"BOD must be low in fresh water"
a . Expand BOD.
b. Define BOD.
c. Write the importance of BOD.

Explanation

a. Biological Oxygen Demand.
b. This is the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidised by the microbes.
c. BOD is the measure of the orgainic matter present in water because BOD test measures the rate of uptake of oxygen by microbes in a sample water. The greater the BOD in sewage , more is its polluting potential.