Describe the role of Microbes in sewage treatment plant.

Explanation

a. The primary effluent is passed into large aeration tanks.
b. This allows vigorous growth of useful aerobic microbes into flocs.
(c) The growth of micorbes consumes the major part of the organic matter in the effluent.
This significantly reduces the BOD (biochemical oxygen demand) of the effluent.
d. BOD refers to the amount of oxygen required to oxidize total organic matter by bacteria, present in one liter of water.
e. BOD is the measures of the organic matter present in the water.
f. Greater the BOD of the waste water more is its polluting potential .
g. Once the BOD of sewage reduced significantly, the effluent is then passed into the settling tank where the bacterial flocs are allowed to sediment. This sediment is called activated sludge.
h. Small part of activated sludge is pumped back to aeration tank to serve as the inoculums.
(i) The remaining sludge is pumped into anaerobic sludge digester.
(j) In the anaerobic sludge digester there is other kinds of baceteria which grow anaerobically, digest the bacteria and fungi in the sludge.
k. During this digestion bacteria produce biogas, (mixture of methane, hydrogen sulphide and carbon dioxide).
(l) The effluent from the secondary treatment plant is released into natural water body like rivers and streams.