Identification and formation regularity of haloacetic acids in the process of chlorine disinfection of tannin containing water

In order to investigate the formation regularity of haloacetic acids (HAAs) in the natural water chlorination process, disinfection experiments were carried out with tannin as natural organic matter (NOM) to simulate drinking water disinfection process. HAAs, reaction products of tannin and chlorine in water, were identified and quantified by gas chromatography-mass spectrometry. Results showed that the reactions of chlorine with tannin mainly produced dichloroacetic acid and trichloroacetic acid which are high risk carcinogens. During the first 2 h of the reaction, the generation of HAAs from the reaction of tannin and chlorine was rapid, but it presented to a certain decline afterward. The generated quantity of HAAs increased with the increase of water temperature, initial concentration of tannin and chlorine dosage, but decreased with the increase of solution pH. The concentration of Br-had great impacts on the production of HAAs. The production of HAAs in chlorination process can be controlled by decreasing chlorine dosage or increasing pH.