Question

Which is the correct ascending arrangement of BOD of sewage (S) distillery effluent (DE), paper mill effluent (PE) and sugar mill effluent (SE)?
A.SEB.PEC.SD.SE

Answer 1

Hint: BOD is the Biological Oxygen Demand that is created when there is an excessive quantity of organic matter in the water body as its decomposition is initiated by the decomposing bacteria which require oxygen for their metabolism (aerobic bacteria).

Complete step by step answer:
-BOD is directly proportional to the organic content of the effluent.The more the amount of organic waste, the higher will be the BOD, hence more will be pollution of the water body. Thus, the BOD of effluent is directly proportional to the amount of organic matter in that effluent
-Since an increased amount of organic matter is deleterious to the water quality, this causes an extreme reduction in the dissolved oxygen content of the water body and this suffocates the aquatic flora and fauna
-Distillery effluent is the richest in organic waste from the given list. It contains leftovers of alcoholic fermentation; hence it has the highest BOD.
-Sugar mill effluents follow the distillery effluents with respect to the concentration of organic content in it. The sewage water contains the excreta and detergents mixed with it.
Papermill effluent has the least concentration of the organic mass, hence it has the lowest BOD.

Hence option B is correct.

Note:
-In a sewage treatment plant, the BOD level decreases gradually along with the different steps of processing as the concentration and the amount of organic matter decreases
-The BOD of a water body is an effective indicator of the quality of it in terms of wildlife and chemical composition
-Nitrates and phosphates in a water body can contribute to high BOD levels. They are plant nutrients and they can cause plant life and algae to grow quickly.