Question

Which one of the following statements is not true?

• A. Clean water should have a BOD value of less than 5 ppm.
• B. Concentration of the DO below 6 ppm is good for the growth of fishes
• C. pH of the drinking water should be between 5.5−9.5
• D. Oxides of sulphur, nitrogen, and carbon are the most widespread air pollutants.

Answer 1

The correct option is C pH of the drinking water should be between 5.5−9.5

The ideal pH of drinking water should be in the range of 6.5−8.5 , preferably less than 8. Natural waters can often have pH in the acidic range as a result of the acidic rain. Hence, this statement cannot be true.
While bottom feeders, crabs, oysters, and worms, require a minimum dissolved oxygen level of 1 - 6 ppm, shallow water fishes need a higher level in the range of 4 - 15 ppm. So, 6 ppm and below is acceptable for certain conditions, hence the statement is correct.
The Biological oxygen Demand of clean water should be 4-5 parts per million hence this is an acceptable value for clean water.
The major pollutants that are emitted from industrial smokes, vehicle emissions, volcanic eruptions, etc. are all Oxides of sulphur, nitrogen, and carbon. Hence this statement is true.
Therefore, the correct option is option A.