The primary treatement of wastewater involves the removal of

Options

A. dissolved impurities
B. stable particles
C. toxic substances
D. harmful bacteria

Answer

B

Explanation

The primary treatment of waste water involves physical removal of both larger and small particles (stable particles) from the sewage through filtration and sedmimentation. These are removed in stages, initially, floating debris is removed by sequential flitration. Then the grit (solid and small pebbles) are removed by sedimentation. All solids that settle form the primary sludge and the supernatant forms the effluent. The effluent is taken for the secondary treatment. The primary treatment does not remove the dissolved impurities (a), toxic substances (c) and harmful bacteria (d).