Question

BOD refers to
A. The amount of oxygen consumed if all the organic matter in 1000ml of water were oxidized by bacteria
B. The amount of oxygen released when all the organic matter was consumed by bacteria in 1 litre of water
C. the oxygen required for bacteria to grow in 1 litre of effluent
D. the amount of oxygen released if all the organic matter in 1000ml of water were oxidized by bacteria

Answer 1

Hint: The amount of pollution is increasing day by day. We need some indicators to know the extent of pollution in both water and air. There are some physical quantities made to know this. Some of them being specific for water pollution determination like BOD and COD.

Complete answer:
BOD means biochemical oxygen demand. It is studied to know the growing pollution in marine areas.
It is defined as the amount of dissolved oxygen required by biological organisms to break down organic material present in 1000ml of the water sample. This occurs at a specified temperature and for a specified time.

> Option A: The amount of oxygen consumed if all the organic matter in 1000ml of water were oxidized by bacteria: The biological organisms consume oxygen in organic matter in 1000mlof water, this is called BOD.

> Option B: The amount of oxygen released when all the organic matter was consumed by bacteria in 1 litre of water: The amount of oxygen needed by an organism is included in the BOD, not the oxygen released by the bacteria.

> Option C: The oxygen required for bacteria to grow in 1 litre of effluent: It is the oxygen needed by bacteria to break down the organic matter, not to grow only in the effluent.

> Option D: the amount of oxygen released if all the organic matter in 1000ml of water were oxidized by bacteria: The amount of oxygen consumed matters, not the oxygen released.

Hence, the correct answer is option (A).

Note: This BOD test takes at least 3-4 days to be completed and show the results. The COD is a more efficient method to determine the pollution in the water. There is a range of BOD value for each water body like above 8mg/ml of value means the water body is highly polluted.