Cationic polyelectrolytes comprise a large group of chemicals designed to react with and flocculate suspended solids. Their primary use is as water clarification aids in the removal of suspended solids from water supplies and from industrial and domestic effluents entering receiving waters. Many of these water-soluble macromolecules exhibit an acute toxicity to aquatic organisms of less than 1.0 mg/L. The interaction of residual amounts of these polymers in receiving waters is unclear. The effects of suspended solids (bentonite, illite, kaolin and silica) and of dissolved organic carbon compounds (humic, fulvic and tannic acids, lignin and lignosite) on the acute toxicities of four cationic water clarification aids to the fathead minnow (Pimephales promelas) and a cladoceran (Daphnia magna) were determined. Bentonite and all of the dissolved organic carbon compounds reduced the toxicities of the polymers by one to two orders of magnitude. The remaining suspended solids had a lesser effect in reducing toxicity.
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Cary et al. (1987) studied this question.