Real Time Monitoring of Disinfection By-Products in Chlorinated Waters by Using Absorbance and Fluorescence Indices

Abstract

This study explored the use of absorbance- and fluorescence based indices to monitor the formation of regulated and emerging disinfection by-products (DBPs) in chlorinated drinking water from different water systems located in Italy and United States. Several classes of DBPs, including trihalomethanes (THM), haloacetic acids (HAA), haloacetonitriles (HAN), halonitromethanes (HNM), chloral hydrate, were considered. The relationships between the formation of these DBPs and the changes in the absorbance or fluorescence of natural organic matter (NOM) were explored in chlorinated and chloraminated raw and coagulated waters with different water quality (e.g. DOC, SUVA, bromide, pH) and varying operating conditions (e.g. chlorine dose, reaction time, temperature). Specific attention was given to the formation of DBPs in treated water in order to evaluate the application of this approach for real time monitoring of DBPs in water distribution systems. The obtained correlations between Spectroscopic indices and DBPs concentrations are very strong even for treated water containing very low concentrations of DBPs species and can be used to control the concentration of individual DBPs as well as the speciation of DBP classes regulated worldwide (i.e. THM, HAA). The examined spectroscopic indexes can be also used to monitor the level and speciation of emerging DBPs (e.g. HAN) in practically important situations. In particular, the application of differential absorbance and/or fluorescence spectroscopy may allow real time monitoring of regulated and emerging DBPs species in water distribution systems.