Question

Which of the following in sewage treatment removes suspended solids?

• A. Tertiary treatment
• B. Secondary treatment
• C. Primary treatment
• D. Sludge treatment

Answer 1

Answer: (C)

Primary treatment is a physical process which involves sequential filtration and sedimentation. Suspended solids are removed in stages; initially, floating debris is removed by sequential filtration. Then the grit (soil and small pebbles) are removed by sedimentation. All solids that settle form the primary sludge and the supernatant forms the effluent. The effluent from the primary settling tank is taken for secondary treatment.