compositions , methods and kits for purifying and clarifying and / or nutrifying contaminated drinking water and which comprise a primary coagulant material , a microbiocidal disinfectant and an oxidant system . highly preferred compositions also contain one or more of a bridging flocculent material , the levels and ratios of coagulant to flocculent preferably falling within certain ranges , a cationic coagulant aid , especially chitosan , a water - soluble alkali , a water - insoluble silicate , and a food additive or nutrient source . the purified water remains free of discoloration for extended periods of storage .