Comparison of emerging contaminant abatement by conventional ozonation, catalytic ozonation, O3/H2O2 and electro-peroxone processes

The abatement of several emerging contaminants (ECs) in groundwater by conventional ozonation and three ozone-based advanced oxidation processes (AOPs) - catalytic ozonation with manganese dioxide (MnO 2 ), conventional peroxone (O 3 /H 2 O 2 ), and electro-peroxone (EP) - was compared in this study. The addition of MnO 2 , H 2 O 2 , or electro-generation of H 2 O 2 during ozonation enhanced ozone transformation to hydroxyl radicals to different extent. These changes did not considerably influence the abatement of ECs with moderate to high ozone reactivities ( k O 3 ≥500  M -1 s -1 ${\text{k}}_{{\text{O}}_3}\text{≥500\hspace{0.17em}}{\text{M}}^{\text{-1}}{\text{s}}^{\text{-1}}$ ), whose abatements were similar with >90 % during all four processes. In comparison, the abatements of ozone-refractory ECs ( k O3 < 15  M -1 s -1 ${\text{k}}_{\text{O3}}\text{<\hspace{0.17em}15\hspace{0.17em}}{\text{M}}^{\text{-1}}{\text{s}}^{\text{-1}}$ ) were lower during conventional ozonation (∼40–85 % abatement), but could be enhanced by ∼10–40 % during the three ozone-based AOPs. Besides enhancing ozone-refractory EC abatement, the three AOPs, especially the O 3 /H 2 O 2 and EP processes, reduced considerably bromate formation compared to conventional ozonation. These results demonstrate that the EP process performs similarly as catalytic ozonation and O 3 /H 2 O 2 processes in terms of EC abatement and bromate control. Considering its more convenient, flexible, and safer way of operation, the EP process may provide an attractive alternative to the two more traditional AOPs for water treatment.