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Coagulation and flocculation is one of the most effective, economic and convenient method for raw water clarification. In recent times, different hydrolysing coagulants, particularly aluminium-based ones are in wide use. In the present study, different aluminium-based salts, polymer and coagulant aid were used to observe their effectiveness as well as side effects, if any. Turbidity was the prime criterion for clarification of the raw water; however, the potentially hazardous residual aluminium was also given due importance.
Poly-aluminium chloride (PACl) enhanced the performance of the potash alum when used in tandem, whereas bentonite powder used as coagulant aid proved ineffective in improving the performance of the potash alum with respect to the removal of the turbidity. PACl when used alone or in tandem with potash alum showed character significantly different from aluminium-based salts only, with respect to the criterion of residual aluminium.
Coagulation, flocculation, hydrolysing coagulants, residual aluminium, river water, turbidity
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