Approaches to Regulating Organic Carbon and the Necessity of Its Obligatory Monitoring in Drinking Water

Abstract

Background: Current accumulation of organogenic elements in surface waters is mainly attributed to intensive anthropogenic activities. Waterborne organic matter may endanger human health when using surface waters for drinking and recreational purposes. Applied techniques of water treatment fail to ensure complete water purification and part of organic substances (their low molecular weight fraction) still remains. Chlorination of drinking water can generate a variety of halogenated by-products having adverse health effects in humans including carcinogenic ones. Our objective was to substantiate the reference value for total organic carbon (TOC) in water disinfected by chlorine. Materials and methods: We analyzed the results of laboratory testing of surface and treated water samples taken in Yekaterinburg in 2013–2014 and 2017, carried out health risk assessment, and built predicative models of by-products formation. Results: We established that, following chlorination, TOC concentrations became 1.5 times lower while chloroform and total trihalomethane concentrations became 24.5–80.2 and 22.9–54.5 times higher than initial values, respectively. The most significant non-carcinogenic risks were estimated for children aged 0-6 years from exposures to chloroform (HQ = 1.150). Individual carcinogenic risks from exposures to bromoform and dibromochloromethane as measured in water before its supplying to the distribution system, referred to the first value range (less than 1×10–6) while risks from bromodichloromethane and chloroform exposures fell in the second range (from 1×10–6 to 1×10–4). The mathematical model of the correlation between predictors (temperature, reaction time, pH, and certain chemical compounds) and levels of by-products was built. Conclusions: Our model makes it possible to predict generation of organochlorine compounds at the design stage of water treatment technique. Total organic carbon is an important indicator that should be monitored at the stages of water treatment to ensure safety of drinking water and efficiency of its disinfection.