Organics, Polymers, and Performance in Direct Filtration

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Abstract
The effects of raw water quality, chemical variables, and physical filter variables on direct filtration performance are examined. Cationic polyelectrolytes as sole coagulants are effective in treating low turbidity, colored waters by direct filtration. The polymer dosage is related to the raw water concentration of dissolved organic carbon. Cationic polymers can remove approximately 40% of the TOC and THM precursors. Filtration rate, direct filtration mode (in‐line versus flocculation), and water temperature did not have a significant effect on removals. Greater removals were achieved by alum. Direct filtration with cationic polymers is a feasible method of treatment for waters containing 5 mg/L TOC or less. For waters containing relatively high concentrations of humic matter (color) or submicron size particles, direct filtration with a flocculation period produces less head loss development and longer filter runs. UV absorbance is an excellent surrogate parameter for monitoring the removals of TOC and T...