Question

Which one of the following statement is not true ?

• A. Oxides of sulphur, nitorgen and carbon are the most widespread air pollutant
• B. $pH$ of drinking water should be between 5.5 - 9.5
• C. Concentration of $DO$ below 3 ppm is good for the growth of fish
• D. Clean water would have a BOD value of less than 5 ppm

Answer 1

The correct option is C Concentration of $DO$ below 3 ppm is good for the growth of fish

(a) There are various air pollutants, among them the most widespread air pollutants are oxides of sulphur such as $S{O}_2$ which is most serious air pollutant leading to formation of smog. Oxides of nitrogen such as nitric oxide, nitrogen dioxide leading to serious effects such as acid rain and oxides of carbon such as carbon monoxide.

(b) There are various water quality parameters and $pH$ is one of them. As per the standard for drinking water $pH$ of healthy drinking water should be between 5.5 - 9.5.

(c) Fish growth and activity usually require 5 - 6 ppm of dissolved oxygen (DO). Dissolved oxygen levels below 3 ppm are stressful to most aquatic organisms. Levels below 2 ppm will not support fish at all.

(d) BOD i.e., Biochemical oxygen demand is a parameter for estimating water pollution. For the clean water it is neccessary that BOD should be less than 5 ppm.