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ICSE Class 9 Answered

What happens during primary treatment in effluent treatment plants?
Asked by Topperlearning User | 04 Jun, 2014, 01:23: PM
answered-by-expert Expert Answer

(1) In primary treatment, waste water is first passed through bar screens, where large objects like sticks, plastic packets and cans are removed. The waste water is passed through a grit chamber to remove sand.

(2) The sewage is then held temporarily in a sedimentation tank, where large, heavy solids, faeces settle at the bottom by sedimentation. The debris that settles at the bottom is called sludge.

(3) Oil, grease, soaps, plastics and other lighter solids float over the surface. The light floatable waste that rises to the top is called scum. The scum is removed with a skimmer.

(4) Once settled and floating materials are removed, the remaining liquid moves to the secondary treatment process.

Answered by | 04 Jun, 2014, 03:23: PM
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