Biological process is carried out in which type of water treatment :

Options

A. Primary
B. Secondary
C. Tertiary
D. Both (1) & (2)

Answer

**Step-by-Step Solution:**

1. **Understanding Water Treatment Types**: Water treatment processes are generally categorized into three types: primary, secondary, and tertiary treatment. Each type has distinct methods and purposes.

2. **Identifying Biological Processes**: Biological processes in water treatment involve the use of microorganisms to break down organic matter. This is crucial for removing biodegradable contaminants from wastewater.

3. **Analyzing Primary Treatment**: Primary treatment primarily focuses on the physical removal of solids from wastewater through processes like sedimentation. It does not involve biological processes.

4. **Analyzing Secondary Treatment**: Secondary treatment is specifically designed to utilize biological processes. It employs microorganisms, such as bacteria and protozoa, to consume organic matter and biodegradable contaminants in the wastewater.

5. **Analyzing Tertiary Treatment**: Tertiary treatment is the final stage of wastewater treatment, which may involve advanced filtration and chemical processes. It does not primarily focus on biological processes.

6. **Conclusion**: Based on the analysis, the biological process is carried out in secondary sewage treatment. Therefore, the correct answer to the question is "secondary."

**Final Answer**: Secondary sewage treatment.

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