Biochemical Oxygen Demand (BOD) may not be a good index for pollution for water bodies receving effiuents from

Options

A. domestic sewage
B. dairy industry
C. petroleum industry
D. sugar industry

Answer

### Step-by-Step Solution:

1. **Understanding Biochemical Oxygen Demand (BOD)**:
- BOD is a measure of the amount of oxygen that microorganisms will consume while decomposing organic matter in water. It is often used as an indicator of the organic pollution level in water bodies.

2. **Identifying Sources of Pollution**:
- Different industries discharge various types of effluents into water bodies. The question asks which type of effluent may not significantly affect BOD.

3. **Analyzing Each Option**:
- **Domestic Sewers**: Typically contain organic matter and nutrients (like nitrogen and phosphorus) that can increase BOD due to microbial activity.
- **Dairy Industry**: Also releases organic waste that can increase BOD due to the presence of lactose and other organic compounds.
- **Sugar Industry**: Discharges organic effluents that can lead to increased BOD due to the high sugar content.
- **Petroleum Industry**: Releases effluents that are often rich in hydrocarbons and toxic substances. These do not promote algal growth and do not contribute to an increase in BOD.

4. **Conclusion**:
- Among the options provided, the **Petroleum Industry** is the one that does not significantly affect BOD because its waste does not support microbial growth or algal blooms, which are the primary contributors to increased BOD levels.

5. **Final Answer**:
- Therefore, the correct answer is **Petroleum Industry** (Option 3).