Question

BOD is a measure of
(a) Industrial waste passed into water bodies
(b) Amount of carbon monoxide combined with hemoglobin
(c) Extent of pollution with organic matter
(d) Amount of oxygen required by plants during the night

Answer 1

Hint: Biologically degradable substances in sewage that are measured in terms of oxygen consumed by the microorganisms in a given period of time.

Complete answer:
The biologically degradable substances in the sewage are measured by biological oxygen demand(BOD). The organic degradable substances are broken down by the microorganisms using oxygen. The amount of oxygen consumed by microorganisms is the measure of oxygen. if oxygen is consumed in a period of 5 days then BOD is 5. it forms an index for measuring the pollution load in the sewage.

Additional Information: - Some of the major Pollutants of water are domestic sewage and industrial effluents. In cities and towns, sewage is the major cause of water pollution.
- Those polluted water are directly released into freshwater rivers or into seas without any treatment.
- Domestic sewage primarily contains organic matter which is biodegradable and it is readily decomposed by microorganisms.
- The content of organic matter which is biodegradable available in the sewage is measured by biological oxygen demand. The oxygen consumed by microorganisms over a period of time is the measure for oxygen demand.
- These biodegradable microorganisms in water consume a lot of oxygen that results in the death of fishes and other aquatic animals
So, the correct answer is 'Industrial waste passed into water bodies'.

Note: One of the serious issues that lead to the death of many aquatic organisms is algal blooms. If the water has more nutrients it results in excessive growth of planktonic algae that impart green color to the water and reduce the quality of water.