Sewage purification is performed by

Options

A. Microbes
B. Fertilizers
C. Antibiotics
D. Antiseptics

Answer

**Step-by-Step Solution:**

1. **Understanding Sewage Purification**: Sewage purification is a process aimed at cleaning wastewater to make it safe for discharge into the environment or for reuse. This process involves the removal of contaminants from sewage.

2. **Identifying the Methods of Sewage Treatment**: Sewage treatment typically occurs in three main stages: primary, secondary, and tertiary treatment. Each stage has a specific role in the purification process.

3. **Primary Treatment**: This initial stage involves the physical separation of solids from the sewage. Large solids are removed through screening and sedimentation.

4. **Secondary Treatment**: This stage focuses on the biological treatment of sewage. It primarily involves the use of microorganisms to break down organic matter. The key here is that aerobic bacteria are commonly used, as they require oxygen to thrive.

5. **Role of Microorganisms**: In secondary treatment, microorganisms consume the organic matter present in sewage, such as sugars and fats. This process can occur in two systems:
- **Fixed Film System**: Bacteria grow on filters, and sewage water passes through these filters.
- **Suspended Growth System**: Activated sludge is mixed directly with sewage, allowing bacteria to decompose the organic material.

6. **Aeration**: To facilitate the growth of aerobic bacteria, the sewage is often mixed with air. This aeration process is crucial as it provides the necessary oxygen for the microorganisms to function effectively.

7. **Tertiary Treatment**: Although not detailed in the transcript, this final stage typically involves additional filtration and disinfection processes to remove any remaining contaminants and pathogens from the treated water.

8. **Conclusion**: Therefore, sewage purification is primarily performed by microorganisms, specifically aerobic bacteria, during the secondary treatment phase of sewage treatment.

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