Which one of these is not a process involved in the purification of water at a water treatment plant?

Options

A. Eutrophication
B. Sedimentation
C. Chlorination
D. Filtration

Explanation

To determine which process is not involved in the purification of water at a water treatment plant, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understand the Options**: The options given are:
- Eutrophication
- Sedimentation
- Chlorination
- Filtration

2. **Analyze Eutrophication**:
- Eutrophication is a natural phenomenon where an excess of nutrients in a water body leads to excessive growth of algae. This process does not purify water; instead, it contributes to water pollution by depleting oxygen levels when the algae die. Therefore, eutrophication is not a process used in water treatment plants.

3. **Analyze Sedimentation**:
- Sedimentation is a process used in water treatment plants to remove solid particles from water. It involves allowing particles to settle at the bottom of a tank, which helps in clarifying the water. This is a common step in the purification process.

4. **Analyze Chlorination**:
- Chlorination is a chemical treatment process where chlorine is added to water to kill harmful microorganisms. This is an essential step in ensuring that the water is safe for consumption.

5. **Analyze Filtration**:
- Filtration is another critical process in water purification. It involves passing water through filters to remove impurities and suspended particles. This ensures that the water is clean and safe for use.

6. **Conclusion**:
- Based on the analysis, the only option that does not involve a purification process at a water treatment plant is **Eutrophication**.

### Final Answer:
**Eutrophication is not a process involved in the purification of water at a water treatment plant.**

---