Question

Which of the following statements is not true?
A.pH of the drinking water should be between $5.5 - 9.5$ .
B.Concentration of the DO below 6 ppm is good for the growth of fishes
C.Clean water should have a BOD value of less than 5 ppm.
D.Oxides of sulphur, nitrogen, and carbon are the most widespread air pollutants.

Answer 1

Hint: Knowledge of different environmental aspects is needed to solve this question. DO is the amount of dissolved oxygen in water while BOD is the Biological Oxygen Demand. A safe water pH is regarded as neutral to slightly alkaline.

Complete step by step solution:
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.

Note:
The pH of the water is an important factor and if varied in higher amounts then the consumption of that water may cause serious side-effects. The dissolved oxygen is non-compound oxygen that is present in water and other fluids.