Major Reports & Review Papers on Bromate
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| Xie, L. and C. Shang (2006). A review on bromate occurrence and removal strategies in water supply. Leading-Edge Strategies and Technologies for Sustainable Urban Water Management. G. H. Chen, C. Shang and X. R. Zhang. 6: 131-136. |
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The need of disinfecting potable water to eliminate potential health risks associated with waterborne pathogens, however inevitably resulting in leaving elevated toxicity in water by forming disinfection by-products (DBPs) is being considered as one of the primary threats to human well-being. Bromate is a carcinogenic DBP mainly formed during ozonation of bromide-containing water. The current maximum contaminant level (MCL) of bromate in the US national primary drinking water standard is set at 10 mu g/L. With continuous improvements in analytical instrumentation and removal technologies, a lower MCL for bromate is expected in the future. Current researches on bromate control strategies involve minimizing bromate formation (like ammonia addition) or removing bromate after formation (like carbon adsorption), however have their own limitations. Seeking for alternative bromate control strategies that can be used alone (or in combine with others) is of great value and in urgent need when water quality standards are getting more stringent. This paper reviews the occurrence of bromate in water supply and evaluates the effectiveness of bromate removal technologies applied, to advance our understanding of bromate fate and degradation in water supply system for future study. |
| Butler, R., A. Godley, et al. (2005). "Bromate environmental contamination: Review of impact and possible treatment." Critical Reviews in Environmental Science and Technology 35(3): 193-217. |
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Contamination of drinking water with bromate (BrO3-) at levels ranging from 0.4 to 60 mu g L-1 may be found following ozonation of water containing background bromide (Br-). Based on rodent studies, bromate is classified as a 'possible human " carcinogen, and drinking water standards of 10-25 mu g L-1 are now implemented in many countries. Bromate is highly soluble, stable in water, and difficult to remove using conventional treatment technologies. This has led to investigations into novel removal techniques, but many have not developed beyond laboratory trials. Analytical advances have recently led to detection of bromate contamination within both rivers and groundwater, which has provided an additional requirement for bromate remediation. This review summarizes bromate environmental characteristics and the regulatory situation, and outlines bromate remediation processes, including filtration, ultraviolet irradiation, catalysis, chemical reduction, activated carbon, and biodegradation. These techniques are evaluated for developmental progress in a potable water system and also for potential application within the natural water environment. |
Bromate Formation & Minimization
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Allard, S., C. E. Nottle, et al. (2013). "Ozonation of iodide-containing waters: Selective oxidation of iodide to iodate with simultaneous minimization of bromate and I-THMs." Water Research 47(6): 1953-1960.
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The presence of iodinated disinfection by-products (I-DBPs) in drinking water poses a potential health concern since it has been shown that I-DBPs are generally more genotoxic and cytotoxic than their chlorinated and brominated analogs. I-DBPs are formed during oxidation/disinfection of iodide-containing waters by reaction of the transient hypoiodous acid (HOI) with natural organic matter (NOM). In this study, we demonstrate that ozone pre-treatment selectively oxidizes iodide to iodate and avoids the formation of I-DBPs. Iodate is non-toxic and is therefore a desired sink of iodine in drinking water. Complete conversion of iodide to iodate while minimizing the bromate formation to below the guideline value of 10 mu g L-1 was achieved for a wide range of ozone doses in five raw waters with DOC and bromide concentrations of 1.1-20 mg L-1 and 170-940 mu g L-1, respectively. Lowering the pH effectively further reduced bromate formation but had no impact on the extent of iodate and bromoform formation (the main trihalomethane (THM) formed during ozonation). Experiments carried out with pre-chlorinated/post-clarified samples already containing I-DBPs, showed that ozonation effectively oxidized I-THMs. Therefore, in iodide-containing waters, in which I-DBPs can be produced upon chlorination or especially chloramination, a pre-ozonation step to oxidize iodide to iodate is an efficient process to mitigate I-DBP formation. |
| Kingsbury, R. S. and P. C. Singer (2013). "Effect of magnetic ion exchange and ozonation on disinfection by-product formation." Water Research 47(3): 1060-1072. |
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The purpose of this research was to investigate the performance of treatment with magnetic ion exchange (MIEX) resin followed by zonation in achieving disinfection goals while controlling bromate and chlorinated disinfection by-product (DBP) formation. Three water samples were collected from raw water supplies impacted by the San Francisco Bay Delta to represent the varying levels of bromide and total organic carbon (TOC) that occur throughout the year. A fourth water was prepared by spiking bromide into a portion of one of the samples. Samples of each water were pre-treated with alum or virgin MIEX resin, and the raw and treated waters were subsequently ozonated under semi-batch conditions to assess the impact of treatment on ozone demand, ozone exposure for disinfection ("CT"), and bromate formation. Finally, aliquots of raw, coagulated, resin-treated, and ozonated waters were chlorinated in order to measure trihalomethane formation potential (THMFP). In the waters studied, MIEX resin removed 41-68% of raw water TOC, compared to 12-44% for alum. MIEX resin also reduced the bromide concentration by 20-50%. The removal of TOC by alum and MIEX resin significantly reduced the ozone demand of all waters studied, resulting in higher dissolved ozone concentrations and CT values for a given amount of ozone transferred into solution. For a given level of disinfection (CT), the amount of bromate produced by zonation of MIEX-treated waters was similar to or slightly less than that of raw water and significantly less than that of alum-treated water. MIEX resin removed 39-85% of THMFP compared to 16-56% removal by alum. zonation reduced THMFP by 35-45% in all cases. This work indicates that in bromide-rich waters in which ozone disinfection is used, MIEX resin is a more appropriate treatment than alum for the removal of organic carbon, as it achieves superior TOC and THM precursor removal and decreases the production of bromate from ozone |
| Gillogly, T., I. Najm, et al. (2001). Bromate Formation and Control During Ozonation of Low Bromide Waters. Denver, CO, AWWARF. |
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Abiotic Reactions
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| Liu, C., U. von Gunten, et al. (2013). "Chlorination of bromide-containing waters: Enhanced bromate formation in the presence of synthetic metal oxides and deposits formed in drinking water distribution systems." Water Research 47(14): 5307-5315. |
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Bromate formation from the reaction between chlorine and bromide in homogeneous solution is a slow process. The present study investigated metal oxides enhanced bromate formation during chlorination of bromide-containing waters. Selected metal oxides enhanced the decay of hypobromous acid (HOBr), a requisite intermediate during the oxidation of bromide to bromate, via (i) disproportionation to bromate in the presence of nickel oxide (NiO) and cupric oxide (CuO), (ii) oxidation of a metal to a higher valence state in the presence of cuprous oxide (Cu2O) and (iii) oxygen formation by NiO and CuO. Goethite (alpha-FeOOH) did not enhance either of these pathways. Non-charged species of metal oxides seem to be responsible for the catalytic disproportionation which shows its highest rate in the pH range near the pK(a) of HOBr. Due to the ability to catalyze HOBr disproportionation, bromate was formed during chlorination of bromide-containing waters in the presence of CuO and NiO, whereas no bromate was detected in the presence of Cu2O and alpha-FeOOH for analogous conditions. The inhibition ability of coexisting anions on bromate formation at pH 8.6 follows the sequence of phosphate >> sulfate > bicarbonate/carbonate. A black deposit in a water pipe harvested from a drinking water distribution system exerted significant residual oxidant decay and bromate formation during chlorination of bromide-containing waters. Energy dispersive spectroscopy (EDS) analyses showed that the black deposit contained copper (14%, atomic percentage) and nickel (1.8%, atomic percentage). Cupric oxide was further confirmed by X-ray diffraction (XRD). These results indicate that bromate formation may be of concern during chlorination of bromide-containing waters in distribution systems containing CuO and/or NiO |
| Liu, C., U. von Gunten, et al. (2012). "Enhanced Bromate Formation during Chlorination of Bromide-Containing Waters in the Presence of CuO: Catalytic Disproportionation of Hypobromous Acid." Environmental Science & Technology 46(20): 11054-11061. |
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Bromate (BrO3-) in drinking water is traditionally seen as an ozonation byproduct from the oxidation of bromide (Br-), and its formation during chlorination is usually not significant. This study shows enhanced bromate formation during chlorination of bromide-containing waters in the presence of cupric oxide (CuO). CuO was effective to catalyze hypochlorous acid (HOCl) or hypobromous acid (HOBr) decay (e.g., at least 10(4) times enhancement for HOBr at pH 8.6 by 0.2 g L-1 CuO). Significant halate concentrations were formed from a CuO-catalyzed hypohalite disproportionation pathway. For example, the chlorate concentration was 2.7 +/- 0.2 mu M (225.5 +/- 16.7 mu g L-1) after 90 min for HOCl (C-o = 37 mu M, 2.6 mg L-1 Cl-2) in the presence of 0.2 g L-1 CuO at pH 7.6, and the bromate concentration was 6.6 +/- 0.5 mu M (844.8 +/- 64 mu g L-1) after 180 min for HOBr (C-o = 35 mu M) in the presence of 0.2 g L-1 CuO at pH 8.6. The maximum halate formation was at pHs 7.6 and 8.6 For HOC or HOBr, respectively, which are close to their corresponding plc values. In a HOCl-Br--CuO system, BrO3- formation increases with increasing CuO doses and initial HOC and Br- concentrations. A molar conversion (Br- to BrO3-) of up to (90 +/- 1)% could be achieved in the HOCl-Br--CuO system because of recycling of Br- to HOBr by HOCl, whereas the maximum BrO3- yield in HOBr CuO is only 26%. Bromate formation is initiated by the formation of a complex between CuO and HOBr/OBr-, which then reacts with HOBr to generate bromite. Bromite is further oxidized to BrO3- by a second CuO-catalyzed process. These novel findings may have implications for bromate formation during chlorination of bromide-containing drinking waters in copper pipes. |
Phillip, N. H., E. Gurten, et al. (2006). "Transformation of bromine species during decomposition of bromate under UV light from low pressure mercury vapor lamps." Ozone-Science & Engineering 28(4): 217-228.
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Bromate decomposition with low pressure mercury vapor lamps (LPMVL) was studied in buffer-free and buffered Milli-Q water by following the fate of bromine species BrO3-, Br-, and free bromine. BrO3- was converted over One to Br- with total free bromine (TFBr) as secondary reaction product. BrO3- decay followed pseudo-first-order kinetics and was independent of [BrO3-](o) (0.06-0.6 mM), pH(o) (6.9-9.5) and HCO3 (0.05-1.0 mM), slightly dependent on acetate (0.06-0.27 mM), highly dependent on and adversely affected by humic acids (HA) and an increasing Junction of photon flux I as measured by potassium ferrioxalate actinometry. Reaction pH dropped by as much as 2.2 units at pH(o) < 8.5 in the buffer-free experiments, while it remained within 0.5 unit at pH(o) > 9. TFBr decay due to exposure to LPMVL resulted in formation of Br- (major) and BrO3- (minor). Decay of HA in the presence of BrO3- was highly augmented by photon emission of LPMVL at 185 nm and was found to substantially contribute to BrO3- decay in the presence of HA. Correlations on the dependency of bromine species decay or formation rates as a function of photon flux are presented. |
Biodegradation of Bromate
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| Liu, J., J. Yu, et al. (2012). "Reduction of bromate in a biological activated carbon filter under high bulk dissolved oxygen conditions and characterization of bromate-reducing isolates." Biochemical Engineering Journal 65: 44-50. |
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A biological activated carbon (BAC) filter was constructed using BAC from a pilot system that exhibited the ability to reduce bromate (BrO3-) and two BrO3--reducing bacteria were isolated and characterized. The BAC filter could almost completely reduce BrO3- (60 mu Br/L) to bromide (Br-) at an influent dissolved oxygen (DO) level of approximately 8.0 mg/L and an empty bed contact time of 30 +/- 2 min using acetate as the electron donor shortly after the start-up. Phylogenetic analysis of the 16S rRNA gene sequences of a biological sample from the BAC filter showed that among the six detected orders, Rhodocyclales- and Burkholderiales-related microorganisms were dominant and Rhodocyclaceae- and Comamonadaceae-related microorganisms may play a role in BrO3- reduction. Two isolated pure cultures, i.e.Sphingomonas sp. 4721 and Deinococcus sp. 4710, exhibited the ability to reduce BrO3- in the presence of NO3-. The result of this study clearly indicated that DO was a competitor of BrO3- as an electron acceptor while NO3- was not. Construction of a BAC filter which could restrict oxygen transfer within a biofilm still remains to be a challenge. |
| Davidson, A. N., J. Chee-Sanford, et al. (2011). "Characterization of bromate-reducing bacterial isolates and their potential for drinking water treatment." Water Research 45(18): 6051-6062. |
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The objective of the current study was to isolate and characterize several bromate-reducing bacteria and to examine their potential for bioaugmentation to a drinking water treatment process. Fifteen bromate-reducing bacteria were isolated from three sources. According to 16S rRNA gene sequencing, the bromate-reducing bacteria are phylogenetically diverse, representing the Actinobacteria, Bacteroidetes, Firmicutes, and alpha-, beta-, and gamma-Proteobacteria. The broad diversity of bromate-reducing bacteria suggests the widespread capability for microbial bromate reduction. While the cometabolism of bromate via nitrate reductase and (per)chlorate reductase has been postulated, five of our bromate-reducing isolates were unable to reduce nitrate or perchlorate. This suggests that a bromate-specific reduction pathway might exist in some microorganisms. Bioaugmentation of activated carbon filters with eight of the bromate-reducing isolates did not significantly decrease start-up time or increase bromate removal as compared to control filters. To optimize bromate reduction in a biological drinking water treatment process, the predominant mechanism of bromate reduction (i.e., cometabolic or respiratory) needs to be assessed so that appropriate measures can be taken to improve bromate removal |
| Assuncao, A., M. Martins, et al. (2011). "Bromate removal by anaerobic bacterial community: Mechanism and phylogenetic characterization." Journal of Hazardous Materials 197: 237-243. |
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A highly bromate resistant bacterial community and with ability for bromate removal was obtained from a sulphate-reducing bacteria enrichment consortium. This community was able to remove 96% of bromate and 99% of sulphate from an aqueous solution containing 40 mu M bromate and 10 mM sulphate. Moreover. 93% of bromate was removed in the absence of sulphate. Under this condition bromate was reduced stoichiometrically to bromide. However, in the presence of sulphate only 88% of bromate was reduced to bromide. Although, bromate removal was not affected by the absence of sulphate, this anion promoted a modification on the structure of the bacterial community. Phylogenetic analysis of 16S rRNA gene showed that the community grown in the presence of bromate and sulphate was mainly composed by bacteria closely to Clostridium and Citrobacter genera, while the community grown in the absence of sulphate was predominantly composed by Clostridium genus. It is the first time that Clostridium and Citrobacter genera are reported as having bromate removal ability. Furthermore, bromate removal by the consortium predominantly composed by Clostridium and Citrobacter genera occurred by enzymatic reduction and by extracellular metabolic products, while the enzymatic process was the only mechanism involved in bromate removal by the consortium mainly composed by Clostridium genus |
| Martin, K. J., L. S. Downing, et al. (2009). "Evidence of specialized bromate-reducing bacteria in a hollow fiber membrane biofilm reactor." Water Science and Technology 59(10): 1969-1974. |
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Bromate is a carcinogenic disinfection by-product formed from bromide during ozonation or advanced oxidation. We previously observed bromate reduction in a hydrogen-based, denitrifying hollow fiber membrane biofilm reactor (MBfR). In this research, we investigated the potential existence of specialized bromate-reducing bacteria. Using denaturing gradient gel electrophoresis (DGGE), we compared the microbial ecology of two denitrifying MBfRs, one amended with nitrate as the electron acceptor and the other with nitrate plus bromate. The DGGE results showed that bromate exerted a selective pressure for a putative, specialized bromate-reducing bacterium, which developed a strong presence only in the reactor with bromate. To gain further insight into the capabilities of specialized, bromate-reducing bacteria, we explored bromate reduction in a control MBfR without any primary electron acceptors. A grown biofilm in the control MBfR reduced bromate without previous exposure, but the rate of reduction decreased over time, especially after perturbations resulting in biomass loss. The decrease in bromate reduction may have been the result of the toxic effects of bromate. We also used batch tests of the perchlorate-reducing pure culture, Dechloromonas sp. PC1 to test bromate reduction and growth. Bromate was reduced without measurable growth. Based on these results, we speculate bromate's selective pressure for the putative, specialized BRB observed in the DGGE was not growth related, but possibly based on resistance to bromate toxicity. |
Bromate Analysis
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| Alsohaimi, I. H., Z. A. Alothman, et al. (2012). "Determination of bromate in drinking water by ultraperformance liquid chromatography-tandem mass spectrometry." Journal of Separation Science 35(19): 2538-2543. |
LC/MS with C18 |
Bromate is a byproduct formed as a result of disinfection of bromide-containing source water with ozone or hypochlorite. The International Agency for Research on Cancer has recognized bromate as a possible human carcinogen, thus it is essential to determine in drinking water. Present work highlights a development of sensitive and fast analytical method for bromate determination in drinking water by using ultraperformance liquid chromatographytandem mass spectrometry. The quality parameters of the developed method were established, obtaining very low limit of detection (0.01 ng/mL), repeatability and reproducibility have been found to be less than 3% in terms of relative standard deviation when analyzing a bromate standard at 0.05 mu g/mL with 0.4 min analysis time. Developed method was applied for the analysis of metropolitan and bottled water from Saudi Arabia; 22 samples have been analyzed. Bromate was detected in the metropolitan water samples (from desalinization source) at concentrations ranging between 3.43 and 75.04 ng/mL and in the bottled water samples at concentrations ranging between 2.07 and 21.90 ng/mL. Moreover, in comparison to established analytical methods such as liquid chromatographytandem mass spectrometry, the proposed method was found to be very sensitive, selective and rapid for the routine analysis of bromate at low level in drinking water. |
| Snyder, S. A., B. J. Vanderford, et al. (2005). "Trace Analysis of Bromate, Chlorate, Iodate, and Perchlorate in Natural and Bottled Waters." Environmental Science & Technology 39(12): 4586-4593. |
HPLC/MS/MS with C12 |
A simple and rapid method has been developed to simultaneously measure sub-mu g/L quantities of the oxyhalide anions bromate, chlorate, iodate, and perchlorate in water samples. Water samples (10 mL) are passed through barium and hydronium cartridges to remove sulfate and carbonate, respectively. The method utilizes the direct injection of 10 mu L volumes of water samples into a liquid chromatography-tandem triple-quadrupole mass spectrometry (LC-MS/MS) system. Ionization is accomplished using electrospray ionization in negative mode. The method detection limits were 0.021 mu g/L for perchlorate, 0.045 ug/L for bromate, 0.070 mu g/L for iodate, and 0.045 mu g/L for chlorate anions in water. The LC-MS/MS method described here was compared to established EPA methods 300.1 and 317.1 for bromate analysis and EPA method 314.0 for perchlorate analysis. Samples collected from sites with known contamination were split and sent to certified laboratories utilizing EPA methods for bromate and perchlorate analysis. At concentrations above the reporting limits for EPA methods, the method described here was always within 20% of the established methods, and generally within 10%. Twenty-one commercially available bottled waters were analyzed for oxyhalides. The majority of bottled waters contained detectable levels of oxyhalides, with perchlorate <= 0.74 mu g/L, bromate <= 76 mu g/L, iodate <= 25 mu g/L, and chlorate :<= 5.8 mu g/L. Perchlorate, iodate, and chlorate were detectable in nearly all natural waters tested, while bromate was only detected in treated waters. Perchlorate was found in several rivers and reservoirs where it was not found previously using EPA 314.0 (reporting limit of 4 mu g/L). This method was also applied to common detergents used for cleaning laboratory glassware and equipment to evaluate the potential for sample contamination. Only chlorate appeared as a major oxyhalide in the detergents evaluated, with concentrations up to 517 mu g/g. Drinking water treatment plants were also evaluated using this method. Significant formations of chlorate and bromate are demonstrated from hypochlorite generation and ozonation. From the limited data set provided here, it appears that perchlorate is a ubiquitous contaminant of natural waters at trace levels |