Direct filtation: polymer in backwash serves dual purpose

Direct filtration has been used as a viable alternative to complete, conventional treatment systems that employ flocculation–sedimentation prior to filtration where the raw water source is relatively unpolluted and is low in color and turbidity. By adding a polymer to the water to be used for filter backwashing, a reduction of the initial turbidity breakthrough period and peak can be obtained in addition to a much Improved settling–thickening rate for the backwash solids.