Consider the following statements about, secondary sewage treatment
I. In secondary treatment useful aerobic microbes grow rapidly and form flocs. Flocs are masses of
bacteria associated with fungal filaments to form mesh-like structures.
II. The growing microbes consume organic matter and thus reduce the biochemical oxygen demand.
When BOD of sewage has reduced, the effluent is passed into settling tank.
III. In settling tank, the bacterial flocs settle and the sediment is called activated sludge.
IV. A small part of the sludge is used as an inoculum in the aeration tank and the remaining part is passed
into large tanks called anaerobic sludge digesters.
V. In the digesters, heterotrophic microbes anaerobically digest bacteria and fungi in sludge producing
mixture of gases such as, carbon dioxide nitrogen and carbon monoxide which form the biogas
Which of the statements given above are correct?
View solution