Zoology - Microbes in Human Welfare Question with Solution | TestHub
Given below are the steps involved in sewage treatment. Arrange them in proper sequence and select the correct option.
A. Passage of primary effluent into large aeration tanks for mechanical agitation and pumping of air.
B. Passage of secondary effluent and formation of activated sludge.
C. Physical removal of particles through filtration and sedimentation.
D. Release of effluent from the secondary treatment plant into natural water bodies.
E. Growth of useful aerobic microbes into flocs which significantly reduce the BOD.
Options:
Answer:
Solution:
The sequence of steps in sewage treatment is as follows:
Primary treatment: This involves the physical removal of all small and large particles from the sewage through filtration and sedimentation. The solids which settle form the primary sludge and the supernatant forms the effluent. The effluent then passes to large aeration tanks for secondary treatment.
Secondary treatment: This involves the following steps:
Constant mechanical agitation of effluent in aeration tank and pumping of air.
As a result, there is the growth of useful aerobic microbes into flocs which consume the majority of the oxygen in the effluent and significantly reduce the Biological Oxygen Demand (BOD).
Passage of effluent into settling tanks where sedimentation of bacterial flocs occurs. This sediment is called the activated sludge.
The effluent from the secondary treatment plant is released into natural water bodies.
