How the biological oxygen demand gets affected with the increased presence of organic matter in water?

Options

A. The oxygen demand increases
B. The oxygen demand decreases
C. The oxygen demand remains unchanged
D. None of the above

Answer

### Step-by-Step Solution:

1. **Understanding Biological Oxygen Demand (BOD)**:
- Biological Oxygen Demand (BOD) is a measure of the amount of oxygen that microorganisms will consume while decomposing organic matter in water. It indicates the level of organic pollution in the water.

2. **Role of Microorganisms**:
- Microorganisms, particularly aerobic bacteria, play a crucial role in breaking down organic matter. They require oxygen to perform this decomposition process.

3. **Impact of Increased Organic Matter**:
- When there is an increase in organic matter in the water, it provides more food for these microorganisms. Consequently, they will need more oxygen to decompose this additional organic material.

4. **Oxygen Consumption**:
- As the microorganisms digest the organic matter, they consume dissolved oxygen present in the water. The more organic matter there is, the more oxygen is required for its decomposition.

5. **Conclusion on BOD**:
- Therefore, with an increase in organic matter, the BOD also increases. This means that the demand for oxygen rises because more oxygen is needed for the microorganisms to break down the larger quantity of organic matter.

6. **Final Answer**:
- The correct conclusion is that the oxygen demand increases with the increased presence of organic matter in water.