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.     

The Evaluation Of Ozonation and Chlorination On Disinfection By-Product Formation for a High-Bromide Water

High-bromide raw water was ozonated or chlorinated with and without hydrogen peroxide to study the effect of the disinfectants on the disinfection by-product (DBP) formation. Less bromate was formed when ozonation was made at the ambient pH of 5.8 as compared to ozonation at pH 7, showing the effectiveness of pH reduction in controlling the bromate formation. When chlorine dose was 1 mg/L instead of 2.3 mg/L, the trihalomethane formation was 50 μg/L instead of >100 μg/L, and the proportional distribution of the trihalomethanes was similar. The use of ozone for this water could provide good results in respect of the DBP formation.     

Bromate Formation during Ozonation of Bromide Containing Drinking Water- a Pilot Scale Study

The effect of bromide ion concentration, pH, temperature, alkalinity, and hydrogen peroxide content on bromate formation was studied. Increase in pH was found to give the greatest increase in bromate formation. Also increase in the ozonation temperature, bromide ion concentration and hydrogen peroxide content increased the observed bromate concentration. Only increased alkalinity decreased the bromate formation during the ozonation experiments. Bromate formation exceeded the EU limit value for bromate ion, 10 μg/l, when the initial bromide ion concentration was around 100 μg/l, except for the alkalinity of 1.4 mmol/1, when the bromate formation was 9.4 μg/l.     

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.     

Prediction of Bromate Formation Using Multi-Linear Regression and Artificial Neural Networks

The main objective of this study was to develop simple models for the prediction of bromate formation in ozonated bottled waters, using rapidly and practically measurable raw water quality and/or operational parameters. A total of 6 multi-linear regression (MLR) with or without principal component analysis (PCA) and 2 artificial neural networks (ANN) models with multilayer perceptron architecture were developed for the prediction of bromate formation. PCA was employed to better identify relations between variables and reduce the number of variables. Experimental data used in modeling was provided from the ozonation of samples from 5 groundwater sources at various applied ozone dose and contact time. MLR models#1 and #2 well-predicted bromate formation although correlations (i.e., the signs of regression constants) among pH (as input variable) and bromate concentrations did not agree with the chemistry. MLR model#6, containing practical input parameters that are measured on-line in full-scale treatment plants, adequately predicted bromate formation and agreed with the chemistry, although fewer input parameters were used compared to MLR#1 and #2. Although both of the ANN models exhibited high regression coefficients (R²) (0.97 for both) ANN#1 was found to provide better prediction of bromate formation based on mean square error (MSE) values. However, since ANN#2 included easily measurable input parameters it may be practically used by water companies employing ozonation. Results overall indicated that ANN models have stronger prediction capabilities of bromate formation than MLR models. ANN modeling appears to be a strong tool in situations where the relations between variables are non-linear, interactive and complex, as in the bromate formation by ozonation.     

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.     

A Survey of Bromate Ion in European Drinking Water

A one-year programme of research on the formation of bromate ion and organobrominated compounds by water ozonation was initiated recently between four French water treatment companies (C.G. Eaux, Lyonnaise des Eaux-Dumez, SAUR and SAGEP), one Spanish company (SGAB), the IARC, the KIWA, the WRc and the University of Poitiers. The programme comprises five aspects. The objective of this paper is to present the entirety of data from the following aspects: (I) inventory of the bromate ion content in distributed drinking water, and (ii) study of the evolution of bromate ion during the water treatment process.     

Modeling Bromate Formation During Ozonation

Bromate formation has been identified as a significant barrier in the application of ozone during water treatment for water sources that contain high levels of bromide. Bromate has been identified as a possible human carcinogen and bromate levels in drinking water are strictly controlled at 10 μg/L in most developed countries. Various models have been proposed to model bromate formation during ozonation based on raw water quality, ozone dose and contact time. Two main approaches for modeling have been used: an empirical regression modeling methodology and kinetic-based methodology. Currently, the benefit of the bromate models lies in their ability to show how process parameters may impact on the amount bromate formed.     

Evaluating Magnetic Ion Exchange Resin (MIEX)® Pretreatment to Increase Ozone Disinfection and Reduce Bromate Formation

Magnetic ion exchange resin, known by its commercial name (MIEX®) provides one pretreatment alternative that could maximize ozonation disinfection while decreasing bromate formation in bromide-containing waters. During a 5-week pilot study, the MIEX® process removed up to 30 % of the dissolved organic carbon (DOC) and reduced ultraviolet absorbance at 254 nm (UV 254) by up to 60%. When MIEX® pretreated water was ozonated, ozone decay rates were reduced, increasing the CT achieved by 40% to 65%. The increased disinfection capability reduced the transferred ozone dosages required for Cryptosporidium inactivation by 15% to 25% and bromate formation by 35%.     

Empirically and Theoretically–Based Models for Predicting Brominated Ozonated By–Products

During water treatment, ozonation of waters containing bromide ion producesboth organic and inorganic disinfection byproducts. Bromide ion concentrations in U.S. waters range from 0.01 to 2 mg/L (Krasner, 1989). Bromoformand dibromoacetic acid (DBAA) are the major organic byproducts and bromateion is the major inorganic byproduct derived from ozonation. Bromoform is a known carcinogen and the existence of bromate ion in water supplies also is of public health concern (Lykins, 1986). Bromate ion causes renal failure and hearing loss in laboratory animals and in human beings (Kruithof, 1992). The provisional guideline for bromate ion as proposed by the World Health Organization is 25 pg/L and may be exceeded in water treatment processesusing ozone. Also draft drinking water regulations in the U.S. will specify a maximum contaminant level (MCL) of 10 µg/L for bromate ion and a bestavailable treatment (BAT) of pH adjustment.     

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.     

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.     

Adsorption of Bromate From Aqueous Solutions by Modified Granular Activated Carbon: Batch and Column Tests

Bromate by-product formation during ozonation of bromide-containing potable water has aroused widespread concern. In this study, cetylpyridinium chloride was selected to modify two different kinds of granular activated carbon (GAC) to improve their bromate adsorption capacity. The adsorption characteristics of modified GAC were studied by batch and column tests, with results suggesting greatly improved bromate adsorption ability: the saturation capacities for bromate were >7 times for modified GAC than for GAC under the experimental conditions used. This enhancement in adsorptive capacity is likely due to an increase in basic functional groups, because the saturated adsorption capacity of bromate on the GAC is positively correlated with the basic functional groups. The increase of the basic functional groups accelerates OH- dissociation from the GAC surface and protonation of the GAC surface, thus resulting in the enhancement in adsorptive capacity. The modified GAC was relatively immune to the impact of pH change over a broad range. Both the Yoon-Nelson model and the Thomas model fit well the breakthrough curves of bromate adsorbed by modified and unmodified GAC under different conditions. Our results provide insight into the sorption process of bromate onto modified GAC.     

Reviewing the 20 Years of Operation of Ozonation Facilities in Hanshin Water Supply Authority with Respect to Water Quality Improvements

More than 20 years have passed since the introduction of advanced water treatment with ozonation and granular activated carbon in the Hanshin Water Supply Authority. Significant improvements have been achieved in eliminating taste and odor compounds in water and in suppressing the formation of disinfection by-products. Regarding the bromate ion, we have managed to suppress its formation by keeping the residual ozone concentration and pH low.     

Use of Ozone for Disinfection and Taste and Odor Control at Proposed Membrane Facility

Zone 7 of Alameda County Flood Control and Water Conservation District, in coordination with Black & Veatch, conducted a 9-month pilot study to determine preliminary design parameters for a new water treatment plant (WTP). The pilot study was performed to verify the performance of membrane filters and to establish preliminary design parameters for the submerged membrane process, followed by ozonation and biological granular activated carbon filtration. The pilot testing was conducted using water from the Patterson Pass WTP reservoir. The process included coagulation with either ferric chloride or polyaluminum chloride, flocculation, sedimentation, membrane filtration, ozonation, and filtration using biological granular activated carbon (BAC). The goals of the study were as follows:

1. Determine the potential effectiveness of ozone and BAC for removing geosmin and MIB.

2. Determine the impacts of different levels of pathogen inactivation, i.e., 0.5-log Giardia and 2-log virus inactivation.

3. Monitor the formation of bromate under various conditions of ozone oxidation for different levels of pathogen inactivation as well as for taste and odor control, and evaluate bromate mitigation strategies, if necessary.

The results of the study showed that the use of ozone achieved 2.0-log virus inactivation and 0.5-log Giardia inactivation. It also decreased the disinfection by-product formation and effectively controlled geosmin and removed a significant fraction of the MIB during a taste and odor event. Because the raw water bromide concentrations were low, bromate formation remained below the regulated level of 0.010 mg/L. However, in one instance, bromate mitigation was utilized by applying sulfuric acid to lower the pH to less than 7.1, which reduced bromate formation to less than 0.010 mg/L.     

Seawater ozonation: effects of seawater parameters on oxidant loading rates,residual toxicity,and total residual oxidants/by-products reduction during storage time

The efficacy of ozonation in different seawater conditions provides an improvement in the water quality and promotes the increment of dissolved oxygen. By-products (bromine, bromate, and bromoform) formation is directly proportional to the ozonation time. Ozone-produced oxidants remain toxic in both closed and dark containers for at least 4 days; however, during long storage period (35 days) in dark and cold conditions, these residual oxidants decrease slowly. These results have practical implications for both the installation of ozone systems on ships ballast water or for recirculating aquaculture system for inactivating undesirable organisms present in seawater.     

纳米金属氧化物催化臭氧氧化抑制溴酸盐形成的效能研究

通过纯水的模拟研究,探讨了纳米SnO2和纳米TiO2催化臭氧氧化抑制溴酸盐形成的情况及不同条件下纳米TiO2的抑制效能.结果表明,纳米SnO2催化及纳米TiO2催化均能有效抑制溴酸盐的形成,相对单独臭氧氧化条件溴酸盐生成量分别降低了45.81％和74.10％;光照对纳米TiO2催化抑制溴酸盐形成的效能影响不大;反应温度在10～26℃之间时,随着温度的升高,纳米TiO2催化抑制溴酸盐形成的作用越明显;纳米TiO2催化抑制溴酸盐生成的效能随着Br-初始质量浓度的增加和pH的上升而降低.     

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.     

Effect of Addition of Ammonia on theBromate Formation During Ozonation

Continuous ozonation experiments of bromide solutions have been conducted in the presence of ammonia. Solutions were prepared with phosphate-buffered NOM-free water (pH = 8) spiked with high levels of bromide and ammonium ions according variable molar ratio R= NH₄ ⁺/Br^?. Our results have shown that in the presence of tertbutanol, the bromate formation presents a delay increasing with the value of R. Bromate formation occurs when total bromine measured by the DPD colorimetric method presents a minimum level and when total bromine measured by the DPD + KI colorimetric method reaches a maximum level. The hypothesis that dibromamine was not quantitatively measured by DPD alone was first made, but unconfirmed, by complementary experiments. So we assumed that, in our experimental conditions, an unknown by-product measured by DPD + KI could be formed by ozonation of bromide in the presence of ammonia. The nitrate formation was found to be lower than expected, probably due to autonomous bromamine decomposition into nitrogen.     

Inhibition of Nano-Metal Oxides on Bromate Formation during Ozonation Process

Simulation studies in pure water were conducted to investigate the effect of nano-metal oxides on bromate (BrO₃^?) formation as catalysts and the catalytic mechanism. Results indicated that compared to ozonation alone, both nano-SnO₂ and nano-TiO₂ could inhibit the formation of bromate during ozonation process. The inhibition efficiency of BrO₃^? formation by nano-TiO₂ enhanced with the increasing of ozone dosage and the decreasing of nano-TiO₂ dosage, Br^? concentrations and the pH value. Possible BrO₃^? minimization mechanism was that nano-TiO₂ accelerated the decomposition of the dissolved O₃ into OH radicals, which rapidly generated H₂O₂, and reduced HOBr/OBr^? to Br^?.