Removing Trihalomethane Precursors by Coagulation

The removal of trihalomethane precursors by coagulation was studied with low turbidity, low alkalinity waters containing high levels of aquatic humic matter. Jar tests were conducted with synthetic and natural waters using alum, high‐molecular‐weight polymers, cationic polymers, and various combinations of these coagulants. Cationic polymers alone were found to be less effective than alum in the coagulation of humic substances. High‐molecular‐weight polymers used as coagulant aids with alum improved turbidity removal but not precursor removal, whereas high‐charge‐density cationic polymers with alum as a coagulant aid provided good precursor removals at low alum dosages.