Advances in Treatment of Brominated Hydrocarbons by Heterogeneous Catalytic Ozonation and Bromate Minimization

Abstract

The formation of carcinogenic bromate ions is a constraint when ozone is used for the remediation of water containing brominated organic materials. With its strong oxidizing ability, ozone rapidly transforms bromide in aqueous media to bromate, through a series of reactions involving hydroxyl radicals. Several strategies, such as limiting the ozone concentration, maintaining pH < 6, or the use of ammonia or hydrogen peroxide were explored to minimize bromate generation. However, most of the above strategies had a negative effect on the ozonation efficiency. The advanced oxidation processes, using catalysts together with ozone, have proven to be a promising technology for the degradation of pollutants in wastewater, but very few studies have been conducted to find ways to minimize bromate formation during this approach. The proposed article, therefore, presents a comprehensive review on recent advances in bromate reduction in water by catalytic ozonation and proposes reaction mechanisms associated with the catalytic process. The main aim is to highlight any gaps in the reported studies, thus creating a platform for future research and a quest to find environment friendly and efficacious catalysts for minimizing bromate formation in aqueous media during ozonation of brominated organic compounds.

Ecological impacts of ballast water loading and discharge: insight into the toxicity and accumulation of disinfection by-products

“…On the basis of Table 3 , DBPs potentially released after ballast water treatment are mostly bromate-, HAA-, and THM-related compounds. Bromate is released from the reaction of bromide in sea/brackish water with ozone under free chlorine existence ( Gounden and Jonnalagadda, 2019 ). HAA and THM are the by-products of chlorination as hypochlorous acid interact with natural organic matter in the sea/brackish water ( de Vera et al., 2016 ; Huang and Shah, 2018 ).…”

“…(1993) stated that natural organic matter in sediment became a major precursor for THM formation when reacted with free halogens (such as chlorine). This explanation may also apply to coastal sediment due to the interaction of DBPs (mostly free chlorine or bromide) with natural organic matter in coastal sediment ( Gounden and Jonnalagadda, 2019 ; Huang and Shah, 2018 ). However, research on this particular matter is currently limited.…”

Catalytic Membrane Ozonation

“…Although, ozone has been applied widely in drinking water and in wastewater treatment, its use may cause secondary problems, when the water to be treated contains bromide (Br − ) at concentrations higher than 50 µg/L. The Br − concentrations in natural waters may usually range between 4 and 1000 µg/L [33]. Due to salt intrusion, Br − is detected in surface waters, as well as in the influent of wastewater treatment plants at concentrations up to 400 µg/L [34].…”

“…The main by-product of the reaction between ozone and Br − is bromate (BrO 3 − ). BrO 3 − once formed, it is neither biodegradable nor removable by the application of conventional treatment [33]. It is considered as a potential carcinogen (Group 2B) by the International Agency for Research on Cancer (IARC) [34].…”

“…The maximum permissible contaminant level for BrO 3 − is 10 µg/L, according to USEPA and Drinking Water Commission of Europe [35]. Due to that the minimization or the prevention of its production in water treatment is crucial [33]. Figure 3 shows the formation of BrO 3 − via the direct ozonation and through the radical mechanism, noting that BrO 3 − is mostly produced by the 2nd (radical) pathway.…”