Brominated Disinfection Byproducts Research Articles

Probing the role of BrCl in benzotriazole transformation during seawater chlorination

A common understanding attributes the formation of brominated disinfection by-products (Br-DBPs) in seawater chlorination to the conversion of hypochlorous acid to hypobromous acid (HOBr) by bromide. In this study, we reveal that bromine chloride (BrCl), mediated by both chloride and bromide in seawater, plays a dominant role in the transformation of 1H-benzotriazole (BTA) and 5-methyl-1H-benzotriazole (MBTA) and in the formation of brominated DBPs. Using anisole as a reference compound, the second-order rate constant for the reaction of BrCl with BTA was determined to be (2.65 ± 0.13) × 105 L mol−1 s−1, which is over 30,000 times higher than that for the reaction between HOBr and BTA. Ten brominated products were identified and showed a successive bromination pattern. The bromination reaction mechanism was elucidated through theoretical calculations, and the pathways were proposed. The concentrations of brominated BTA and MBTA in seawater were 5.7 and 7.9 times higher than in bromide-only solutions, respectively. BrCl significantly promoted brominated product generation and increased the toxicity of blended DBPs. These results suggest that focusing solely on bromide's effect on brominated product generation may significantly underestimate the potential for DBP formation during seawater chlorination.

Increased formation of brominated disinfection by-products and toxicities during low-H2O2-mediated ozonation of reclaimed water

Reusing reclaimed water requires stringent disinfection but inevitably generates disinfection by-products (DBPs). H2O2/O3 treatment is an efficient and environmentally benign disinfection method. For the first time, our bioassay results elucidate that low H2O2/O3 ratio (molar) treated water increased unignorable toxicity effect compared to that of the high H2O2/O3 ratio. To clarify this finding, individual organic brominated DBPs (Br-DBPs), bromate, and adsorbable organic bromine (AOBr) were considered due to their potential risk. Organic Br-DBPs were mainly generated from ozone-induced pathways. Individual organic Br-DBPs were not the primary concern in this scenario because they are typically only produced in observable quantities at bromide concentrations exceeding 500 μg/L, and even then, they often remain below detection limits when treated with H2O2/O3. On the contrary, both bromate and AOBr were detectable at low H2O2/O3 ratios. Furthermore, bromate is produced from HOBr and bromine radicals induced by HO•. Moreover, bromate formation was promoted because of increased HO• formation, particularly at H2O2/O3 ratios <0.24. To prevent HO•-induced pathways from being dominant, higher H2O2/O3 ratios (>0.48) were required. Toxicity assays revealed that AOBr-included organic extracts of ozonated reclaimed water induced more toxic effects. The toxicity induced by the organic fraction resulted from its decreased oxidation level, which was, in turn, driven by the increased formation of bromate. Enhanced toxicity effects were observed when cells were exposed to a bromate and organic extract mixture. It indicates that both the AOBr and bromate present in low-H2O2-O3-treated reclaimed water pose potential risks, and their coexistence further elevates these risks. Increasing the H2O2/O3 ratio markedly decreased the generation of intracellular oxidative substances and oxidative damage. In conclusion, when treated with H2O2/O3, shifting from HO•-induced pathways to ozone-induced pathways by a relatively high H2O2/O3 ratio decreased the amounts of DBPs produced and controlled the toxic effects to ensure the safety of ozonated reclaimed water.

Molecular characterization of nontarget brominated disinfection byproducts formed during the ozonation in the presence of bromide and ammonium and their potential toxicity implications

While there is extensive literature covering byproducts formed during various water treatment processes, there is limited research focusing on the generation of brominated disinfection byproducts (Br-DBPs) specifically during ozonation in the presence of bromide (Br−) and ammonium (NH4+). This study used Orbitrap mass spectrometry and a custom halogen extraction code to selectively pinpoint 109 Br-DBPs generated during the ozonation of Suwannee River natural organic matter (SRNOM) containing Br− and NH4+. The Br-DBPs are predominantly distributed ranging from m/z 190 to 320, with elemental compositions consisting of CHOBr and CHONBr. They mainly fell within the H/C (0.5–1.5) and O/C (0.2–1.0) zones, with 16 % being aromatic compounds. NH4+ suppressed Br-DBP formation in CHOBr1-2 subgroups but promoted it in CHONBr1-2 subgroups compared to Br−-containing SRNOM ozonation. Kendrick mass defect diagram revealed 64 identical Br-DBP formulas in the CHOBr1-2 subgroups in both systems, and among them, 13 brominated carboxylic acids were identified, whose formation was suppressed by the addition of NH4+. Moreover, bromonitrophenol and bromobenzonitrile were identified in CHONBr1-2 subgroups, and their formation pathways were proposed. Nitrogen-containing Br-DBPs, especially the aromatic nitrogen-containing ones, exhibited higher toxicity. Caution is necessary to minimize toxic Br-DBPs formation during Br− and NH4+-involved ozonation. This study offers insights into Br-DBP characterization, formation mechanisms and toxicity, guiding enhanced water treatment strategies.

Bromate-induced oxidation of carbamazepine and toxicity assessment of transformation products in the freezing-sunlight process: Effects of trivalent chromium

Bromate (BrO3-)-induced pharmaceutical and personal care products (PPCPs) oxidation is enhanced in freezing systems. Reduced forms of metals are widely present, often coexisting with various contaminants. However, their effects on the interaction of PPCPs with BrO3- in ice in cold regions may have been overlooked. Herein we investigated the effects of representative reducing metal Cr(III) on the interaction between the representative PPCP carbamazepine (CBZ) and BrO3- in the freezing system. Our findings demonstrated that the degradation rate constants of CBZ by BrO3- and Cr(III) were 29.4%–60.3% lower than those by BrO3- in ice, revealing the inhibition of Cr(III) on CBZ degradation by BrO3- in ice. In BrO3-/freezing/sunlight system, BrO3- contributed 62.8% to CBZ degradation. In BrO3-/Cr(III)/freezing/sunlight system, Cr(III) promoted the generation of hydroxyl radical (·OH), leading to 51.0% contribution of ·OH to CBZ degradation. Oxidants were consumed by Cr(III) to form Cr(VI) rather than reacting with CBZ, thereby decreasing CBZ degradation by BrO3- in ice. Due to sunlight-induced Cr(VI) reduction in ice, only 0.3% of Cr(III) was converted to Cr(VI) in BrO3-/Cr(III)/freezing/sunlight system. BrO3--induced CBZ degradation rate in ice decreased in order of Fe(II), Cr(III), and Mn(II), which was due to the different reducing capabilities. An effective reduction in comprehensive toxicity of systems followed the freezing-sunlight process, even in the presence of Cr(III). This work sheds new light on the environmental behaviors and fate of PPCPs, brominated disinfection by-products, and reducing metals during seasonal freezing.

A highly specific colorimetric fluorescent probe for rapid detection of hypobromous acid and its application in the environment

The highly reactive hypobromous acid (HOBr), which is generated after chlorination process of tap water, acts as a precursor of toxic brominated disinfection by-products (Br-DBPs) and further reacts with organic matter. In addition, HOBr produced from the oxidation of Br− during the degradation of pollutants by peroxymonosulfate (PMS, HSO5−) can be considered as the cause of the expedited degradation of pollutants. Therefore, it is particularly important to detect HOBr level in the water environment. Resazurin was selected as a fluorescent probe for selective recognition of HOBr in the water environment. The probe exhibited excellent spectral performance and showed high sensitivity to HOBr (LOD = 515 nM). This method has a relatively ideal recovery rate for HOBr detection in environmental water samples. Furthermore, the HOBr production during the chlorination disinfection process was simulated and the HOBr generated from this process was detected by the probe. Importantly, the process of HOBr recognition by the probe is accompanied by the change of color. Based on this, the relationship between the change of color B/G value and HOBr concentration was successfully constructed. The probe was loaded on the filter paper to make a test strip, which was utilized to the detection of HOBr. Collectively, this work provided a promising and powerful method for HOBr detection in the environment.

Sunlight enhanced the formation of tribromomethane from benzotriazole degradation during the sunlight/free chlorine treatment in the presence of bromide

The coexistence of free chlorine and bromide under sunlight irradiation (sunlight/FC with Br−) is unavoidable in outdoor seawater swimming pools, and the formation of brominated disinfection byproducts could act more harmful than chlorinated disinfection byproducts. In this study, benzotriazole was selected as a model compound to investigate the degradation rate and the subsequent formation of disinfection byproducts via sunlight/FC with Br− process. The rate constants for the degradation of benzotriazole under pseudo first order conditions in sunlight/FC with Br− and sunlight/FC are 2.3 ± 0.07 × 10−1 min−1 and 6.0 ± 0.7 × 10−2 min−1, respectively. The enhanced degradation of benzotriazole can be ascribed to the generation of HO•, bromine species, and reactive halogen species (RHS) during sunlight/FC with Br−. Despite the fact that sunlight/FC with Br− process enhanced benzotriazole degradation, the reaction results in increasing tribromomethane (TBM) formation. A high concentration (37.8 μg/L) of TBM was detected in the sunlight/FC with Br−, which was due to the reaction of RHS. The degradation of benzotriazole was notably influenced by the pH value (pH 4 − 11), the concentration of bromide (0 − 2 mM), and free chlorine (1 − 6 mg/L). Furthermore, the concentration of TBM increased when the free chlorine concentrations increased, implying the formation potential of harmful TBM in chlorinated seawater swimming pools.

Phototransformation of Brominated Disinfection Byproducts and Toxicity Elimination in Sunlit-Ozonated Reclaimed Water.

Ozonation is universally used during water treatment but can form hazardous brominated disinfection byproducts (Br-DBPs). While sunlight exposure is advised to reduce the risk of Br-DBPs, their phototransformation pathways remain insufficiently understood. Here, sunlight irradiation was found to reduce adsorbable organic bromine by 63%. Applying high-resolution mass spectrometry, the study investigated transformations of dissolved organic matter in sunlit-ozonated reclaimed water, revealing the number and abundance of assigned formulas decreased after irradiation. The Br-DBPs with O/C < 0.6 and MW > 400 Da were decreased or removed after irradiation, with the majority being CHOBr compounds. The peak intensity reduction ratio of CHOBr compounds correlated positively with double bound equivalent minus oxygen ratios but negatively with O/C, suggesting that photo-susceptible CHOBr compounds were highly unsaturated. Mass difference analysis revealed that the photodegradation pathways were mainly oxidation aligned with debromination. Three typical CHOBr molecular structures were resolved, and their photoproducts were proposed. Toxicity estimates indicated decreased toxicity in these photoproducts compared to their parent compounds, in line with experimentally determined values. Our proposed phototransformation pathways for Br-DBPs enhance our comprehension of their degradation and irradiation-induced toxicity reduction in reclaimed water, further illuminating their transformation under sunlight in widespread environmental scenarios.

Effects of ozone dose on brominated DBPs in subsequent chlor(am)ination: A comprehensive study of aliphatic, alicyclic and aromatic DBPs

Ozone‒chlor(am)ine is a commonly used combination of disinfectants in drinking water treatment. Although there are quite a few studies on the formation of some individual DBPs in the ozone‒chlor(am)ine disinfection, an overall picture of the DBP formation in the combined disinfection is largely unavailable. In this study, the effects of ozone dose on the formation and speciation of organic brominated disinfection byproducts (DBPs) in subsequent chlorination, chloramination, or chlorination‒chloramination of simulated drinking water were investigated. High-molecular-weight, aliphatic, alicyclic and aromatic brominated DBPs were selectively detected and studied using a powerful precursor ion scan method with ultra performance liquid chromatography/electrospray ionization triple quadrupole mass spectrometry (UPLC/ESI-tqMS). Two groups of unregulated yet relatively toxic DBPs, dihalonitromethanes and dihaloacetaldehydes, were detected by the UPLC/ESI-tqMS for the first time. With increasing ozone dose, the levels of high-molecular-weight (m/z 300–500) and alicyclic and aromatic brominated DBPs generally decreased, the levels of brominated aliphatic acids were slightly affected, and the levels of dihalonitromethanes and dihaloacetaldehydes generally increased in the subsequent disinfection processes. Despite different molecular compositions of the detected DBPs, increasing ozone dose generally shifted the formation of DBPs from chlorinated ones to brominated analogues in the subsequent disinfection processes. This study provided a comprehensive analysis of the impact of ozone dose on the DBP formation and speciation in subsequent chlor(am)ine disinfection.

Comparative formation of chlorinated and brominated disinfection byproducts from chlorination and bromination of amino acids

Amino acids are the main components of dissolved organic nitrogen in algal- and wastewater-impacted waters, which can react with chlorine to form toxic halogenated disinfection by-products (DBPs) in the disinfection process. In the presence of bromide, the reaction between amino acids and secondarily formed hypobromous acid can lead to the formation of brominated DBPs that are more toxic than chlorinated analogues. This study compares the formation of regulated and unregulated DBPs during chlorination and bromination of representative amino acids (AAs) (e.g., aspartic acid, asparagine, tryptophan, tyrosine, and histidine). In general, concentrations of brominated DBPs (trihalomethanes, haloacetonitriles, and haloacetamides, 24.9–5835.0 nM) during bromination were higher than their chlorinated analogues (9.3–3235.3 nM) during chlorination. This indicates the greater efficacy of bromine as a halogenating agent. However, the formation of chlorinated haloacetic acids during chlorination was higher than the corresponding brominated DBPs from bromination. It is likely that an oxidation pathway is required for the formation of haloacetic acids and chlorine is a stronger oxidant than bromine. Moreover, chlorine forms higher levels of haloacetaldehydes (74.4–1077.8 nM) from amino acids than bromine (1.0–480.2 nM) owing to the instability of brominated species. The DBP formation yields depend on the types of functional groups in the side chain of AAs. Eight intermediates resulting from chlorination/bromination of tyrosine were identified by triple quadrupole mass spectrometer, including N-chlorinated/brominated tyrosine, 3-chloro/bromo-tyrosine, and 3,5-dichloro/dibromo-tyrosine. These findings provided new insights into the DBP formation during the chlorination of algal- and wastewater-impacted waters with elevated bromide.

Halogenated aliphatic and phenolic disinfection byproducts in chlorinated and chloraminated dairy wastewater: Occurrence and ecological risk evaluation

The increasing demand for dairy products has led to the production of a large amount of wastewater in dairy plants, and disinfection is an essential treatment process before wastewater discharge. Disinfection byproducts (DBPs) in disinfected dairy wastewater may negatively influence the aquatic organisms in receiving water. During chlorine and chloramine disinfection of dairy wastewater, the concentrations of aliphatic DBPs increased from below the detection limits to 485.1 μg/L and 26.6 μg/L, respectively. Brominated and iodinated phenolic DBPs produced during chlor(am)ination could further react with chlorine/chloramine to be transformed. High level of bromide in dairy wastewater (12.9 mg/L) could be oxidized to active bromine species by chlorine/chloramine, promoting the formation of highly toxic brominated DBPs (Br-DBPs), and they accounted for 80.3% and 71.1% of the total content of DBPs in chlorinated and chloraminated dairy wastewater, respectively. Moreover, Br-DBPs contributed 49.9–75.9% and 34.2–96.4% to the cumulative risk quotient of DBPs in chlorinated and chloraminated wastewater, respectively. The cumulative risk quotient of DBPs on green algae, daphnid, and fish in chlorinated wastewater was 2.8–11.4 times higher than that in chloraminated wastewater. Shortening disinfection time or adopting chloramine disinfection can reduce the ecological risks of DBPs.

Formation and estimated toxicity of trihalomethanes and haloacetic acids from chlorination of nonylphenol-containing water: Effect of chlorine and bromide concentration, contact time, and pH

The presence of nonylphenol (NP), an endocrine-disrupting chemical (EDC), in water sources can form toxic chlorination disinfection by-products (DBPs) during the water disinfection process using chlorine. This study investigated the formation of trihalomethanes-4 (THM4) and haloacetic acids-5 (HAA5) as regulated DBPs during the chlorination process of NP-containing water. The effects of chlorine dose, bromide concentration, pH, chlorine contact time, and the presence of NP in real natural water on THM4 and HAA5 formation were investigated. The increase of chlorine dose increased all of the THM4 and HAA5 formation especially chlorinated DBPs (Cl-DBPs), including trichloromethane (TCM) (0.140 %) and dichloroacetic acid (DCAA) (0.722 %) when the chlorine concentration was 5 times higher than NP. However, the increase of bromide concentration increased the formation of brominated DBPs (Br-DBPs), reaching concentration yields of 1.615 % for tribromomethane (TBM) and 0.421 % for dibromoacetic acid (DBAA), but decreased the chlorinated (Cl-DBPs formation). Similarly, the increase of chlorine contact time and pH increased the DBPs formation significantly especially Br-DBPs. The TBM and DBAA concentration yields reached 1.615 % and 0.676 %, respectively, when chlorinated at pH 9 and reached 0.653 % and 0.751 %, respectively, when chlorinated for 168 h. The addition of NP in natural water also raised the hydrophilicity of dissolved organic matter (DOM), indicated by the decrease of specific ultraviolet absorbance (SUVA) value, which enhanced the formation of certain species including THM4 and HAA5. Based on toxicity calculation, the regulated DBPs formed were cytotoxic rather than genotoxic.

A novel benzothiazolin-based fluorescent probe for hypobromous acid and its application in environment and biosystems

Studies have shown that hypobromous acid (HOBr) produced during chlorination disinfection of tap water can react with some organic matter in water to form toxic brominated disinfection byproducts (Br-DBPs) and HOBr also plays an important role during the process of micro pollutants degradation. Hence, real-time monitoring of HOBr in water environment plays a significant role in controlling the generation of Br-DBPs and degradation of micro pollutants. Herein, a novel highly specific fluorescent probe (PBE-HOBr) for accurate detection of HOBr was constructed based on the HOBr-induced oxidation elimination of benzothiazoline moiety employing the photo-induced electron transfer (PET) mechanism. PBE-HOBr has high sensitivity and linear response to HOBr with a low detection limit of 119 nM. PBE-HOBr not only has the ability to detect endogenous and exogenous HOBr in cells and zebrafish, but also has been used to monitor the formation of HOBr in water treatment. In addition, benzothiazoline group was demonstrated for the first time to be able to be used as a new recognition receptor for developing highly specific fluorescent probes for HOBr.

Formation and speciation of hazardous trihalomethanes and haloacetic acids during chlorinated washing of brined kimchi cabbage in the presence of bromide

Brominated disinfection byproducts (Br-DBPs) may be generated in high concentrations during the chlorinated washing of brined kimchi cabbage (BKC) in kimchi manufacturing. However, the generation of these DBPs is not sufficiently understood. Therefore, in this study, we investigated the formation and speciation of the DBPs trihalomethanes (THMs) and haloacetic acids (HAAs) during the chlorinated washing process. The average bromide content in 22 salt products sourced from various regions of Korea was 1600 ± 468 mg/kg. Increasing bromide content shifted the speciation of DBPs from chlorinated to mixed bromochloro to brominated species, which would be more harmful than their chlorinated analogs. DBP formation during the washing of BKC at average bromide levels changed based on the brine salinity, salting temperature, and disinfectant type. Based on our findings, we recommend that low salinity and low temperature should be maintained during the salting of KC and that NaOCl should be used as the disinfectant rather than slightly acidic electrolyzed water during the chlorinated washing of KC to alleviate the formation of Br-DBPs. Moreover, we recommend the use of salts with low bromide levels for the salting of KC and the addition of a rinse step after chlorinated washing.

Increasing bromide removal by graphene-silver nanocomposites: Nanoparticulate silver enhances bromide selectivity through direct surface interactions

Bromide forms toxic brominated disinfection by-products during disinfection. Current bromide removal technologies are often non-specific and costly due to naturally occurring competing anions. A silver-impregnated graphene oxide (GO) nanocomposite is reported here that reduced the amount of Ag needed for Br− removal by increasing its selectivity towards Br−. GO was impregnated with ionic (GO-Ag+) or nanoparticulate Ag (GO-nAg) and compared against Ag+ or unsupported nAg to identify molecular level interactions. In nanopure water, Ag+ and nAg had the highest Br− removal (∼0.89 mol Br−/mol Ag+) followed by GO-nAg at 0.77 mol Br−/mol Ag+. However, under anionic competition, the Ag+ removal was reduced to 0.10 mol Br−/mol Ag+ while all nAg forms retained good Br− removal. To understand the removal mechanism, anoxic experiments were performed to prevent nAg dissolution, which resulted in higher Br− removal for all nAg forms compared to oxic conditions. This suggests that reaction of Br− with the nAg surface is more selective than with Ag+. Finally, jar tests showed that anchoring nAg on GO enhances Ag removal during coagulation/flocculation/sedimentation compared to unsupported nAg or Ag+. Thus, our results identify strategies that can be used to design selective and silver-efficient adsorbents for Br− removal in water treatment.

Removal of Haloacetic Acids via Adsorption and Biodegradation in a Bench-Scale Filtration System

Brominated disinfection byproducts (DBPs) are a concern to drinking water utilities due to their toxicity and increasing prevalence in water systems. Haloacetic acids (HAAs) are a class of DBPs that are partially regulated by the United States Environmental Protection Agency (USEPA), but regulations are likely to increase as evidenced by the brominated HAAs listed on the USEPA Fourth Unregulated Contaminant Monitoring Rule and Fifth Contaminant Candidate List. Utilities often use a pre-oxidant to assist in their treatment training, but this can lead to increased HAA formation during treatment. In this study, tap water was spiked with bromine (Br2) at varying concentrations to simulate bromine-to-chlorine ratios found in the natural environment and the DBPs that may be formed from those waters. The water was fed through a bench-scale biological filter (biofilter) with a small layer of fresh granular activated carbon (GAC) media followed by acclimated anthracite media. The HAA species studied were found to be removable by an average of 89.5% through combined GAC filtration and biofiltration. Biodegradation occurred predominantly in the first five minutes for the acclimated anthracite, with minimal additional removal observed at longer empty bed contact times (15 and 30 min EBCT). This study provides recommendations on biofilter parameters for utilities to reduce the formation of both regulated and unregulated HAAs during the drinking water treatment process.

Enhanced formation of haloacetonitriles during chlorination with bromide: Unveiling the important roles of organic bromamines

The formation of brominated disinfection byproducts (Br-DBPs) is an emerging issue in drinking water disinfection because its toxicity is tens to hundreds of times higher than that of chlorinated analogues and because of the widespread presence of bromide in source water. However, the mechanism and pathways of Br-DBPs formation remain unclear. In this study, we used glycine, alanine, and serine as model precursors and observed that brominated haloacetonitriles (Br-HANs) were more likely to be formed than brominated trihalomethanes. The results showed that there is not only one important way to HAN formation in the presence of bromide. We propose that organic bromamines, similar to organic chloramines, play a significant role in the formation of Br-HANs. Both the experimental and theoretical results confirmed that the decay of organic bromamines was faster than that of organic chloramines, which verified our assumption. The effect of the pH was investigated to further confirm the role of organic bromamines. In addition, we found that the formation of Br-HANs was significantly inhibited when monochloramine was used as a disinfectant, because the formation of organic bromamines was blocked. However, the formation of Br-HANs was promoted during the UV/chlorine process because of the faster decay of organic bromamines under UV photolysis. Overall, our study reveals the formation mechanism of Br-HANs and provides an alternative method to prevent Br-HAN formation.

Degradation of Tetrabromobisphenol S by thermo-activated Persulphate Oxidation: reaction Kinetics, transformation Mechanisms, and brominated By-products

ABSTRACT Brominated flame retardants (BFRs) are a group of contaminants of emerging environmental concern. In this study, systematic exploration was carried out to investigate the degradation of tetrabromobisphenol S (TBBPS), a typical emerging BFRs, by thermally activated persulfate (PDS) oxidation. The removal of 5.0 μM TBBPS was 100% after 60 min oxidation treatment under 60°C. Increasing the temperature or initial PDS concentration facilitated the degradation efficiency of TBBPS. The quenching test indicated that TBBPS degradation occurred via the attack of both sulphate radicals and hydroxyl radicals. Natural organic matter (NOM) decreased the removal rate, however, complete disappearance of TBBPS could still be obtained. Six intermediate products were formed during reactions between TBBPS and radicals. Transformation pathways including debromination, β-Scission, and cross-coupling were proposed. Brominated disinfection by-products (DBPs) in situ formed during the degradation of TBBPS were also investigated, such as bromoform and dibromoacetic acid. The presence of NOM reduced the formation rates of brominated DBPs. Results reveal that although thermo-activated PDS is a promising method for TBBPS-contaminated water, it can lead to potential brominated DBPs risks, which should be paid more attention to when SO4 •−-based oxidation technology is applied.

Aquatic photolysis of the pharmaceutical ambroxol: The role of 2,4-dibromoaniline chromophore and heavy atom effect of bromine

As one of the most effective expectorant class drugs, ambroxol (AMB) has been frequently used to treat acute and chronic bronchitis. Extensive use and human excretion result in the widespread occurrence of AMB in wastewater. Herein, we reported the photolysis of AMB in aqueous solution upon 254 nm ultraviolet radiation (UV254). Spectroscopic characterization showed that 2,4-dibromoaniline (DBA) moiety is the core chromophore of AMB. Quantum yield of DBA changed little at pH 4.0 - 9.0; however, AMB showed higher quantum yield at pH > 8.0. Both DBA and AMB have high photoreactivity, which can be attributed to the “heavy atom” effect of bromine substituents. The photolysis of AMB occurred through photoreduction, photoionization, photonucleophilic substitution, side-chain cleavage, and coupling reactions. Both AMB and DBA underwent debromination with yields reaching 80% under 3200 mJ cm−2 UV fluence. Photo-debromination occurred preferentially at the para-position. The presence of natural organic matter inhibited the photodegradation, mainly due to the light-screening effect. The photolysis of AMB was slightly enhanced in the presence of NO3− likely due to radical-induced oxidation. Bioluminescence inhibition assay revealed that photoproducts were not toxic. The results show that UV254 radiation with fluences relevant to advanced oxidation processes was effective for the abatement of AMB in wastewater. However, UV254 treatment of wastewater containing higher concentrations (˃ μg L−1) of AMB should be done with caution because the released Br− can be converted to toxic brominated disinfection byproducts and bromate in subsequent oxidation process.

Insights into the oxidation of bisphenol A by peracetic acid enhanced with bromide: The role of free bromine

Peracetic acid (PAA) has received great attention in wastewater treatment as an alternative to free chlorine. However, wastewater constituents such as bromide (Br−) may affect the PAA-based oxidation process. In this study, we reported a detailed kinetic and mechanistic study on bisphenol A (BPA, 20 μM) oxidation by PAA in the presence of Br−. When the concentration of Br− was increased from 20 to 100 μM, the removal rate of BPA was significantly increased, which was attributed to the formation of secondary oxidant hypobromous acid. When BPA was treated with 5 mM PAA in the presence of 100 µM Br− at pH 7.0, ∼26 % of bromide was converted into organic bromine in 24 h. Brominated disinfection byproducts (Br-DBPs) accounted for ∼8.2 % of total organic bromine generated, among them the concentrations of bromoform (CHBr3), dibromoacetic acid (DBAA), and tribromoacetic acid (TBAA), were determined to be 0.94, 0.99, and 0.21 µM, respectively. A total of 23 transformation products were identified by high-resolution mass spectrometry (HRMS) analyses. Three transformation pathways, including CC (C1-C2 and C2-C4) bridge bond cleavage, phenyl ring bromination, and stepwise oxidation were proposed and rationalized by theoretical calculations. In conclusion, the presence of Br− can enhance the degradation efficiency of BPA in the PAA disinfection process; however, the formation of potentially carcinogenic brominated intermediates in Br−-containing wastewaters should be scrutinized.

Monthly variations of unregulated brominated disinfection by-products in chlorinated water are correlated with total bromine

Brominated disinfection by-products (Br-DBPs) can form during chlorination of drinking water in treatment plants (DWTP). Regulations exist for a small subset of Br-DBPs; However, hundreds of unregulated Br-DBPs have been detected and limited information exists on their occurrence, concentrations, and seasonal trends. Here, a data-independent precursor isolation and characteristic fragment (DIPIC-Frag) method was optimized to screen chlorinated waters for Br-DBPs. There were 553 Br-DBPs detected with m/z values ranging from 170.884 to 497.0278 and chromatographic retention times from 2.4 to 26.2 min. With MS 2 information, structures for 40 of the 54 most abundant Br-DBPs were predicted. The method was then applied to a year-long study in which raw, clear well, and finished water were analyzed monthly. The 54 most abundant unregulated Br-DBPs were subjected to trend analysis. Br-DBPs with higher oxygen-to-carbon (O/C) and bromine-to-carbon (Br/C) ratios increased as water moved from the clear well to the finished stage, which indicated the dynamic formation of Br-DBPs. Monthly trends of unregulated Br-DBPs were compared to raw water parameters such as natural organic matter, temperature, and total bromine, but no correlations were observed. It was found that total concentrations of bromine (TBr) in finished water (0.04–0.12 mg/L) were consistently and significantly greater than in raw water (0.013–0.038 mg/L, P < 0.001), suggesting the introduction of bromine during the disinfection process. Concentrations of TBr in treatment units, rather than raw water, were significantly correlated to 34 of the Br-DBPs at α = 0.05. This study provides the first evidence that monthly trends of unregulated Br-DBPs can be associated with the concentration of TBr in treated waters. - Ultrahigh resolution mass spectrometry was used to identify novel brominated disinfection byproducts in a Canadian water treatment facility. - Several hundred novel brominated compounds were identified of which 54 were assigned chemical structures. - Seasonal variation in the generated DBPs were assessed over 11 months of sampling. - Increases in total bromine in drinking water was noted with progress thru the treatment process.