Conditions Affecting Bromate Formation During Ozonation of Bottled Water

Bromate concentration, ozone lifetime and ozone exposure (CT value) measured in bottled water in full-scale runs, were in good agreement to those measured in laboratory experiments. Ozone lifetime in bottled water was high enough to result in a CT value greater than 5 even for ozone dose as low as 0.1?mgO₃/L, at a water pH of 7.6. Bromate was gradually formed during the ozone lifetime. Bormate formation and ozone exposure were significantly influenced by pH. In full-scale runs, an ozone dose of 0.15?mgO₃/L at pH=7.6 resulted in a CT of 10.3 and a bromate concentration of 13.5?µg/L, while at pH=7.25 the values of CT and BrO₃ ^? were 12.6 and 9.6?µg/L, respectively. By decreasing further the pH to 6.8, an increase of CT value to 15.8 and a reduction of bromate to 5.5?µg BrO₃ ^?/L were observed. In addition, results in full-scale runs showed that ozone exposure and bromate concentrations were linearly related to ozone dose in the working range of 0.1 to 0.25?mgO₃/L.     

Effect of Ammonia and Chloramine Pretreatment during the Ozonation of a Colored Groundwater with Elevated Bromide

Ozone coupled with pre-chloramination was evaluated as an effective color removal and bromate control method for groundwater at Mesa Water's Well #8. A modified solution ozone test procedure was employed to simulate the sidestream ozone injection. Satisfactory color removal (<10 PtCo CU) was achieved with 2 mg/L of ozone in the presence or absence of preformed monochloramine or ammonia. While bromate formation was reduced by 67% and 83% with 0.3 and 0.6 mg/L of ammonia-N alone, respectively, 68% and 92% of bromate formation was suppressed with 1.0 and 2.0 mg/L of monochloramine as Cl₂, respectively. Only the pre-treatment with 2.0 mg/L of monochloramine provided sufficient bromate control to meet its maximum contaminant level of 10 μg/L. UV and fluorescence analyses showed effective destruction of color-causing organics by ozone in the presence of preformed monochloramine.     

Evaluation of Process Control Alternatives for the Inactivation of Escherichia coli,MS2 Bacteriophage,and Bacillus subtilis Spores during Wastewater Ozonation

Dissolved ozone concentration integrated over time (CT) is a reliable indicator of disinfection efficacy in drinking water treatment. However, ozone CT may not be measurable in some wastewater ozone applications. In this study, alternative process control parameters, specifically ozone to total organic carbon (O₃:TOC) ratio, differential UV₂₅₄ absorbance (ΔUV₂₅₄), and differential total fluorescence (ΔTF), were correlated with the inactivation of Escherichia coli, the bacteriophage MS2, and Bacillus subtilis spores in five secondary wastewater effluents. CT values greater than 9 mg-min/L were generally required for measurable inactivation of B. subtilis spores, and CT values of 1 and 2 mg-min/L consistently achieved greater than 6- and 5-log inactivation of MS2 and E. coli, respectively. The O₃:TOC, ΔUV_254, and ΔTF correlations for MS2 and B. subtilis were useful for predicting inactivation, while those of E. coli were characterized by greater variability. [Supplementary materials are available for this article. Go to the publisher's online edition of Ozone: Science & Engineering for the following free supplemental resources: additional figures and data tables.]     

Parameters Affecting the Formation of Bromate Ion During Ozonation

Batch type ozone experiments conducted on aquatic humic substances solutions spiked with bromide ion were developed to evaluate the importance of various parameters that may affect the formation of bromate ion during ozonation. The nature of the NOM, the alkalinity, the bromide ion content and the presence of ammonia were found to significantly affect the bromate ion production. Temperature and pH can be considered as minor factors. The ozonation of a clarified surface water using a continuous flow ozone contactor have shown that the addition of a low quantity of ammonia (0.05 to 0.1 mg/L NNH₄ ⁺) appeared to be an interesting option for controlling the bromate formation. On the contrary, the addition of hydrogen peroxide may enhance or reduce the bromate ion production, depending on the applied hydrogen peroxide/ozone ratio.     

Bromate control in phenol-contaminated water treated by UV and ozone processes

Formation of bromate is of a great concern whenever ozone-based technologies are used for treating highly bromide-containing water ever since bromate was classified as a potential carcinogen. Saudi Arabian groundwater is coincidentally high in bromide content, and the potential of forming bromate during the treatment of such water is high. This study investigated the extent of bromate formation under different treatment conditions of ozone-based Advanced Oxidation Processes (AOPs) when used for the treatment of phenol-contaminated water. The results of the study showed that continuous ozonation at a rate of 1 L/min has completely removed 50 ppm of phenol from contaminated water in less than 5 min. However, as high as 8.85 ppm of bromate (BrO₃⁻) was detected when treating the water which has high concentration of bromide ion (5 ppm). Results also showed that by adjusting the pH to 6 and adding ammonia (NH₃) at a dosage of 1.5 ppm, bromate formation was diminished drastically to non-detected levels.     

Efficacy of Ozone to Reduce Chlorinated Disinfection By-Products in Quebec (Canada) Drinking Water Facilities

The impact of ozonation on the reduction of chlorinated disinfection by-products formation was investigated in 15 full-scale and lab-scale drinking water facilities of Québec (Canada). Total trihalomethanes (TTHM) and the sum of six haloacetic acids (HAA6) were measured after chlorination under uniform formation conditions (UFC). Results showed that before ozonation TTHM and HAA6 average concentrations were 89.4 and 45.3 μg/L, respectively. In full-scale ozonation conditions TTHM-UFC and HAA6-UFC reductions averaged respectively 27 and 32%. After lab-scale ozonation at a O₃/C of 1:1, a decrease of only 9% of TTHM was calculated, while for HAA6, reduction was not significantly impacted (30%). For BDOC, average concentrations of 0.13, 0.46, and 0.69 mg C/L were measured before and after and lab-scale ozonation, respectively. Chlorine demand (Cl₂D) and immediate ozone demand (IOD) were found to be the most appropriate indicators to evaluate NOM reactivity after ozonation.     

Bromate in Drinking Water A problem in Switzerland?

Ozonation of bromide-containing waters causes the formation of bromate which is considered to be potentially carcinogenic. An investigation in Switzerland on water works using ozone (85) has shown that the new drinking water standard of 10?µg/L for bromate is generally not exceeded. This is mainly due to the relatively small bromide concentrations which are typically below 25?µg/L. There is a characteristic relationship between bromate formation and the ozone exposure in a particular water type. This can be used to estimate the integral ozone exposure from the bromate formation which allows the assessment of the efficiency of the disinfection. This new concept is illustrated by means of two examples.     

Preliminary Data on the Fate of Bromate Ion in Simulated Gastric Juices

Ozone is a drinking water disinfectant that quickly and efficiently kills many types of pathogens. However, the ozonation of bromide ion containing waters can form the disinfection byproduct, bromate ion. Bromate ion is a possible human carcinogen that is regulated by the US EPA at a Maximum Contaminant Level (MCL) of 10 micrograms per liter (μg/L). The lifetime risk at the MCL was calculated from studies where laboratory animals received large doses of bromate ion that would produce effects in their lifetimes. The data from these large doses was fitted to a low-dose linear extrapolation (also called a linearized dose-response) model. The model assumes there is a finite, albeit small, risk at any dose above zero of a genotoxic carcinogen. The validity of the linearized dose-response model projection at low doses is being questioned (i.e., the actual shape and slope of the dose/response as the dose approaches zero). The test system is bromate ion in synthetic and real gastric juices. The results reported here show that the bromate ion half-life, in the presence of typical H⁺, Cl^?, and H₂S concentrations found in the stomach, is 1.5–2 minutes. Thus, as much as 99% of the ingested bromate ion should be decomposed, while it is retained in the stomach. The results of these experiments will be used in the development of a more scientifically rigorous methodology for determining low level effects of bromate ion.     

Evaluation Of Genotoxicity Of Bromate Ion Produced During Ozonation

Bromate ion formation during ozonation processes in water works is regarded as an issue of great interest because of its potential for carcinogenicity. In this research, genotoxicity of bromate ion was investigated by the umu-test using Salmonella typhimurium TA 1535/pSK1002. The time-course study showed that the umuC gene related to error-prone repair of damaged DNA was induced by bromate ion after 12 hours exposure of the test strain. However, a further study revealed that this induction was inactivated by metabolism with rat liver microsome when bromate ion concentration was less than 0.88 mg BrO₃ ^?/mg as protein of the S9 fraction. This inactivation was assumed to depend on -SH compounds in liver microsome.     

Impact of Water Temperature on Resolving the Challenge of Assuring Disinfection While Limiting Bromate Formation

Intensive pilot studies were performed to study the impact of ozone dose (0.6 to 3.5 mg/L), pH (6.0 to 7.5), and contact time (12 to 38 min) on bromate (BrO₃) formation, for different sand-filtered water qualities from the Neuilly-sur-Marne Treatment Plant (COT = 1.3 to 2.2 mg/L, TAC = 190 to 230 mg CaCO₃, [Br^?] = 25 to 50 μg/L, and T = 5°C to 26°C). Whatever the water quality studied, the main factors influencing bromate formation were ozone dose, pH, and a cross factor between them. Bromate formation was shown to be proportional to bromide concentration, and to increase only slightly with temperature, depending on the ozone dose and the pH. As on the contrary temperature has an important impact on disinfection, especially when considering Cryptosporidium inactivation, resolving the challenge of ensuring disinfection while limiting bromate formation was shown to be quite easily achievable, at intermediate temperature, and with more stringent conditions at high temperature (because of bromate formation) or at low temperature (because of disinfection).     

Results Of Bromide And Bromate Monitoring At Several Water Treatment Plants

The ozonation of water is a widely used technology within the water industry. Recent toxicological studies have shown that high bromate ion intake induces a high incidence of tumors in rats. Bromate ion formation from oxidation of water containing bromide ion was examined at nine treatment plants and one pilot. We found bromate ion (> 2 μg/L) in drinking water containing bromide ion when treated with ozone at pH greater than 7.0, even in the presence of ammonia. Bromate ion formation increased with the applied ozone dose. But bromate ion must be considered also as a byproduct of commercial sodium hypochlorite solutions. Under commercial conditions, chlorine dioxide and granular activated carbon had no effects on bromate levels.     

Bromate Formation in Ozone and Advanced Oxidation Processes

Both the direct ozone reaction and the indirect hydroxyl radical reaction are important in ozonation of drinking water. This article investigates the effectiveness of ozone versus the advanced oxidation process of ozone coupled with hydrogen peroxide in the formation of bromate. The investigation was conducted on a pilot scale at various H₂O₂:O₃ dose ratios of 0.1, 0.2, and 0.35 at different times of the year. The results of this study show a reduction in bromate with the addition of hydrogen peroxide to an ozone system versus ozone alone. It was also observed that bromate increased with increased H₂O₂:O₃ ratios; however, concentrations were still lower than those in the ozone only system.     

Study on By-Products of Ozonation during Ammonia Removal under the Existence of Bromide: Factors Affecting Formation and Removal of the By-Products

Factors affecting the formation of by-products of ozonation during ammonia removal under the existence of bromide were investigated. The presence of reducible N compounds could significantly reduce the formation of bromate and brominated organics; however, it was difficult to completely prevent formation of the by-products. It was therefore concluded that while the method used in this study was an effective process to decompose ammonia, it should be applied to the treatment of wastewaters containing low concentration of TOC. For power plant condensate demineralization wastewater containing TOC of 3 to 4mg/L, TOX formed during ammonia removal ranged from 0.20 to 0.30 mgBr L^?1. The only halogenated organic substance of the power plant wastewater detected on GC spectrum was bromoform, whose concentration varied from 0.11 to 0.14 mg L^?1. Column test results indicated that bromate could almost completely be decomposed to bromide by activated carbon under proper space velocity and pH. Activated carbon was also very effective in adsorption of CHBr₃: 1 g activated carbon adsorbed ca. 20.3 mg of CHBr₃.     

Effect of Ozonation on Trihalomethane and Haloacetic Acid Formation and Speciation in a Full-Scale Distribution System

Disinfection by-product (DBP) formation was evaluated before and after ozone implementation at two full-scale drinking water facilities in Las Vegas, NV USA. The two treatment plants used preozonation for primary disinfection followed by direct filtration with subsequent chlorination for secondary disinfection. DBP data was evaluated from the finished water of the two treatment plants along with six locations in the distribution system. Results showed that preozonation reduced the formation of total trihalomethanes (TTHM) by up to 10 μg/L and the sum of five haloacetic acids (HAA5) by up to 5 g/L. These reductions were primarily due to decreases in the di- and trichlorinated DBPs such as chloroform, bromodichloromethane, and trichloroacetic acid. Ozonation appeared to shift the speciation of TTHMs and HAA5 to favor increased formation of the di- and tribrominated species such as bromoform, chlorodibromomethane, and dibromoacteic acid. A bromide mass balance showed that <30% of the raw water bromide was accounted for by the formation of TTHMs (8–21%), HAAs (2–3%) and bromate (5%). Reducing the concentration of THMs and HAAs is often not the primary purpose of ozonation, but it can assist utilities in meeting regulatory requirements during drinking water treatment.     

Comparing Static Mixer Performances at Pilot and Full Scale for Ozonation,Inactivation of Bacillus subtilis,and Bromate Formation in Water Treatment

The potential benefits of using a static mixer for ozone dissolution was evaluated through comprehensive pilot- and full-scale studies under a variety of operating conditions and source waters. The static mixer pilot unit was operated side-by-side to a full-scale plant which also employed static mixers for ozonation. Based on the results obtained from this pilot study (and at other sites), it appears that an optimal ozone dose (≤0.5mgO₃/mgC) applied through a static mixer dissolution system integrated with a well-designed downstream contactor can result in enhanced microbial inactivation while keeping bromate formation below 10μg/L.     

Thermodynamic analysis on calcium dissolution in the system of Ca(II)-NH3-NH4Cl-H2O

Based on the principles of ionic balance, electro-neutrality and the existing thermodynamic data, the thermodynamics equilibrium on calcium dissolution in the system of Ca(II)-NH₃-NH₄Cl-H₂O was theoretically calculated. The results show that the equilibrium pH values in the system vary from 11.43 to 12.59, and the solubility of Ca(II) is significant in the system of NH₄Cl-NH₃-H₂O. The c(NH₄OH) has little influence on c(Ca²⁺)_T and when the ammonia concentration is kept constant, the total calcium concentration (c(Ca²⁺)_T) with a maximum concentration of 2.03 mol/L increases linearly with the increase of concentration of c(NH₄Cl). Calcium mainly presents in the form of calcium-bearing complexes instead of calcium ion in the system. The reaction degrees of Ca²⁺ with ammonium hydroxide and H₂O are less in the system. The absolute average error of calcium equilibrium concentration between the experimental and theoretical calculated values is 7.07% in confirmatory experiments. The results are helpful to clarify the leaching behaviour of calcium ions in the system of Ca(II)-NH₃-NH₄Cl-H₂O and provide the theoretical foundation to improve the calcium yield and remove impurities in the leaching stage of the indirect aqueous CO₂ sequestration process.     

饮用水中臭氧消毒副产物溴酸盐含量的控制技术探讨

在阐述臭氧化过程中溴酸盐的生成机理的前提下,从原水预处理、溴酸盐形成过程控制、溴酸盐形成后消除3个阶段来分析研究控制饮用水中溴酸盐含量的方法。经过探讨和实践表明,采用膜分离技术(控制原水电导率和微生物含量)、加氨、采用新型消毒剂和多种消毒剂组合使用、优化臭氧消毒工艺和活性炭吸附技术等是较为可行的控制途径。饮用水生产企业根据水源特点,生产能力,企业规模、运行成本等条件进行选择尝试,从而实现臭氧、微生物和溴酸盐之间的平衡。     

Bromate Surveys in French Drinking Waterworks

Two bromate surveys were made recently in order to evaluate the frequency of bromate appearance in drinking waters issued from waterworks including one or two ozonation steps. The First survey was carried out on 47 waterworks. Two sampling campaigns were analyzed in cool and warm seasons. The objective of the second survey was to follow, during 4 to 10 months, at 12 selected waterworks.

The aim of this paper is to present the data obtained and to try to model for some waterworks the bromate formation by means of some important parameters (Br, O₃/DOC, T° and pH) of water to ozonate.

The main conclusion is that the bromate presence in distributed drinking waters is a reality for waterworks using ozonation steps, especially in warm period of the year. In the case of some waterworks, disinfection by sodium hypochlorite increased bromate levels in distributed water.

As shown by others on a laboratory-scale level, a multi-linear regression allows us the prediction of the bromate formation from some determining parameters, for some waterworks. However, the poor values of the linear regression lead us to have some doubts about its universal application in the real situation of an operating waterworks. A better evaluation of “C.t” will be required in the future in order to get a better prediction by the use of multi linear regression.     

Threshold Levels for Bromate Formation In Drinking Water

Ozone is a sufficiently strong oxidant to cause the oxidation of bromide ion and formation of bromate ion. In this study, bromate ion formation in a wide variety of drinking water sources was analyzed, with bromate ion formed in all sources under drinking water treatment conditions. Threshold levels for pH, bromide ion concentration, and ozone dose were found to be source-specific. Two non-linear empirical models were developed to predict bromate ion formation; these models are easy to use and require only several water quality and treatment variables. The models were tested against several literature data and a good simulation was found in other bench-scale tests, whereas the model tended to under-predict bromate ion formation in pilot-scale and full-scale programs.     

Modeling of Ozonation for Dissolved Ozone Dosing

Experimental research was carried out for calibration and validation of a model describing ozone decay and ozone exposure (CT), decrease in UV absorbance at 254 nm (UVA₂₅₄), increase in assimilable organic carbon concentration and bromate formation. The model proved to be able to predict these parameters on the basis of the applied ozone dosage. The experimental ozone dosages ranged from 0.4 mg-O₃/L to 0.9 mg-O₃/L for natural water with a dissolved organic carbon concentration of 2.4 mg-C/L. The UVA₂₅₄ was found to be an effective parameter for estimation of rapid ozone decay for natural water under experimental conditions tested. The experimental setup consisted of a bench-scale plug flow reactor (approximately 100 L/h) with dissolved ozone dosing.