Prediction of brominated disinfection byproducts in chlorinated drinking water in Japan using data on trihalomethanes and chlorinated disinfection byproducts.

The occurrence of 20 disinfection byproducts (DBPs) in four DBP classes was investigated in chlorinated drinking water across Japan during four sampling campaigns (October 2021-July 2022). The four DBP classes were trihalomethanes (THMs), haloacetic acids (HAAs), dihaloacetonitriles (DHANs), and trihaloacetaldehydes (THALs). The total DBP concentrations in drinking water from 20 drinking water treatment plants (DWTPs), excluding one where only HAAs were analyzed, ranged from 14.2 to 124.8 μg/L (median, 44.5 μg/L). The concentrations of DBPs in drinking water, except for dihaloacetic acids (DHAAs), were higher at higher water temperatures, and THMs were correlated with other DBPs (trihaloacetic acids, DHANs, and THALs). In contrast, DHAA concentrations at some DWTPs were lower at higher water temperatures, likely because of DHAA decrease in distribution systems. For such DWTPs, the DHAA decrease was observed at water temperatures above approximately 10 °C when chlorine levels were approximately 0.3 mg Cl/L. At higher water temperatures, the DHAA decrease was also observed at higher chlorine levels. The bromine substitution factor for THMs in drinking water correlated with those for other DBPs, including DHAAs. The equations for the prediction of monobrominated DBP species in drinking water were constructed using THMs and the corresponding chlorinated DBP species of their monobrominated ones. These equations were applied to estimate monobrominated DBP concentrations in nationwide drinking water in Japan using DBP data from the Water Supply Statistics database by the Japan Water Works Association.