AWWA JAW10335

This article describes a pilot-plant system that was used to compare the effects of two predisinfection schemes, free chlorine and chloramines, on trihalomethane (THM) precursor (THMP) removal, THM formation, and microbial population control with a continuous-flow treatment system. The pilot-plant flow scheme consisted of two parallel water treatment trains that provided alum coagulation, sedimentation, filtration, and carbon adsorption. The Missouri River was the raw water source, and the two units were operated identically except for the predisinfection step. Ammonium sulfate and chlorine were applied to the inlet water in one unit, and chlorine was applied to the inlet water of the second unit. The following conclusions are made: both prechlorination procedures were equally effective in the removal and control of THMP; the chloramine procedure produced more consistent control of the standard plate count (SPC) organisms than did the free chlorine procedure; alum coagulation appeared to result in significant removal of THMP, but not THMs; and increases in THMP concentrations were observed in effluents of both units after prolonged operation. (Abstract also appears in Spanish) Includes 20 references, table, figures.