EFFECT OF REACTION-TIME ON THE FORMATION OF DISINFECTION BY-PRODUCTS

The effect of reaction lime on the trihalomethane and nonpurgeable tot al organic-halide formation potentials was determined by chlorinating water samples from the Mississippi, Missouri, and Ohio Rivers. Samples were collected for three seasons at 12 locations on the Mississippi f rom Minneapolis, Minnesota, to New Orleans, Louisiana, and on the Miss ouri and Ohio 1.6 kilometers above their confluences with the Mississi ppi. Both types of compounds formed rapidly during the initial stages of the reaction-time period, with formation rates decreasing with time . The ratio of the nonpurgeable total organic-halide and trihalomethan e concentrations decreased with time, with the nonpurgeable total orga nic-halide compounds forming faster during the first stages of the tim e period and the trihalomethane compounds forming faster during the la tter stages of the time period. Variation with distance along the Miss issippi River of the formation rates approximately paralleled the vari ation of the dissolved organic carbon concentration, indicating that t he rates of formation, as well as the concentrations of the compounds formed, depended on the dissolved organic carbon concentration. (C) Pu blished by Elsevier Science Ltd.