High Bromide Concentrations Research Articles

The influence of precursors and treatment process on the formation of Iodo-THMs in Canadian drinking water

The National Survey of Disinfection By-Products and Selected Emerging Contaminants investigated the formation of various disinfection by-products and contaminants in 65 water treatment systems (WTSs) across Canada. Results for six iodo-trihalomethanes (iodo-THMs) are reported in this paper. The participating water treatment systems included large, medium and small systems using water sources and treatment processes which were representative of Canadian drinking water. Five water samples (source water, treated water and three water samples along the distribution system) were collected from each treatment system, both under winter and summer conditions. Samples were stabilized, shipped cold and analysed for six iodo-THMs (dichloroiodomethane–DCIM; dibromoiodomethane–DBIM; bromochloroiodomethane–BCIM; chlorodiiodomethane–CDIM; bromodiiodomethane–BDIM and triiodomethane or iodoform–TIM), using a SPME-GC-ECD method developed in our laboratory (MDLs from 0.02 μg/L for iodoform to 0.06 μg/L for bromodiiodomethane). Concentrations of relevant precursors like dissolved organic carbon (DOC), bromide, iodide and total iodine, as well as other water quality parameters, were also determined. Detailed information about the treatment process used at each location was recorded using a questionnaire. The survey showed that one or more iodo-THMs were detected at 31 out of 64 water treatment systems (WTSs) under winter conditions and in 46 out of 64 WTSs under summer conditions (analytical results from one site were excluded due to sampling challenges). Total iodo-THM concentrations measured during this survey ranged from 0.02 μg/L to 21.66 μg/L. The highest total iodo-THM concentration was measured in WTS 63 where all six iodo-THMs were detected and iodoform was present in the highest concentration. The highest iodo-THM formation was found to occur in treatment systems where water sources had naturally occurring ammonium as well as high bromide, high iodide and/or total iodine concentrations. In two such water systems the total concentration of iodo-THMs exceeded the concentration of regulated THMs.

Application of sensitive electrochemical sensing system for detecting bromate from disinfection process in desalination plant

Chlorination is the most commonly used in disinfection to prevent from the bacterial growth in both intake and distribution pipelines or storage tanks. However, the disinfection treatment can result in an undesirable by-product, such a bromate (BrO3−), which is a suspected human carcinogen. Seawater has a high potential of BrO3− formation because of high bromide (Br−) concentration (around 65mg/L) which can be transformed by chlorination in disinfection process. Therefore, the measurement or monitoring of BrO3− formation is necessary. This study aims to apply the sensitive amperometric sensing system for detecting BrO3− in free chlorine condition. A linear dynamic ranged from 60 to 200nM of BrO3− even in 28μM free chlorine solution with a sensitivity of 108.8μA/μM. The detection limit level of BrO3− was 38.6nM and the limit of quantification value of BrO3− was 113.7nM (at pH7). This detection limit value was half of global guideline value for drinking water. The proposed technique had no noticeable interference to the sensing of BrO3− over various potentially interfering agents and other chlorinated disinfection by-products. The data measured by multilayered sensor system was in a good agreement for detecting BrO3− with validated data measured by using a conventional UV–vis spectroscopic method. As a final demonstration, the proposed amperometric sensing system would significantly contribute to the on-site detection of BrO3− concentration from chlorinating disinfection process within drinking water treatment plants, including desalination, and water quality monitoring applications.

Halide-Enhanced Catalytic Activity of Palladium Nanoparticles Comes at the Expense of Catalyst Recovery

In this communication, we present studies of the oxidative homocoupling of arylboronic acids catalyzed by immobilised palladium nanoparticles in aqueous solution. This reaction is of significant interest because it shares a key transmetallation step with the well-known Suzuki-Miyaura cross-coupling reaction. Additives can have significant effects on catalysis, both in terms of reaction mechanism and recovery of catalytic species, and our aim was to study the effect of added halides on catalytic efficiency and catalyst recovery. Using kinetic studies, we have shown that added halides (added as NaCl and NaBr) can increase the catalytic activity of the palladium nanoparticles more than 10-fold, allowing reactions to be completed in less than half a day at 30 °C. However, this increased activity comes at the expense of catalyst recovery. The results are in agreement with a reaction mechanism in which, under conditions involving high concentrations of chloride or bromide, palladium leaching plays an important role. Considering the evidence for analogous reactions occurring on the surface of palladium nanoparticles under different reaction conditions, we conclude that additives can exert a significant effect on the mechanism of reactions catalyzed by nanoparticles, including switching from a surface reaction to a solution reaction. The possibility of this switch in mechanism may also be the cause for the disagreement on this topic in the literature.

Formation and control of nitrogenous DBPs from Western Australian source waters: Investigating the impacts of high nitrogen and bromide concentrations

We studied the formation of four nitrogenous DBPs (N-DBPs) classes (haloacetonitriles, halonitromethanes, haloacetamides, and N-nitrosamines), as well as trihalomethanes and total organic halogen (TOX), after chlorination or chloramination of source waters. We also evaluated the relative and additive toxicity of N-DBPs and water treatment options for minimisation of N-DBPs. The formation of halonitromethanes, haloacetamides, and N-nitrosamines was higher after chloramination and positively correlated with dissolved organic nitrogen or total nitrogen. N-DBPs were major contributors to the toxicity of both chlorinated and chloraminated waters. The strong correlation between bromide concentration and the overall calculated DBP additive toxicity for both chlorinated and chloraminated source waters demonstrated that formation of brominated haloacetonitriles was the main contributor to toxicity. Ozone–biological activated carbon treatment was not effective in removing N-DBP precursors. The occurrence and formation of N-DBPs should be investigated on a case-by-case basis, especially where advanced water treatment processes are being considered to minimise their formation in drinking waters, and where chloramination is used for final disinfection.

Effect of operational and water quality parameters on conventional ozonation and the advanced oxidation process O3/H2O2: Kinetics of micropollutant abatement, transformation product and bromate formation in a surface water

The efficiency of ozone-based processes under various conditions was studied for the treatment of a surface water (Lake Zürich water, Switzerland) spiked with 19 micropollutants (pharmaceuticals, pesticides, industrial chemical, X-ray contrast medium, sweetener) each at 1 μg L−1. Two pilot-scale ozonation reactors (4–5 m3 h−1), a 4-chamber reactor and a tubular reactor, were investigated by either conventional ozonation and/or the advanced oxidation process (AOP) O3/H2O2. The effects of selected operational parameters, such as ozone dose (0.5–3 mg L−1) and H2O2 dose (O3:H2O2 = 1:3–3:1 (mass ratio)), and selected water quality parameters, such as pH (6.5–8.5) and initial bromide concentration (15–200 μg L−1), on micropollutant abatement and bromate formation were investigated. Under the studied conditions, compounds with high second-order rate constants kO3>104 M−1 s−1 for their reaction with ozone were well abated (>90%) even for the lowest ozone dose of 0.5 mg L−1. Conversely, the abatement efficiency of sucralose, which only reacts with hydroxyl radicals (OH), varied between 19 and 90%. Generally, the abatement efficiency increased with higher ozone doses and higher pH and lower bromide concentrations. H2O2 addition accelerated the ozone conversion to OH, which enables a faster abatement of ozone-resistant micropollutants. Interestingly, the abatement of micropollutants decreased with higher bromide concentrations during conventional ozonation due to competitive ozone-consuming reactions, except for lamotrigine, due to the suspected reaction of HOBr/OBr− with the primary amine moieties. In addition to the abatement of micropollutants, the evolution of the two main transformation products (TPs) of hydrochlorothiazide (HCTZ) and tramadol (TRA), chlorothiazide (CTZ) and tramadol N-oxide (TRA-NOX), respectively, was assessed by chemical analysis and kinetic modeling. Both selected TPs were quickly formed initially to reach a maximum concentration followed by a decrease of their concentrations for longer contact times. For the studied conditions, the TP's concentrations at the outlet of the reactors ranged from 0 to 61% of the initial parent compound concentration, CTZ being a more persistent TP against further oxidation than TRA-NOX. Finally, it was demonstrated in both reactors that the formation of bromate (BrO3−), a potentially carcinogenic oxidation by-product, could be controlled by H2O2 addition with a general improvement on micropollutant abatement. Post-treatment by granular activated carbon (GAC) filtration enabled the reduction of micropollutants and TPs concentrations but no changes in bromate were observed. The combined algae assay showed that water quality was significantly improved after oxidation and GAC post-treatment, driven by the abatement of the spiked pesticides (diuron and atrazine).

Effect of medium-pressure UV-lamp treatment on disinfection by-products in chlorinated seawater swimming pool waters

Several brominated disinfection by-products (DBPs) are formed in chlorinated seawater pools, due to the high concentration of bromide in seawater. UV irradiation is increasingly employed in freshwater pools, because UV treatment photodegrades harmful chloramines. However, in freshwater pools it has been reported that post-UV chlorination promotes the formation of other DBPs. To date, UV-based processes have not been investigated for DBPs in seawater pools. In this study, the effects of UV, followed by chlorination, on the concentration of three groups of DBPs were investigated in laboratory batch experiments using a medium-pressure UV lamp. Chlorine consumption increased following post-UV chlorination, most likely because UV irradiation degraded organic matter in the pool samples to more chlorine-reactive organic matter. Haloacetic acid (HAA) concentrations decreased significantly, due to photo-degradation, but the concentrations of trihalomethanes (THMs) and haloacetonitriles (HANs) increased with post-UV chlorination. Bromine incorporation in HAAs was significantly higher in the control samples chlorinated without UV irradiation but decreased significantly with UV treatment. Bromine incorporation was promoted in THM and HAN after UV and chlorine treatment. Overall, the accumulated bromine incorporation level in DBPs remained essentially unchanged in comparison with the control samples. Toxicity estimates increased with single-dose UV and chlorination, mainly due to increased HAN concentrations. However, brominated HANs are known in the literature to degrade following further UV treatment.

Synthesis of stable iron oxide nanoparticle dispersions in high ionic media

A novel one-pot method was developed in this work to synthesize and disperse nanoparticles in a binary base fluid. As an example, stable magnetite iron oxide (Fe3O4) dispersions, i.e., nanofluids, were produced in a high ionic media of binary lithium bromide-water using a microemulsion-mediated method. The effects of temperature and precursor concentration on morphology and size distribution of produced nanoparticles were evaluated. An effective steric repulsion force was provided by the surface functionalization of nanoparticles during the phase transfer, supported by the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The formed nanoparticles exhibited a superior stability against agglomeration in the presence of high concentrations of lithium bromide, i.e., from 20 to 50 wt.%, which make them good candidates for a range of novel applications.

Copper Bromide Chemistry Analysis for Use in Large Scale Energy Storage and Beyond

Copper redox flow batteries have been recently studied in a high halide environment [1, 2]. The halide chemistry allows for the stabilization of the copper I oxidation state and the complexation also prevents the disproportionation reaction from taking place [3]. Historically, the copper halide chemistry has been used for electrowinning. Although the chemistry has been used for many years, little has been done to characterize the diffusion of bromide ion in the presence of high concentrations of bromide, the diffusion of the copper bromide complexes, and the kinetic parameters of electrodeposition from the copper I bromide complex. We have conducted charge and discharge experiments on the copper redox flow battery in a bromide electrolyte. It was observed that the battery is able to charge at higher current densities than it can discharge. During charging experiments, the battery was able to achieve a geometric current density over 200mA/cm2. However, during discharging experiments the battery was not able to achieve 125mA/cm2as shown in Figure 1. This is most likely due to an intermediate insoluble complex formed during discharge that passivates the surface. In this study, bromide ion diffusion, copper I diffusion, and copper I kinetics have been explored. A preliminary model, based on these precepts, has been developed and the applicability of these results to redox flow batteries and other systems are discussed. [1] L. Sanz, D. Lloyd, E. Magdalena, J. Palma, K. Kontturi, Journal of Power Sources, 268 (2014) 121-128. [2] D. Lloyd, E. Magdalena, L. Sanz, L. Murtomäki, K. Kontturi, Journal of Power Sources, 292 (2015) 87-94. [3] H. Zhao, J. Chang, A. Boika, A.J. Bard, Analytical Chemistry, 85 (2013) 7696-7703. Figure 1

Influence of bromide on the performance of the amphipod Hyalella azteca in reconstituted waters.

Poor performance of the amphipod Hyalella azteca has been observed in exposures using reconstituted waters. Previous studies have reported success in H. azteca water-only exposures with the addition of relatively high concentrations of bromide. The present study evaluated the influence of lower environmentally representative concentrations of bromide on the response of H. azteca in 42-d water-only exposures. Improved performance of H. azteca was observed in reconstituted waters with >0.02 mg Br/L. Environ Toxicol Chem 2016;35:2425-2429. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US Government work and, as such, is in the public domain in the United States of America.

Treatment of Groundwater Contaminated with 1,4-Dioxane, Tetrahydrofuran, and Chlorinated Volatile Organic Compounds Using Advanced Oxidation Processes

ABSTRACTOzonation and four types of advanced oxidation processes, including O3/H2O2, O3/UV, O3/H2O2/UV, and UV/H2O2, were evaluated for the treatment of contaminated groundwater at a Superfund site in Simpsonville, South Carolina using bench-scale, batch ozone and UV apparatuses. Although the contaminants of concern were 1,4-dioxane, 1,1-dichloroethene, and trichloroethene, several other chlorinated organics as well as tetrahydrofuran were found in the groundwater samples. The O3/H2O2 treatment with O3 and H2O2 doses of 6 and 1.5 mg/L, respectively, and the UV/H2O2 treatment with UV and H2O2 doses of 1,000 mJ/cm and 20 mg/L, respectively, were sufficient to degrade 200 µg/L of 1,4-dioxane, 110 µg/L of 1,1-dichloroethene, and 10 µg/L of trichloroethene below their performance standards of 10, 7, and 4 µg/L, respectively. Due to a high bromide concentration (0.35 mg/L) in the groundwater sample, bromate formation was found to be significant in ozone-based treatment, including O3/H2O2.

MtDNA depleted PC3 cells exhibit Warburg effect and cancer stem cell features.

Reducing mtDNA content was considered as a critical step in the metabolism restructuring for cell stemness restoration and further neoplastic development. However, the connections between mtDNA depletion and metabolism reprograming-based cancer cell stemness in prostate cancers are still lack of studies. Here, we demonstrated that human CRPC cell line PC3 tolerated high concentration of the mtDNA replication inhibitor ethidium bromide (EtBr) and the mtDNA depletion triggered a universal metabolic remodeling process. Failure in completing that process caused lethal consequences. The mtDNA depleted (MtDP) PC3 cells could be steadily maintained in the special medium in slow cycling status. The MtDP PC3 cells contained immature mitochondria and exhibited Warburg effect. Furthermore, the MtDP PC3 cells were resistant to therapeutic treatments and contained greater cancer stem cell-like subpopulations: CD44+, ABCG2+, side-population and ALDHbright. In conclusion, these results highlight the association of mtDNA content, mitochondrial function and cancer cell stemness features.

Origin of high bromide concentration in the water sources in Jordan and in the Dead Sea water

The Dead Sea is worldwide a major bromine provider for industry with an average concentration of 5.2 g/l of bromide compared to 0.065 mg/l in seawater and with a Cl/Br weight ratio in the Dead Sea water of about 42 compared to around 300 in oceanic water. The origin of the high bromide concentration in the Dead Sea has not yet been adequately clarified. In the course of this study, the bromide concentrations in the different surface and groundwater bodies in Jordan were analyzed and the types of rocks with which these waters were in contact were identified. Analyses carried out up to about 30 years ago and recent analyses confirm the natural origin of bromide in the water and also confirm that the analyzed sources are not polluted by anthropogenic bromide sources. It was found that a variety of these surface and groundwater sources contain high concentrations of bromide which discharges into the Dead Sea and contribute to its high bromide concentration. The present study concludes that the late Cretaceous early Tertiary oil shale deposits form the major source of the bromine species in the surface and groundwater feeding the Dead Sea. Some bromide is also contributed by the Triassic and Jurassic rocks containing evaporate salts containing bromides. Phosphate rocks of late Upper Cretaceous age contribute also with appreciable amounts of bromine species to the different water sources and hence to the Dead Sea water. At present, dissolution and erosion of bromide-rich sediments laid down by the predecessor water bodies of the present Dead Sea such as the Lisan Lake are being transported into the Dead Sea and contribute relatively large amounts of secondary bromide to the Dead Sea water.

Effects of bromide on inactivation efficacy and disinfection byproduct formation in photocatalytic inactivation

Abstract The high effectiveness of TiO2-UVA system in bacterial disinfection has gained attention to use this technology in water treatment on different source waters, including desalinated sea water and grey water. However, source waters containing a significant level of bromide could have different chemical pathways during TiO2-UVA disinfection process because reactive bromine species could be formed. To illustrate the water safety from the Br-TiO2-UVA system, this study investigated bacterial inactivation efficiency and disinfection byproduct (DBP) formation under different pH, TiO2 dosages and bromide concentrations in a laboratory setting. At a high bromide concentration (65 mg/L, equivalent to the concentration of natural sea water), the bacterial inactivation rate increased 2 times at pH 5 and more than 5 times at pH 8. However, a significant increase of brominated DBPs, which were considered more carcinogenic and toxic than chlorinated DBPs, was observed. The bacterial inactivation pattern was shifted from the “shoulder-log” to the “log-tail” under different bromide concentrations, suggesting the existence of bromide altered the bacterial inactivation mechanisms. We also observed that the inactivation kinetics of Br-TiO2-UVA system was greatly influenced by water pH. Our laboratory experiments demonstrated that bromide could improve the performance of photocatalytic inactivation, but it also could reduce the water safety by generating a higher level of brominated-DBPs in treated water. Water engineers should pay attention to the brominated DBP formation when applying TiO2-UVA photocatalysis on source waters with a significant level of bromide.

Formation of iodinated trihalomethanes after ferrate pre-oxidation during chlorination and chloramination of iodide-containing water

Iodinated disinfection by-products (I-DBPs) are responsible for taste and odor issues, and more toxic than their brominated and chlorinated analogs. Ferrate salt (Fe(VI)) is green, efficient and multifunctional in drinking water treatment. Iodinated trihalomethanes (I-THMs) formation of iodide containing water pretreated by ferrate during chlorination/chloramination was investigated in this paper. The results indicated that I-THMs can be reduced significantly by ferrate pre-oxidation due to the oxidation of iodide to iodate. During chlorination, no detectable I-THMs were found at pH < 8 after ferrate pre-oxidation. However, I-THMs formation increased significantly at pH 8–9. I-THMs formation decreased drastically with increasing ferrate dosage and no detectable I-THMs were found at high ferrate dosage (>2 mg/L). The presence of high bromide concentration could restrain the transformation from iodide to iodate during ferrate pre-oxidation. However, no obvious changes in the amount and speciation of I-THMs were observed with increasing bromide addition. The yield of I-THMs was within 15 ± 2 µg/L when bromide addition varied. During chloramination, compared to the samples without bromide, the formation of I-THMs was restrained too. However, increasing bromide concentration in chloraminated solutions would lead to significant increase in the I-THMs formation and could contribute to the changes in speciation. The yield of I-THMs increased from 16.11 µg/L to 33.28 µg/L when bromide concentration is 25 µM and 100 µM, respectively. Ferrate pre-oxidation can be employed to reduce the I-THMs formation in drinking water treatment for iodide-containing water.

Kinetics and Mechanism of the Chlorate-Bromide Reaction.

The chlorate-bromide reaction, ClO3(-) + 6Br(-) + 6H(+) → 3Br2 + Cl(-) + 3H2O, was followed at the Br3(-)/Br2 isosbestic point (446 nm). A fifth-order rate law was found: (1)/3 d[Br2]/dt = k[ClO3(-)][Br(-)][H(+)](3) (k = 5.10 × 10(-6) s(-1) L(4) mol(-4)) at 25 °C and I = 2.4 mol L(-1). At high bromide concentrations, the bromide order becomes close to zero, indicating a saturation profile on bromide concentration, similar to the chloride saturation profile observed in the chlorate-chloride reaction. A mechanism is proposed that considers the formation of the intermediate BrOClO2(2-), similar to the intermediate ClOClO2(2-) proposed in the mechanism of the chlorate-chloride reaction.

Mechanistic Study on the Formation of Cl-/Br-/I-Trihalomethanes during Chlorination/Chloramination Combined with a Theoretical Cytotoxicity Evaluation.

Chlorination followed by chloramination can be used to mitigate the formation of potentially toxic iodinated disinfection byproducts (I-DBPs) while controlling the formation of regulated chloro-bromo-DBPs (Cl-/Br-DBPs). Water samples containing dissolved organic matter (DOM) isolates were subjected to 3 disinfection scenarios: NH2Cl, prechlorination followed by ammonia addition, and HOCl alone. A theoretical cytotoxicity evaluation was carried out based on the trihalomethanes (THMs) formed. This study demonstrates that the presence of bromide not only enhances the yield and rate of iodate formation, it also increases the formation of brominated I-THM precursors. A shift in the speciation from CHCl2I to the more toxic CHBr2I, as well as increased iodine incorporation in THMs, was observed in the presence of bromide. For low bromide concentrations, a decrease in I-THM formation and theoretical cytotoxicity was achieved only for high prechlorination times, while for high bromide concentrations, a short prechlorination time enabled the full conversion of iodide to iodate. For low DOM concentrations or DOM with low reactivity, Br-/I-THMs were preferentially formed for short prechlorination times, inducing high cytotoxicity. However, for high chlorine exposures, the cytotoxicity induced by the formation of regulated THMs might outweigh the benefit of I-THM mitigation. For high DOM concentrations or DOM with higher reactivity, mixed I-THMs were formed together with high concentrations of regulated THMs. In this case, based on the cytotoxicity of the THMs formed, the use of NH2Cl is recommended.

Degradation of iohexol by UV/chlorine process and formation of iodinated trihalomethanes during post-chlorination

Degradation kinetics of iohexol by UV/chlorine advanced oxidation process (AOP) and the formation of iodinated trihalomethanes (I-THMs) during post-chlorination were investigated in this study. Iohexol, a commonly detected iodinated contrast media in water, can be effectively removed during UV/chlorine process with pseudo-first-order reaction kinetics due to the combination of UV photolysis and oxidation of hydroxyl radicals. The second-order rate constant between iohexol and hydroxyl radicals was determined as 3.8×109M−1s−1 by competition kinetic experiment. Five intermediates were identified by ultra performance liquid chromatography–electrospray ionization-mass spectrometry analysis and degradation pathways of iohexol during UV/chlorine were proposed. Effects of chlorine dose, pH and bromide concentration on iohexol degradation and I-THM formation during post-chlorination were also studied. The results showed that iohexol degradation was accelerated with the increase of chlorine concentration as well as the decrease of pH and bromide concentration. On the other hand, I-THM formation from post-chlorination of UV/chlorine treated iohexol favored relatively low chlorine doses, high bromide concentrations at circumneutral conditions. Raw water experiments showed that I-THM formation after post-chlorination of UV/chlorine-treated iohexol was lower compared to that from UV irradiation, indicating that UV/chlorine is superior to UV alone in controlling I-THM formation.

Removal and inactivation of virus by drinking water treatment in the presence of bromide or iodide

The inactivation of virus in raw water was conducted in a continuous flow pilot scale system. Coliphage MS2 was used as model organism for human enteric virus. The effect of disinfection technologies (single or combined process of ozonation and chlorination) and interfering substances (bromide or iodide) on inactivation of virus, and the removal performance of virus in raw water by the pilot scale system (Train A and B) were investigated. The results indicated that bromide or iodide in water was detrimental to ozonation but beneficial to chlorination for virus inactivation. After bromide or iodide was added, the removal of MS2 by ozonation unit was much lower than before (p < 0.01), the removal of MS2 by chlorination unit was significantly higher than before (p < 0.05). Both Train A and B could remove and inactivate MS2 in raw water completely even at high concentration of bromide (675.24 μg/dm3) and iodide (52.33 μg/dm3). The processes of Train A and B can effectively guarantee the virological safety of drinking water.

Decomposition of 1,4-dioxane by vacuum ultraviolet irradiation: Study of economic feasibility and by-product formation

We report the first use of vacuum ultraviolet (VUV) treatment to decompose 1,4-dioxane, a persistent organic contaminant that is difficult to remove by conventional drinking water treatment processes. The efficiency of VUV treatment was compared to that of VUV- and UV-based advanced oxidation processes (AOPs) (VUV/TiO2, VUV/H2O2, UV/TiO2, and UV/H2O2), and by-product formation was investigated. VUV treatment decomposed 1,4-dioxane more rapidly than did UV and UV/TiO2 treatments. The decomposition rate was enhanced when VUV irradiation was combined with TiO2 or H2O2. VUV/H2O2 decomposed 1,4-dioxane more rapidly than UV/H2O2 at a low H2O2 dose (1mg/L), but the rate difference became small at a high H2O2 dose (5mg/L). Electrical energy per order analysis revealed that VUV treatment, and the VUV- and UV-based AOPs, were economically feasible for 1,4-dioxane decomposition. Using raw water samples, we investigated by-product formation during VUV treatment and the effect of VUV irradiation on chlorinated disinfection by-product formation potential. Although the samples contained high concentrations of bromide, no bromate was produced by VUV treatment. VUV treatment slightly decreased trihalomethane formation potential (THMFP), whereas haloacetic acid formation potential (HAAFP) was unchanged, and total aldehyde concentration increased. The trend in HAAFP agreed with that had been reported for the VUV irradiation with much higher dose (Buchanan et al., 2006), whereas the trend in THMFP was different from that with much higher dose. THMFP, HAAFP, and aldehyde concentration were reduced by subsequent treatment with granular activated carbon (GAC) or biological activated carbon (BAC). Nitrite was produced by VUV treatment but disappeared after subsequent BAC treatment. These results suggest that VUV treatment should be combined with GAC or BAC treatment to suppress by-product formation.

Addition of hydrogen peroxide for the simultaneous control of bromate and odor during advanced drinking water treatment using ozone

Complete removal of the characteristic septic/swampy odor from Huangpu River source water could only be achieved under an ozone dose as high as 4.0 mg/L in an ozone-biological activated carbon (O3-BAC) process, which would lead to the production of high concentrations of carcinogenic bromate due to the high bromide content. This study investigated the possibility of simultaneous control of bromate and the septic/swampy odor by adding H2O2 prior to the O3-BAC process for the treatment of Huangpu River water. H2O2 addition could reduce the bromate concentration effectively at an H2O2/O3 (g/g) ratio of 0.5 or higher. At the same time, the septic/swampy odor removal was enhanced by the addition of H2O2, although optimization of the H2O2/O3 ratio was required for each ozone dose. At an ozone dose of 2.0 mg/L, the odor was removed completely at an H2O2/O3 ratio of 0.5. The results indicated that H2O2 application at a suitable dose could enhance the removal of the septic/swampy odor while suppressing the formation of bromate during ozonation of Huangpu River source water.