Question

Write a descriptive note on BOD.

Hint:

Recall that BOD is the oxygen used by microbes to break down organic waste over five days.

Answer 1

Understanding the Question:
BOD stands for Biochemical Oxygen Demand, a measure used to judge how polluted a water sample is with organic waste.

Detailed Explanation:
BOD is defined as the amount of oxygen, in milligrams per litre, that microorganisms use up while decomposing the organic matter present in a water sample over five days at 20 degrees Celsius.
Clean water has a low BOD because it contains little organic matter for microbes to break down, so little oxygen gets consumed.
Water polluted with sewage or industrial organic waste has a high BOD, because a large population of decomposer microbes uses up a lot of dissolved oxygen while digesting the extra organic load, leaving too little oxygen for fish and other aquatic life.
BOD is therefore routinely used as a simple, reliable indicator of the degree of organic pollution in a water body.

Final Answer:
BOD measures the oxygen consumed by microbes decomposing organic waste in water over five days, and a higher BOD value directly indicates heavier organic pollution.