Question

Secondary sewage treatment is mainly a

• A. Biological process
• B. Chemical process
• C. Mechanical process
• D. Physical process

Answer 1

The correct option is A

Biological process

The correct option is A.

Explanation of the correct option:

Option A:

1. The treatment of sewage is majorly a biological process as it involves the treatment of microorganisms.
2. These microbes function to reduce the toxicity of the waste which is tested by measuring the BOD (biological oxygen demand) and COD (chemical oxygen demand) value of the water.
3. The microbes help in treating the sludge produced by the wastewater.
4. Hence, it is called a biological process.

Explanation of the incorrect option:

Option B:

1. This is not a chemical process as it does not involve a change in chemical state and production of different chemicals.
2. This process does not occur by itself, i.e., non-spontaneous.

Option C:

1. No objects interact to generate mechanical energy in secondary sewage treatment.

Option D:

1. A physical process involves gradual change through transient states.
2. The treatment of sewage water is not a physical process.

Final answer: Secondary sewage treatment is mainly a biological process.