The primary treatement of wastewater involves the removal of

Options

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

Answer

B

Explanation

Primary or physical treatment is the process of removal of small and large, floating and suspended solids from sewage through two processes of filtration and sedimentation. First floating and suspended matter is removal through sequential filtration with progressively smaller pore filters. the filrate is then kept in large opne settling tanks where grit (sand, small pebbles) settles down. Aluminium or iron sulphate is added in certain places for flocculation and settling down of solids. The sediment is called primary sludge while the supernatant is called effluent.