Water pollution is less if `BOD` is

Options

A. less than 5 ppm
B. less than 15 ppm
C. less than 50 ppm
D. less than 100 ppm

Answer

To determine the relationship between BOD (Biochemical Oxygen Demand) and water pollution, follow these steps:

### Step 1: Understand BOD
BOD stands for Biochemical Oxygen Demand. It measures the amount of oxygen that microorganisms will consume while decomposing organic matter in water. A higher BOD indicates a higher level of organic pollution.

**Hint:** Remember that BOD is a measure of the organic matter present in water and its effect on oxygen levels.

### Step 2: Analyze the Effect of BOD on Water Quality
When the BOD value is high, it means that there is a lot of organic matter in the water. This leads to increased oxygen consumption by bacteria and other microorganisms, resulting in lower levels of dissolved oxygen.

**Hint:** Think about how oxygen levels relate to the health of aquatic ecosystems.

### Step 3: Determine the Implication of BOD Levels
If BOD is low (for example, less than 5 ppm), it indicates that there is less organic matter present. This means that the water is cleaner and less polluted, as there is sufficient dissolved oxygen for aquatic life.

**Hint:** Associate low BOD with better water quality and higher purity.

### Step 4: Conclude the Relationship
Therefore, we can conclude that water pollution is less if BOD is low. Specifically, if BOD is less than 5 ppm, the water is considered to be pure and less polluted.

**Hint:** Remember the threshold of 5 ppm for BOD when assessing water quality.

### Final Answer
Water pollution is less if BOD is less than 5 ppm.