Sewage Treatment (brief introduction)

Sewage Treatment

Sewage, before disposed off either in river streams or on land, has to be treated, so as to make it safe.

Sewage has to be treated for the following reasons:

1. To prevent pollution of water into which the sewage is let off, as water may be used downstream for drinking water supply. This causes health hazard as sewage contains pathogenic bacteria.
2. To prevent offensive odor in the water if water is used for swimming, boating, etc., and to the people living near the water or land where sewage is disposed off as it causes health hazard.
3. To prevent destruction of fish and other aquatic life.
4. If sewage has to be disposed of on land, soil will become sewage sick after some time and cannot take any more sewage. 

Sewage treatment process

It can be classified into the following four categories:

1. Primary sedimentation
2. Primary treatment
3. Secondary or biological treatment
4. Final or tertiary treatment(Disinfection).