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What are the various constituents of dom...

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

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Domestic sewage contains four kind of impurities :
(i) Suspended solids : They are soil particles such as sand and silt.
(ii) Colloidal particles : They are inorganic and organic materials such as faecal matter, bacteria, paper and cloth.
(iii) Dissolved solids : They are nitrates, phosphates, ammonia, sodium, calcium and other nutrients.
(iv) Pathogens: Domestic sewage has pathogens of various diseases such as typhoid, cholera, dysentery, diarrhoea, etc. Effect of sewage discharge on river are :
(a) Eutrophication. (b) Growth of pathogenic bacteria. (c) Ageing of river where silt and decaying
matters start accumulating and filling river. (d) Increase in BOD. (e) Destruction of flora and fauna of that river.
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