Waste water can be passed into rivers after

Options

A. Primary treatment
B. Secondary treatment
C. tertiary treatment
D. both 1 and 2

Answer

### Step-by-Step Solution:

1. **Understanding Wastewater Treatment**: Wastewater treatment is a process aimed at removing contaminants from sewage and industrial wastewater to make it safe for release into the environment.

2. **Identifying Treatment Stages**: There are three main stages of wastewater treatment:
- **Primary Treatment**: This involves the physical removal of solid waste. Wastewater is held in a tank where heavier solids settle at the bottom, and lighter materials float to the surface. The settled sludge is then removed.
- **Secondary Treatment**: This is a biological process that further reduces the organic content of the wastewater. Microorganisms are used to decompose organic matter into carbon dioxide, water, and energy. This stage often involves aeration and filtration.
- **Tertiary Treatment**: This is the final stage where remaining contaminants, such as phosphates and nitrates, are removed. This may involve advanced filtration methods, including activated carbon and sand.

3. **Determining the Necessary Treatments Before Discharge**:
- Wastewater must undergo at least **primary treatment** to remove large solids.
- Following this, it must undergo **secondary treatment** to further reduce organic matter and ensure that the water is safe for discharge.
- Tertiary treatment is optional and only performed if further purification is necessary.

4. **Conclusion**: Therefore, wastewater can be safely passed into rivers after completing both primary and secondary treatments. Tertiary treatment is not always required unless additional purification is needed.

5. **Final Answer**: The correct answer is **both 1 and 2** (Primary and Secondary Treatment).