Question

BOD (biological oxygen demand) is
A. Amount of oxygen consumed by microorganisms for decaying organic matter per unit volume of water.
B. Amount of carbon dioxide consumed by microorganisms per unit of sewage water.
C. Amount of oxygen required by aquatic plants for survival
D. None of the above

Answer 1

Hint: Biological oxygen demand (BOD) refers to the amount of oxygen required for the complete process of decomposition of organic matter present in the water body by the decomposing bacteria. More the organic matter or mass, the higher will be the BOD and more will be the level of pollution in that water body. As more and more oxygen will be consumed, the aquatic animals present like fishes will die due to hypoxia. Their dead bodies will further enhance the organic matter or mass.

Complete answer:
Biochemical oxygen demand (BOD) displays the amount of oxygen consumed by bacteria along with other microorganisms while they decompose on organic mass and matter under aerobic conditions at a defined temperature.
When you look at a water body such as a lake the one main thing you don't see is oxygen present in the body. In a way, we think that water is the opposite of air, but the common water bodies such as lakes or streams do contain small amounts of oxygen, which is in the form of.

Hence, the correct answer is option A - 'Amount of oxygen consumed by microorganisms for decaying organic matter per unit volume of water'.

Note: The waste organic mass or matter is stabilized or can be said as made un-objectionable through its decomposition by living bacterial organisms which need oxygen to complete the process. BOD is used, often in wastewater-treatment plants too, it displays the degree of organic pollution in water.