A significant number of drinking water utilities that practice conventional watertreatment using aluminum sulfate (alum), fluoridate near the point of coagulationaddition. A study was conducted to evaluate the effect of fluoride onconventional drinking water treatment using alum. Bench-scale jar test,pilot-scale studies, and chemical equilibrium modeling were used. Data showedthat the presence of fluoride can negatively affect settled water quality (i.e.,increased particle counts, turbidity, and residual aluminum levels). The impactof fluoride was a function of pH and alum concentrations. Includes 12 references, tables, figures.