Article

Enhanced Bromate Formation during Chlorination of Bromide-Containing Waters in the Presence of CuO: Catalytic Disproportionation of Hypobromous Acid

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Abstract

Bromate (BrO(3)(-)) 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 μM (225.5 ± 16.7 μg L(-1)) after 90 min for HOCl (C(o) = 37 μM, 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 μM (844.8 ± 64 μg L(-1)) after 180 min for HOBr (C(o) = 35 μM) 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 HOCl or HOBr, respectively, which are close to their corresponding pK(a) values. In a HOCl-Br(-)-CuO system, BrO(3)(-) formation increases with increasing CuO doses and initial HOCl and Br(-) concentrations. A molar conversion (Br(-) to BrO(3)(-)) 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 BrO(3)(-) 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 BrO(3)(-) 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.

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... Metals (Cu(II) and Fe(II)) have been shown to enhance the decomposition rate of monochloramine (Fu et al., 2009a(Fu et al., , 2009bVikesland and Valentine, 2000). Copper oxide (CuO) has been extensively investigated as it can catalyse oxidants (ClO 2 , NH 2 Cl, HOCl, and HOBr) decay in the drinking water distribution pipeline (Hu et al., 2021a;Liu et al., 2014Liu et al., , 2013aLiu et al., 2012;Zhang et al., 2008b). For example, CuO catalysed HOCl and HOBr disproportionation, leading to the formation of toxic chlorite, chlorate and bromate (Liu et al., 2013a(Liu et al., , 2012. ...
... Copper oxide (CuO) has been extensively investigated as it can catalyse oxidants (ClO 2 , NH 2 Cl, HOCl, and HOBr) decay in the drinking water distribution pipeline (Hu et al., 2021a;Liu et al., 2014Liu et al., , 2013aLiu et al., 2012;Zhang et al., 2008b). For example, CuO catalysed HOCl and HOBr disproportionation, leading to the formation of toxic chlorite, chlorate and bromate (Liu et al., 2013a(Liu et al., , 2012. ...
... Ammonium chloride, ammonium sulfate, potassium bromide and copper(II) sulfate pentahydrate were obtained from Chem-Supply Pty Ltd. CuO powder was prepared according to the method described previously, and it was insoluble at pH 8.6 (Liu et al., 2012). Stock copper solutions (2 g/L) were prepared by dissolving copper(II) sulfate in deionized water. ...
Article
This study demonstrates that Cu(II) can significantly enhance the decomposition rate of bromamines. Apparent second order rate constants of 2.31 ± 0.01 M⁻¹s⁻¹ and 0.36 ± 0.01 M⁻¹s⁻¹ at pH 7.5 were determined for the reaction of Cu(II) with bromamines and the self-decomposition of bromamines, respectively. Increasing the pH from 6.0 to 8.5, the rate of bromamines self-decomposition decreased while the rate of Cu(II)-catalysed decomposition of bromamines increased. Species-specific rate constants indicated that Cu(OH)2 was the most reactive copper species towards NH2Br and NHBr2. Experiments were carried out with ¹⁵N-labeled bromamines to analyze the nitrogenous degradation products of bromamines in the presence and absence of Cu(II). Nitrogen gas (N2) was found to be the major product from the self-decomposition of bromamines, with N2O, NO2⁻, and NO3⁻ as additional minor products. When Cu(II) was present, the product distribution changed and NO2⁻ and N2O became significant, while N2 and NO3⁻ were produced at low levels. Increasing the Cu(II) concentration from 1.0 to 5.0 mg/L increased the N2O production while decreased the NO2⁻ formation. Based on these results, a mechanism for Cu(II)-catalysed decomposition of bromamines is proposed. This work provides new insights related to the chemistry of bromamines in chloraminated drinking water distribution systems where copper is present.
... How the presence of copper influences bacterial sensitivity to RCS has not been investigated before this study. However, it is important to note that Cu chemically catalyzes the decomposition of HOCl to nontoxic O 2 and Cl - (59)(60)(61)(62). We first used growth curves in the presence of copper and HOCl to identify how combinations of HOCl and extracellular copper influenced the sensitivity of wild-type and ΔrclA mutant E. coli ( Fig. 5A and B). ...
... Based on the effect of copper starvation on the HOCl sensitivity of the ΔrclA mutant, the sequence homology between RclA and MerA, and the predicted oxidoreductase activity of RclA (47), we hypothesized that the substrate of RclA might be copper. The reaction between copper and HOCl is known to generate strong oxidizing intermediates, most likely highly reactive Cu(III) (59)(60)(61)(62)(63). HOCl is also capable of oxidizing other transition metals, including iron (64, 65) and manganese (66,67). ...
... RclA also retained a remarkable 35.8% of full activity after being equilibrated in 6 M urea (Fig. 8C). Finally, we used circular dichroism (CD) spectroscopy to measure the melting temperature (T m ) of RclA, which was 65°C ( Fig. 8D; see also Fig. S7F), indicating that RclA is thermostable relative to the rest of the E. coli proteome, which has an average T m of 55°C (standard deviation [SD] ϭ 5.4°C) (60,77). ...
Article
Full-text available
Enterobacteria, including Escherichia coli , bloom to high levels in the gut during inflammation and strongly contribute to the pathology of inflammatory bowel diseases. To survive in the inflamed gut, E. coli must tolerate high levels of antimicrobial compounds produced by the immune system, including toxic metals like copper and reactive chlorine oxidants such as hypochlorous acid (HOCl). Here, we show that extracellular copper is a potent detoxifier of HOCl and that the widely conserved bacterial HOCl resistance enzyme RclA, which catalyzes the reduction of copper(II) to copper(I), specifically protects E. coli against damage caused by the combination of HOCl and intracellular copper. E. coli lacking RclA was highly sensitive to HOCl when grown in the presence of copper and was defective in colonizing an animal host. Our results indicate that there is unexpected complexity in the interactions between antimicrobial toxins produced by innate immune cells and that bacterial copper status is a key determinant of HOCl resistance and suggest an important and previously unsuspected role for copper redox reactions during inflammation. IMPORTANCE During infection and inflammation, the innate immune system uses antimicrobial compounds to control bacterial populations. These include toxic metals, like copper, and reactive oxidants, including hypochlorous acid (HOCl). We have now found that RclA, a copper(II) reductase strongly induced by HOCl in proinflammatory Escherichia coli and found in many bacteria inhabiting epithelial surfaces, is required for bacteria to resist killing by the combination of intracellular copper and HOCl and plays an important role in colonization of an animal host. This finding indicates that copper redox chemistry plays a critical and previously underappreciated role in bacterial interactions with the innate immune system.
... In Holland, copper concentrations between 0.2 and 3.8 mg/L were observed in tap water standing for 16 h (Dietrich et al., 2004). CuO was shown to catalyse the decomposition of chlorine and induced the formation of chlorate by disproportionation (Liu et al., 2012). The formation of bromate was also observed in chlorinated distribution systems where bromide and CuO were present (Liu et al., 2012). ...
... CuO was shown to catalyse the decomposition of chlorine and induced the formation of chlorate by disproportionation (Liu et al., 2012). The formation of bromate was also observed in chlorinated distribution systems where bromide and CuO were present (Liu et al., 2012). This was unexpected as chlorine is not able to oxidise bromine to bromate and the formation of bromate is usually associated to the use of ozone (Von Gunten, 2003). ...
... This was unexpected as chlorine is not able to oxidise bromine to bromate and the formation of bromate is usually associated to the use of ozone (Von Gunten, 2003). Similar to chlorine, it was found that CuO complexed with HOBr/OBr − and induced a catalytic disproportionation of HOBr that led to the production of bromate (Liu et al., 2012). Chlorination of iodide-containing waters in the presence of CuO also exhibited a catalytic formation of iodate and periodate (Liu et al., 2014). ...
Article
Copper oxide (CuO), a common corrosion product found in copper pipes, has been shown to catalyse the decay of different oxidants in drinking water, including chlorine, bromine, iodine, and chlorine dioxide. However, its impact on monochloramine (NH2Cl), a disinfectant commonly used in long distribution system worldwide is still unknown. In this study, the effect of CuO on NH2Cl decay in the absence or presence of bromide was investigated. Results showed that in the presence of CuO and the absence of bromide, NH2Cl slightly decayed under acidic conditions. When bromide was present in NH2Cl solutions, the total oxidant concentration (sum of the different bromo-chloro-amines) was significantly decreased by CuO. This was primarily due to the degradation of bromochloramine (NHBrCl) by CuO which was evidenced by membrane inlet mass spectrometry. The decomposition rate of the total oxidant was similar for different CuO dosages (0.02–0.2 g/L) but increased with increasing bromide concentration (0–80 μM) and decreasing pH (6.5–8). An apparent second-order rate constant of 0.73 M⁻¹ s⁻¹ was determined with respect to NH2Cl and bromide concentrations for a CuO concentration of 0.05 g/L. Our findings suggest that, during water transportation in copper pipes or in distribution systems where copper oxide is present, special attention should be given to the stability of chloramines when bromide-containing waters are chloraminated.
... CuO particles were prepared by the CTAB-assisted hydrothermal method with a pH PZC (pH at the point of zero charge) and specific surface area of 8.3 and 12.8 m 2 g −1 , respectively (Text S2) (Liu et al., 2012). HOCl, Br − and Cu 2+ were spiked in the forms of NaOCl solution (N10%, w/w), KBr and Cu(NO 3 ) 2 (Sinopharm Chemical Reagent, Shanghai), respectively. ...
... The specific surface area of CuO was measured by a TriStar II 3020 surface area and porosity analyzer (Micromeritics). The pHpzc of CuO particles was determined by a potentiometric titration (Liu et al., 2012). ...
... On the other hand, the CuOinduced polarization greatly promoted the chlorine decay via disproportionation and oxygen generation (Eqs. (1) and (2)) (Liu et al., 2012): ...
Article
Biofilm formation is ubiquitous on the corroded inner surface of water distribution pipes. Extracellular polymeric substances (EPS) secreted by biofilm microorganisms are nonnegligible precursors of disinfection byproducts (DBPs). The aim was to study the catalysis of copper corrosion products (CCPs, CuO and Cu²⁺) on the formation of carbonaceous and nitrogenous DBPs (C-DBPs and N-DBPs) with EPS as a precursor. Results indicate that CCPs had a remarkable enhancement on the formation of DBPs, especially N-DBPs. The enhancement by Cu²⁺ was mainly via homogeneous catalysis initiating from its complexation with EPS, while that by CuO was primarily through heterogeneous catalysis initiating from the polarization of Cl atom in HOCl/OCl⁻. The enhancement was more evident as pH increased because an alkaline condition favored the electrostatic interactions of CCPs with EPS and HOCl/OCl⁻. The presence of Br⁻ weakened the enhancement, which may be attributed to that HOBr/OBr⁻ had a much higher reaction rate than HOCl/OCl⁻ towards the low reactive moieties in EPS. Due to more phenolic or unsaturated/conjugated groups, EPS proteins had a higher catalytic formation of DBPs than EPS polysaccharides. Among the major amino acids in EPS proteins for DBPs formation, tyrosine had the highest enhancement on the formation of trihalomethanes, while histidine had the highest catalytic formation of halogenated acetic acids, acetonitriles and acetamides. The study helps to understand the formation of DBPs by the joint actions of EPS and CCPs in drinking water distribution systems.
... It is also well established that the disproportionation of hypohalites (eq (2)) is a very slow process and the formation of halates is generally negligible during water treatment and distribution. However, Liu et al. (2012) reported that a significant amount of chlorate was formed in HOCleCuO system, and a CuO-catalysed disproportionation pathway (eq (3)) of chlorine was suggested for the first time. During the chlorination of bromide-containing water, bromide is oxidised to hypobromous acid and hypobromite (k HOCl/Br À ¼ 1.5 Â 10 3 M À1 s À1 ; k OCl À / Br À ¼ 9.0 Â 10 À4 M À1 s À1 ) (Deborde and von Gunten, 2008). ...
... During the chlorination of bromide-containing water, bromide is oxidised to hypobromous acid and hypobromite (k HOCl/Br À ¼ 1.5 Â 10 3 M À1 s À1 ; k OCl À / Br À ¼ 9.0 Â 10 À4 M À1 s À1 ) (Deborde and von Gunten, 2008). Similarly, it is also found that CuO can catalyse the decay of bromine (Liu et al., 2012). In HOCleCuOeBrsystem, bromide produced from decomposition and disproportionation is re-oxidised by chlorine to bromine which further undergoes disproportionation and decomposition until chlorine depletes completely, converting most bromide to bromate (Liu et al., 2012). ...
... Similarly, it is also found that CuO can catalyse the decay of bromine (Liu et al., 2012). In HOCleCuOeBrsystem, bromide produced from decomposition and disproportionation is re-oxidised by chlorine to bromine which further undergoes disproportionation and decomposition until chlorine depletes completely, converting most bromide to bromate (Liu et al., 2012). Note that in bromide-containing waters, the formation of chlorate is expected to be negligible, and bromate should be the main formed halate (Liu et al., 2012). ...
Article
The present study investigated the effect of oxoanions on catalytic behaviour of copper corrosion products (CCPs) during chlorination of bromide-containing waters. Three types of oxoanions (carbonate, sulphate, and phosphate) and four types of CCPs (Cu2+, Cu(OH)2, Cu2O, and CuO) were involved in investigation and the effect of oxoanions concentration was also examined. The result indicated that carbonate and sulphate slightly inhibited oxidant decay in the presence of CCPs, but the formation of brominated disinfection by-products (Br-DBPs) remained largely unchanged. In contrast, the presence of phosphate (0.2-1 mM) almost eliminated the catalytic effect of Cu2+. For CCP solids (i.e. Cu(OH)2, Cu2O, and CuO), phosphate preferentially inhibited the formation of bromate rather than Br-DBPs. Despite the catalysis by CCP solids was reduced to some extent, the oxidant decay rate and bromate and Br-DBP formation were still significantly higher than blank groups, even at high phosphate concentration. By testing different addition scheme (simultaneous/sequential addition), it was proposed that phosphate was a strong competitor for hypohalites, rapidly destroying CCPs-hypohalites complexes on some adsorption sites. However, there were some specific sites that can only be adsorbed by hypohalites, leading to the incomplete inhibition of phosphate. Finally, the inhibition effect of phosphate on CCPs catalysis was tested in real water matrix. For Cu2+, higher reduction of bromate and Br-DBPs was found in raw water rather than filtered water, while converse pattern was true for Cu(OH)2 and Cu2O, and this discrepancy can be ascribed to the difference in catalytic mechanism between Cu2+ and CCP solids.
... The effect of metal oxides on the formation of BrO 3 À during the chlorination of Br À containing water was examined as a function of pH and amount of metal oxides and anions [130,131]. Fig. 6 depicts the decay of chlorine and the formation of bromate as a function of time at pH 8.6. The decay of chlorine was not affected by the presence of a-FeOOH, while a slight increase in chlorine decay was observed with the Cu 2 O surfaces in the chlorine-Br À system (Fig. 6A). ...
... Formation of BrO 3 À from the decay of HOBr is enhanced due to the presence of CuO and NiO (Fig. 6B). The values of k 0 for decay of HOBr in the presence of CuO at different pH are given in Table 4 [130]. The rates increased with increasing pH. ...
... This suggests the importance of OBr À species (see Eq. (4)). In addition to the formation of BrO 3 À from the decay of HOBr, the release of oxygen was also determined [130]. A study on the effect of anions (phosphate, sulfate, and carbonate) on the CuO catalyzed decay of HOBr was studied [131]. ...
Article
Global production of engineered nanoparticles (ENPs) continues to increase due to the demand of enabling properties in consumer products and industrial applications. Release of individual or aggregates of ENPs have been shown to interact with one another subsequently resulting in adverse biological effects. This review focuses on silver nanoparticles (AgNPs), which are currently used in numerous applications, including but not limited to antibacterial action. Consequently, the release of AgNPs into the aquatic environment, the dissociation into ions, the binding to organic matter, reactions with other metal-based materials, and disruption of normal biological and ecological processes at the cellular level are all potential negative effects of AgNPs usage. The potential sources of AgNPs includes leaching of intact particles from consumer products, disposal of waste from industrial processes, intentional release into contaminated waters, and the natural formation of AgNPs in surface and ground water. Formation of natural AgNPs is greatly influenced by different chemical parameters including: pH, oxygen levels, and the presence of organic matter, which results in AgNPs that are stable for several months. Both engineered and natural AgNPs can interact with metal and metal oxide particles/nanoparticles. However, information on the chemical and toxicological interactions between AgNPs and other nanoparticles is limited. We have presented current knowledge on the interactions of AgNPs with gold nanoparticles (AuNPs) and titanium dioxide nanoparticles (TiO2 NPs). The interaction between AgNPs and AuNPs result in stable bimetallic Ag-Au alloy NPs. Whereas the interaction of AgNPs with TiO2 NPs under dark and light conditions results in the release of Ag⁺ ions, which may be subsequently converted back into AgNPs and adsorb on TiO2 NPs. The potential chemical mechanisms and toxic effects of AgNPs with AuNPs and TiO2 NPs are discussed within this review and show that further investigation is warranted.
... The effect of metal oxides on the formation of BrO 3 À during the chlorination of Br À containing water was examined as a function of pH and amount of metal oxides and anions [130,131]. Fig. 6 depicts the decay of chlorine and the formation of bromate as a function of time at pH 8.6. The decay of chlorine was not affected by the presence of a-FeOOH, while a slight increase in chlorine decay was observed with the Cu 2 O surfaces in the chlorine-Br À system (Fig. 6A). ...
... Formation of BrO 3 À from the decay of HOBr is enhanced due to the presence of CuO and NiO (Fig. 6B). The values of k 0 for decay of HOBr in the presence of CuO at different pH are given in Table 4 [130]. The rates increased with increasing pH. ...
... This suggests the importance of OBr À species (see Eq. (4)). In addition to the formation of BrO 3 À from the decay of HOBr, the release of oxygen was also determined [130]. A study on the effect of anions (phosphate, sulfate, and carbonate) on the CuO catalyzed decay of HOBr was studied [131]. ...
Article
Disinfection of drinking water is important to prevent microbial infection and disease. However, chlorine as a disinfectant is capable of reacting with inorganic and organic constituents of water to produce hazardous chlorinated disinfection byproducts (Cl-DBPs). Brominated and iodinated DBPs (Br-DBPs and I-DBPs), which are more genotoxic and cytotoxic than their chlorinated analogs, may also be formed in the presence of bromide (Br⁻) and iodide (I⁻) in water. This paper first reviews the formation of Cl-DBPs and Br-DBPs by considering the rates of the reactions of chlorine with natural organic matter (NOM) and its model compounds. The reactions of chlorine with Br⁻ and I⁻ yield acids (HOBr/OBr⁻ and HOI/OI⁻, respectively), which subsequently either disproportionate or react with NOM to form Br-DBPs and iodate/I-DBPs, respectively. The mechanisms of the formation of DBPs in the presence of metal ions and metal oxides (which already exist in water and are released from pipes) and nanoparticles (NPs) (input from the use of consumer products) are then reviewed. Water parameters (pH, cationic and anionic constituents, and types and concentration of NOM) also influence the production of DBPs. Plausible mechanisms of the influence of metal ions on the formation of bromate involve complexation of metal ions with moieties of NOM. Metal oxides catalyze the reactions accountable for the formation of Br-DBPs. Only a few studies have been conducted on the effect of NPs on DBP production during chlorination. More research is needed to understand the variation in NP chemistry under environmental conditions (pH, dissolution, and light), and whether NPs influence DBP formation during chlorination.
... can enhance the reactivity of free chlorine on the surfaces of cupric oxide, and promotes the formation of chlorite over chlorate. 51,131 Instead of inducing a disproportionation reaction Lead oxide has been shown to speciate into three different surfaces, which vary depending on pH: >Pb(IV)OH, >Pb(IV)O -, and >Pb(IV)OH2 + . 125,130 The surface is deprotonated at pH above the pHpzc and protonated at pH below the pHpzc. ...
... Previous studies have shown cupric oxide to polarize chlorine through complexation, making the atom more electrophilic, and catalyzing chlorine dioxide decay to its byproducts. 51,131,146 The adsorption conformation of chlorine dioxide on the lead oxide surface seems to corroborate this theory. ...
Thesis
The oxidants used in water treatment to inactivate pathogens are powerful and, consequently, react with other constituents they encounter, notably organic matter and pipe corrosion scale. Moreover, the complex relationships between said reactions remains poorly understood. Reactions with organic matter produce disinfection byproducts, many of which are regulated by the United States Environmental Protection Agency (EPA) due to their toxicity. To remove these byproducts and meet EPA standards, water treatment facilities add chemicals that can exacerbate corrosion and increase the concentration of dissolved metals in drinking water. Chlorine dioxide, the focus of this dissertation, has been used as an alternative to free chlorine, the most commonly used disinfectant, because it does not produce organic disinfection byproducts. Additionally, chlorine dioxide has a disinfecting power equal to or higher than that of free chlorine, its disinfection capabilities are independent of pH, and it can be used as either a primary or secondary disinfectant. From a corrosion standpoint, chlorine dioxide has a high oxidation-reduction potential, which promotes the formation of passivating scale layers on metal pipe surfaces, thereby preventing dissolution of heavy metals into drinking water. Chlorine dioxide does, however, produce two toxic inorganic byproducts, chlorite and chlorate. Despite the drawbacks associated with inorganic byproduct formation, chlorine dioxide is a disinfectant worthy of investigation with regards to three reactions: pathogen disinfection mechanisms; drinking water pipe corrosion; and formation of inorganic byproducts. The first part of this dissertation addresses the inactivation of the H1N1 influenza virus using computational models. Both computational and experimental methods identified tryptophan 153, an amino acid residue key in the binding of H1N1 to its human host cell, as the primary target of chlorine dioxide oxidation. Part two of this work shows results from batch reactor experiments of chlorine dioxide with lead and copper minerals commonly found in corrosion scale layers. Decay of chlorine dioxide in the presence of lead oxide and lead carbonate was significantly faster and produced different byproducts than decay in the presence of cupric oxide. It was further revealed that the relationship between pH and reaction rate is likely dependent upon surface charge for lead oxide but not for cupric oxide. These findings were the impetus for the third and final part of this dissertation which employed computational methods to model the subtle differences between surface adsorption on cupric oxide and lead oxide, of either the chlorine dioxide monomer or dimer, in the presence or absence of hydroxide. The results of the calculations suggest that the chlorine dioxide degradation pathway on the cupric oxide surface favors dimerization of chlorine dioxide and its ensuing disproportionation into chlorite and chlorate, whereas the lead oxide surface favors direct electron transfer and formation of chlorite. These findings add to the body of knowledge on the alternative disinfectant, chlorine dioxide, and its chemical interactions with pathogens and corrosion scale. The results suggest that chlorine dioxide may have highly specific mechanisms of virus inactivation and computational methods could be valuable tools for elucidating these mechanisms. Further conclusions suggest that chlorine dioxide decay caused by mineral scales in lead-containing water supply networks may be more pronounced than in those assembled from copper pipes.
... Bromide (Br ⁻ ) is ubiquitous in source waters, with highly variable levels in a range of <10 to >1000 mg/L (Liu et al., 2012). The usage of desalinated seawaters, seawater intrusion, and anthropogenic activities such as hydraulic fracturing and coal-fired power plants lead to elevated Br ⁻ levels (Good and VanBriesen, 2016;Kim et al., 2015). ...
... The kinetics for the MC reactions with chlorine and bromine were determined at pH 7.5 (10 mM phosphate buffer) and 21 C (room temperature) in Milli-Q water under pseudo-first-order conditions where chlorine or bromine was at least 10-fold in excess. Bromine solutions were prepared by the reaction of chlorine with Br ⁻ according to a previously described method (Liu et al., 2012). The reaction was initiated by injecting 50 mL of the chlorine (or bromine) stock solution into 5 mL of solutions containing MCs which were capped with PTFE-faced silica septum. ...
Article
Seasonal algal blooms in surface waters can impact water quality through an input of algal organic matter (AOM) to the pool of dissolved organic matter as well as the release of cyanotoxins. The formation and speciation of disinfection byproducts (DBPs) during chlorination of algal-impacted waters, collected from growth of Microcystis aeruginosa were studied. Second-order rate constants for the reactions of microcystins (MCs) with chlorine and bromine were determined. Finally, the toxicity of chlorinated algal-impacted waters was evaluated by Chinese hamster ovary (CHO) cytotoxicity and genotoxicity assays. Under practical water treatment conditions, algal-impacted waters produced less regulated trihalomethanes (THMs) and haloacetic acids (HAAs), haloacetonitriles (HANs), and total organic halogen (TOX) than natural organic matter (NOM). For example, the weight ratios of DBP formation from AOM to NOM (median levels) were approximately 1:5, 1:3, 1:2 and 1:3 for THMs, HAAs, HANs, and TOX, respectively. Increasing initial bromide level significantly enhanced THM and HAN concentrations, and therefore unknown TOX decreased. The second-order rate constant for the reactions of MC-LR (the most common MC species) with chlorine was 60 M⁻¹ s⁻¹ at pH 7.5 and 21 °C, and the rate constants for MC congeners follow the order: MC-WR > MC-LW > MC-YR > MC-LY > MC-LR ≈ MC-RR. The reaction rate constant of bromine with MC-LR is two orders of magnitude higher than that of chlorine. Unchlorinated algal-impacted waters were toxic owning to the presence of MCs, and chlorination enhanced their cytotoxicity and genotoxicity due to the formation of toxic halogenated DBPs. However, the toxicity of treated waters depended on the evolution of cyanotoxins and formation of DBPs (particularly unknown or emerging DBPs).
... The effects of pH on the HNMs formation were attributed to the changes of various reactive species. At pH 6.0, HOCl and HOBr are the absolute dominant species, while OCl − and OBr − are the main forms of chlorine and bromine, respectively, at pH 8.0 (Liu et al., 2012). Also, the deprotonation process caused by a high pH weakened the reactivity of HOCl and HOBr to nitrate. ...
Article
UV/chlor(am)ine are efficient for achieving multiple-barrier disinfection and maintaining residuals, while bromide (Br⁻) has notable impacts on the formation and toxicity of halonitromethanes (HNMs) during UV/chlor(am)ine disinfection. This study investigated the effects of Br⁻ on HNMs formation and toxicity alteration during UV/chlor(am)ine disinfection of nitrate containing humic acid (HA) water. Results reveal that the maximum concentration of HNMs during UV/chlorine disinfection was 12.03 μg L⁻¹ with 0.2 mg L⁻¹ Br⁻, which was 22.5% higher than that without Br⁻, and the predominant species of HNMs were converted from trichloronitromethane (TCNM) to dibromonitromethane (DBNM) and tribromonitromethane (TBNM). However, the maximum concentration of HNMs during UV/chloramine disinfection was 3.69 μg L⁻¹ with 0.2 mg L⁻¹ Br⁻, which was increased by 26.0% than that without Br⁻, and the predominant species of HNMs were converted from dichloronitromethane (DCNM) to bromochloronitromethane (BCNM) and DBNM. Notably, the HNMs species and yields during UV/chloramine disinfection were less than those during UV/chlorine disinfection, primarily due to the higher concentrations of HO• and reactive chlorine/bromine species in UV/chlorine. Also, in the ranges of the Br⁻:Cl2 molar ratio from 0 to 0.32 and pH from 6.0 to 8.0, the Br⁻:Cl2 molar ratio of 0.16 and acidic pH contributed to the HNMs formation during UV/chlorine disinfection, and a high Br⁻:Cl2 molar ratio and neutral pH contributed to the HNMs formation during UV/chloramine disinfection. Note that the incorporation of Br⁻ significantly improved the calculated cytotoxicity (CTI) and genotoxicity (GTI) of HNMs formed, and the calculated CTI and GTI of HNMs formed during UV/chloramine disinfection were 28.19 and 48.90% of those during UV/chlorine disinfection. Based on the diversity of nitrogen sources, the possible formation pathways of HNMs from nitrate containing HA water were proposed during UV/chlor(am)ine disinfection in the presence of Br⁻. Results of this study indicated that UV/chloramine can reduce the formation and toxicity of HNMs efficiently.
... BrO 2 þ O À 3 ; k 4 ¼ 8:910 4 M À 1 s À 1 ½4� Besides ozonation, bromate can be formed in advanced oxidation processes when hydrogen peroxide coupled with O 3 and in ferrate (VI) oxidation (Arvai, Jasim, Biswas 2012;Huang et al. 2016). Bromate was also detected in water after other advanced treatment methods such as ultraviolet combined treatments with chlorine (UV/chlorine), with persulfate (UV/persulfate) and cupric oxide (CuO) chlorination (Huang, Gao, Deng 2008;Fang and Shang, 2012;Liu, von Gunten, Croué 2012). During chlorination, chlorine, in the form of hypochlorous acid (HOCl), oxidizes Br − to hypobromous acid (HOBr), which is further oxidized to bromous acid (HBrO 2 ) to finally produce bromate, as shown in following reactions 5-7 (Tynan, Lunt, Hutchison 1993). ...
Article
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In this study, the removal of bromate, a regulated ozone by-product, was evaluated using a strong-base anion (SBA) exchange resin in batch and column experiments. The kinetics studies in batch mode showed that film diffusion-controlled bromate exchange in SBA and the isotherm studies showed that the Langmuir model fitted the experimental results with a maximum exchange capacity of 296.66 mg BrO3⁻/g (~1.3 meq/mL resin). In the fixed-bed column studies, breakthrough curves were obtained under different operating conditions to examine the effects of feed flow rate, inlet bromate concentration, and bed height on column performance. A modified n-order Bohart and Adams model (n-BAM-c), which considered the asymmetry of the breakthrough curve and flow channeling, was applied for the first time to describe the experimental data obtained from the column and to predict the breakthrough curves. It was found that n-BAM-c fitted the experimental data well (R² > 0.99) and the effects of the key operating conditions on the model parameters were determined. Overall, the results show that SBA exchange is suitable for bromate removal from water and n-BAM-c could be a powerful tool for the design and upscaling of bromate ion exchange columns.
... During disinfection processes chlorine, hypochlorites and ozone may oxidize bromide (Br-) to bromine (Br 2 ) and further to bromate (Huang et al. 2008;Liu et al. 2012;Shi et al. 2013;Fang et al. 2014). Bromide ions (Br-) react rapidly to hypobromite (OBr-) in the presence of ozone (1) and may subsequently and unintentionally disproportionate to bromate (BrO 3 − ) at elevated pH-values, or may also be oxidized to bromate by ozone (2). 1 The yield of bromate generated during ozonation of water is dependent on several factors such as pH, total dissolved organic carbon (TOC), ammonia, bromide and temperature. ...
Article
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Bromate, classified as a EU CLP 1B carcinogen, is a typical by-product of the disinfection of drinking and swimming pool water. The aim of this study was (a) to provide data on the occurrence of bromate in pool water, (b) to re-evaluate the carcinogenic MOA of bromate in the light of existing data, (c) to assess the possible exposure to bromate via swimming pool water and (d) to inform the derivation of cancer risk-related bromate concentrations in swimming pool water. Measurements from monitoring analysis of 229 samples showed bromate concentrations in seawater pools up to 34 mg/L. A comprehensive non-systematic literature search was done and the quality of the studies on genotoxicity and carcinogenicity was assessed by Klimisch criteria (Klimisch et al., Regul Toxicol Pharmacol 25:1–5, 1997) and SciRAP tool (Beronius et al., J Appl Toxicol, 38:1460–1470, 2018) respectively. Benchmark dose (BMD) modeling was performed using the modeling average mode in BMDS 3.1 and PROAST 66.40, 67 and 69 (human cancer BMDL10; EFSA 2017). For exposure assessment, data from a wide range of sources were evaluated for their reliability. Different target groups (infants/toddlers, children and adults) and exposure scenarios (recreational, sport-active swimmers, top athletes) were considered for oral, inhalation and dermal exposure. Exposure was calculated according to the frequency of swimming events and duration in water. For illustration, cancer risk-related bromate concentrations in pool water were calculated for different target groups, taking into account their exposure using the hBMDL10 and a cancer risk of 1 in 100,000. Convincing evidence was obtained from a multitude of studies that bromate induces oxidative DNA damage and acts as a clastogen in vitro and in vivo. Since statistical modeling of the available genotoxicity data is compatible with both linear as well as non-linear dose–response relationships, bromate should be conservatively considered to be a non-threshold carcinogen. BMD modeling with model averaging for renal cancer studies (Kurokawa et al., J Natl. Cancer Inst, 1983 and 1986a; DeAngelo et al., Toxicol Pathol 26:587–594, 1998) resulted in a median hBMDL10 of 0.65 mg bromate/kg body weight (bw) per day. Evaluation of different age and activity groups revealed that top athletes had the highest exposure, followed by sport-active children, sport-active adults, infants and toddlers, children and adults. The predominant route of exposure was oral (73–98%) by swallowing water, followed by the dermal route (2–27%), while the inhalation route was insignificant (< 0.5%). Accepting the same risk level for all population groups resulted in different guidance values due to the large variation in exposure. For example, for an additional risk of 1 in 100,000, the bromate concentrations would range between 0.011 for top athletes, 0.015 for sport-active children and 2.1 mg/L for adults. In conclusion, the present study shows that health risks due to bromate exposure by swimming pool water cannot be excluded and that large differences in risk exist depending on the individual swimming habits and water concentrations.
... Bromate formation mainly occurs during ozonation (Shah et al., 2015a;von Sonntag and von Gunten, 2012). Chlorination typically does not lead to bromate formation, unless it is in electro-chlorination treatment or when the process is catalyzed by metal oxides such as copper oxide (Jung et al., 2014;Liu et al., 2012). ...
Article
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Oxidative treatment of seawater in coastal and shipboard installations is applied to control biofouling and/or minimize the input of noxious or invasive species into the marine environment. This treatment allows a safe and efficient operation of industrial installations and helps to protect human health from infectious diseases and to maintain the biodiversity in the marine environment. On the downside, the application of chemical oxidants generates undesired organic compounds, so-called disinfection by-products (DBPs), which are discharged into the marine environment. This article provides an overview on sources and quantities of DBP inputs, which could serve as basis for hazard analysis for the marine environment, human health and the atmosphere. During oxidation of marine water, mainly brominated DBPs are generated with bromoform (CHBr3) being the major DBP. CHBr3 has been used as an indicator to compare inputs from different sources. Total global annual volumes of treated seawater inputs resulting from cooling processes of coastal power stations, from desalination plants and from ballast water treatment in ships are estimated to be 470 – 800 × 10⁹ m³, 46 × 10⁹ m³ and 3.5 × 10⁹ m³, respectively. Overall, the total estimated anthropogenic bromoform production and discharge adds up to 13.5 – 21.8 × 10⁶ kg/a (kg per year) with contributions of 11.8 – 20.1 × 10⁶ kg/a from cooling water treatment, 0.89 × 10⁶ kg/a from desalination and 0.86 × 10⁶ kg/a from ballast water treatment. This equals approximately 2 – 6 % of the natural bromoform emissions from marine water, which is estimated to be 385 – 870 × 10⁶ kg/a.
... The dissociation constant ( pK a ) values of HOCl and HOBr were 7.5 and 8.6, respectively. At pH 6.0, HOCl and HOBr are the dominant species, while OCl − and OBr − account for more than 60% and 15% of free chlorine and bromine, respectively, at pH 8.0 ( Liu et al., 2012 ). First, the deprotonation process at a higher pH weakened the substitution reaction of free bromine and chlorine with methylamine. ...
Article
The UV/Cl2 process is commonly used to achieve a multiple-barrier disinfection and maintain residuals. The study chose methylamine as a precursor to study the formation of high-toxic halonitromethanes (HNMs) in the presence of bromide ions (Br⁻) during UV/Cl2 disinfection. The maximum yield of HNMs increased first and then decreased with increasing concentration of Br⁻. An excessively high concentration of Br⁻ induced the maximum yield of HNMs in advance. The maximum bromine incorporation factor (BIF) increased, while the maximum bromine utilization factor (BUF) decreased with the increase of Br⁻ concentration. The maximum yield of HNMs decreased as pH value increased from 6.0 to 8.0 due to the deprotonation process. The BUF value remained relatively higher under an acidic condition, while pH value had no evident influence on the BIF value. The maximum yield of HNMs and value of BUF maximized at a Cl2:Br⁻ ratio of 12.5, whereas the BIF value remained relatively higher at low Cl2:Br⁻ ratios (2.5 and 5). The amino group in methylamine was first halogenated, and then released into solution as inorganic nitrogen by the rupture of C-N bond or transformed to nitro group by oxidation and elimination pathways. The maximum yield of HNMs in real waters was higher than that in pure water due to the high content of dissolved organic carbon. Two real waters were sampled to verify the law of HNMs formation. This study helps to understand the HNMs formation (especially brominated species) when the UV/Cl2 process is adopted as a disinfection technique.
... Besides organic contaminants, inorganic ones have also attracted much attention such as bromate (BrO 3 − ). BrO 3 − is usually produced as a by-product of oxidation of bromide (Br − ) or brominated organics by various oxidation processes such as O 3 oxidation [17], and HO•/SO 4 • − based AOPs [18][19][20][21]. Since BrO 3 − has the risk of human carcinogen and gene-toxicity [22], its allowable concentration is recommended to be lower than 10 μg L − 1 in drinking water by the WHO and US-EPA [23,24]. ...
Article
Reduction of bromate (BrO3⁻) by various technologies has been extensively investigated, while the fate of oxygen and bromine atoms in BrO3⁻ in these processes has been largely ignored. In this study, reduction of BrO3⁻ by Fe(II) ions was investigated under various conditions via electron spin resonance (ESR), laser flash photolysis (LFP), probe of phenol and quenching experiments. It was found that reduction of BrO3⁻ by Fe(II) ions produced HO•, O2•⁻ and reactive bromine species (eg., Br• and Br2•⁻). HO• and O2•⁻ were generated from release of one/two oxygen atoms in BrO3⁻ and its reduction intermediates (BrO2⁻ and BrO⁻) at one time, while Br• and Br2•⁻ were generated from activation of hypobromous acid by Fe(II) and reactions of HO• with formed Br⁻. Due to the formation of these reactive species, the tested ten organic pollutants with diverse structures can be efficiently degraded, which including carbamazepine (CBZ), ibuprofen, phenol, benzoic acid, paracetamol, bisphenol a, 4-chlorophenol, oxcarbazepine, diclofenac and sulfamethoxazole. CBZ degradation intermediates by BrO3⁻/Fe(II) system were specially identified by liquid chromatography (LC)-mass spectrometry (MS), and three pathways of hydroxylation, ring contraction-amine cleavage and bromination for CBZ degradation were proposed accordingly. This study might shed new fundamental insights to bromate reduction and its implication for transformation of co-existed organic pollutants.
... Bromate ions can be also found in drinking water as a result of secondary pollution of tap water. The presence of bromates in treated drinking water is associated primarily with the ozone reacting with bromide ions, which are naturally present in all types of water, as well as with the presence of bromates as an impurity of hypochlorites used to disinfect water [9][10][11][12][13][14][15][16]. ...
Article
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Background The article presents the results of studies performed in order to develop a new method of airborne potassium bromate(V) determination at workplaces. Methods The method is based on a collection of inhalable fraction of potassium bromate(V) using the IOM Sampler, then extraction of bromates with deionized water and chromatographic analysis of the obtained solution. The analysis was performed using ion chromatography with conductometric detection. The tests were performed on a Dionex IonPac®AS22 analytic column (250 x 4mm, 6μm) with AG22 precolumn (50x4mm 11μm). Results The method provides for potassium bromate(V) determination within the concentration range of 0.043 ÷ 0.88 mg/m³ for an air sample of 0.72 m³ in volume, i.e. 0.1 to 2 times the exposure limit value as proposed in Poland. The method was validated in accordance with PN-EN 482. The obtained validation data are as follows: measuring range: 3.1-63.4 μg/mL, limit of detection (LOD) = 0.018 μg/mL and limit of quantification (LOQ) = 0.053 μg/mL. The developed method has been tested in the work environment, on laboratory employees having contact with potassium bromate(V). Conclusion The analytical method allowed the determination of the inhalable fraction of airborne potassium bromate(V) at workplaces and can be used to assess occupational exposure.
... The hypobromite stock solution was prepared by reacting NaOCl with Br − at a molar Br/Cl ratio of 1.05 at pH 11 adjusted by sodium hydroxide (Lei et al., 2004). This solution was stored at 4°C and the concentration was determined by monitoring the absorbance at λ max 329 nm (ε = 332 M −1 cm −1 ) (Liu et al., 2012). ...
Article
A Membrane Introduction Mass Spectrometry (MIMS) method was developed to differentiate and quantify the different chlorinated and brominated-amines, present in drinking water during chloramination. The representative mass to charge ratios (m/z) of 53, 85, 97, 175 and 131 corresponding to the mass of the parent compounds were selected to monitor NH2Cl, NHCl2, NH2Br, NHBr2 and NHBrCl and the detection limits were found to be 0.034, 0.034, 0.10, 0.12 and 0.36 mg/L as Cl2, respectively. NHCl2, NHBr2 and NHBrCl fragments interfere with the analysis/quantification of NH2Cl and NH2Br via protonation reactions at hot metal surfaces inside the mass spectrometer. To accurately quantify NH2Cl or NH2Br in mixtures of NH2Cl/NHCl2 or NH2Br/NHBr2, the interference from NHCl2 or NHBr2 was subtracted to the signal of the parent compound. If NHBrCl is present, NH2Br and NH2Cl cannot be accurately quantified since the interference from the NHBrCl fragment cannot be distinguished from the signal of the parent compound. Under drinking water conditions, the interference from NHBrCl on NH2Cl was negligible. The different halamines were monitored and quantified for the first time in two surface waters and one seawater that were chloraminated to mimic a realistic disinfection scenario.
... The dissolved Pb was determined by an inductively coupled plasma mass spectrometer (Thermo iCAP 70 0 0). The pHpzc of PbO 2 was measured by the potentiometric titration method ( Liu et al., 2012 ). The chronic cytotoxicity was tested by Chinese Hamster Ovary (CHO) cells ( Dong et al., 2016 ). ...
Article
Lead dioxide (PbO 2) is an important form of lead mineral scales in drinking water pipes. Iodide (I −) widely presents in source waters and can be thermodynamically oxidized by PbO 2 to the reactive iodine species (I 2 /HOI). Biofilm extracellular polymeric substances (EPS) are nonnegligible precursors of disin-fection byproducts (DBPs). The aim was to study the oxidation of I − by PbO 2 and formation of iodinated DBPs (I-DBPs) from EPS. At a high molar ratio of PbO 2 to I − (> 100), the observed rate constants of I − oxidation decreased as pH increased from 6.0 to 9.0 with an H + dependence of 0.79, and the rate constant (k) was 1.6 × 10 11 M −2.79 s −1. Most of formed I 2 /HOI (> 92%) was transformed to organic iodine in the presence of EPS. EPS had a lower formation potential (FP) of carbonaceous I-DBPs (C-IDBPs), while a higher that of nitrogenous I-DBPs (N-IDBPs) than HA, resulting in a higher Chinese Hamster Ovary cell cytotoxicity. Generally, the formation of I-DBPs decreased with the increase of pH due to the reduction of surface positive charge and electrochemical driving force. PbO 2 dose and I − concentration also had a significant effect on the I-DBPs formation. EPS proteins had a higher FP of both C-and N-IDBPs than polysaccharides on account of more electrophilic sites and higher nitrogen content. In proteins, aspartic acid was the main contributor to triiodomethane and iodoacetic acids formation, whereas aspartic acid, asparagine and tyrosine were the major precursors of diiodoacetonitrile and diiodoacetamide. The study helps to improve the control strategy of I-DBPs when biofilm outbreaks in lead-containing water pipes.
... Bromide (Br À ) is detected in surface water in the range from 10 to 1000 mg L À1 as an important parameter for the formation of brominated DBPs. 19 During chlorination, Br À could be oxidized to form hypobromous (HOBr and OBr À ) products, which had stronger oxidation ability to react with AOM to form brominated DBPs. 20 A few studies have reported THM and HAA formation during chlorination at initial Br À concentrations of 50 and 100 mg L À1 . ...
Article
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Blue-green algae commonly bloom in fresh water in summer, producing extra- and intra-cellular algal organic matters, which are important precursors for disinfection byproduct (DBP) formation. In this study, we evaluated the effect of pre-oxidation with ferrate(VI) (FeO4²⁻, Fe(VI)) on the characterization of intracellular organic matter (IOM) and extracellular organic matter (EOM). The results indicated that soluble microbial-like products of EOM and IOM decreased and humic acid-like products of IOM increased, which would influence the DBP formation in the subsequent chlorination step. Therefore, in this study, the effect of Fe(VI) pre-oxidation on the DBP formation from IOM and EOM with subsequent chlorination was also investigated. For Chlorella sp., EOM presented no significant change, and IOM presented a reduction of THMs (8.2%) after Fe(VI) oxidation at a dosage of 16 mg L⁻¹. For P. limnetica, EOM and IOM both exhibited reduction of trihalomethanes (THMs) and chloral hydrate (CH) after Fe(VI) oxidation. Besides, THMs had the lowest concentration at pH 8.0 in all four solutions. Haloacetonitriles (HANs) and haloketones (HKs) showed slight changes with increasing pH values. Due to the frequent detection of bromide (Br⁻) in surface water, the effect of bromide existence on THM formation was also investigated. The results indicated that all brominated DBPs increased, and chlorinated DBPs decreased with the increase in bromide concentration. In addition, the bromine substitution factor (BSF) of Chlorella sp. and P. limnetica both increased with the increase in Br⁻ concentration.
... Studies [5][6][7][8][9][10][11] have shown a link between the formations of bromate in drinking water produced by desalination when treated with sodium hypochlorite solution and reported significant amount of bromate formation explained by the following reaction. Product water produced from the desalination of seawater contains significantly more bromide than freshwaters, making this an issue of greater concern for desalination than for treatment of inland waters. ...
Article
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Enhanced bromate formation has been observed in desalination-derived drinking water containing bromide disinfected by chlorination under alkaline conditions. As an alternative to chlorine disinfection in drinking water, chlorine dioxide (ClO 2) was investigated to elucidate its performance in curtailing the bromate formation in the seawater reverse osmosis product water. The occurrence of disinfection by-products (DBPs), viz., chlorite, chlorate and trihalomethanes (THMs) was also monitored during the whole period of the tests at varying distances of 10, 50 and 3,500 m. Bromate concentrations throughout the trial were found to be <2 ppb indicating negligible or no bromate formation at the optimum residual ClO 2 in the range of 0.18-0.20 ppm. Chlorite (<0.01-0.1 ppm), chlo-rate (<0.05-0.14 ppm) and calculated total THMs were found to be within the range of the regulatory limits (<1) set by the World Health Organization (WHO). Biological analyses showed total coliforms and E. coli were negative indicating ClO 2 to be very efficient at the optimum residual in the range of 0.18-0.20 ppm. The chlorine dioxide generating system used in this test was found to be efficient in generating chlorine dioxide with minimum amounts of DBPs.
... In addition to four trihalomethanes (THM4) and five haloacetic acids (HAA5), which are currently regulated by the United States Environmental Protection Agency (US EPA) (U.S. Environmental Protection Agency, 2001), unregulated DBPs including haloacetaldehydes (HALs), haloketones (HKs), haloacetonitriles (HANs), and halonitromethanes (HNMs) were of particular concern due to their much higher toxicity even though their concentrations are much lower than regulated DBPs . Bromide (Br À ) and iodide (I À ) levels in fresh surface waters which are highly variable range from <10 to >1000 mg/L and 0.5e20 mg/L, respectively (Liu et al. 2012(Liu et al. , 2014. However, the median concentrations of Br À and total iodine (including I À and iodate) are much higher in seawater (e.g., ca. ...
Article
Seasonal algal blooms in freshwater and marine water can increase the input of algal organic matter (AOM) to the pool of dissolved organic matter. The impact of bromide (Br-) and iodide (I-) on the formation of regulated and unregulated disinfection byproducts (DBPs) was studied from chlorination of AOM solutions extracted from three species of cultured isolates of freshwater and marine algae (Microcystis aeruginosa (MA), Synechococcus (SYN), and Alexandrium tamarense (AT)). Comparable concentrations of DBPs were formed from three types of AOM. In the absence of Br-, trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetaldehydes (HALs) were the main groups of DBP formed, and haloacetonitriles (HANs) were formed at lower concentrations. In contrast, the formation of iodinated THMs was <8 nM (1.7 μg/L) since most of initial I- was oxidized to iodate. Increasing initial Br- concentrations increased the formation of THMs and HANs, while concentrations of total organic halogen and HAA remained stable. On the contrary, total HAL concentrations decreased due to the instability of bromated HALs. Decreasing the specific UV absorbance (SUVA) value of AOM favours bromine substitution since bromine more preferentially reacts with low reactivity organic matter than chlorine. Increasing the pH enhanced the formation of THMs but decreased the formation of HANs. Concentrations of HANs and HALs decreased at high pH (e.g., 9.0), high initial chlorine concentration and long reaction time due to the decomposition. Based on the cytotoxicity calculations, unregulated HANs and HALs were the main contributors for the total toxicity of DBPs measured, even though based on the weight regulated THMs and HAAs predominated.
... (2) and (11)-(13)] [33,34]. Further research on the role of bromide in chlorimuron-ethyl chlorination is required. ...
... Obviously, NO 3 − dosage is the most influential factor inhibiting the removal of BrO 3 − with the UV/sulfite system. The results in Fig. 8 further substantiate our claim in Section 3.1 that the presence of NO 3 − and DOC in real water would prohibit the degradation of BrO 3 − in this pilot study.Additionally, the economic efficiency of the UV/sulfite process for decomposition of BrO3 − under different conditions was compared by using UV-254 fluence (mJ/cm 2 ) and electrical energy (EE/kWh/m 3 ), as shown in Eqs.(5) and(6)[38][39][40]. The electricity cost ($/m 3 ) of this process for BrO 3 − reduction was calculated using the following Eq. ...
Article
The degradation of bromate (BrO3⁻) with UV/sulfite processes attracts much attention because of its high removal rate and easier combination with ultraviolet (UV) disinfection. This pilot study demonstrated the effectiveness of UV/sulfite systems and further investigated influences of typical environmental parameters such as UV fluence, pH, concentrations of sulfite ([S(IV)T]), humic acid (HA), bicarbonate (HCO3⁻), and nitrate (NO3⁻) on BrO3⁻ degradation. Results showed that the decomposition was increased with the enhanced UV irradiance and [S(IV)T], whereas a considerable improvement was observed with enhancing pH only over pH 4.5–8.0 ranges probably due to the variation of sulfite species with pH in UV/sulfite systems. In contrast, the dosing of 2–5 mg/L HA proportionally suppressed BrO3⁻ removal in UV/sulfite systems. The obvious inhibitory effect on removal kinetics suggests that HA acted primarily as a scavenger for active species. 2–8 mM HCO3⁻ addition slightly depressed BrO3⁻ degradation, indicating a weak inhibitor of HCO3⁻ in photochemical processes. Moreover, scavenging experiments with NO3⁻ demonstrated that the aqueous electron was responsible for decomposition of BrO3⁻ by UV/sulfite systems in pilot studies. All the bromine atoms in BrO3⁻ were reduced to Br⁻. Principal component analysis further substantiated that high NO3⁻ and HA levels in authentic water inhibited the removal of BrO3⁻ in a lower extent in pilot studies than that in laboratory experiments. The cost evaluation proved UV/sulfite processes to be economical, indicating its full-scale potential in BrO3⁻ removal from drinking water.
... The formation of BrO 3 À is generally insignificant during chlorination of bromide-containing waters (Margerum and Huff Hartz, 2002). However, CuO, a corrosion product of copper pipes, can catalyze HOBr disproportionation to produce Br À and BrO 3 À (Liu et al., 2012a(Liu et al., , 2013a. This catalysis in turn can lead to elevated BrO 3 À concentrations in chlorinated distributed waters (Liu and Croue, 2016). ...
Article
While disinfection provides hygienically safe drinking water, the disinfectants react with inorganic or organic precursors, leading to the formation of harmful disinfection byproducts (DBPs). Biological filtration is a process in which an otherwise conventional granular filter is designed to remove not only fine particulates but also dissolved organic matters (e.g., DBP precursors) through microbially mediated degradation. Recently, applications of biofiltration in drinking water treatment have increased significantly. This review summarizes the effectiveness of biofiltration in removing DBPs and their precursors and identifies potential factors in biofilters that may control the removal or contribute to formation of DBP and their precursors during drinking water treatment. Biofiltration can remove a fraction of the precursors of halogenated DBPs (trihalomethanes, haloacetic acids, haloketones, haloaldehydes, haloacetonitriles, haloacetamides, and halonitromethanes), while also demonstrating capability in removing bromate and halogenated DBPs, except for trihalomethanes. However, the effectiveness of biofiltration mediated removal of nitrosamine and its precursors appears to be variable. Increased nitrosamine precursors after biofiltration was ascribed to the biomass sloughing off from media or direct nitrosamine formation in the biofilter under certain denitrifying conditions. Operating parameters, such as pre-ozonation, media type, empty bed contact time, backwashing, temperature, and nutrient addition may be optimized to control the regulated DBPs in the biofilter effluent while minimizing the formation of unregulated emerging DBPs. While summarizing the state of knowledge of biofiltration mediated control of DBPs, this review also identifies several knowledge gaps to highlight future research topics of interest.
... A humic acid (HA) stock solution was prepared by dissolving HA solids (SigmaAldrich, Shanghai, China) into deionized water and then filtered through 0.45-mm membrane filters. CuO particles were prepared by a CTAB-assisted hydrothermal method (Liu et al., 2012). d-MnO 2 particles were prepared by a modified hydrothermal process by reduction of KMnO 4 (Wang et al., 2015). ...
Article
Ultraviolet (UV)/chlorine process is considered as an emerging advanced oxidation process for the degradation of micropollutants. This study investigated the degradation of chloramphenicol (CAP) and formation of disinfection by-products (DBPs) during the UV/chlorine treatment. It was found that CAP degradation was enhanced by combined UV/chlorine treatment compared to that of UV and chlorination treatment alone. The pseudo-first-order rate constant of the UV/chlorine process at pH 7.0 reached 0.016 s(-1), which was 10.0 and 2.0 folds that observed from UV and chlorination alone, respectively. The enhancement can be attributed to the formation of diverse radicals (HO and reactive chlorine species (RCSs)), and the contribution of RCSs maintained more stable than that of HO at pH 5.5-8.5. Meanwhile, enhanced DBPs formation during the UV/chlorine treatment was observed. Both the simultaneous formation and 24-h halonitromethanes formation potential (HNMsFP) were positively correlated with the UV/chlorine treatment time. Although the simultaneous trichloronitromethane (TCNM) formation decreased with the prolonged UV irradiation, TCNM dominated the formation of HNMs after 24 h (>97.0%). According to structural analysis of transformation by-products, both the accelerated CAP degradation and enhanced HNMs formation steps were proposed. Overall, the formation of diverse radicals during the UV/chlorine treatment accelerated the degradation of CAP, while also enhanced the formation of DBPs simultaneously, indicating the need for DBPs evaluation before the application of combined UV/chlorine process.
Chapter
Procedures were developed for degrading bulk amounts of pharmaceuticals in research laboratories. Pharmaceutical compounds are designed to achieve the maximum biological effect per gram, so it seems a reasonable proposition that a degradation reaction will produce compounds of lesser biological activity. Pharmaceuticals can be degraded by potassium permanganate in acidic, basic, or neutral solution. Nickel–aluminum alloy in an aqueous base is a powerful reductant that cleaves N–N, N–O, and carbon–halogen bonds. In all cases, destruction was greater than 99.8% except for pharmaceutical preparations of mechlorethamine. A variety of pharmaceuticals in aqueous solutions can be degraded using ozonation. Potassium ferrate is a powerful oxidizing agent. Pharmaceuticals can be degraded using persulfates. In all cases, destruction was greater than 99.8% except for pharmaceutical preparations of mechlorethamine. This chapter focuses on the photolysis of pharmaceuticals without the presence of hydrogen peroxide.
Article
Seawater chlorination has three main industrial uses: disinfection of water and installations, control of biofouling, and preventing the transport of aquatic invasive species. Once in contact with seawater, chlorine reacts rapidly with water constituents (e.g. bromide ions, ammonia, and nitrogen-containing compounds) to form a range of oxidative species (e.g. bromine and N-haloamines), termed “chlorine-produced oxidants” (CPOs) or “total residual oxidants” (TRO). The chemical nature of CPOs and their concentration are a function of two categories of parameters related to treatment modality (e.g. chlorine dose) and water quality (e.g. temperature, pH, ammonia concentration, and organic constituents). The chlorination process may result in continuous or intermittent releases of CPOs in seawater. The reactivity and potential ecotoxicity of CPO species largely depend on their physical and chemical properties. Therefore, evaluation of the biocidal effectiveness of chlorination and its potential impacts requires not only determining the sum of CPOs (via a bulk parameter), but also their chemical speciation. The aim of this article – which is the first of a trilogy dedicated to the chemical speciation of CPOs in seawater – is to provide an overview of current knowledge about chlorine chemistry in seawater and to discuss the biocidal efficacy and the environmental fate of resulting CPOs. The 2nd and 3rd articles delineate a comprehensive and critical review of analytical methods and approaches for the determination of CPOs in seawater.
Article
Lead oxide (PbO2) formed by the oxidation of lead pipes and lead-containing plumbing materials is an important corrosion product in some drinking water distribution systems. Under certain conditions it acts as an oxidant, and we report here the effects of pH on the oxidation of I¯ by PbO2, which leads to the formation of iodine (I2) and iodate (IO3¯) as well as dissolution of Pb²⁺. Oxidation of I¯ by PbO2 is a multi-step pH-dependent reaction, the rate of which can be expressed as: R = 6.92 × 10⁹ × [SA]0.67 × [I¯]2.19 × [H⁺]0.59 (where SA is the PbO2 surface area). I2 was the major intermediate product formed along with some HOI, and was then further oxidized to IO3¯. Based on these results, a kinetic model was developed to simulate the evolution of I¯, I2 and IO3¯ in the PbO2/I¯ reaction system. In addition, the formation of iodinated disinfection by-products (I-DBPs) in the PbO2/I¯/NOM system was evaluated under different water quality conditions, and was found to be influenced by the form of the lead corrosion products in the order: Pb3O4 > PbO2 > Pb(CO3)2(OH)2 > PbCO3. Iodoform and monoiodoacetic acid were identified as the main I-DBPs, and their formation decreased with increasing pH. It is concluded that oxidation of I¯ by lead oxides in water distribution pipes probably contributes to the formation of I-DBPs as well as Pb²⁺ in tap water.
Article
Bromate is a commonly identified carcinogenic and genotoxic disinfection byproduct in water. In the present work, bimetallic Ru-Cu catalyst supported on carbon nanotube (RuCu/CNT) was prepared and the structural properties of the catalysts were characterized. The results show that the presence of Ru enhances the dispersion and reduction of Cu particles in the RuCu/CNT catalyst in comparison with the monometallic Cu catalyst supported on CNT (Cu/CNT). For electrocatalytic reaction on Cu/CNT, bromate is reduced on metallic Cu surface via a redox process. For Ru/CNT, highly active H* radicals are generated on metallic Ru surface via the Volmer process and are used for bromate reduction. As for the RuCu/CNT, bromate is reduced through two main pathways, including direct redox reaction on metallic Cu and indirect reduction by active H* radicals on Ru surface. Accordingly, RuCu/CNT exhibits the highest catalytic activity, ascribed to the synergistic effect between metallic Ru and Cu. Furthermore, the bimetallic catalyst displays much higher catalytic efficiency as compared with previously reported results. The pH, initial bromate concentration, in-situ electrochemical reduction of the electrodes and working potential have strong impacts on the removal efficiency of bromate on RuCu/CNT.
Article
In recent years, the UV/sulfite process has shown high superiority in removing toxic halogenated organic compounds and oxyanions. Herein, the reduction of bromate (BrO3ˉ) in this process was reinvestigated. The reduction of BrO3ˉ in this process was influenced by some key coexisting species. A significant inhibition on the reduction of BrO3ˉ was observed in the presence of dissolved oxygen (DO). Nevertheless, increasing sulfite dosage could effectively mitigate the negative impact of DO on the reduction of BrO3ˉ. Humic acid (HA) could influence the reduction of BrO3ˉ through the enhancement of hydrated electron (eaqˉ) yield or the scavenging of eaqˉ. It should be noted that the presence of Cl⁻ and HCO3⁻ had an insignificant influence on the reduction of BrO3ˉ. In this process, besides eaqˉ, sulfite radical (SO3•−) also contributed to the reduction of BrO3ˉ, which was evidenced by scavenging experiments and fitting of a kinetic model. Moreover, the energy efficiency of this process for BrO3ˉ removal was found to be enhanced by increasing sulfite dosage, as indicated by calculation of electrical energy per order (EE/O). Meanwhile, this process was proven to be economical for BrO3ˉ removal. This study might provide a new outlook on the UV/sulfite process for real applications.
Article
Cupric oxide (CuO) is able to catalyze the reactions among disinfectant, extracellular polymeric substances (EPS) and bromide (Br⁻) in copper pipes, which may deteriorate the water quality. This study aimed to investigate the metabonomic and transcriptomic modulations of HepG2 cells caused by the CuO-catalyzed formation of disinfection byproducts (DBPs) from EPS. The presence of CuO favored the substitution reactions of chlorine and bromine with EPS, inducing a higher content of total organic halogen (TOX). In addition, DBPs were shifted from chlorinated species to brominated species. A total of 182 differential metabolites (DMs) and 437 differentially expressed genes (DEGs) were identified, which were jointly involved in 38 KEGG pathways. Topology analysis indicates that glycerophospholipid and purine metabolism were disturbed most obviously. During glycerophospholipid metabolism, the differential expression of genes GPATs, AGPATs, LPINs and DGKs impacted the conversion of glycerol-3-phosphate to 2-diacyl-sn-glycerol, which further affected the conversion among phosphatidylcholine, phosphatidylserine and phosphocholines. During purine metabolism, it was mainly the differential expression of genes POLRs, RPAs, RPBs, RPCs, ENTPDs and CDs that impacted the transformation of RNA into guanine-, xanthosine-, inosine- and adenosine monophosphate, which were further successively transformed into their corresponding nucleosides and purines. The study provides an omics perspective to assess the potential adverse effects of overall DBPs formed in copper pipes on human.
Article
Bromate formation has been found in the SO4•−-based oxidation processes, but previous studies primarily focused on the bromate formation in the homogeneous SO4•−-based oxidation processes. The kinetics and mechanisms of bromate formation are poorly understood in the heterogeneous SO4•−-based oxidation processes, although which have been widely studied in the eliminations of micropollutants. In this work, we found that the presence of CuO, a common heterogeneous catalyst of peroxymonosulfate (PMS), appreciably enhanced the bromate formation from the oxidation of bromide by PMS. The conversion ratio of bromide to bromate achieved over 85% within 10 min in this process. CuO was demonstrated to play a multiple role in the bromate formation: (1) catalyzed PMS to generate SO4•−, which then oxidizes bromide to bromate; (2) catalyzed the formed free bromine to disproportionate to bromate; (3) catalyzed the formed free bromine to decomposed back into bromide. In the CuO-PMS-Br system, bromate formation increases with increasing CuO dosages and initial CuO and bromide concentrations, but decreases with increasing bicarbonate concentrations. The presence of NOM (natural organic matter) resulted in a lower formed bromate accompanied with organic bromine formation. Notably, CuO catalyzes PMS to transform more than 70% of initial bromide to bromate even after recycled used for six times. The formation of bromate in the PMS catalysis by CuO system was also confirmed in real water.
Article
The application of oxidants for disinfection or micropollutant abatement during drinking water and wastewater treatment is accompanied by oxidation of matrix components such as dissolved organic matter (DOM). To improve predictions of the efficiency of oxidation processes and the formation of oxidation products, methods to determine concentrations of oxidant-reactive phenolic, olefinic or amine-type DOM moieties are critical. Here, a novel selective oxidative titration approach is presented, which is based on reaction kinetics of oxidation reactions towards certain DOM moieties. Phenolic moieties were determined by oxidative titration with ClO2 and O3 for five DOM isolates and two secondary wastewater effluent samples. The determined concentrations of phenolic moieties correlated with the electron-donating capacity (EDC) and the formation of inorganic ClO2-byproducts (HOCl, ClO2⁻, ClO3⁻). ClO2-byproduct yields from phenol and DOM isolates and changes due to the application of molecular tagging for phenols revealed a better understanding of oxidant-reactive structures within DOM. Overall, oxidative titrations with ClO2 and O3 provide a novel and promising tool to quantify oxidant-reactive moieties in complex mixtures such as DOM and can be expanded to other matrices or oxidants.
Chapter
Bromine chloride is a toxic reddish-yellow mobile liquid or gas and a strong oxidizing agent. The substance shows initial corrosive effects on the eyes, skin, and respiratory tract causing chronic inflammation and impaired functions. Inhalation may cause asthma, pneumonitis, or lung edema. Bromine chloride has application as a brominating agent in the preparation of fire-retardant chemicals, pharmaceuticals, high-density brominated liquids, agricultural chemicals, dyes, and bleaching agents. This chapter provides a comprehensive and detailed overview of the bromine chloride toxicity, management, and analysis of risk issues involved. The goal is to provide the most current research, safety measures, and related handling and storage.
Article
Maintaining a residual disinfectant/oxidant (e.g., chlorine and chlorine dioxide), is a generally used strategy to control microbial contaminants and bacterial regrowth in distribution systems. Secondarily oxidant, such as hypobromous acid (HOBr), can be formed during chlorination of bromide-containing waters. The decay of oxidants and formation of disinfection byproducts (DBPs) due to the interaction between oxidants and selected metal oxides were studied. Selected metal oxides generally enhanced the decay of these halogen-containing oxidants via three pathways: (1) catalytic disproportionation to yield an oxidized form of halogen (i.e., halate) and reduced form (halide for chlorine and bromine or chlorite for chlorine dioxide), (2) oxygen formation, and (3) oxidation of a metal in a reduced form (e.g., cuprous oxide) to a higher oxidation state. Cupric oxide (CuO) and nickel oxide (NiO) showed significantly strong abilities for the first pathway, and oxygen formation was a side reaction. Cuprous oxide can react with oxidants via the third pathway, while goethite was not involved in these reactions. The ability of CuO on catalytic disproportionation of HOBr remained stable up to four cycles. In chlorination process, bromate formation tends to be important (exceeding 10 µg/L) when initial bromide concentration is above 400 µg/L in the presence of dissolved organic matter. Increasing initial bromide concentrations increased the formation of DBPs and calculated cytotoxicity, and the maximum was observed at pH 8.6 during chlorination process. Therefore, the possible disinfectant loss and DBP formation should be carefully considered in drinking water distribution systems.
Article
This work reports gold-catalyzed 1,4-oxofunctionalizations of 3-en-1-ynamides with nitrones, yielding two distinct E-configured products. We obtained 1,4-oxoarylation products from 3-en-1-ynamides bearing C(4)-electron-donating substituents and 1,4-oxoamination products from those analogues bearing C(4)-aryl substituents. We propose that if vinylgold carbenes are stable, imines undergo a para-arylation on these gold carbenes. If vinylgold carbenes are highly electron-deficient, this N-attack is irreversible to enable 1,4-oxoaminations.
Article
Chlorine dioxide (ClO2), an alternative disinfectant to free chlorine, has been used to reduce the formation of organic disinfection byproducts during water treatment. ClO2 is highly reactive, and its decay is enhanced in the presence of lead oxide (PbO2), lead carbonate (PbCO3), and cupric oxide (CuO), minerals commonly found in the corrosion scale on distribution system pipes. Reactions of these corrosion minerals with chlorine dioxide and the byproducts created during said reactions were investigated. In addition to corrosion mineral, initial concentration of ClO2 and pH were both varied. Reaction took place in a batch reactor, ClO2 was measured via ultraviolet-visible spectrophotometry, and byproducts were quantified using ion chromatography. Only chlorite is produced from ClO2 decay when lead minerals are present, whereas both chlorite and chlorate are produced by disproportionation when CuO is present. ClO2 decay occurs at a significantly higher rate on PbO2 compared to CuO. The reaction rate for ClO2 decay, in the presence of PbO2, peaks at pH 8.3, which corresponds to the point of zero charge of PbO2. This indicates that surface charge may play a significant role in lead mineral-assisted decay reactions with disinfectants, including ClO2. The reaction rate dependence for ClO2 decay on PbO2 is well described by a pseudo-second-order adsorption kinetic model. These findings highlight the need for chlorite, but not chlorate, byproduct management when ClO2 is used as a disinfectant in water distribution systems with lead-based pipes. Robust strategies for management of a chlorine dioxide residual must be implemented in both copper and lead-based service lines to ensure a disinfectant persists and protects against microbial contamination in premise plumbing.
Article
In the past two decades, ozone-based advanced oxidation processes, known as enhanced ozonation processes (EOPs), have been extensively investigated for the removal of emerging organic contaminants in water, such as pesticides, endocrine-disrupting compounds, and pharmaceuticals. EOPs offer an advantage by producing highly oxidizing radicals, such as hydroxyl radicals, to oxidize recalcitrant organic compounds. Although the EOPs are able to effectively remove emerging contaminants, several studies reported the formation of bromate, which has drawn significant attention because of its potential carcinogenicity. This issue becomes challenging for the utilization of EOPs on bromide containing water. Therefore, this work critically reviews and summarizes the mechanisms, influencing factors, advantages and disadvantages, and control strategies for bromate formation by four EOPs, i.e., peroxone and e-peroxone, photolytic ozonation, heterogeneous ozonation, and sonolytic ozonation. Various economic and technical characteristics of EOPs were also compared. Mathematical modeling, pilot and full-scale data, and secondary pollutant potential (toxic metals leaching from catalyst) have been identified as knowledge gaps, and future research should seek to address these issues.
Article
Drinking water is an important source of human exposure to bromate, an ubiquitous environmental contaminant and a suspect human carcinogen. Nevertheless, little is known with regard to bromate exposure from water produced by thermal desalination of seawater. The purpose of this study was to determine the occurrence of bromate in desalinated drinking water and groundwater from Kuwait and estimate associated exposure and health risks to consumers. In this study, 194 tap and ground water samples collected from Kuwait were analyzed for the presence of bromate and bromide (reduced form of bromine). Bromate was found in almost all tap water samples with a mean concentration of 19.6 μg/L, which is higher than the maximum acceptable contaminant level (MCL) of 10 μg/L. The mean concentration of bromide in tap water samples was 46.2 μg/L. In bottled water, lower mean bromate concentration was found (2.89 μg/L) with mean bromide levels at 76.1 μg/L. Saline brackish water had bromate concentration at 9.48 μg/L while bromate was not detected in saline groundwater/well water samples. The mean estimated daily intake (EDI) of bromate by the Kuwaiti population through tap water and commonly consumed bottled water was 21.7 μg/d and 3.21 μg/d, respectively. Among the five age groups, 3 to 5-year-old children had the highest EDI of bromate at 15.4 μg/d. The excess cancer risk due to ingestion of bromate in tap water was estimated to be 3.92 × 10-4, which is approximately one order of magnitude higher than the maximum acceptable level of risk (2× 10-5). This study highlights the significance of desalinated water as a source of bromate exposure.
Article
Pilot testing of direct potable reuse (DPR) using multi-stage ozone and biological filtration as an alternative treatment train without reverse osmosis (RO) was investigated. This study examined four blending ratios of advanced treated reclaimed water from the F. Wayne Hill Water Resources Center (FWH WRC) in Gwinnett County, Georgia, combined with the existing drinking water treatment plant raw water supply, Lake Lanier, for potable water production. Baseline testing with 100 percent (%) Lake Lanier water was initially conducted; followed by testing blends of 15, 25, 50, and 100% reclaimed water from FWH WRC. Finished water quality from the DPR pilot was compared to drinking water standards, and emerging microbial and chemical contaminants were also evaluated. Results were benchmarked against a parallel indirect potable reuse (IPR) pilot receiving 100% of the raw water from Lake Lanier. Finished water quality from the DPR pilot at the 15% blend complied with the United States primary and secondary maximum contaminant levels (MCLs and SMCLs, respectively). However, exceedances of one or more MCLs or SMCLs were observed at higher blends. Importantly, reclaimed water from FWH WRC was of equal or better quality for all microbiological targets tested compared to Lake Lanier, indicating that a DPR scenario could lower acute risks from microbial pathogens compared to current practices. Finished water from the DPR pilot had no detections of microorganisms, even at the 100% FWH WRC effluent blend. Microbiological targets tested included heterotrophic plate counts, total and fecal coliforms, Escherichia coli, somatic and male-specific coliphage, Clostridium perfringens, Enterococci, Legionella, Cryptosporidium, and Giardia. There were water quality challenges, primarily associated with nitrate originating from incomplete denitrification and bromate formation from ozonation at the FWH WRC. These challenges highlight the importance of upstream process monitoring and control at the advanced wastewater treatment facility if DPR is considered. This research demonstrated that ozone with biological filtration could achieve potable water quality criteria, without the use of RO, in cases where nitrate is below the MCL of 10 mg nitrogen per liter and total dissolved solids are below the SMCL of 500 mg per liter.
Article
Chemical oxidation processes have been extensively utilized in disinfection and removal of emerging organic contaminants in recent decades. Some undesired byproducts, however, are produced in these processes. Of them, bromate has attracted the most intensive attention. It was previously regarded as a byproduct that typically occurred in ozone-based oxidation processes. However, for the past decade, bromate formation has been detected in other oxidation processes such as CuO-catalyzed chlorination, SO4--based oxidation, and ferrate oxidation processes. This review summarizes the occurrences, mechanisms, influencing factors, risk assessment, and control strategies of bromate formation in the four oxidation processes, i.e., ozone-based oxidation, chlorine-based oxidation, SO4--based oxidation, and ferrate oxidation. Besides, some unresolved issues for future studies are provided: (1) Clarification of the relative contributions of SO4- and Br to the oxidation of bromine for bromate formation in SO4--based oxidation processes; (2) evaluation of the role of different reactive species in the bromate formation in the process of UV/HOCl; (3) quantification of the dual role of alkalinity in bromate formation during ozonation; (4) assessment of the risks of bromate formation in SO4--based oxidation processes for practical applications; and (5) exploration of strategies for inhibiting bromate formation in SO4--based oxidation, UV/chlorine, and metal oxide-catalyzed chlorination processes.
Article
In this work, the kinetics and mechanisms of the reductive removal of BrO3ˉ by sulfite in air atmosphere were determined. BrO3ˉ could be effectively reduced by sulfite at pHini 3.0–6.0 and the reduction rate of BrO3ˉ increased with decreasing pH. The co-existing organic contaminants with electron-rich moieties could be degraded accompanying with BrO3ˉ reduction by sulfite. The reaction stoichiometries of −Δ[sulfite]/Δ[bromate] were determined to be 3.33 and 15.63 in the absence and presence of O2, respectively. Many lines of evidence verified that the main reactions in BrO3ˉ/sulfite system in air atmosphere included the reduction of BrO3ˉ to HOBr and its further reduction to Brˉ, as well as the oxidation of H2SO3 by BrO3ˉ to form SO3ˉ and its further transformation to SO4ˉ. Moreover, SO4ˉ rather than HOBr was determined to be the major active oxidant in BrO3ˉ/sulfite system. SO3ˉ played a key role in the over-stoichiometric sulfite consumption because of its rapid reaction with dissolved oxygen. However, the formed SO3ˉ was further oxidized by BrO3ˉ in N2 atmosphere. BrO3ˉ reduction by sulfite is an alternative for controlling BrO3ˉ in water treatment because it was effective in real water at pHini ≤ 6.0.
Article
Red Mud is a hazardous byproduct of the Bayer process, used to produce alumina from bauxite, with ability to adsorb anions from water. Acid activation and enrichment with CetylTrimethylAmmonium Chloride (CTAC), a cationic surfactant, are employed to enable it to remove bromate initially from spiked double-distilled water. CTAC enrichment is found to substantially improve Red Mud’s bromate removal ability in comparison to acid activation alone. Fourier Transformation Infrared Spectroscopy is used to evaluate the effectiveness of the enrichment process. Maximum CTAC loading is 0.037g per g acid activated Red Mud (AARM). Adsorption is faster after CTAC enrichment. pH increase is found to adversely affect both AARM and acid activated CTAC enriched Red Mud’s (CTAC-AARM) bromate removal capability, yet CTAC-AARM’s ability proves more resistant to pH changes. Adsorption data fit best the Langmuir isotherm model for both adsorbers. The R² values for AARM and CTAC-AARM are 0.955 and 0.964 respectively. Maximum adsorbable bromate quantity is almost 2.5 times higher for CTAC-AARM in comparison to AARM. Finally, both Red Mud adsorbers are compared with respect to their ability to remove bromate from cooling water; an industrial matrix rich in competing ions. As cycles of concentration and pH appreciate, bromate adsorption is hindered regardless of the adsorber used. However CTAC-AARM still performs better in removing bromate. It is proven that after suitable processing, Red Mud can re-enter the industrial cycle by playing a role in bromate removal from industrial waters.
Article
A redox chemistry approach has been employed to synthesize an assortment of acids in the subterranean environment for the purpose of enhancing productivity from hydrocarbon-bearing rock formations. Experimental studies revealed that bromate selectively oxidizes a series of ammonium salts NH4X where X = F-, Cl-, Br-, SO42-, and CF3CO2- to produce 5-17 wt % HX. Importantly, the in situ method allows strategic placement of the acid in the zone of interest where the fluid is heated, and the reaction is triggered. Ammonium counteranions are shown to influence the kinetics of the bromate-ammonium reaction, and the conditions are tailored to promote oxidation of ammonium at reservoir temperatures. The reaction is observed to be acid-catalyzed, where the formation of bromous acid (HBrO2) is involved in the rate-limiting step. As a result, an induction period that scales with the p Ka of the acid being formed is followed by rapid formation of the reaction products.
Article
The catalytic effect of copper corrosion products, including copper ions, cupric oxide, and cuprous oxide, on the formation of haloacetamides and haloacetonitriles during chlorination of natural organic matter (NOM), model nitrogenous precursors, and real water samples was investigated. During chlorination of NOM, the presence of these copper corrosion products facilitated chlorine decay, and enhanced the formation of dichloroacetonitrile (DCAN) and dichloroacetamide (DCAcAm) with enhancement ratios of 45–59% and 64–137% after 10 h contact time, respectively. Six amino acids were selected as nitrogenous NOM surrogates for chlorination, and the results show that the enhancement of DCAN and DCAcAm formation by copper corrosion products was only observed for slow reacting amino acids, including glutamine, glutamic acid, and phenylamine, suggesting that copper corrosion products may enhance DCAN and DCAcAm formation by catalyzing NOM portions that are relatively inefficient precursors. When bromide and copper corrosion products were present, the formation of dihaloacetonitriles (DHANs) and dihaloacetamides (DHAcAms) could be enhanced during chlorination of NOM, but the degrees of bromine substitution for DHANs and DHAcAms decreased. Although copper corrosion products facilitated DHAN and DHAcAm hydrolysis with the facilitation increasing as the halogens shifted from chlorine to bromine, increased DHAN and DHAcAm concentrations was observed during chlorination of real water samples in the presence of copper corrosion products, confirming that the copper corrosion products had a catalytic effect on DHAN and DHAcAm formation that exceeded their catalytic effect on DHAN and DHAcAm hydrolysis. This study provides basic knowledge of disinfectant residuals and the fate of haloacetonitriles and haloacetamides in drinking water distribution systems where copper is used, which will be helpful for the management of safe water distribution.
Article
Disinfection of water for human use is essential to protect against microbial disease; however, disinfection also leads to formation of disinfection by-products (DBPs), some of which are of health concern. From a chemical perspective, swimming pools are a complex matrix, with continual addition of a wide range of natural and anthropogenic chemicals via filling waters, disinfectant addition, pharmaceuticals and personal care products and human body excretions. Natural organic matter, trace amounts of DBPs and chlorine or chloramines may be introduced by the filling water, which is commonly disinfected distributed drinking water. Chlorine and/or bromine is continually introduced via the addition of chemical disinfectants to the pool. Human body excretions (sweat, urine and saliva) and pharmaceuticals and personal care products (sunscreens, cosmetics, hair products and lotions) are introduced by swimmers. High addition of disinfectant leads to a high formation of DBPs from reaction of some of the chemicals with the disinfectant. Swimming pool air is also of concern as volatile DBPs partition into the air above the pool. The presence of bromine leads to the formation of a wide range of bromo- and bromo/chloro-DBPs, and Br-DBPs are more toxic than their chlorinated analogues. This is particularly important for seawater-filled pools or pools using a bromine-based disinfectant. This review summarises chemical contaminants and DBPs in swimming pool waters, as well as in the air above pools. Factors that have been found to affect DBP formation in pools are discussed. The impact of the swimming pool environment on human health is reviewed.
Article
Bromate (BrO3⁻), as a contaminant producing from bromide (Br⁻) oxidation, has been revealed for generation in sulfate radical involved processes. In this work, reduced graphene oxide (rGO) was firstly applied to inhibit the formation of BrO3⁻ in thermally activated peroxymonosulfate (thermal/PMS) treatment. In the presence of 5–35 mg/L rGO, the decomposition rate of PMS was slightly increased from 0.0162 ± 0.0013 min⁻¹ to 0.0200 ± 0.0010 min⁻¹, corresponding to removal rate of target pollutant increasing from 0.0157 ± 0.0012 min⁻¹ to 0.0204 ± 0.0022 min⁻¹. This suggested the decay of PMS, the concentration and distribution of radicals were not influenced dramatically by the addition of rGO, which was partly supported by the almost unchanged HPLC chromatograms as compared with that in the absence of rGO. However, the produced BrO3⁻ was significantly lowered by 67%–100% with the addition of rGO in a wide range of pH at 5–9 and activation temperature at 60–80 °C. Moreover, a quick reduction of hypobromous acid (HOBr) to Br⁻ was achieved with addition of rGO at room temperature, whilst no abatement of BrO3⁻ and Br⁻ was observed in the same conditions. Therefore, masking HOBr was probably the role of rGO on bromate inhibition in thermal/PMS process. Because HOBr is a requisite intermediate for BrO3⁻, the inhibition effect of rGO is likely irrelevant of oxidation processes, which was inevitably showed by the good performance of rGO on BrO3⁻ suppress in ozonation. Therefore, the addition of rGO in tens of mg/L is a promising measure to avoid the formation of unwanted bromine species in advanced oxidation processes.
Article
Copper(II) hydroxide complexes catalyze the decomposition of OCl- and OBr- via two pathways, one first order and one second order in copper. The latter pathway produces small amounts of a yellow intermediate, B, which is a dimeric copper(III) OX- →Cu(II)kAB B →kBC 1/2 O2 + X- kBC ≫ kAB hydroxide complex. The spectrum of this complex has maxima at 270 and 362 nm (each with ∈ ∼ 18 800 M-1 cm-1). Chloride has no effect on reactions of OCl-. Bromide suppresses both the concentration of B and the rate of oxygen evolution during the decomposition of OBr- because of the reversibility of the formation of B. This is used to establish the stoichiometry of the dimer and its electrode potential: CuIII2(O)(OH)73- + H2O + 2e- → 2CuII(OH)42- + OH-; E° = 0.82 V (vs. NHE). The half-life of this dimer (producing oxygen) is 10.5 s in 1 M NaOH at 25°C. The monomeric pathway does not produce measurable amounts of Cu(III).
Article
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.
Article
The aim of this work is to assess the performance of different corrosion products as an effective copper corrosion protection in synthetic tap water. The major objective of this study was to evaluate the stability of copper oxide film and naturally formed heterogeneous corrosion products under the influence of synthetic tap water. The influence of copper products on the corrosion behavior in neutral synthetic tap water was investigated using electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The EIS plot was changed from two time constants to three time constants due to the enrichment of cuprous oxide (Cu2O) on the copper surface. Copper experienced only uniform corrosion. As the protective oxide film thickened, it did not separate from the copper surface.
Article
The catalyzed decomposition of sodium hypochlorite has been examined; the catalysts tried were manganese, iron, cobalt, nickel, and copper oxides. It was shown that in no case was the decomposition to chlorate and chloride accelerated, only the reaction to chloride and oxygen. Manganese and iron did not catalyze even the latter reaction, or only to a very small extent; this was in fairly concentrated sodium hypochlorite containing some sodium hydroxide. The manganese and iron are largely oxidized to permanganate and ferrate under these conditions. It was found that copper could catalyze the formation of permanganate and ferrate, and nickel the formation of permanganate. Cobalt catalyzed the reaction going to oxygen, and the rate was proportional to the cobalt added, but little dependent on the hypochlorite concentration; the same is true of nickel. Copper (as reported earlier) gives a catalyzed reaction not far from first order in hypochlorite. The activation energies were measured, and were consistent with the relative catalytic activity of these metals. The mechanism of the reaction is briefly discussed.
Article
The kinetics of the decomposition of hypobromite solutions were investigated in a limited range of pH and initial concentrations by measuring the change of concentration of both hypobromite and bromite. The results can be satisfactorily explained on the basis of two second-order consecutive reactions, the first involving the formation of bromite, and the second a comparatively fast reaction between bromite and hypobromite. The decomposition of the intermediate, bromite, was investigated separately and was found in the main to follow an analogous mechanism, hypobromite now taking the role of intermediate. In the pH range considered, the assumption that the reactions take place exclusively between an undissociated acid molecule and an anion does not give satisfactory agreement with experiment; much better agreement is obtained by assuming, in addition, reactions involving either free bromine or two uncharged molecules of acid.
Article
Rate equations for the decomposition of aqueous alkaline NaClO were integrated with inclusion and exclusion of the effects of first-order Cu(II) catalysis, yielding new time-dependent expressions for [ClO-], evolved oxygen, and [ClO3-]. Using a gravimetric technique, uncatalyzed and Cu(II)-catalyzed rate constants for oxygen evolution and CIO- loss were measured and consolidated with previous results. Activation parameters of the uncatalyzed rate-limiting reactions to ClO2- and oxygen could be approximated as linear functions of ionic strength mu, allowing estimation of the respective rate constants k1 and k(o) at 40-70-degrees-C in the mu range 2-5. For Cu(II) catalysis at 40-70-degrees-C in the mu range 4.2-4.7, E(a), DELTAH(double dagger), and DELTAS(double dagger) values of 83 300 J g-mol-1, 80 550 J g-mol-1, and -14.6 J K-1 g-mol-1, respectively, were derived from previous and current results, allowing k(Cu) also to be estimated and used in the system of integrated equations.
Article
The rate expression for the oxidation of bromide by HOCl and OCl - is -d[OCl -] T/dt = h HA[HA][OCl -] T[Br -], where [OCl -] T = [OCl -] + [HOCl] and HA is a general acid (H 2O, HPO 42-, HCO 3-, CH 3COOH, ClCH 2COOH, or H 3O +). The k HA value for H 3O + + OCl - + Br - is 3.65 × 10 10 M -2 s -1 (this path requires HOCl as an intermediate), while the k HA value for H 3O + + HOCl + Br - is 1.32 × 10 6 M -2 s -1. In terms of second-order expressions, the rate constant for HOCl and Br - is 1.55 × 10 3 M -1 s -1, while the rate constant for OCl - + Br - is only 0.90 × 10 -3 M -1 s -1. The proposed mechanism for the acid-assisted reactions (except for H 3O + + OCl -) is a simultaneous proton transfer (from HA to OCl - or to HOCl) and Cl + transfer to Br - (to give BrCl, which reacts rapidly to give OBr - or Br 2 and Br 3-). The Brønsted α value is 0.75 for the reactions of HA with OCl - and Br -, and the α value is 0.27 for the reactions of HA with HOCl and Br -. The α values reflect the degree of proton transfer in the transition state.
Article
The decomposition of hypochlorous acid in the neutral pH region was studied in 1.0 M NaClO4 from 15 to 50-degrees-C. The pK(a) of HOCl was also determined under these conditions. Hypochlorous acid has a maximum decomposition rate at pH 6.89. The decomposition is a third-order process. The values of DELTA-H(double dagger) and DELTA-S(double dagger) are 64.0 +/- 0.6 kJ/mol and -67 +/- 2 J/mol K, respectively. A mechanism for the decomposition of HOCl is proposed involving Cl2O.H2O and ClO2- as intermediates. Rate constants for the rate-determining steps of the mechanism are presented. Above pH 6, the rate-determining step is proposed to be as follows: OCl- + Cl2O.H2O --> HCl2O2- + HOCl. Below pH 6, this process is proposed to be in competition with a parallel pathway: HOCl + Cl2O-H2O --> H2Cl2O2 + HOCl. The proposed mechanism was tested by mathematical simulation of the experimental data using the GEAR algorithm. The simulation gives additional support for the proposed mechanism.
Article
Bromate formation in ozone-based advanced oxidation processes (AOPs) was investigated by laboratory experiments in combination with kinetic modeling. Oxidant concentra tions were monitored during the experiments, which allows us to account for the relative contributions of ozone and OH radical pathways. It has been shown by γ-ir radiation of bromide-containing solutions in the pH range 6−8 that bromate can be formed by a pure OH radical mechanism and that hypobromous acid/hypobromite (HOBr/OBr-) is a requisite intermediate in bromate formation. The presence of hydrogen peroxide (H2O2), as in H2O2-based AOPs, leads to a reduction of HOBr/OBr- and therefore becomes a key reaction for the control of bromate formation. The steady-state concentration of OH radicals in AOPs is usually not high enough to compensate for this reduction reaction. Therefore, in γ-irradiation experiments, no bromate was formed in the presence of H2O2 because OH radicals were the only possible oxidants to further oxidize HOBr/OBr-. However, in ozone-based AOPs at pH 7, where ozone is present in combination with H2O2, bromate was still formed. This was attributed to the oxidation of Br• by O3, which was investigated at pH 7. Our experimental findings could be best explained by a corresponding second-order rate constant k = 1.5 × 108 M-1 s-1.
Article
Ozone oxidizes Br- under water treatment conditions to form HOBr. HOBr reacts further with O3, but only in its ionized form, OBr-. OBr- is oxidized not only to BrO3- but also to a species that regenerates Br-. The results are consistent with the following scheme of reactions: (1) O3 + Br- k1 → O2 + OBr-; (2) O3 + OBr- k2 → 2O2 + BR-; (3) 2O3 + OBr- k3 → 2O2 + BrO3-; where k1 = 160 ± 20 M-1 s-1, k2 = 330 ± 60 M-1 s-1, and k3 = 100 ± 20 M-1 s-1 at 20°C. Thus, a catalytic decomposition of O3 via reactions and 2 is observed. The maximum intermediate HOBr concentration is greater the lower the pH. In the presence of organic matter, HOBr reacts to form bromo organics. Thus, more bromoform was produced with humic acid at pH 6.1 than at pH 8.8. The range of conditions conducive to haloform formation is narrower than during chlorination.
Article
HOBr can be formed in various oxidation processes in engineered and natural systems. The rate of HOBr reduction by H2O2 is decisive to avoid formation of brominated organic compounds and bromate during ozone or hydrogen peroxide-based advanced or naturally occurring oxidation processes. From the pH dependence of this rate that was determined by stopped-flow measurements we conclude that either OBr− and H2O2 or HOBr and HO−2 react with each other. Assuming that either one of the reactions takes place the corresponding second-order rate constants were determined to be kOBr−·H2O2 = (1.2 ± 0.2)·106M−1s−1 and kHOBr·HO−2 = (7.6 ± 1.3)·108M−1s−1. Mechanistic considerations lead to the conclusion that a nucleophilic attack of HO−2 on HOBr must be the dominant reaction in the system. From the determined rate constants it can be estimated that the half-life for HOBr is less than a few seconds for a H2O2 concentration of 0.1 mg L−1 (3 μM) at pH 8. However, at a lower pH of 5, as encountered in cloud waters, the half-life of HOBr is several hours for the same H2O2 concentration.
Article
The kinetics of chlorine dioxide consumption by a wide range of inorganic and organic compounds, including a comprehensive series of phenols, have been determined using conventional batch-type and stopped-flow methods. In all cases, the rate law was first-order in chlorine dioxide and first-order in substrate. The methods allowed us to determine second-order rate constants over a range from 10−5 to 105 M−1s−1. Measured rate constants were high for nitrite, hydrogen peroxide, ozone, iodide, iron (II), and, whenever the pH was not very low, for phenolic compounds, tertiary amines, and thiols. Bromide, ammonia, structures containing olefinic CC double bonds, aromatic hydrocarbons, primary and secondary amines, aldehydes, ketones and carbohydrates were unreactive under conditions of water treatment. For substrates that are weak acids, such as phenols, or weak bases, the effect of pH on the reaction rate showed that the rate constants for the deprotonated compounds are much higher than those for the protonated species.
Article
This study investigated the effect of copper corrosion products, including Cu(II), Cu(2)O, CuO and Cu(2)(OH)(2)CO(3), on chlorine degradation, HAA formation, and HAA speciation under controlled experimental conditions. Chlorine decay and HAA formation were significantly enhanced in the presence of copper with the extent of copper catalysis being affected by the solution pH and the concentration of copper corrosion products. Accelerated chlorine decay and increased HAA formation were observed at pH 8.6 in the presence of 1.0 mg/L Cu(II) compared with that observed at pH 6.6 and pH 7.6. Further investigation of chlorine decay in the presence of both Suwannee River NOM and Cu(II) indicated that an increased reactivity of NOM with dissolved and/or solid surface-associated Cu(II), rather than chlorine auto-decomposition, was a primary reason for the observed rapid chlorine decay. Copper corrosion solids [Cu(2)O, CuO, Cu(2)(OH)(2)CO(3)] exhibited catalytic effects on both chlorine decay and HAA formation. Contrary to the results observed when in the absence of copper corrosion products, DCAA formation was consistently predominant over other HAA species in the presence of copper corrosion products, especially at neutral and high pH. This study improves the understanding for water utilities and households regarding chlorine residuals and HAA concentrations in distribution systems, in particular once the water reaches domestic plumbing where copper is widely used.
Article
Kinetic simulations have been tested by laboratory experiments to evaluate the major factors controlling bromate formation during ozonation of waters containing bromide. In the presence of an organic scavenger for OH radicals, bromate formation can be accurately predicted by the molecular ozone mechanism using published reaction rate data, even for waters containing ammonium. In the absence of scavengers, OH radical reactions contribute significantly to bromate formation. Carbonate radicals, produced by the oxidation of bicarbonate with OH radicals, oxidize the intermediate hypobromite to bromite, which is further oxidized by ozone to bromate. During drinking water ozonation, molecular ozone controls both the initial oxidation of bromide and the final oxidation of bromite. OH radical reactions contribute to the oxidation of the intermediate oxybromine species. Bromate formation in advanced oxidation processes can be explained by a synergism of ozone and OH radicals.
Article
A rapid reaction between free chlorine and the cupric hydroxide [Cu(OH)2] solids commonly found on pipe walls in premise plumbing can convert free chlorine to chloride and rapidly age Cu(OH)2 to tenorite (CuO). This reaction has important practical implications for maintaining free chlorine residuals in premise plumbing, commissioning of new copper pipe systems, and maintaining low levels of copper in potable water. The reaction stoichiometry between chlorine and Cu(OH)2 is consistent with formation of CuO through a metastable Cu(III) intermediate, although definitive mechanistic understanding requires future research. Natural levels of silica in water (0-30 mg/L), orthophosphate, and higher pH interfere with the rate of this reaction.
Article
This study shows that iodinated organic compounds can be produced when iodide-containing waters are in contact with manganese oxide birnessite (delta-MnO2) in the pH range of 5-7. In the absence of natural organic matter (NOM), iodide is oxidized to iodate that is also adsorbed onto delta-MnO2. In the presence of iodide and NOM, adsordable organic iodine compounds (AOI) are formed at pH < 7 because of the oxidation of iodide to iodine by delta-MnO2 and the reactions of iodine with NOM. In addition, iodoacetic acid and iodoform have been identified as specific iodinated byproducts. Formation of iodoform is not observed for high NOM/delta-MnO2 ratios due to inhibition of the catalytic effect of delta-MnO2 by NOM poisoning. Experiments with model compounds such as resorcinol and 3,5-heptanedione confirmed that the delta-MnO2/l(-) system is very effective for the formation of iodinated organic compounds. These results suggest that birnessite acts as a catalyst through the oxidation of iodide to iodine and the polarization of the iodine molecule, which then reacts with NOM moieties. Furthermore, our results indicate that during water treatment in the presence of manganese oxide, iodinated organic compounds may be formed, which may lead to taste and odor or toxicological problems.
Article
The kinetics of aqueous hypobromous acid disproportionation are measured at 25.0 degrees C from p[H(+)] 0.2 to 10.2. The reactions are second order in HOBr with a maximum rate at pH 3-8. The rate of disproportionation decreases significantly above pH 8 as OBr(-) forms. Another suppression observed below pH 3 is attributed to the reversibility of initial steps in the decomposition. The rate expression is given by -d[Br(I)]/dt = n{(c/(c + [H(+)])k(1a) + k(B)[B])[HOBr](2) + k(1b)[OBr(-)](2)}, where k(1a) = 2 x 10(-)(3) M(-)(1) s(-)(1), k(B)[B] is a general-base-assisted pathway, k(1b) = 6 x 10(-)(7) M(-)(1) s(-)(1), n is a stoichiometric factor that ranges from 2 to 5, and c is a ratio of rate constants that is equal to 0.03 M. Decomposition is catalyzed by HPO(4)(2)(-) (k(B) = 0.05 M(-)(2) s(-)(1)) and by CO(3)(2)(-) (k(B) = 0.33 M(-)(2) s(-)(1)). Above pH 8, the first observable product is BrO(2)(-) (initially n = 2). Below pH 4, n = 5 due to Br(2) and BrO(3)(-) formation. From pH 4 to 7, n varies from 5 to 3. A detailed mechanism is presented.
Article
The effects of pH, hypochlorite and chloride ion concentration, temperature, and ionic strength on the kinetics and mechanism of decomposition of concentrated hypochlorite ion and the formation of chlorate ion and oxygen in the pH 9-14 region has been investigated. In the absence of catalytic levels of transition-metal ions, the rate of chlorate ion formation is 8.7 times faster than the rate of oxygen formation for the concentration range of 0.7-3.0 M hypochlorite ion with various levels of chloride ion in 0.001-1.0 M OH(-) at 15-55 degrees C. Under these same conditions, the equation that describes the effect of temperature and ionic strength on the decomposition of OCl(-) is the following: log k(2) = 0.149&mgr; + log[2.083 x 10(10)T exp(-1.018 x 10(5)/RT) exp(-56.5/R)] where k(2) has units of M(-)(1) sec(-)(1) and &mgr; is between 1 and 6 molar. Numerical simulation of the decomposition of OCl(-) was carried out while taking into account the effect of each of the above experimental variables. Evidence is presented suggesting chloride ion catalyzed decomposition of hypochlorite ion in the pH 9-10 region that is in addition to the contribution of chloride ion to the ionic strength.
Article
Bromide ion is rapidly converted to HOBr via BrCl by reaction with HOCl. The subsequent slow reactions of (HOCl, OCl−)/(HOBr, OBr−) mixtures are monitored directly by multiwavelength UV–vis absorbance methods and simultaneously by ion chromatographic measurement of ClO2−, ClO3−, and BrO3− (p[H+] 5.6–7.6). A first-order loss of HOCl is observed which is catalyzed by trace concentrations of Br− and BrCl. Chlorite ion forms first and is subsequently oxidized to ClO3−. The loss of HOBr is slower and is second-order in HOBr, so that BrO3− formation takes longer than ClO3− formation. Under the conditions of this work, the relative yield of BrO3− increases with increase in pH. The decomposition of HOCl by bromide proceeds primarily by a series of halogen(I) cation-transfer reactions with subsequent halide release. The presence of HOCl increases the BrO3− yield three-fold from HOBr decay alone.
Article
Ozone is an excellent disinfectant and can even be used to inactivate microorganisms such as protozoa which are very resistant to conventional disinfectants. Proper rate constants for the inactivation of microorganisms are only available for six species (E. coli, Bacillus subtilis spores, Rotavirus, Giardia lamblia cysts, Giardia muris cysts, Cryptosporidium parvum oocysts). The apparent activation energy for the inactivation of bacteria is in the same order as most chemical reactions (35-50 kJ mol(-1)), whereas it is much higher for the inactivation of protozoa (80 kJ mol(-1)). This requires significantly higher ozone exposures at low temperatures to get a similar inactivation for protozoa. Even for the inactivation of resistant microorganisms, OH radicals only play a minor role. Numerous organic and inorganic ozonation disinfection/oxidation by-products have been identified. The by-product of main concern is bromate, which is formed in bromide-containing waters. A low drinking water standard of 10 microg l(-1) has been set for bromate. Therefore, disinfection and oxidation processes have to be evaluated to fulfil these criteria. In certain cases, when bromide concentrations are above about 50 microg l(-1), it may be necessary to use control measures to lower bromate formation (lowering of pH, ammonia addition). Iodate is the main by-product formed during ozonation of iodide-containing waters. The reactions involved are direct ozone oxidations. Iodate is considered non-problematic because it is transformed back to iodide endogenically. Chloride cannot be oxidized during ozonation processes under drinking water conditions. Chlorate is only formed if a preoxidation by chlorine and/or chlorine dioxide has occurred.
Article
Bromate is a contaminant of commercially produced solutions of sodium hypochlorite used for disinfection of drinking water. However, no methodical approach has been carried out in U.S. drinking waters to determine the impact of such contamination on drinking water quality. This study utilized a recently developed method for quantitation of bromate down to 0.05 microg/L to determine the concentration of bromate present in finished waters that had been chlorinated using hypochlorite. Forty treatment plants throughout the United States using hypochlorite in the disinfection step were selected and the levels of bromate in the water both prior to and following the addition of hypochlorite were measured. The levels of bromate in the hypochlorite feedstock were also measured and together with the dosage information provided by the plants and the amount of free chlorine in the feedstock, it was possible to calculate the theoretical level of bromate that would be imparted to the water. A mass balance was performed to compare the level of bromate in finished drinking water samples to that found in the corresponding hypochlorite solution used for treatment. Additional confirmation of the source of elevated bromate levels was provided by monitoring for an increase in the level of chlorate, a co-contaminant of hypochlorite, atthe same point in the treatment plant where bromate was elevated. This study showed that bromate in hypochlorite-treated finished waters varies across the United States based on the source of the chemical feedstock, which can add as much as 3 microg/L bromate into drinking water. Although this is within the current negotiated industry standard that allows up to 50% of the maximum contaminant level (MCL) for bromate in drinking water to be contributed by hypochlorite, it would be a challenge to meet a tighter standard. Given that distribution costs encourage utilities to purchase chemical feedstocks from local suppliers, utilities in certain regions of the United States may be put at a distinct disadvantage if future lower regulations on bromate levels in finished drinking water are put into place. Moreover, with these contaminant levels it would be almost impossible to lower the maximum permissible contribution to bromate in finished water from hypochlorite to 10% of the MCL, which is the norm for other treatment chemicals. Until this issue is resolved, it will be difficult to justify a lowering of the bromate MCL from its current level of 10 to 5 microg/L or lower.
Article
The reaction between BrO2(-) and excess HOCl (p[H+] 6-7, 25.0 degrees C) proceeds through several pathways. The primary path is a multistep oxidation of HOCl by BrO(2)(-) to form ClO(3)(-) and HOBr (85% of the initial 0.15 mM BrO(2)(-)). Another pathway produces ClO(2) and HOBr (8%), and a third pathway produces BrO(3)(-) and Cl(-) (7%). With excess HOCl concentrations, Cl(2)O also is a reactive species. In the proposed mechanism, HOCl and Cl(2)O react with BrO(2)(-) to form steady-state species, HOClOBrO(-) and ClOClOBrO(-). Acid facilitates the conversion of HOClOBrO(-) and ClOClOBrO(-) to HOBrOClO(-). These reactions require a chainlike connectivity of the intermediates with alternating halogen-oxygen bonding (i.e. HOBrOClO(-)) as opposed to Y-shaped intermediates with a direct halogen-halogen bond (i.e. HOBrCl(O)O(-)). The HOBrOClO(-) species dissociates into HOBr and ClO(2)(-) or reacts with general acids to form BrOClO. The distribution of products suggests that BrOClO exists as a BrOClO.HOCl adduct in the presence of excess HOCl. The primary products, ClO(3)(-) and HOBr, are formed from the hydrolysis of BrOClO.HOCl. A minor hydrolysis path for BrOClO.HOCl gives BrO(3)(-) and Cl(-). An induction period in the formation of ClO(2) is observed due to the buildup of ClO(2)(-), which reacts with BrOClO.HOCl to give 2 ClO(2) and Br(-). Second-order rate constants for the reactions of HOCl and Cl(2)O with BrO(2)(-) are k(1)(HOCl) = 1.6 x 10(2) M(-1) s(-1) and k(1)(Cl)()2(O) = 1.8 x 10(5) M(-)(1) s(-)(1). When Cl(-) is added in large excess, a Cl(2) pathway exists in competition with the HOCl and Cl(2)O pathways for the loss of BrO(2)(-). The proposed Cl(2) pathway proceeds by Cl(+) transfer to form a steady-state ClOBrO species with a rate constant of k(1)(Cl2) = 8.7 x 10(5) M(-1) s(-1).
Article
The seminal work of Rook initiated a considerable body of research regarding the formation of trihalomethanes (THMs) and other by-products of chlorine-based disinfection. Since that time, a broad spectrum of compounds has been identified as precursors to THM formation. More recently, it has been demonstrated that the presence of copper in solution enhances THM formation. Copper is known to catalyze a number of reactions that are similar to the conventional haloform reaction. A study was therefore initiated to investigate the specific role played by copper in the formation of chloroform during chlorination of water supplies. Aqueous solutions containing a number of known THM precursors were chlorinated in the presence and absence of copper, and subjected to time-course monitoring of chloroform concentration. The results of experiments with humic acid demonstrated an apparent catalytic effect on the part of copper in chloroform formation. To examine the role of copper in greater detail, a series of experiments involving aqueous solutions of pure compounds of humic substance structural units was conducted. Of the pure compounds investigated as THM precursors, only citric acid demonstrated enhanced chloroform formation in the presence of copper. A detailed matrix of experiments conducted with citric acid as a precursor demonstrated that copper, at environmentally relevant concentrations, can have a profound effect on chloroform formation. Based on previously published information regarding the mechanism of chloroform formation from citric acid and the results of these experiments, it is hypothesized that copper promotes chloroform formation from chlorination of citric acid through catalysis of oxidative decarboxylation, and the subsequent chlorination of beta-ketoglutaric acid.
Article
The objectives of this study are to investigate the kinetics of bromamine decomposition and to identify the corresponding relevant reactions. Experiments were performed with a stopped-flow spectrophotometer system. Experimental variables investigated included pH (6.5-9.5), bromamines concentration (0.15-0.50 mM), ammonia to bromine ratio (5-100), and phosphate and carbonate buffers concentration (5-40 mM). The experimental results were consistent with a reaction scheme that involved the reversible disproportionation of monobromamine into dibromamine and ammonia (2NH2Br (k1)<=>(k(-1)) NHBr2 + NH3), followed by irreversible decomposition of monobromamine and dibromamine into products (2NHBr2 (k2) --> products and NH2Br + NHBr2 (k3) --> products). The monobromamine disproportionation reaction was found to undergo general acid catalysis, and the two subsequent decomposition reactions were found to experience base catalysis. Experimental results were analyzed for the determination of catalysis terms corresponding to H+, NH4+, H2PO4-, HCO3-, and H2O for rate constants k1 and k(-1); HPO4(2-) and H2O for k2; and OH-, CO3(2-), and H2O for k3. These constants were fitted with the Brønsted relationship, and the resulting fitting expressions were used to calculate any relevant catalysis rate constants that could not be determined at the range of experimental conditions used.
Article
Little is known about how the growth of trihalomethanes (THMs) in drinking water is affected in copper pipe. The formation of THMs and chlorine consumption in copper pipe under stagnant flow conditions were investigated. Experiments for the same water held in glass bottles were performed for comparison. Results showed that although THMs levels firstly increased in the presence of chlorine in copper pipe, faster decay of chlorine as compared to the glass bottle affected the rate of THMs formation. The analysis of water phase was supplemented by surface analysis of corrosion scales using X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDX). The results showed the scales on the pipe surface mainly consisted of Cu(2)O, CuO and Cu(OH)(2) or CuCO(3). Designed experiments confirmed that the fast depletion of chlorine in copper pipe was mainly due to effect of Cu(2)O, CuO in corrosion scales on copper pipe. Although copper(II) and copper oxides showed effect on THMs formation, the rapid consumption of chlorine due to copper oxide made THM levels lower than that in glass bottles after 4h. The transformations of CF, DCBM and CDBM to BF were accelerated in the presence of copper(II), cupric oxide and cuprous oxide. The effect of pH on THMs formation was influenced by effect of pH on corrosion of copper pipe. When pH was below 7, THMs levels in copper pipe was higher as compared to glass bottle, but lower when pH was above 7.
Article
Chlorinated waters are being introduced into estuarine and coastal areas in increasing quantities. In such systems, the chlorine reacts with the natural bromide and ammonia to produce the highly toxic hypobromous acid, hypobromite ion, and haloamines. Sunlight causes up to 50 percent conversion to bromate ion, which is persistent in natural waters and has an unknown toxicity.
Article
Bormate (BrO3(-)) is a carcinogenic chemical produced in ozonation or chlorination of bromide-containing water. Although its formation in seawater with or without sunlight has been previously investigated, the formation of bromate in dilute solutions, particularly raw water for water treatment plant, is unknown. In this article, the results of bench scale tests to measure the formation rates of bromate formation in dilute solutions, including de-ionized water and raw water from Yangtze River, were presented in dark chlorination and ultraviolet (UV)/chlorination processes. And the effects of initial pH, initial concentration of NaOCl, and UV light intensity on bromate formation in UV/chlorination of the diluted solutions were investigated. Detectable bromate was formed in dark chlorination of the two water samples with a relatively slow production rate. Under routine disinfecting conditions, the amount of formed bromate is not likely to exceed the national standards (10 microg/L). UV irradiation enhanced the decay of free chlorine, and, simultaneously, 6.6%--32% of Br was oxidized to BrO3(-). And the formation of bromate exhibited three stages: rapid stage, slow stage and plateau. Under the experimental conditions (pH = 4.41--11.07, Ccl2 = 1.23--4.50 mg/L), low pH and high chlorine concentration favored the generation of bromate. High light intensity promoted the production rate of bromate, but decreased its total generation amount due to acceleration of chlorine decomposition.
Bromate in chlorinated drinking waters: Occurrence and implications for future regulation Bromate ion formation in dark chlorination and ultraviolet/chlorination processes for bromide-containing water Sunlight induced bromate formation in chlorinated seawater
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Decomposition of sodium hypochlorite: The catalyzed reaction Effects of copper(II) and copper oxides on THMs formation in copper pipe
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Copper catalysis in chloroform formation during water chlorination Catalysis of copper corrosion products on chlorine decay and HAA formation in simulated distribution systems
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National survey of bromide in drinking waters
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