Comparison of pre-oxidation between O₃ and O₃/H₂O₂ for subsequent managed aquifer recharge using laboratory-scale columns

A hybrid process of managed aquifer recharge with pre-oxidation was investigated as part of a multiple-barrier approach for safe water production. This study evaluated O₃ and O₃/H₂O₂ for the pre-oxidation of urban surface water prior to managed aquifer recharge (MAR) and compared their effectiveness with respect to trace organic contaminants (TrOCs), biostability, and trihalomethane formation potential. The combination of pre-oxidation and MAR was performed using long-term column studies, and the results confirmed the removal of 64 and 56% dissolved organic carbon by using O₃ and O₃/H₂O₂, respectively. MAR combined with O₃ and O₃/H₂O₂ achieved >50% removal of dissolved organic carbon with the first 5 days of residence time. O₃ alone showed better performance in alleviating trihalomethane formation potential during chlorination compared to using O₃/H₂O₂. The pre-oxidation of urban surface water was effective in attenuating selected TrOCs (35 - >99% removal), and subsequent MAR achieved >99% removal of selected TrOCs within the first 5 days, regardless of pretreatment methods examined in this study. The results of this study provide an understanding of the effects of O₃ and O₃/H₂O₂ as pre-oxidation processes on urban surface water prior to MAR, as well as the resulting impact on MAR.