The removal of color from water supplies using alum, polymers, and alum-polymer combinations is described. Humic acid was used as the natural color colloid and the results indicate that: (1)Alum alone requires relatively high dosages; (2)low molecular weight cationic polyelectrolytes used alone chemically interact with humic acid, and (3)alum combined with high molecular weight polymers is an effective coagulation process. Stoichiometry between the raw water humic acid concentration and the optimum coagulant dosage is reviewed. Experimental results are used to examine the stability of humic acid and mechanisms of particle destabilization.