Question

Design of septic tank requires consideration of space for the following item(s).

• A. Settling of incoming sewage
• B. Storage of digested sludge
• C. Installation of liner to allow seepage of effluent
• D. Digestion of the settled sludge

Hint:

Septic tank = Settling + Digestion + Sludge Storage. Effluent seepage occurs in soak pits, not in the septic tank itself.

Answer 1

The Correct Option is A, B, D

Step 1: Function of septic tank.
A septic tank is designed to collect sewage, allow settling of solids, and partially digest organic matter through anaerobic action.

Step 2: Requirements of space.
- (A) Correct → Space for settling of incoming sewage is essential, where heavier solids settle to the bottom. ✓
- (B) Correct → Septic tanks must provide storage for sludge that accumulates over time. ✓
- (C) Wrong → Tanks are watertight; liners do not allow effluent seepage (that happens in soak pits, not septic tanks). ✗
- (D) Correct → Space for anaerobic digestion of sludge must be provided. ✓

Step 3: Conclusion.
The correct considerations are (A), (B), and (D).

Final Answer: \[ \boxed{\text{(A), (B), and (D)}} \]