Department of Applied Chemistry, Calcutta University Manuscript received 6 September 1973; revised 31 July 1974; accepted 23 September 1974 Alum-sludge (aging less than one hour) and fly-ash (aggregate less than 100 mesh) after treat­ment with sulphuric acid and phosphoric acid separately could be used as adjuncts to coagulation in Municipal Water treatment. Those were found to be efficient in reducing the actual alum re­quirement. Sulphuric acid treated sludge was proved to be most effective adjunct, specially in the higher turbidity range. These also possessed the capability of diminishing the coliform count in supply water and initiated flocculation of both phyto and zooplanktons usually present in river water.