In domestic sewage, impurities in the form of suspended solids, colloidal materials and dissolved materials, are about

Options

A. ` 0.1 %`
B. ` 2.1`
C. ` 5.0 %`
D. ` 10.0 %`

Answer

**Step-by-Step Solution:**

1. **Understanding Domestic Sewage Composition**: Domestic sewage contains various impurities, which can be categorized into suspended solids, colloidal materials, and dissolved materials.

2. **Identifying the Types of Impurities**:
- **Suspended Solids**: These are large particles that do not dissolve in water and can be physically removed.
- **Colloidal Materials**: These are smaller particles that remain suspended in water and can be broken down by microorganisms.
- **Dissolved Materials**: These are substances that have dissolved in water and can also be decomposed by microbes.

3. **Percentage of Impurities**: The video mentions that the total impurities in domestic sewage are approximately 0.1%. This indicates that the majority of the sewage consists of water and other non-impurities.

4. **Biodegradability of Impurities**: The impurities in sewage are mostly organic, and non-biodegradable materials (like plastics) are first removed during treatment processes because microbes cannot decompose them.

5. **Treatment Processes**:
- **Primary Treatment**: Involves anaerobic bacteria that function without oxygen to break down organic matter.
- **Secondary Treatment**: Involves aerobic bacteria that require oxygen to further reduce the organic content.

6. **Conclusion**: Based on the information provided, the correct answer regarding the percentage of impurities in domestic sewage is 0.1%.

**Final Answer**: The impurities in domestic sewage, in the form of suspended solids, colloidal materials, and dissolved materials, are about 0.1%.

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