DURING the past few years there have been numerous published reports of water treatment difficulties that have been ascribed to the presence of synthetic detergents (1-5). These difficulties include, among others, interference with coagulation, rising floe, inability to remove turbidity, taste and odor production, and dramatic foaming. Howells and Sawyer (6) found that interference with color removal by alum coagulation does not occur with various anionic and nonionic surfaceactive agents (surfactants) in concentrations of 10 ppm or less. Smith, Cohen, and Walton (7) found that the surfactant component of synthetic detergents does not interfere with alum coagulation at concentrations of up to 20 ppm. Serious interference does occur, however, when as little as 1 ppm of polyphosphate is present. This interference can be overcome by increasing the alum dose, the amount necessary varying linearly with the concentration of polyphosphate. Howells and Sawyer (6) are in general agreement with these findings and with the use of color removal rather than turbidity as a measure of coagulation efficiency. This investigation is an extension of a previous work (7) to include the effects of synthetic-detergent components on coagulation with ferric sulfate and includes a detailed study of the removal of surfactants.
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