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 the physical removal of both larger and smaller particles (stable particles) from the sewage with the help of filtration and sedimentation. These removals occur in the following stages: (i) Initially, floating debris is removed by sequential filtration. (ii) After that grit (made of soil and small pebbles) are removed by sedimentation. All these solids particles that settled 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, toxic substances and harmful bacteria.