Domestic sewage of large cities

Options

A. has a high BOD as it contains both aerobic and anaerobic bacteria
B. is processed by aerobic and then anaerobic bacteria in the secondary treatment in Sewage Treatment Plants (STPs)
C. when treated in STPs does not really require the aeration step as the sewage contains adequate oxygen
D. has every high amounts of suspended solids and dissolved salts

Answer

B

Explanation

Sewage is waste water having food residue, animal and human excreta, detergents, discharges from commercial and industrial establishments. The domestic sewage is processed first by aerobic and then by anaerobic bacteria in secondary treatment in Sewage Treatment Plant (STPs) and then recycled for further use.