Question

Important functions of a septic tank includes:

(A) Storage of sludge and scum

(B) Removal of solids from the sewage

(C) Decomposition of solid sewage under aerobic conditions

(D) Decomposition of solid sewage under anerobic conditions

Choose the correct answer from the options given below:

• A. (A), (B) and (C) only.
• B. (A), (B) and (D) only.
• C. (A), (C) and (D) only.
• D. (B), (C) and (D) only.

Hint:

Remember a septic tank is completely closed, with no air pumped in, and think about what kind of decomposition that allows.

Answer 1

The Correct Option is B

Think of a septic tank as doing three jobs in sequence, and check each listed statement against that sequence.

First, it slows down incoming sewage so solids drop out of suspension, this matches (B).

Second, it holds those settled solids as sludge and the floating fats as scum instead of letting them pass on, this matches (A).

Third, whatever slow bacterial breakdown happens to that stored sludge takes place inside a sealed tank with no oxygen supply, so it can only be anaerobic, matching (D), never aerobic, ruling out (C).

So three of the four statements hold, (A), (B) and (D), and the aerobic claim in (C) is the odd one out.

\[ \text{Correct statements} = \boxed{A,\ B,\ D} \]