Question

The value of dissolved oxygen in polluted water is:

• A. $>4$ ppm
• B. $<4$ ppm
• C. $=4$ ppm
• D. $=6$ ppm

Answer 1

The correct option is A $>4$ ppm

The amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water is called Biochemical Oxygen Demand.

Clean water has less than 5 ppm BOD value, whereas, highly polluted water has a BOD value of 17 ppm or more.

Thus, the correct answer is option A.