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The domestic sewage in large cities
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- has a high BOD as it contains both aerobic and anaerobic bacteria.
- is processed by aerobic and then anaerobic bacteria in the secondary treatment in Sewage Treatment Plants (STPs).
- when treated in STPs does not really require the aeration step as the sewage contains adequate oxygen.
- has very high amounts of suspended solids and dissolved salts.
Correct Option: B
Sewage treatment is the process of removing contaminants from wastewater and household sewage, both runoff (effluents) and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants. Sewage treatment generally involves three stages, called primary, secondary and tertiary treatment. It is processed by aerobic and then anaerobic bacteria in the secondary treatment in Sewage Treatment Plants (STPs).
