Influence of UV/H2O2 processes on C- and N-disinfection by-products formation in different water matrices

Abstract

The aim of this study was to investigate the influence of UV/H2O2 advanced oxidation process on the natural organic matter content and disinfection by-products formation potential of different water matrices. Three water matrices (two natural waters and a synthetic humic acid solution) with different natural organic matter characteristics and concentrations were analysed. The carbonaceous disinfection by-products: trihalomethanes, haloacetic acids and haloketones, as well as nitrogenous disinfection by-products: haloacetonitriles and chloropicrin were investigated after chlorination. The UV/H2O2 treatment resulted in significant trihalomethane and haloacetic acids precursors removal (up to 53% and 30%, respectively) in humic acid solution in conditions ≥ 1.0 mg H2O2/mg DOC, in combination with a dose of UV irradiation ≥ 3000 mJ/cm2. Under the same reaction conditions, in natural groundwater rich in hydrophobic natural organic matter, the advanced process was less effective in DBP precursors removal. On the other hand, the advanced process was very effective in trihalomethaneprecursors removal (up to 76%) in groundwater with hydrophyilic natural organic matter. Haloketones were formed after treatment in very low concentrations. Nitrogenous disinfection by-products were only formed in the natural water containing hydrophilic organic matter, during the advanced process at 3.0 mg H2O2/mg DOC. The UV/H2O2 process resulted in negligible organic matter mineralization, but increased the brominated disinfection by-products formation in waters with low to medium bromide contents. It was concluded that under the same advanced oxidation process reaction conditions different natural organic matter structures showed different reactivities with chlorine toward the formation of the investigated disinfection by-products.