Investigation of the effective factors on the mutagen X formation in drinking water by response surface methodology

Abstract

Mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) is known as a potent factor in inducing DNA damage and increasing cancer risk. MX is a chlorination disinfection byproduct that comes from the reaction of humic acids and chlorine in drinking water. The purpose of this study was to evaluate the effects of significant factors (including pH, reaction time, chlorine and the concentration of organic materials (TOC)) and their interactions on the MX formation rate in chlorinated drinking water using Box-Behnken Design (BBD) and response surface method (RSM). For this purpose, the simulation of water chlorination disinfection process was carried out in a laboratory scale. A quadratic model was chosen to determine the mathematical relations between the response and the effective factors. All linear parameters, as well as second-degree components except chlorine, were statistically significant. Also, the interactions of contact time with TOC, free chlorine residual with TOC, and chlorine with pH were also statistically significant. Statistical results showed that the pH had a great effect on the potential of MX formation, and then the factors of TOC, chlorine and contact time were effective, respectively. The percentage of contribution (PC) of each component in the formation of MX. The highest significant percentage of contribution (48.36%) was allocated to the pH. Under the optimum conditions (contact time of 48.38 min, chlorine concentration of 0.79 mg/L, TOC concentration of 0.53 mg/L, and pH of 7.98), minimum value of MX was equal to 28.6.