In a sewage treatment plant, primary treatment is

Options

A. Physical process which involves sedimentation only
B. Physical process which involves both filtration any sedimentation
C. Biological process which involves formations of primary sludge and effluent
D. Biological process which involves both filtration and sedimentation

Answer

**Step-by-Step Solution:**

1. **Understanding Sewage Treatment**: Sewage treatment is a process designed to remove contaminants from wastewater, primarily from household, industrial, or municipal sources.

2. **Identifying Primary Treatment**: The primary treatment of sewage involves physical processes aimed at removing solid waste from the sewage. This is crucial as it prepares the sewage for further treatment.

3. **Processes Involved in Primary Treatment**:
- **Filtration**: This process involves passing sewage through a sieve or mesh to remove larger debris and solid particles. The debris collected during this step is a mixture of organic and inorganic materials.
- **Sedimentation**: After filtration, the sewage undergoes sedimentation. In this process, heavier solid particles settle at the bottom of the treatment tank due to gravity, forming what is known as primary sludge. Meanwhile, lighter materials, such as oils and greases, float to the surface, forming a scum layer.

4. **Distinguishing Primary from Secondary Treatment**: It is important to note that biological processes, which involve the use of microorganisms to break down organic matter, are part of secondary treatment and not primary treatment.

5. **Conclusion**: Therefore, the primary treatment in a sewage treatment plant is primarily focused on the physical removal of solids through filtration and sedimentation.

**Final Answer**: In a sewage treatment plant, primary treatment is the physical removal of solids through filtration and sedimentation.

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