Abstract
Bromate formation characteristics of six-physicochemical oxidation processes, UV irradiation, single addition of hydrogen peroxide, ozonation, UV irradiation with hydrogen peroxide addition (UV/H2O2), ozonation with hydrogen peroxide addition (O3/H2O2), and ozonation with UV irradiation (O3/UV) were investigated using 1.88 μM of potassium bromide solution with or without 6.4 μM of 4-chlorobenzoic acid. Bromate was not detected during UV irradiation, single addition of H2O2, and UV/H2O2, whereas ozone-based treatments produced . Hydroxyl radicals played more important role in bromate formation than molecular ozone. Acidification and addition of radical scavengers such as 4-chlorobenzoic acid were effective in inhibiting bromate formation during the ozone-based treatments because of inhibition of hydroxyl radical generation and consumption of hydroxyl radicals, respectively. The H2O2 addition was unable to decompose 4-chlorobenzoic acid, though O3/UV and O3/H2O2 showed the rapid degradation, and UV irradiation and UV/H2O2 showed the slow degradation. Consequently, if the concentration of organic contaminants is low, the UV irradiation and/or UV/H2O2 are applicable to organic contaminants removal without bromate formation. However, if the concentration of organic contaminants is high, O3/H2O2 and O3/UV should be discussed as advanced oxidation processes because of their high organic removal efficiency and low bromate formation potential at the optimum condition.
Highlights
Nowadays, the world demand for water is growing because of the rapid population growth
If the concentration of organic contaminants is low, the UV irradiation and/or UV irradiation with H2O2 addition (UV/H2O2) are applicable to organic contaminants removal without BrO3− formation, though it is necessary to beware nitrite formation
BrO3− formation potential of UV irradiation, H2O2 addition, ozonation, UV/H2O2, O3/H2O2, and O3/UV treatment were discussed for organic contaminants
Summary
The world demand for water is growing because of the rapid population growth. As a result of this situation, water supply section has made efforts to supply a plenty of safe drinking water In this context, various advanced water treatment like UV disinfection, ozonation, and adsorption processes [5,6,7] have been introduced to water purification plants. UV irradiation and ozone-based chemical oxidation are widely used as advanced water purification processes. These processes can achieve higher level of disinfection and organic pollutants removal [9, 10]. Ozonation of bromide-containing water produces BrO3− via ozone and International Journal of Photoenergy hydroxyl radical pathways [8], but pH depression [12] and ammonia addition [12, 13] successfully decrease BrO3− formation. BrO3− formation in UV irradiation, H2O2 addition, ozonation, and their combination processes, UV irradiation with H2O2 addition (UV/H2O2), ozonation with H2O2 addition (O3/H2O2), and ozonation with UV irradiation (O3/UV), were discussed using the same reactor and the same water matrix to provide comparable information of their features of BrO3− formation and its control
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