Primary treatment of sewage is

Options

A. Physical process
B. Biological process
C. Chemical process
D. Biochemical process

Answer

### Step-by-Step Solution:

1. **Understanding Sewage Treatment**: Sewage treatment involves a series of processes to remove contaminants from wastewater. It is typically divided into three main stages: primary, secondary, and tertiary treatment.

2. **Identifying Primary Treatment**: The question specifically asks about the primary treatment of sewage. This stage is focused on the initial removal of solid materials from sewage.

3. **Processes Involved in Primary Treatment**:
- The primary treatment is primarily a **physical process**.
- It involves two main methods: **filtration** and **sedimentation**.

4. **Filtration Process**:
- In the filtration process, sewage is passed through mesh wire screens.
- This step helps in removing floating debris and larger particles from the sewage.

5. **Sedimentation Process**:
- After filtration, the sewage undergoes sedimentation, where heavier particles such as soil and small pebbles settle at the bottom.
- The settled material is referred to as **primary sludge**.

6. **Output of Primary Treatment**:
- The liquid that remains after the sedimentation process is called **primary effluent** or **supernatant**.
- This primary effluent is then sent for secondary treatment, which involves biological processes.

7. **Conclusion**: Therefore, the primary treatment of sewage is classified as a **physical process**.

### Final Answer:
The primary treatment of sewage is a **physical process**.

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