Effect of Common Ions in Natural Water on the Generation of Trihalomethanes by Chlorination

Abstract In the present study, the effect of common ions, such as Br-, NH4+, Na+, K+, Ca2+, Mg2+, Fe3+ and Al3+ in natural water on the generation of THMs in the process of chlorination has been investigated. The effect of Br- and NH4+ was significant while in the case of Na+ and K+ was not significant. Furthermore, divalent metal ions (Ca2+, Mg2+) and trivalent metal ions (Fe3+ and Al3+) have the ability to form complexes with humic acids. Thus, the trend of THMs generation was complicated in different conditions. It can be seen that Ca2+ ions had little effect on the formation of THMs. In contrast, the effect of Mg2+ was more obviously, showing a trend of decreasing first and then increasing. The effect of Fe3+ and Al3+ on THMs was similar to that of Mg2+, the concentration of THMs also showed a trend of decreasing firstly and then increasing.