Question

Arrange the given products formed during sewage treatment in correct sequence:
(A) Biogas
(B) Activated sludge
(C) Flocs
(D) Primary sludge

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

Hint:

Sewage treatment involves primary, secondary, and further stages, with each stage producing specific by-products like primary sludge, flocs, activated sludge, and biogas.

Answer 1

The Correct Option is C

Sewage treatment involves sequential stages yielding by-products. The formation order is:
Step 1: Primary treatment (D) - Primary sludge.
Solids (dirt, grit, debris) are removed from sewage, producing primary sludge for further treatment.
Step 2: Secondary treatment (C) - Flocs.
Aerobic and biological treatment of remaining sewage occurs. Microorganisms consume waste, forming flocs (bacterial clumps) that aid organic breakdown.
Step 3: Further treatment (B) - Activated sludge.
Flocs are processed into activated sludge, rich in bacteria that decompose sewage organics. Activated sludge is further processed or discarded.
Step 4: Final product (A) - Biogas.
Biogas, mainly methane, is generated during treatment, particularly under anaerobic conditions, and can serve as a renewable energy source.
Step 2: Conclusion.
The correct product sequence is: (C) Flocs → (D) Primary sludge → (B) Activated sludge → (A) Biogas.
Final Answer:
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