Humic substances as precursors for trihalomethanes yields upon chlorination

The role of humic substances (HSs) in the formation of trihalomethanes (THMs) through the chlorination process in drinking water purification plants was investigated. A series of batch experiments, under different experimental conditions (reaction time, levels of HSs, and pH) were designed. In addition, trihalomethanes formation potential (THMFP) was assessed. The results showed that the average concentration of total THMs formed was 7.63g/L. Chloroform was the main species of THMs, while bromoform was not generated during this study. Prolonging the reaction time with increasing HSs concentrations and alkaline pH resulted in increasing the total THMs formed. The contribution of humic acid to the THM precursor was greater than fulvic acid. Therefore, the complete removal of HSs, or at least optimizing the operating conditions, is recommended to minimize the formation of THMs.