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12th Biology 2016 Set1 Delhi Board Paper Solution

Question 8

List the events that reduce the Biological Oxygen Demand (BOD) of a primarty effluent during sewage treatment.

Answer

The events that reduce the BOD of a primarty effluent are:

 Primary effluent is passed into large aeration tanks where it is mechanically agitated and air is pumped into it.  Mechanical agitation of primary effluent leads to growth of aerobic microbes which reduce the BOD.