A comparative study of the effects of ozonation and TiO<inf>2</inf>-catalyzed ozonation on the selected chlorine disinfection by-product precursor content and structure

Abstract

This study compares the effects of ozonation (0.4-3.0mgO3/mg DOC) and TiO2-catalyzed ozonation - TiO2-O3 (0.4-3.0mgO3/mg DOC; 1.0mgTiO2/L) at pH 6 on the content and structure of natural organic matter (NOM) and trihalometane (THM) and haloacetonitrile (HAN) precursors in groundwater. The investigated groundwater from Northern Serbia is rich in NOM (9.85mg/L DOC) which is mostly of hydrophobic character (65% fulvic acid and 14% humic acid fraction). It was found that the TiO2-catalyzed process, by favoring the radical mechanism of NOM oxidation, resulted in a more effective reduction in the content of total NOM (up to 18% DOC) compared to ozonation alone (up to 6% DOC). The use of TiO2 also resulted in an improvement of ozonation in terms of THM precursor content removal (up to 80%). On the other hand, the application of both oxidation treatments resulted in an increase in the HANFP compared to the raw water. NOM oxidation during ozonation and TiO2-O3 caused changes in their structure in the direction of an increased proportion of the hydrophilic fraction (up to 70%), which has the most reactive THM and HAN precursors, as well as the fraction with the highest content of their brominated species. © 2012 Elsevier B.V.