Question

Four students were assigned a science project to find out the pollution levels of lakes in their surrounding. After analysing the quality of water samples, the BOD values were found as follows :
Which among the following water samples is highly polluted ?

• A. 0.16 mg/L
• B. 0.6 mg/L
• C. 0.06 mg/L
• D. 6 mg/L

Answer 1

The Correct Option is D

BOD (Biochemical Oxygen Demand) is a measure of the amount of oxygen required by microorganisms to decompose the organic matter in a water sample. Higher BOD values indicate higher pollution levels because more oxygen is consumed to break down organic waste.

• 0.16 mg/L: This is a low BOD value, indicating less pollution and relatively clean water.
• 0.6 mg/L: This is still a moderate value, suggesting slightly polluted water.
• 0.06 mg/L: This is the lowest among the options, showing very low pollution levels.
• 6 mg/L: This is a very high BOD value, indicating that the water sample has a large amount of organic matter that is being decomposed by microorganisms, signifying high pollution levels.

Thus, the water sample with a BOD value of 6 mg/L is the most polluted among the given options.

The correct answer is (D) : 6 mg/L.

Answer 2

The correct answer is: (D) 6 mg/L.

The Biological Oxygen Demand (BOD) is a critical parameter in assessing water quality. It measures the amount of oxygen required by microorganisms to break down organic material in the water. The higher the BOD value, the greater the amount of organic matter present in the water, which in turn indicates higher levels of pollution.

In general, a BOD value of less than 3 mg/L is considered to indicate clean water, while values between 3-5 mg/L suggest moderate pollution. A value greater than 5 mg/L, such as 6 mg/L in this case, signals highly polluted water, as it indicates that a significant amount of oxygen is being consumed by microorganisms to decompose the organic pollutants.

Thus, the sample with a BOD of 6 mg/L is highly polluted compared to the others, which suggests that it has a higher concentration of biodegradable organic matter.