Brominated Disinfection Byproducts Research Articles

Comprehensive GC×GC-qMS with a mass-to-charge ratio difference extraction method to identify new brominated byproducts during ozonation and their toxicity assessment

Ozonation might increase the risk of wastewater due to byproduct formation, especially in the presence of bromide. In this study, a new analytical method was developed to identify new brominated disinfection byproducts (Br-DBPs) during ozonation, using comprehensive two-dimensional gas chromatography-single quadrupole mass spectrometry (GC×GC-qMS) connected with an electron capture detector in parallel. The obtained data were analyzed using a mass-to-charge ratio (m/z) difference extraction method. Over 1304 DBPs were detected in an ozonated phenylalanine solution. Further screening of 635 DBPs was conducted using the m/z difference extraction method. Finally, the structures for 12 Br-DBPs were confirmed and for 4 Br-DBPs were tentatively proposed by comparison with the NIST library and standard compounds. Eight of the confirmed Br-DBPs are first reported and identified: 2-bromostyrene, 1-bromo-1-phenylethylene, 2-bromobenzaldehyde, 3-bromobenzaldehyde, 4-bromobenzaldehyde, 2-bromophenylacetonitrile, 3-bromophenylacetonitrile and 4-bromophenylacetonitrile. These DBPs and 2,4,6-tribromophenol were detected at nanogram- to microgram-per-liter concentrations during ozonation of authentic water samples like algal bloom waters, wastewater treatment plant effluents, and surface water. The toxicities of these compounds were generally higher than that of bromate. The developed analytical method is a powerful technique for analyzing complex compounds and provides a novel way of identifying byproducts in future studies.

Activated carbon and organic matter characteristics impact the adsorption of DBP precursors when chlorine is added prior to GAC contactors

Pre-chlorination (i.e. dosing chlorine prior to granular activated carbon (GAC) contactors) was recently introduced as a promising method to reduce the formation of disinfection byproducts (DBPs). However, our understanding on the effect of natural organic matter (NOM) and GAC characteristics on pre-chlorination efficiency is still elusive. Thus, we have designed this systematic study to investigate the effects of GAC characteristics (i.e. surface area, pore size, and surface charge) on the subsequent reduction of DBP formation using five well-characterized adsorbents with three different NOM under three initial Br− concentrations. The results revealed that the adsorption of halogenated DBPs precursors mostly occurs in the mesoporous region (i.e. 2 nm < pore size <50 nm) of the adsorbents. Subsequently, pre-chlorination before treatment with HD3000 (i.e. GAC with the highest mesoporous surface area) decreased the formation of DBPs by 58%. Furthermore, oxidation of GAC increased the surface acidity and negatively impacted the adsorption of halogenated DBP precursors, which suggests basic GACs as promising adsorbents when applying pre-chlorination. In addition, experiments with different NOM showed that pre-chlorination was effective with higher aromatic NOM (i.e. high specific ultraviolet absorbance (SUVA254)). However, pre-chlorination of NOM with low SUVA254 has decreased the adsorption of some DBP precursors which resulted in increased formations of haloacetic acid (HAA) and total organic halogen (TOX). Also, experiments with effluent organic matter (EfOM) showed that pre-chlorination did not increase the adsorption of DBP precursors in low SUVA254 wastewater effluents. Besides, increasing initial Br− concentration increased the formation of brominated DBPs (Br-DBPs) and the adsorbed Br-DBP precursors. This study gives in-depth understanding of the mechanisms, advantages, and limitations of pre-chlorination as a potential method to control DBPs formation.

Roles of bromine radicals, HOBr and Br2 in the transformation of flumequine by the UV/chlorine process in the presence of bromide

In the presence of bromide (Br−), new reactive species, such as bromine and reactive bromine species (RBS), are formed by the UV/chlorine process. In this study, the effects of Br− on the kinetics, products, and pathways of flumequine (FLU) transformation by the UV/chlorine process were investigated. The pseudo first-order rate constant (k′) for FLU degradation in the UV/chlorine process was enhanced by 2.5 times by 50 μM Br− at pH 7, as HOBr, Br2, RBS and HO• were formed, and they contributed 29.2%, 7.8%, 57.4% and 4.8% to k′, respectively. The second-order rate constants (k) of FLU reacting with HOBr, OBr−, Br2 and Br• were determined to be 115.6 M−1 s−1, negligible, 1.5 × 106 M−1 s−1 and 2.4 × 108 M−1 s−1, respectively. The contribution of Br2 was enhanced at a higher Br− level and a lower pH, which accounted for 48.2% of k′ at pH 6. The overall k′ value decreased by 97.9% from pH 6 to 9, during which k′ by HOBr, Br2 and RBS decreased significantly. The formation of brominated products was mainly attributed to HOBr and Br2, while RBS and HO• primarily promoted hydroxylation and ketonization during UV/chlorine treatment with Br−. The formation of total organic bromine (TOBr) by the UV/chlorine process with Br− was comparable to that during dark chlorination with Br−, while the yield of brominated disinfection byproducts in the former was much higher, further indicating that RBS and HO• promoted the formation of small-molecule products. In addition, the acute toxicity of FLU was significantly reduced during the UV/chlorine process with Br−. This is the first study to reveal the significant roles of Br2 and Br• in the degradation of micropollutants by the UV/chlorine process in Br−-containing water.

Highly Efficient Bromide Removal from Shale Gas Produced Water by Unactivated Peroxymonosulfate for Controlling Disinfection Byproduct Formation in Impacted Water Supplies.

Shale gas extraction processes generate a large amount of hypersaline wastewater, whose spills or discharges may significantly increase the bromide levels in downstream water supplies and result in the formation of brominated disinfection byproducts (DBPs) upon chlorination. Although a few studies have investigated selective bromide removal from produced water, the low removal efficiencies and complex system setups are not desirable. In this study, we examined a simple cost-effective approach for selective bromide removal from produced water relying on the oxidation by unactivated peroxymonosulfate. More than 95% of bromide was removed as Br2(g) in less than 10 min under weakly acidic conditions without significant formation of Cl2(g) even when the chloride concentration was more than 2 orders of magnitude higher. A kinetic model considering the involved reactions was then developed to describe the process well under various reaction conditions. The organic compounds in the produced water neither noticeably lowered the bromide removal efficiency nor reacted with the halogen species to form halogenated byproducts. The tests in batch and continuously stirred tank reactor systems suggested that it was feasible to achieve both high bromide removal and neutral effluent pH such that further pH adjustment was not necessary before discharge. After the treatment, the effect of the produced water on DBP formation was largely eliminated.

Microplastics release precursors of chlorinated and brominated disinfection byproducts in water

Microplastics (MPs) are prevalent global pollutants that are being detected in aquatic ecosystems and drinking water sources around the world. In addition to plastic polymers, MPs contain various chemical substances (known as “additives”) that can leach and risk water quality. In this paper, we investigated for the first time the potential release of disinfection byproducts (DBPs) precursors when MPs are exposed to hydrolysis and/or degradation by simulated sunlight. Seventeen MPs with seven different polymer types were collected either as commercial products (e.g. drinking water bottles, shopping bags, recycled plastics, etc.) or pure/virgin polymers. Results showed high release of dissolved organic carbon (DOC) from five MP samples and a significant increase in bromide concentrations from four MPs. DBPs formation potential (DBPFP) experiments with MPs’ leachates showed higher concentrations of chlorinated trihalomethanes (THMs), haloacetonitriles (HANs), and total organic halogens (TOX) in three samples, while a significant shift to brominated DBPs was observed in samples containing bromide. Extending the leaching experiments to four consecutive cycles showed that the leaching of DOC and DBPs’ precursor significantly decreased after the second leaching cycle. Further analysis revealed that the reactivity of the leached DOC – indicated by THMFP yields – was comparable to those of several raw waters that supply drinking water treatment plants. The leached THMs and TOX from MPs that were exposed to UVA irradiation were in general higher than MPs that were run under dark conditions.

Experimental and simulation investigations of UV/persulfate treatment in presence of bromide: Effects on degradation kinetics, formation of brominated disinfection byproducts and bromate

Bromide (Br−), which is omnipresent in water bodies, can not only affect the degradation kinetics of target pollutants but may also form undesired byproducts (such as bromate (BrO3-) and brominated disinfection byproducts (Br-DBPs)) through sulfate radical (SO4∙-)-based advanced oxidation processes (AOPs). This study found that Br− significantly suppressed the degradation of diethyl phthalate (DEP) based on the ultraviolet (UV)/persulfate (PS) treatment and was efficiently converted into reactive species (radicals and free bromine) by the SO4∙- or hydroxyl radical (HO) generated in the UV/PS system. These reactive bromine species could, in turn, brominate the phenolic degradation intermediates of DEP as well as natural organic matter (NOM), yielding Br-DBPs, including tribromomethane (TBM), which was observed when Br−, DEP and/or NOM coexisted in this UV/PS system. However, the Br-DBPs were a short-lived form of bromine during the transformation of Br– and were degraded by the excessive oxidants (e.g., SO4∙- and HO). Instead, Br− was eventually transformed into BrO3-, with free bromine acting as the requisite intermediate. The BrO3- formation initially showed a delay before increasing monotonically. In general, raising the PS dosage and the initial Br− concentrations enhanced both the maximum concentration of TBM and the formation of BrO3-, while increasing the amounts of DEP and NOM facilitated the former and inhibited the latter. The maximum concentration of TBM increased while the formation of BrO3- was suppressed with increasing pH from 5.0 to 8.0. In addition, through simulating the steady-state concentration of radicals, it was found that the contribution of bromine atom radical (Br) towards oxidizing free bromine to BrO3- was far greater than those of SO4∙- and HO. The findings demonstrate the potential negative effects of Br− on SO4∙--based AOPs, which need to be considered when this technology is applied in practice.

Identification, formation and control of polar brominated disinfection byproducts during cooking with edible salt, organic matter and simulated tap water

Edible salt is essential to the health of humans and serves as a seasoning universally. Besides chloride, edible salt also contains other anions such as bromide, fluoride, sulfate, and carbonate due to incomplete removal during raw salt refinement. In a household cooking (e.g., soup making) process, a chlorine/monochloramine residual in tap water could react with bromide in edible salt and organic matter in food (e.g., rice, wheat) to form numerous brominated disinfection byproducts (Br-DBPs) at significant levels, which might induce adverse health effects to human beings. In this study, we solicited 20 edible salts of different types (i.e., sea salts, well and rock salts, lake salts, and bamboo salts) from nine countries and determined their bromide levels to be 67–375 mg/kg, with an average level of 173 mg/kg. A total of 25 polar Br-DBPs were detected and identified with structures/formulae in cooking water samples using ultra performance liquid chromatography/electrospray ionization-triple quadruple mass spectrometry (UPLC/ESI-tqMS) and high-resolution mass spectrometry. Effects of cooking conditions (e.g., disinfectant type and level, edible salt dose, organic matter type and dose, sequence and time interval of adding organic matter and salt, etc.) on the formation of polar Br-DBPs were investigated, and optimized cooking conditions with minimized formation of polar Br-DBPs were determined. Further aided with an Hep G2 cell cytotoxicity assay, it was found that the overall cytotoxicity of chlorinated and chloraminated cooking water samples prepared after cooking condition optimization was reduced by 57% and 22%, respectively, compared with those prepared before cooking condition optimization.

Tracking the formation of new brominated disinfection by-products during the seawater desalination process

Ultrahigh resolution mass spectrometry revealed substantial dissolved organic matter changes and the formation of numerous bromine-containing disinfection by-products during the seawater desalination process.

Degradation of triclosan in a peroxymonosulfate/Br− system: Identification of reactive species and formation of halogenated byproducts

Peroxymonosulfate (PMS), a widely used in situ chemical oxidation agent, has attracted increasing attention in ground water/soil remediation. PMS is relatively stable with lifetime from months to even years in subsurface. The residual PMS can react with various of organics or inorganics species in environment, which may pose long term environmental effects. In this study, reaction between PMS and bromide (Br−) in water, and thus to the transformation of triclosan (TCS), an antibiotic agent, was studied. We found that TCS cannot be degraded by PMS alone but was efficiently removed in the presence of both PMS and Br−. This was due to the formation of free bromine upon the oxidation of Br− by PMS. Formation of bromine radical (Br) in PMS/Br− system was unlikely according to quenching tests. Reaction between free bromine and TCS generated brominated TCS intermediates which underwent further degradation to brominated disinfection byproducts (DBPs), of which bromoform (CHBr3) and dibromoacetic acid (DBAA) were the most prominent ones. Their yields reached 1.31 µM and 0.49 µM in 24 h, respectively, when 1 mg/L TCS was treated with 100 µM PMS and 100 µM Br−. Presence of humic acid (HA) remarkably enhanced the formation of monobromoacetic acid (MBAA), DBAA, and bromochloroacetic acid (BCAA) but inhibited the formation of CHBr3 and dibromochloromethane (CHClBr2). Thus, even though certain phenolic contaminants like TCS can be effectively removed in PMS/Br− system, formation of free bromine and DBPs makes it not a good treatment strategy. Particular attention should be paid when Br− is presented in PMS-based oxidation process.

Effect of oxoanions on oxidant decay, bromate and brominated disinfection by-product formation during chlorination in the presence of copper corrosion products

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.

Comprehensive study on the formation of brominated byproducts during heat-activated persulfate degradation

Applying the highly oxidative sulfate radical (SO4-·) to pollutant degradation may cause it to react with the coexisting bromide (Br−) to form undesired byproducts. This study investigated the transformation of Br− during the degradation process of a contaminant (diethyl phthalate (DEP)) via heat-activated persulfate (PS). Dibromoacetonitrile and bromoform formed with Br− and natural organic matter (NOM) in the solution, while only bromoform was detected without NOM. The formation of these brominated disinfection byproducts (Br-DBPs) can be ascribed to the reactions between the phenolic groups of DEP degradation intermediates or NOM and reactive bromine species (free bromine and radical bromine) generated through the oxidation of Br− by SO4-·. Br-DBPs were degraded by excessive SO4-·, which indicates that organic bromine is a temporary phase during the turnover of Br−. The time-dependent formation of organic and inorganic bromines suggests that Br− may have cycled several times between organic and inorganic forms before eventually turning into bromate. The bromate formation showed a lag phase before continuously increasing. Generally, increasing the temperature, PS dosage, and Br− and organic matter (DEP and NOM) concentrations increased the maximum concentration of Br-DBPs. Additionally, these reaction parameters facilitated bromate formation except for organic matter, whose inhibitory effect is probably due to the consumption of reactive species by organic matter and the generated superoxide anion. The total organic carbon concentration of the solution exhibited a relatively quick reduction followed by a slow decrease. These results highlight the potential risks of PS activation technologies and can help prevent such risks in actual practice.

Removal of bromide from natural waters: Bromide-selective vs. conventional ion exchange resins

The presence of bromide (Br−) in water results in the formation of brominated disinfection byproducts (DBPs) after chlorination, which are much more cytotoxic and genotoxic than their chlorinated analogs. Given that conventional water treatment processes (e.g., coagulation, flocculation, and sedimentation) fail to remove Br− effectively, in this study, we systematically tested and compared the performance of different anion exchange resins, particularly two novel Br-selective resins, for the removal of Br−. The resins performance was evaluated under both typical and challenging background water conditions by varying the concentrations of anions and organic matter. The overall Br− removal results followed the trend of Purolite-Br ≥ MIEX-Br > IRA910 ≥ IRA900 > MIEX-Gold > MIEX-DOC. Further evaluation of Purolite-Br resin showed Br− removal efficiencies of 93.5 ± 4.5% for the initial Br− concentration of 0.25 mg/L in the presence of competing anions (i.e., Cl−, NO3−, NO2−, SO42−, PO43−, and a mixture of all five), alkalinity and organic matter. In addition, experiments under challenging background water conditions confirmed the selectivity of the resins (i.e. Purolite-Br and MIEX-Br) in removing Br−, with SO42− and Cl− exhibiting the greatest influence upon the resin performance followed by NOM concentration, regardless of the NOM characteristic. After Br− removal, both the subsequent formation of brominated DBPs (trihalomethanes, haloacetic acids, and haloacetonitriles), and the total organic halogens (TOX), decreased by ∼90% under the uniform formation conditions. Overall, Br-selective resins represent a promising alternative for the efficient control of Br-DBPs in water treatment plants.

Formation of Brominated Organic Compounds and Molecular Transformations in Dissolved Organic Matter (DOM) after Ballast Water Treatment with Sodium Dichloroisocyanurate Dihydrate (DICD).

Estuarine water treated with a ballast water management system (BWMS) using a solution of dissolved dichloroisocyanurate dihydrate (DICD) resulted in the formation of newly described brominated disinfection byproducts (Br-DBPs). Analysis of dissolved organic matter (DOM) in untreated water with ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) identified 3897 m/z ions and their exact molecular formulas. After DICD treatment, a total of 213 halogenated molecular ions with relative abundance of at least 1% were assigned and confirmed using isotope simulation. Halogenated ions were assigned in four DBP elemental groups including CHOBr (180), CHONBr (13), CHOCl (16), and CHOBrCl (4). Forty-nine of the 197 brominated formulas have not been previously reported. We also were able to tentatively assign possible structures to the formula C3HBr3N2 due to very limited isomeric possibilities. The tentatively assigned compound found at 6.4% relative abundance was identified as either tribromoimidazole or tribromopyrazole. Our results show the formation of complex halogenated DBPs that are formed in the treatment of water with a novel BWMS that employs granular DICD as a biocide. The toxicological and mutagenic properties as well as the fate of these newly identified brominated DBPs are unknown.

Assessment of individual and mixed toxicity of bromoform, tribromoacetic-acid and 2,4,6 tribromophenol, on the embryo-larval development of Paracentrotus lividus sea urchin.

Water chlorination is the most widely used technique to avoid microbial contamination and biofouling. Adding chlorine to bromide-rich waters leads to the rapid oxidation of bromide ions and leads to the formation of brominated disinfection by-products (bromo-DBPs) that exert adverse effects on various biological models. Bromo-DBPs are regularly encountered within industrialized embayments, potentially impacting marine organisms. Of these, bromoform, tribromoacetic acid and tribromophenol are among the most prevalent. In the present study, we tested the potential toxicity and genotoxicity of these disinfection by-products, using sea urchin, Paracentrotus lividus, embryos. We highlighted that tribromophenol showed higher toxicity compared to bromoform and tribromoacetic acid. Furthermore, a synergistic effect was detected when tested in combination. Pluteus cells exposed for 1h to mixtures of DBPs at several concentrations demonstrated significant DNA damage. Finally, when compared to a non-exposed population, sea urchins living in a bromo-DPB-polluted area produced more resistant progenies, as if they were locally adapted. This hypothesis remains to be tested in order to better understand the obvious impact of complex bromo-DBPs environments on marine wildlife.

The influence of bromide on the degradation of sulfonamides in UV/free chlorine treatment: Degradation mechanism, DBPs formation and toxicity assessment

The degradation of sulfonamides (SAs) in the presence of bromide during the UV/free chlorine process was investigated in this study. The reactions followed pseudo first-order kinetics. With increasing bromide concentrations of 1, 5, 10–20 µM, the degradation rate was gradually raised. The contribution of different reactive species has been calculated. The degradation products and DBPs formed by SAs were determined. The mechanisms of the degradation of SAs in the presence of bromide included hydroxylation, cleavage of the pyrimidinyl group, and bromine and chlorine electrophilic addition. The concentration of brominated disinfection by-products, including DBCM, TBM and DBAN, increased with increasing bromide dosage and degradation time, while 1, 1, 1-TCP and 1, 1-DCP decreased. In an acute toxicity test, the inhibition rate decreased in the first 5–10 min then increased after 10 min degradation when 10 µM Br− was added to the system. The initial decrease may due to the formation of low toxicity substances after the cleavage of the pyrimidinyl group, while the subsequent increase may be attributable to the increased formation of DBPs.

Degradation kinetic of phthalate esters and the formation of brominated byproducts in heat-activated persulfate system

The degradation kinetics of two phthalate esters (PAEs) (i.e., diethyl phthalate (DEP) and dibutyl phthalate (DBP)) in heat-activated persulfate (PS) system were studied and followed pseudo-first-order kinetics. Results demonstrated that both sulfate radical (SO4-·) and hydroxyl radical (HO) were responsible for degrading DEP and DBP. The pseudo-first-order rate constant (kobs) enhanced remarkably as reaction temperature and PS dosages increased, while it decreased as the initial PAEs concentrations increased. Lower pH values promoted the degradation over the pH range chosen here (5.0–8.0). Natural organic matter (NOM) and HCO3- showed inhibitory effects on PAEs degradation by quenching SO4-· and HO. At any pH value studied here, Cl− enhanced PAEs degradation at lower concentrations while it suppressed degradation as Cl− concentration further increased. The coexisting Br− hindered the degradation of PAEs mainly by suppressing SO4-·. Significant formation of dibromoacetonitrile (DBAN) and bromoform (TBM) was verified with Br− and NOM in the degradation system, while only TBM was detected without NOM. Bromate was also detected in the Br− containing degradation system. Generally, NOM facilitated the formation of brominated disinfection byproducts (Br-DBPs), while it suppressed the generation of bromate. Additionally, it is noteworthy that the degradation efficiency of DBP was higher than that of DEP probably owing to the longer alkyl side chain of DBP. The DBP degradation system was observed to form slightly more Br-DBPs than DEP, while bromate had an opposite trend. Besides, the potential initial degradation pathways of DEP and DBP were discussed by the computational analysis.

Influence of (photo)bromination on the transformation, aggregation and sedimentation of graphene oxide

The rapidly increasing use of graphene oxide (GO) necessitates the immediate investigation of the environmental fate and effects of this unique material. To date, little is known about the transformation of GO in environmental media, especially in water and wastewater treatment systems. This study explored the changes in the physicochemical properties of GO that result from (photo)bromination by simulating the reactions experienced by GO during water and wastewater treatment. The surface oxygen functionalities of GO considerably changed upon treatment. Specifically, the COH and COOH groups of GO were lost under bromination, and the reduction of GO was enhanced under photobromination. GO sheets wrinkled and fragmented under bromination, and GO decomposition was enhanced by photobromination. The decreases in O/C ratio and GO decomposition in the presence of bromine were mainly attributed to the relatively high oxidation potential of bromine, which can oxidize carbon nanosheets. The oxidation of carbon nanosheets, in turn, resulted in the decomposition and formation of brominated disinfection by-products. Irradiation, hypobromous acid/hypobromite (HOBr/OBr−), and reactive radicals, such as OH, Br, BrO and Br2−, may all affect the physicochemical transformation of GO in the presence of bromine and simulated solar light. Bromination and photobromination drastically changed the aggregation and sedimentation behavior of GO. The findings of this study advance knowledge on the transformations of GO in water treatment systems and provide insight on the environmental fate of the transformation products of GO.

Biodegradation of 2,6-dibromo-4-nitrophenol by Cupriavidus sp. strain CNP-8: Kinetics, pathway, genetic and biochemical characterization.

Compound 2,6-dibromo-4-nitrophenol (2,6-DBNP) with high cytotoxicity and genotoxicity has been recently identified as an emerging brominated disinfection by-product during chloramination and chlorination of water, and its environmental fate is of great concern. To date, the biodegradation process of 2,6-DBNP is unknown. Herein, Cupriavidus sp. strain CNP-8 was reported to be able to utilize 2,6-DBNP as a sole source of carbon, nitrogen and energy. It degraded 2,6-DBNP in concentrations up to 0.7 mM, and the degradation of 2,6-DBNP conformed to Haldane inhibition model with μmax of 0.096 h-1, Ks of 0.05 mM and Ki of 0.31 mM. Comparative transcriptome and real-time quantitative PCR analyses suggested that the hnp gene cluster was likely responsible for 2,6-DBNP catabolism. Three Hnp proteins were purified and functionally verified. HnpA, a FADH2-dependent monooxygenase, was found to catalyze the sequential denitration and debromination of 2,6-DBNP to 6-bromohydroxyquinol (6-BHQ) in the presence of the flavin reductase HnpB. Gene knockout and complementation revealed that hnpA is essential for strain CNP-8 to utiluze 2,6-DBNP. HnpC, a 6-BHQ 1,2-dioxygenase was proposed to catalyze the ring-cleavage of 6-BHQ during 2,6-DBNP catabolism. These results fill a gap in the understanding of the microbial degradation process and mechanism of 2,6-DBNP.

17β-estradiol as precursors of Cl/Br-DBPs in the disinfection process of different water samples

During chlorine disinfection process, reactions between the disinfectant and 17β-estradiol (E2) lead to the formation of halogenated disinfection byproducts (DBPs) which can be a risk to both ecosystem and human health. The degradation and transformation products of E2 in sodium hypochlorite (NaClO) disinfection processes of different water samples were investigated. The reaction kinetics research showed that the degradation rates of E2 were considerably dependent on the initial pH value and the types of water samples. In fresh water, synthetic marine aquaculture water and seawater, the reaction rate constant was 0.133 min−1, 2.067 min−1 and 2.592 min−1, respectively. The reasons for the above phenomena may be due to the different concentrations of bromide ions (Br−) in these three water samples which could promote the reaction between NaClO and E2. Furthermore, Br− could also cause the formation of brominated DBPs (Br-DBPs). The main DBPs, reaction centers and conceivable reaction pathways were explored. Seven halogenated DBPs have been observed including three chlorinated DBPs (Cl-DBPs) and four Br-DBPs. The active sites of E2 were found to be the pentabasic cyclic ring and the ortho position of the phenol moiety as well as C9-C10 position. The identified Cl/Br-DBPs were also confirmed in actual marine aquaculture water from a shrimp pond. The comparison of bio-concentration factors (BCF) values based on calculation of EPI-suite showed that the toxicities of the Br-DBPs were stronger than that of their chloride analogues. The absorbable organic halogens (AOX) analysis also suggested that the DBPs produced in the marine aquaculture water were more toxic than that in the fresh water system.

Bromide and Other Halide Ion Removal From Drinking Waters Using Silver‐Amended Coagulation

High bromide ion concentrations are of concern because of formation of brominated disinfection byproducts in drinking water, which may be more toxic than their chlorinated analogs. Jar tests dosed with alum and silver were performed on several water samples with chloride‐to‐bromide (Cl:Br) ratios ranging from 15 to 866 mg Cl/mg Br. In lower‐chloride waters (15 mg Cl/mg Br), silver‐amended coagulation (SAC) removed 20–90% of the initial bromide. In higher‐chloride water (525 mg Cl/mg Br), a silver dose of 15 mol Ag/mol Br achieved 40% bromide removal. Iodide and chloride removal also occurred during silver addition. SAC did not influence total organic carbon or turbidity removal, and residual silver was below the secondary maximum contaminant level but was successful in decreasing trihalomethane (THM) formation from 44 to 28 μg/L by shifting away from brominated THM species. SAC may only be applicable and cost‐effective in a narrow range of waters with lower Cl:Br ratios, and other technologies should be developed for waters with &gt;300 mg Cl/mg Br.