Question no 6
Please find below the solution to the asked query
Biochemical Oxygen demand or BOD is the amount of dissolved oxygen needed in a water body by aerobic microorganisms usually bacteria to decompose biodegradable organic matter present in the water body for certain temperature and time period.
BOD of a polluted water body is high than a clean water body as their will be more waste in polluted water body. So, increase in organic waste leads to increased BOD level and decreased dissolved oxygen. More oxygen will be required by the aerobic microorganism to decompose it as compared to a clean water body. BOD and dissolved oxygen (DO) are inversely related to each other because as the BOD increases, the DO will be utilised in the decomposition and thus it will decrease and if BOD decreases, there will be less requirement of oxygen for decomposition and the DO will increase as more oxygen will be available to aquatic plants and animals
Hope this information will clear your doubts about the topic.