BOD and its relation to polluting potential of waste water

The Biochemical Oxygen Demand (BOD) is a measure of the amount of dissolved oxygen required by microorganisms to break down organic matter in water. It is commonly used as an indicator of the level of pollution in waste water. The higher the BOD value, the more organic matter is present in the water, indicating a higher level of pollution. Therefore, statement (a) is true.

Explanation:
1. Biochemical Oxygen Demand (BOD)
- BOD is a measure of the oxygen required by microorganisms to decompose organic matter in water.
- Organic matter in waste water comes from various sources such as sewage, agricultural runoff, and industrial discharges.
- The decomposition of organic matter by microorganisms consumes oxygen from the water.

2. BOD and pollution potential
- The BOD of waste water is directly related to its polluting potential.
- When waste water with a high BOD is discharged into a water body, the microorganisms present in the water consume a large amount of oxygen to break down the organic matter.
- This leads to a decreased concentration of dissolved oxygen in the water, which can have negative effects on aquatic organisms.
- In severe cases, the depletion of oxygen can result in the death of fish and other aquatic life forms.

3. Understanding the given statements
- Statement (a): "The greater the BOD of waste water more is its polluting potential."
- This statement is true. Higher BOD indicates a higher concentration of organic matter, which leads to a greater demand for oxygen during decomposition. Consequently, it increases the pollution potential of the waste water.

- Statement (b): "The greater the BOD of waste water less is its polluting potential."
- This statement is incorrect. It contradicts the relationship between BOD and pollution potential. Higher BOD indicates a higher pollution potential.

- Statement (c): "The lesser the BOD of waste water more is its polluting potential."
- This statement is incorrect. Lower BOD indicates a lower pollution potential as there is less organic matter to be decomposed.

- Statement (d): "The lesser the BOD of waste water less is its polluting potential."
- This statement is incorrect. It contradicts the relationship between BOD and pollution potential. Lower BOD indicates a lower pollution potential.

Conclusion:
The correct statement is (a): "The greater the BOD of waste water more is its polluting potential." Higher BOD values indicate a higher pollution potential due to the increased concentration of organic matter, leading to a greater demand for oxygen during decomposition.

Only a.