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 multiple steps to break down organic waste and produce several by-products. The sequence in which the products are formed is as follows:
Step 1: Primary treatment (D) - Primary sludge.
In the first step of sewage treatment, solid particles like dirt, grit, and large debris are removed from sewage. This process results in the formation of primary sludge, which is solid waste that can be further treated.
Step 2: Secondary treatment (C) - Flocs.
In the second step, aeration and biological treatment of the remaining sewage occur. Microorganisms consume organic waste, forming flocs (clumps of bacteria and other microorganisms). These flocs help in the further breakdown of organic material in the water.
Step 3: Further treatment (B) - Activated sludge.
The flocs are then treated to form activated sludge, which contains a high concentration of bacteria that break down the organic matter in the sewage. Activated sludge is typically removed and further processed or disposed of.
Step 4: Final product (A) - Biogas.
During the treatment process, especially in anaerobic conditions, biogas is produced. This gas, primarily methane, can be used as a renewable energy source.
Step 2: Conclusion.
The correct sequence of sewage treatment products formed is: (C) Flocs → (D) Primary sludge → (B) Activated sludge → (A) Biogas.
Final Answer: \[ \boxed{\text{The correct answer is (3) (C), (D), (B), (A).}} \]