Effects of Ozonation and Catalytic Ozonation on the Removal of Natural Organic Matter from Groundwater

Abstract

This paper presents a comparison of the effects of ozonation [0.4–3.0 mg ozone (O3)/mg (DOC)] and titanium dioxide–catalyzed ozonation (TiO2-O3) (0.4–3.0 mg O3/mg DOC; 1.0 mg TiO2/L) at pH 7.46 on the removal of natural organic matter (NOM) from groundwater from the central Banat region (northern Serbia). This groundwater is rich in NOM (9.85 mg/L DOC), which is mostly of hydrophobic character (65% fulvic acid, 14% humic acid fraction). Ozonation and TiO2-O3 resulted in almost identical degrees of DOC content reduction (up to 30%), with the maximum efficacy of both processes achieved with 3.0 mg O3/mg DOC. The application of oxidation treatments resulted in complete humic acid oxidation, and increased the content of the hydrophilic fraction (up to 72%). The use of TiO2-O3 did not result in an improvement in the removal of trihalomethane precursors in comparison with ozonation (up to 48%) but produced less brominated species, whereas use of the TiO2-O3 process resulted in better removal of haloacetonitrile precursors (up to 44% removal) than did ozonation, which had less effect.