During the treatment of sewage water, the chemical process is carried out in which step of water treatment?

Options

A. Tertiary
B. Secondary
C. Primary
D. Quaternary

Answer

### Step-by-Step Solution:

1. **Understanding Sewage Water Treatment**:
- Sewage water treatment involves several steps to make wastewater safe for discharge or reuse. The main steps are primary, secondary, and tertiary treatment.

2. **Identifying the Steps**:
- **Primary Treatment**: This step involves the physical removal of large and small particles from sewage through processes like filtration and sedimentation. It does not involve any chemical processes.
- **Secondary Treatment**: This is a biological treatment where microbes (bacteria and fungi) are used to decompose organic matter and reduce biochemical oxygen demand (BOD). Again, this step does not involve chemical processes.
- **Tertiary Treatment**: This is the final step of sewage treatment, which focuses on improving the quality of water by removing inorganic compounds and substances such as nitrogen and phosphorus. This step often involves chemical processes to achieve these goals.

3. **Conclusion**:
- Since the question asks about the step in sewage treatment where a chemical process is carried out, the correct answer is **tertiary treatment**.

### Final Answer:
The chemical process is carried out in the **tertiary treatment** step of sewage water treatment.

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