Sewage Management.

Explanation

(i) In villages , domestic sewage is disposed off either in nearby soil or in biogas plant.
In cities sewage is carried to processing unit for microbial action.
(iii) Microbes are mixed with sewage to decompse compounds as well as pathogens.
(iv) They release Methane and `CO_(2)` by decomposition of carbon compounds present in sewage.
(v) Phenol oxidising bacteria decompose the xenobiotic chemicals present in sewage.
(vi) The sludge that settles down in this process can again be used as fertilizer.
(vii) Water released after microbial treatment is environmentally safe.
(viii) Microbes are used for bioremediation of environment polluted due to sewage.