Which of the following can be used to disinfect the clean water in a sewage treatment plant before releasing it into the distribution system?
A. Iodine B. Ozone C.Oxygen D. Chlorine

Options

A. A and B
B. B and C
C. B and D
D. only D

Answer

To determine which of the following can be used to disinfect clean water in a sewage treatment plant before it is released into the distribution system, we need to analyze each option based on their properties and effectiveness as disinfectants.

### Step-by-Step Solution:

1. **Understanding Disinfection**:
- Disinfection is the process of removing or killing pathogens (harmful microorganisms) in water to make it safe for distribution.

2. **Analyzing Option A: Iodine**:
- Iodine is known as an antiseptic, but it is not effective for disinfecting large volumes of water. It is primarily used for topical applications and is not suitable for water treatment on a large scale.
- **Conclusion**: Iodine is not a suitable disinfectant for water. (Incorrect)

3. **Analyzing Option B: Ozone**:
- Ozone (O3) has strong germicidal properties and can effectively kill bacteria, viruses, and protozoa. It reacts rapidly with these pathogens, making it a powerful disinfectant.
- **Conclusion**: Ozone can be used to disinfect water. (Correct)

4. **Analyzing Option C: Oxygen**:
- Oxygen (O2) is essential for life but does not possess any germicidal properties. It does not kill pathogens and is not used for disinfection purposes.
- **Conclusion**: Oxygen is not a disinfectant. (Incorrect)

5. **Analyzing Option D: Chlorine**:
- Chlorine (Cl2) is a well-known disinfectant used in water treatment. It effectively removes pathogens and helps control odors and other impurities in water. It also prevents septicity, which is the condition caused by microorganisms consuming oxygen in water.
- **Conclusion**: Chlorine can be used to disinfect water. (Correct)

6. **Final Conclusion**:
- Based on the analysis, both Ozone (Option B) and Chlorine (Option D) can be used to disinfect clean water in a sewage treatment plant before it is released into the distribution system.

### Answer:
**B. Ozone and D. Chlorine can be used to disinfect the clean water in a sewage treatment plant.**

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