficiency.
Why the other options are wrong
A) The mixture in the aeration tank is termed mixed liquor suspended solids. B) Sludge settled in the humus tank comes from trickling filter systems. D) Activated sludge is primarily characterized by its active microbial mass rather than nutrient content.
Shortcut
Activated sludge = Microbe-rich sludge in the secondary settling tank.
Common mistake
Confusing activated sludge with aerated sludge in the aeration basin or ordinary digested sludge.
Correct answer: C) sludge in the secondary tank after aeration and rich in microbial mass