BOD values of three water samples A, B and C were recorded as 20 mg/L, 10 mg/L and 50 mg/L. Which of the sample is/are the most polluted?

C

The correct answer is Option (4) → C

Biochemical Oxygen Demand (BOD) is a measure of the amount of oxygen that microorganisms require to decompose the organic matter present in water. It is an indicator of the level of pollution in water. The higher the BOD value, the more polluted the water is, as it indicates a high level of organic waste that requires a greater amount of oxygen for decomposition.

Given the BOD values of the three water samples:

• Sample A: 20 mg/L
• Sample B: 10 mg/L
• Sample C: 50 mg/L

Analysis:

• Sample C has the highest BOD value (50 mg/L), indicating that it is the most polluted among the three samples.
• Higher BOD means more organic matter is present, leading to more microbial activity and greater consumption of dissolved oxygen in the water.

So, Sample C is the most polluted water sample based on its BOD value.