Question

Write the full form of BOD.

Answer 1

Hint: It is related to water pollution. It is used for measuring the pollution level in the water body.

Complete answer:
The full form of BOD is Biological Oxygen Demand. BOD is the amount of dissolved oxygen required for biological oxidation of organic matter by aerobic microorganisms in a unit volume of water. BOD values are generally closer to the amount of oxidisable organic matter present in water and therefore, BOD is used as a measure of degree of water pollution and waste level.
The sufficient quantity of oxygen in water (Dissolved oxygen, DO) is important for the maintenance of the aquatic life and quality of water in water bodies.
Microorganisms living in water bodies use dissolved oxygen for oxidative degradation of the organic compounds. During this process they release energy which they use for their growth and reproduction. Number of microorganisms increases with increase in the amount of organic matter in water.
Addition of sewage and waste materials in water bodies results in a tremendous increase in the number of microorganisms, which in turn increases the consumption of oxygen. This results in the depletion in the oxygen levels in water. Thus, biological oxygen demand (BOD) in such water bodies will be more.
So, we can say that the more the BOD value the more will be the amount of organic matter in water. Thus, BOD values are useful for evaluation of water quality of a water body and for possible control measures of water pollution.

Note: The BOD value is expressed in milligrams of oxygen consumed per litre of water sample at 20 °C temperature. The incubation time in the BOD test is a minimum 5 days.