Index >> Waste Water Microbiology >> Screeing and Straining

Screeing and Straining - The first stage of preliminary treatment process involves screening or straining to remove large solids. Coarse screens with openings of about 75mm are used to prevent large objects. Main screens are provided with openings of 5-20mm through which the incoming water passes.

To prevent overloading of the main screen with collected solids, the screen is slowly rotated so that the solids can be removed at regular intervals. In wastewater treatment, the high content of papers and rags in wastewater treatment makes it difficult to keep the mesh screen clean. Hence instead of mesh screens bar screen arrangements, with a spacing of 20-60mm between bars, are used.