Question

Arrange the following options in ascending order of their BOD value:
(I) sample of highly polluted pond water (II) sample of unpolluted pond water (III) distilled water

• A. III - I - II
• B. II - III - I
• C. III - II - I
• D. I - III - II

Answer 1

The correct option is C III - II - I

Biochemical Oxygen Demand is a measure of the quantity of oxygen used by microorganisms (e.g., aerobic bacteria) in the oxidation of organic matter. So the higher the degree of pollution, greater is the requirement of oxygen by microorganisms for decomposition. So, highly polluted water has maximum BOD and distilled water has least BOD, as the latter does not contain microorganisms.