Question

When huge amount of $C{O_2}$ ​ is dumped into a river, the BOD will
(A) Increase
(B) Slightly decrease
(C) Remain unchanged
(D) Decrease

Answer 1

Hint : BOD stands for Biological oxygen demand. It is a criterion that is used to determine the amount of dissolved oxygen in the water which is utilized by the different types of microorganisms that are present in water during the process of decomposition of organic matter.

Complete Step By Step Answer:
The presence of a minimum concentration of dissolved oxygen is very crucial to sustain the aquatic life and aesthetic quality of different types of water bodies. To determine how organic matter affects the concentration of oxygen (DO) in a stream or lake is very integral in the process of water- quality management. When the organic matter is decayed in these water bodies, it is measured as biochemical or chemical oxygen demand. It is the measure of the number of oxidizable substances that are present in a water sample that can lower DO concentrations.
There are some environmental and other human-induced factors like introduction of excess fertilizers and hot temperatures in the summer that can decrease the amount of dissolved oxygen in the water body, which further affects the local aquatic life. One way of analysing water which is used to have a deeper understanding of the effect of bacteria and other microorganisms on the amount of oxygen they consume when they decompose the organic matter under aerobic conditions. Hence, when a huge amount of $C{O_2}$ ​ is dumped into a river, the BOD does not get affected, it remains the same.
Therefore, option (C) is correct.

Note :
BOD is expressed in milligrams per litre of the sample and is used to find the degree of pollution in the water bodies. It is also used in treatment of sewage and wastewater treatment to kill and decay organic wastes with the help of the aerobic organisms.