REGRESSION EQUATIONS FOR DISINFECTION BY-PRODUCTS FOR THE MISSISSIPPI, OHIO AND MISSOURI RIVERS

Trihalomethane and nonpurgeable total organic-halide formation potenti als were determined for the chlorination of water samples from the Mis sissippi, Ohio and Missouri Rivers. Samples were collected during the summer and fall of 1991 and the spring of 1992 at twelve locations on the Mississippi from New Orleans to Minneapolis, and on the Ohio and M issouri 1.6 km upstream from their confluences with the Mississippi. F ormation potentials were determined as a function of pH, initial free- chlorine concentration, and reaction time. Multiple linear regression analysis of the data indicated that pH, reaction time, and the dissolv ed organic carbon concentration and/or the ultraviolet absorbance of t he water were the most significant variables. The initial free-chlorin e concentration had less significance and bromide concentration had li ttle or no significance. Analysis of combinations of the dissolved org anic carbon concentration and the ultraviolet absorbance indicated tha t use of the ultraviolet absorbance alone provided the best prediction of the experimental data. Regression coefficients for the variables w ere generally comparable to coefficients previously presented in the l iterature for waters from other parts of the United States.