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Artificial Sewage Treatemnt

Sewage Treatment

Sewage Treatment

The artificial sewage treatment ( Waste water treatment ) process, called sewerage, involves the following steps :

(1) Preliminary process causes removal of large and coarse solids, inorganic matter—suspended or floating in the sewage. This involves in passing the waste water ( sewage ) through bar screens (to remove large suspended and floating matter) and mesh screens (to remove coarse solids, gravels, silt, etc.).

(2) Settlement process removes grearer proportion of the suspended inorganic and organic solids from the liquid sewage. For this ‘continuous flow type’ sedimentation tanks are employed. Chemical treatment is ‘sometimes’ given to sewage just prior to sedimentation. This results in more rapid and complete removal of suspended matter. The chemicals employed are alum, ferrous sulphate, etc. These produce large gelatinous flocs, which entraps finely divided organic matter and settles rapidly.

Al2(SO4)3 6H20 ——— 2Al(OH)34, 3H2SO4 (at pH>5)


The chief value of adding chemical co-agulant is its ability to remove colloidal material.