What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on river.

Explanation

Effect of sewage discharge on river are
(i) A sharp decline in dissolved oxygen and increase in BOD. Low oxygen levels in the water cause death of fish and other aquatic creatures
(ii) Algal bloom which results from the presence of organic matter in wate. It causes
(a) deterioration of the water quality.
(b) fish mortality.
(c) toxicity to humans and animasl.
(iii) Biological magnification of a few toxic substances, as DDT causing harmful effects in living species.
(iv) Accelerated eutrophication, i.e. ageing of lakes and other water bodies due to human activites.