Bromate formation control by enhanced ozonation: A critical review

In the past two decades, ozone-based advanced oxidation processes, known as enhanced ozonation processes (EOPs), have been extensively investigated for the removal of emerging organic contaminants in water, such as pesticides, endocrine-disrupting compounds, and pharmaceuticals. EOPs offer an advantage by producing highly oxidizing radicals, such as hydroxyl radicals, to oxidize recalcitrant organic compounds. Although the EOPs are able to effectively remove emerging contaminants, several studies reported the formation of bromate, which has drawn significant attention because of its potential carcinogenicity. This issue becomes challenging for the utilization of EOPs on bromide containing water. Therefore, this work critically reviews and summarizes the mechanisms, influencing factors, advantages and disadvantages, and control strategies for bromate formation by four EOPs, i.e., peroxone and e-peroxone, photolytic ozonation, heterogeneous ozonation, and sonolytic ozonation. Various economic and technical characteristics of EOPs were also compared. Mathematical modeling, pilot and full-scale data, and secondary pollutant potential (toxic metals leaching from catalyst) have been identified as knowledge gaps, and future research should seek to address these issues.