Factors affecting formation of haloacetonitriles and haloketones during chlorination/monochloramination of Jinlan Reservoir water

Formations of haloacetonitriles (HANs) and haloketones (HKs) from chlorination and chloramination from Jinlan Reservoir water under different treatment conditions were investigated in this study. Results showed that monochloramine rather than chlorine produced significant lower concentrations of HANs and HKs. In chlorination, the formation of HANs and HKs increased with the reaction time and chlorine dose. Addition of bromide significantly enhanced the total HANs yields but reduced total HKs formation due to the unavailability of bromine-containing HKs. HANs yields increased as the temperature was raised, yet HKs yields increased first and decreased later with temperature. As for the influence of pH, the HKs yields generally increased as the pH decreased, yet no obvious pattern was observed for HANs formation. On the other hand, in monochloramination, the yields of HANs and HKs generally increased with reaction time, temperature and the monochloramine dose. Higher HANs and HKs yields formed at low pH, and the addition of bromide significantly increased the total HANs yields. Range analysis further revealed that avoiding the bromide contamination, lowering the chlorine/monochloramine dose as well as reducing the reaction time were the effective ways to control HANs and HKs formation for drinking water sourced from Jinlan Reservoir water.