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Rex A. Pegram - One of the best experts on this subject based on the ideXlab platform.
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in vitro biotransformation and genotoxicity of the drinking water Disinfection Byproduct bromodichloromethane dna binding mediated by glutathione transferase theta 1 1
Toxicology and Applied Pharmacology, 2004Co-Authors: Matthew K Ross, Rex A. PegramAbstract:The drinking water Disinfection Byproduct bromodichloromethane (CHBrCl2) was previously shown to be mutagenic in Salmonella typhimurium that overexpress rat glutathione transferase theta 1-1 (GSTT1-1). Several experimental approaches were undertaken in this study to investigate the DNA covalent binding potential of reactive intermediates generated by GSTT1-1-mediated metabolism of CHBrCl2. First, rodent hepatic cytosol incubations containing [14C]CHBrCl2, supplemented glutathione (GSH), and calf thymus DNA resulted in approximately 3-fold (rat liver cytosol) and 7-fold (mouse liver cytosol) greater amounts of total radioactivity (RAD) associated with the purified DNA as compared to a control (absence of rodent cytosol) following liquid scintillation counting (LSC) of isolated DNA. The relative increase in DNA labeling is consistent with the conjugation activity of these rodent cytosols toward CHBrCl2. Second, exposure of GSTT1-1-expressing S. typhimurium to [14C]CHBrCl2 resulted in a concentration-dependent increase of bacterial DNA-associated total radioactivity. Characterization of DNA-associated radioactivity could not be assigned to a specific deoxynucleoside adduct(s) following enzymatic hydrolysis of DNA and subsequent HPLC analysis. A possible explanation for this observation was formation of a ‘transient’ adduct that was unstable in the DNA isolation and hydrolysis procedures employed. To circumvent problems of adduct instability, reactions of [14C]CHBrCl2 with GSH catalyzed by recombinant rat GSTT1-1 were performed in the presence of calf thymus DNA or, alternatively, the model nucleophile deoxyguanosine. Hydroxyapatite chromatography of [14C]-labeled DNA or HPLC chromatography of [14C]-labeled deoxyguanosine derivatives demonstrated the covalent binding of [14C]CHBrCl2-derived metabolites to DNA and deoxyguanosine in low yield (approximately 0.02% of [14C]CHBrCl2 biotransformed by GSTT1-1 resulted in DNA adducts). Cytochrome P450 (CYP)- and GST-catalyzed biotransformation of CHBrCl2 in rat tissues (kidney and large intestine) that develop tumors following chronic CHBrCl2 exposure were compared with rat liver (a nontarget tissue). Rat liver had a significant capacity to detoxify CHBrCl2 (to carbon dioxide) compared with kidney and large intestine as a result of CYP-catalyzed oxidation, liver was approximately 16-fold more efficient than kidney and large intestine when intrinsic clearance values (Vmax/Km) were compared. In contrast, the efficiency of GST-mediated GSH conjugation of CHBrCl2 in kidney and large intestine was only slightly lower than liver (approximately 2- to 4-fold lower), thus, the relative amounts of reactive intermediates that are produced with the capacity to covalently modify DNA may be enhanced in these extrahepatic tissues. The significance of these findings is that conjugation of CHBrCl2 with GSH can result in the covalent modification of DNA and that cancer target tissues in rats have a much reduced detoxification capacity, but only a modest decrease in bioactivation capacity, as compared to the liver (a nontarget tissue in rats).
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Glutathione transferase theta 1-1-dependent metabolism of the water Disinfection Byproduct bromodichloromethane.
Chemical Research in Toxicology, 2003Co-Authors: Matthew K Ross, Rex A. PegramAbstract:Bromodichloromethane (CHBrCl 2 ), a prevalent drinking water Disinfection Byproduct, was previously shown to be mutagenic in Salmonella that express rat GSH transferase (GST) theta 1-1 (GST T1-1). In the present study, in vitro experiments were performed to study the kinetics of CHBrCl 2 reactions mediated by GST in different species as well as the isoform specificity and reaction products of the GST pathway. Conjugation activity of CHBrCl 2 with GSH in mouse liver cytosol was time- and protein-dependent, was not inhibited by the GST a, μ, and π inhibitor S-hexyl-GSH, and correlated with GST T1-1 activity toward the substrate 1,2-epoxy-3-(4'-nitrophenoxy)propane. Conjugation activities in hepatic cytosols of different species toward CHBrCl 2 followed the order mouse > rat > human. As compared with CH 2 Cl 2 , the catalytic efficiency (k c a t /K m ) of conjugation of CHBrCl 2 with GSH by pure recombinant rat GST T1-1 was ∼3-6-fold less. Taken together, this suggests that GST T1-1 is the primary catalyst for conjugation of CHBrCl 2 with GSH and that flux through this pathway is less than for CH 2 Cl 2 . The initial GSCHCl 2 conjugate formed was unstable and degraded to several metabolites, including GSCH 2 OH, S-formyl-GSH, and HCOOH. Addition of NAD + to cytosol did not alter the rate of conjugation of CHBrCl 2 with GSH; however, it did increase the amount of [ 1 4 C]-HCOOH produced (∼10-fold). A similar result was seen in a reaction containing pure rat GST T1-1 and GSH-dependent formaldehyde dehydrogenase, indicating that GSCH 2 OH was formed as a precursor to S-formyl-GSH. The half-life of synthetic S-formyl-GSH in pH 7,4 buffer was ∼1 h at ambient temperature and decreased to ∼7 min in pH 9.0 buffer, and it does not react with deoxyguanosine. In conclusion, GST T1-1 conjugation of CHBrCl 2 has been definitively demonstrated and the kinetics of conjugation of CHBrCl 2 with GSH characterized in mouse, rat, and human hepatic cytosols. The significance of this GST pathway is that reactive GSH conjugates are produced resulting in possible formation of DNA adducts. Comparisons with CH 2 Cl 2 suggest that the reactive intermediates specific to GSH conjugation of CHBrCl 2 are more mutagenic/genotoxic than those derived from CH 2 Cl 2 .
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glutathione transferase theta 1 1 dependent metabolism of the water Disinfection Byproduct bromodichloromethane
Chemical Research in Toxicology, 2003Co-Authors: Matthew K Ross, Rex A. PegramAbstract:Bromodichloromethane (CHBrCl(2)), a prevalent drinking water Disinfection Byproduct, was previously shown to be mutagenic in Salmonella that express rat GSH transferase (GST) theta 1-1 (GST T1-1). In the present study, in vitro experiments were performed to study the kinetics of CHBrCl(2) reactions mediated by GST in different species as well as the isoform specificity and reaction products of the GST pathway. Conjugation activity of CHBrCl(2) with GSH in mouse liver cytosol was time- and protein-dependent, was not inhibited by the GST alpha, mu and pi inhibitor S-hexyl-GSH, and correlated with GST T1-1 activity toward the substrate 1,2-epoxy-3-(4'-nitrophenoxy)propane. Conjugation activities in hepatic cytosols of different species toward CHBrCl(2) followed the order mouse > rat > human. As compared with CH(2)Cl(2), the catalytic efficiency (k(cat)/K(m)) of conjugation of CHBrCl(2) with GSH by pure recombinant rat GST T1-1 was approximately 3-6-fold less. Taken together, this suggests that GST T1-1 is the primary catalyst for conjugation of CHBrCl(2) with GSH and that flux through this pathway is less than for CH(2)Cl(2). The initial GSCHCl(2) conjugate formed was unstable and degraded to several metabolites, including GSCH(2)OH, S-formyl-GSH, and HCOOH. Addition of NAD(+) to cytosol did not alter the rate of conjugation of CHBrCl(2) with GSH; however, it did increase the amount of [(14)C]HCOOH produced ( approximately 10-fold). A similar result was seen in a reaction containing pure rat GST T1-1 and GSH-dependent formaldehyde dehydrogenase, indicating that GSCH(2)OH was formed as a precursor to S-formyl-GSH. The half-life of synthetic S-formyl-GSH in pH 7.4 buffer was approximately 1 h at ambient temperature and decreased to approximately 7 min in pH 9.0 buffer, and it does not react with deoxyguanosine. In conclusion, GST T1-1 conjugation of CHBrCl(2) has been definitively demonstrated and the kinetics of conjugation of CHBrCl(2) with GSH characterized in mouse, rat, and human hepatic cytosols. The significance of this GST pathway is that reactive GSH conjugates are produced resulting in possible formation of DNA adducts. Comparisons with CH(2)Cl(2) suggest that the reactive intermediates specific to GSH conjugation of CHBrCl(2) are more mutagenic/genotoxic than those derived from CH(2)Cl(2).
Matthew K Ross - One of the best experts on this subject based on the ideXlab platform.
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in vitro biotransformation and genotoxicity of the drinking water Disinfection Byproduct bromodichloromethane dna binding mediated by glutathione transferase theta 1 1
Toxicology and Applied Pharmacology, 2004Co-Authors: Matthew K Ross, Rex A. PegramAbstract:The drinking water Disinfection Byproduct bromodichloromethane (CHBrCl2) was previously shown to be mutagenic in Salmonella typhimurium that overexpress rat glutathione transferase theta 1-1 (GSTT1-1). Several experimental approaches were undertaken in this study to investigate the DNA covalent binding potential of reactive intermediates generated by GSTT1-1-mediated metabolism of CHBrCl2. First, rodent hepatic cytosol incubations containing [14C]CHBrCl2, supplemented glutathione (GSH), and calf thymus DNA resulted in approximately 3-fold (rat liver cytosol) and 7-fold (mouse liver cytosol) greater amounts of total radioactivity (RAD) associated with the purified DNA as compared to a control (absence of rodent cytosol) following liquid scintillation counting (LSC) of isolated DNA. The relative increase in DNA labeling is consistent with the conjugation activity of these rodent cytosols toward CHBrCl2. Second, exposure of GSTT1-1-expressing S. typhimurium to [14C]CHBrCl2 resulted in a concentration-dependent increase of bacterial DNA-associated total radioactivity. Characterization of DNA-associated radioactivity could not be assigned to a specific deoxynucleoside adduct(s) following enzymatic hydrolysis of DNA and subsequent HPLC analysis. A possible explanation for this observation was formation of a ‘transient’ adduct that was unstable in the DNA isolation and hydrolysis procedures employed. To circumvent problems of adduct instability, reactions of [14C]CHBrCl2 with GSH catalyzed by recombinant rat GSTT1-1 were performed in the presence of calf thymus DNA or, alternatively, the model nucleophile deoxyguanosine. Hydroxyapatite chromatography of [14C]-labeled DNA or HPLC chromatography of [14C]-labeled deoxyguanosine derivatives demonstrated the covalent binding of [14C]CHBrCl2-derived metabolites to DNA and deoxyguanosine in low yield (approximately 0.02% of [14C]CHBrCl2 biotransformed by GSTT1-1 resulted in DNA adducts). Cytochrome P450 (CYP)- and GST-catalyzed biotransformation of CHBrCl2 in rat tissues (kidney and large intestine) that develop tumors following chronic CHBrCl2 exposure were compared with rat liver (a nontarget tissue). Rat liver had a significant capacity to detoxify CHBrCl2 (to carbon dioxide) compared with kidney and large intestine as a result of CYP-catalyzed oxidation, liver was approximately 16-fold more efficient than kidney and large intestine when intrinsic clearance values (Vmax/Km) were compared. In contrast, the efficiency of GST-mediated GSH conjugation of CHBrCl2 in kidney and large intestine was only slightly lower than liver (approximately 2- to 4-fold lower), thus, the relative amounts of reactive intermediates that are produced with the capacity to covalently modify DNA may be enhanced in these extrahepatic tissues. The significance of these findings is that conjugation of CHBrCl2 with GSH can result in the covalent modification of DNA and that cancer target tissues in rats have a much reduced detoxification capacity, but only a modest decrease in bioactivation capacity, as compared to the liver (a nontarget tissue in rats).
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Glutathione transferase theta 1-1-dependent metabolism of the water Disinfection Byproduct bromodichloromethane.
Chemical Research in Toxicology, 2003Co-Authors: Matthew K Ross, Rex A. PegramAbstract:Bromodichloromethane (CHBrCl 2 ), a prevalent drinking water Disinfection Byproduct, was previously shown to be mutagenic in Salmonella that express rat GSH transferase (GST) theta 1-1 (GST T1-1). In the present study, in vitro experiments were performed to study the kinetics of CHBrCl 2 reactions mediated by GST in different species as well as the isoform specificity and reaction products of the GST pathway. Conjugation activity of CHBrCl 2 with GSH in mouse liver cytosol was time- and protein-dependent, was not inhibited by the GST a, μ, and π inhibitor S-hexyl-GSH, and correlated with GST T1-1 activity toward the substrate 1,2-epoxy-3-(4'-nitrophenoxy)propane. Conjugation activities in hepatic cytosols of different species toward CHBrCl 2 followed the order mouse > rat > human. As compared with CH 2 Cl 2 , the catalytic efficiency (k c a t /K m ) of conjugation of CHBrCl 2 with GSH by pure recombinant rat GST T1-1 was ∼3-6-fold less. Taken together, this suggests that GST T1-1 is the primary catalyst for conjugation of CHBrCl 2 with GSH and that flux through this pathway is less than for CH 2 Cl 2 . The initial GSCHCl 2 conjugate formed was unstable and degraded to several metabolites, including GSCH 2 OH, S-formyl-GSH, and HCOOH. Addition of NAD + to cytosol did not alter the rate of conjugation of CHBrCl 2 with GSH; however, it did increase the amount of [ 1 4 C]-HCOOH produced (∼10-fold). A similar result was seen in a reaction containing pure rat GST T1-1 and GSH-dependent formaldehyde dehydrogenase, indicating that GSCH 2 OH was formed as a precursor to S-formyl-GSH. The half-life of synthetic S-formyl-GSH in pH 7,4 buffer was ∼1 h at ambient temperature and decreased to ∼7 min in pH 9.0 buffer, and it does not react with deoxyguanosine. In conclusion, GST T1-1 conjugation of CHBrCl 2 has been definitively demonstrated and the kinetics of conjugation of CHBrCl 2 with GSH characterized in mouse, rat, and human hepatic cytosols. The significance of this GST pathway is that reactive GSH conjugates are produced resulting in possible formation of DNA adducts. Comparisons with CH 2 Cl 2 suggest that the reactive intermediates specific to GSH conjugation of CHBrCl 2 are more mutagenic/genotoxic than those derived from CH 2 Cl 2 .
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glutathione transferase theta 1 1 dependent metabolism of the water Disinfection Byproduct bromodichloromethane
Chemical Research in Toxicology, 2003Co-Authors: Matthew K Ross, Rex A. PegramAbstract:Bromodichloromethane (CHBrCl(2)), a prevalent drinking water Disinfection Byproduct, was previously shown to be mutagenic in Salmonella that express rat GSH transferase (GST) theta 1-1 (GST T1-1). In the present study, in vitro experiments were performed to study the kinetics of CHBrCl(2) reactions mediated by GST in different species as well as the isoform specificity and reaction products of the GST pathway. Conjugation activity of CHBrCl(2) with GSH in mouse liver cytosol was time- and protein-dependent, was not inhibited by the GST alpha, mu and pi inhibitor S-hexyl-GSH, and correlated with GST T1-1 activity toward the substrate 1,2-epoxy-3-(4'-nitrophenoxy)propane. Conjugation activities in hepatic cytosols of different species toward CHBrCl(2) followed the order mouse > rat > human. As compared with CH(2)Cl(2), the catalytic efficiency (k(cat)/K(m)) of conjugation of CHBrCl(2) with GSH by pure recombinant rat GST T1-1 was approximately 3-6-fold less. Taken together, this suggests that GST T1-1 is the primary catalyst for conjugation of CHBrCl(2) with GSH and that flux through this pathway is less than for CH(2)Cl(2). The initial GSCHCl(2) conjugate formed was unstable and degraded to several metabolites, including GSCH(2)OH, S-formyl-GSH, and HCOOH. Addition of NAD(+) to cytosol did not alter the rate of conjugation of CHBrCl(2) with GSH; however, it did increase the amount of [(14)C]HCOOH produced ( approximately 10-fold). A similar result was seen in a reaction containing pure rat GST T1-1 and GSH-dependent formaldehyde dehydrogenase, indicating that GSCH(2)OH was formed as a precursor to S-formyl-GSH. The half-life of synthetic S-formyl-GSH in pH 7.4 buffer was approximately 1 h at ambient temperature and decreased to approximately 7 min in pH 9.0 buffer, and it does not react with deoxyguanosine. In conclusion, GST T1-1 conjugation of CHBrCl(2) has been definitively demonstrated and the kinetics of conjugation of CHBrCl(2) with GSH characterized in mouse, rat, and human hepatic cytosols. The significance of this GST pathway is that reactive GSH conjugates are produced resulting in possible formation of DNA adducts. Comparisons with CH(2)Cl(2) suggest that the reactive intermediates specific to GSH conjugation of CHBrCl(2) are more mutagenic/genotoxic than those derived from CH(2)Cl(2).
Alex T. Chow - One of the best experts on this subject based on the ideXlab platform.
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throughfall dissolved organic matter as a terrestrial Disinfection Byproduct precursor
ACS Earth and Space Chemistry, 2019Co-Authors: Huan Chen, Alex T. Chow, Kuopei Tsai, Junjian WangAbstract:More than half of the drinking water supply in the United States originates from forest watersheds, where terrestrial dissolved organic matter (DOM) is known as an important Disinfection Byproduct (DBP) precursor. Throughfall-derived DOM, a significant portion of terrestrial DOM, has seldom been evaluated for its formation potential of DBPs. Here, we collected throughfall and leaf extracts of an evergreen (loblolly pine, Pinus taeda L.) and a deciduous tree species (turkey oak, Quercus cerris L.) in South Carolina to explore their seasonal DOM quantity, optical properties, and DBP formation potential. Elevated dissolved organic carbon (DOC) from rainwater (1.2 ± 0.4 mg/L) to pine (26.0 ± 19.7 mg/L) and oak throughfall (38.8 ± 37.8 mg/L) indicated canopy can be a significant DOM source. DOM aromaticity (indicated by specific ultraviolet absorbance at 254 nm) was higher in oak than pine throughfall and higher in throughfall than leaf extracts. The throughfall DOM characteristics were seasonally more stable ...
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dynamic changes of Disinfection Byproduct precursors following exposures of microcystis aeruginosa to wildfire ash solutions
Environmental Science & Technology, 2017Co-Authors: Kuopei Tsai, Habibullah Uzun, Tanju Karanfil, Alex T. ChowAbstract:Wildfires can elevate dissolved organic matter (DOM) levels due to ash input and algal growth in source waters, and consequently impacting Disinfection Byproduct (DBP) formation in finished water; however, it remains unclear how quality and quantity of overall allochthonous and autochthonous DOM as well as associated DBP formation are changed during an entire algal life cycle. Microcystis aeruginosa was cultured in the medium containing low and high concentrations [10% and 65% (v/v)] of black and white ash water extracts (BE and WE) to study dynamic changes of carbonaceous, nitrogenous, and oxygenated DBP precursors during algal growth. DOM was characterized by absorption and fluorescence spectroscopy and chlorination/chloramination-based DBP formation experiments. Throughout the entire experiment, C-DBP precursors in the control ranged from 2.41 to 3.09 mmol/mol-C. In the treatment with 10% BE, the amount of C-DBP precursors decreased from 6.8 to 3.0 mmol/mol-C at initial-exponential phase then increased...
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Dynamic Changes of Disinfection Byproduct Precursors following Exposures of Microcystis aeruginosa to Wildfire Ash Solutions
2017Co-Authors: Kuopei Tsai, Habibullah Uzun, Tanju Karanfil, Alex T. ChowAbstract:Wildfires can elevate dissolved organic matter (DOM) levels due to ash input and algal growth in source waters, and consequently impacting Disinfection Byproduct (DBP) formation in finished water; however, it remains unclear how quality and quantity of overall allochthonous and autochthonous DOM as well as associated DBP formation are changed during an entire algal life cycle. Microcystis aeruginosa was cultured in the medium containing low and high concentrations [10% and 65% (v/v)] of black and white ash water extracts (BE and WE) to study dynamic changes of carbonaceous, nitrogenous, and oxygenated DBP precursors during algal growth. DOM was characterized by absorption and fluorescence spectroscopy and chlorination/chloramination-based DBP formation experiments. Throughout the entire experiment, C-DBP precursors in the control ranged from 2.41 to 3.09 mmol/mol-C. In the treatment with 10% BE, the amount of C-DBP precursors decreased from 6.8 to 3.0 mmol/mol-C at initial-exponential phase then increased to 4.2 mmol/mol-C at death phase. The same trend was observed for O-DBP precursors. However, these dynamic changes of C- and O-DBP precursors exhibited opposite patterns in 65% extracts. Similar patterns were also observed in the WE treatments. On the other hand, N-DBP precursors continuously declined in all treatments. These results indicate that postfire ash loading and algal bloom stage may significantly affect DBP formation in source water
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temporal variations of Disinfection Byproduct precursors in wildfire detritus
Water Research, 2016Co-Authors: Junjian Wang, Randy A. Dahlgren, Tanju Karanfil, Mahmut S Ersan, Alex T. ChowAbstract:The Rim Fire ignited on August 17, 2013 and became the third largest wildfire in California history. The fire consumed 104,131 ha of forested watersheds that were the drinking water source for 2.6 million residents in the San Francisco Bay area. To understand temporal variations in dissolved organic matter (DOM) after the wildfire and its potential impacts on Disinfection Byproduct (DBP) formation in source water supply, we collected the 0-5 cm ash/soil layer with surface deposits of white ash (high burn severity) and black ash (moderate burn severity) within the Rim Fire perimeter in Oct 2013 (pre-rainfall) for five sequential extractions, and in Dec 2013 (∼87 mm cumulative precipitation) and Aug 2014 (∼617 mm cumulative precipitation) for a single water extraction. Water-extractable DOM was characterized by absorption and fluorescence spectroscopy and DBP formation tests. Both increasing cumulative precipitation in the field or number of extractions in the lab resulted in a significant decrease in specific conductivity, dissolved organic carbon, and DBP formation potential, but an increase in DOM aromaticity (reflected by specific UV absorbance). However, the lab sequential leaching failed to capture the increase of the NOx(-)-N/NH4(+)-N ratio and the decrease in pH and dissolved organic carbon/nitrogen ratio of ash/soil extracts from Oct 2013 to Aug 2014. Increasing cumulative precipitation, inferring an increase in leaching after fire, led to an increase in DOM reactivity to form trihalomethanes, haloacetic acids, and chloral hydrate, but not for haloketones, haloacetonitrile, or N-nitrosodimethylamine, which were more related to the original burn severity. This study highlights that fire-affected DBP precursors for different DBP species have distinct temporal variation possibly due to their various sensitivity to biogeochemical alterations.
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Disinfection Byproduct formation from chlorination of pure bacterial cells and pipeline biofilms
Water Research, 2013Co-Authors: Junjian Wang, Alex T. Chow, Po Keung Wong, Xin Liu, Jiewen XiaoAbstract:Disinfection Byproduct (DBP) formation is commonly attributed to the reaction between natural organic matters and disinfectants, yet few have considered the contribution from disinfecting bacterial materials – the essential process of water Disinfection. Here, we explored the DBP formation from chlorination and chloramination of Escherichia coli and found that most selected DBPs were detectable, including trihalomethanes, haloacetonitriles, chloral hydrate, chloropicrin, and 1,1,1-trichloro-2-propanone. A positive correlation (P = 0.08–0.09) between DBP formation and the log reduction of E. coli implied that breaking down of bacterial cells released precursors for DBP formation. As Pseudomonas aeruginosa is a dominant bacterial species in pipeline biofilms, the DBP formation potentials (DBPFPs) from its planktonic cells and biofilms were characterized. Planktonic cells formed 7–11 times greater trihalomethanes per carbon of those from biofilms but significantly lower (P < 0.05) chloral hydrate, highlighting the bacterial phenotype's impact on the bacteria-derived DBPFP. Pipe material appeared to affect the DBPFP of bacteria, with 4–28% lower bromine incorporation factor for biofilms on polyvinyl chloride compared to that on galvanized zinc. This study revealed both the in situ Disinfection of bacterial planktonic cells in source water and ex situ reaction between biofilms and residual chlorine in pipeline networks as hitherto unknown DBP sources in drinking water.
Yuefeng F Xie - One of the best experts on this subject based on the ideXlab platform.
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impacts of shale gas production wastewater on Disinfection Byproduct formation an investigation from a non bromide perspective
Water Research, 2018Co-Authors: Kuan Z Huang, Hao L Tang, Yuefeng F XieAbstract:The rapid rise of shale gas development has triggered environmental and human health concerns due to its impacts on water resources, especially on Disinfection Byproduct (DBP) formation upon chlorination. Despite the recently reported results on bromide, the effects of non-bromide ions in production wastewater at extremely high levels are vaguely defined. In this study, we investigated the effects of production wastewater, with bromide and non-bromide species, on the formation of DBPs when production wastewater was spiked into surface waters at various percentages. Results showed that the introduction of debrominated production wastewater led to increased formation of some chlorinated DBP species in selected surface water and wastewater. As the spiking percentage of debrominated production wastewater increased, the chlorinated DBP species increased. The contributions of individual cations to DBP formation followed a sequence of magnesium > calcium > barium at 0.10% spiking percentage due to the different catalytic effects of their chelates with organic precursors. The study of anions suggested that the discharge of treated production wastewater containing elevated sulfate may further enhance DBP formation. The significance of this study lies in the fact that in addition to bromide concerns from production wastewater, non-bromide species also contributed to DBP formation. The gas production wastewater management decision should consider the negative impacts from both bromide and non-bromide species to better protect the receiving water resources.
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effects of metal ions on Disinfection Byproduct formation during chlorination of natural organic matter and surrogates
Chemosphere, 2016Co-Authors: Yu Zhao, Yuefeng F Xie, Hongwei Yang, Shiting Liu, Shun Tang, Xiaomao WangAbstract:The effects of calcium, cupric, ferrous and ferric ions on the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) were investigated using natural organic matter (NOM), small molecular weight NOM surrogates and natural water samples. The results showed that the effects were greatly dependent on the Disinfection Byproduct (DBP) precursor structure and molecular weight, and metal ions species. While using NOM as precursors, addition of 4.00 mM calcium ions increased the formation of THMs, dihaloacetic acids (DHAAs) and trihaloacetic acids (THAAs) by 24-47%, 51-61% and 15-25%, respectively. Addition of cupric ions at 0.02 mM increased the formation of THMs and DHAAs by 74-83% and 90-100%, respectively, but decreased the formation of THAAs by 26-27%. Similar effect was not observed when 0.04 mM ferrous or ferric ions were added. The effects of calcium and cupric ions on DBP formation were generally more evident for the NOM surrogates than that for NOM. The primary catalytic effect of calcium ions was due to complexation and less sensitive to molecular structure or weight, while that of cupric ions was attributed to redox reactions and greatly dependent on molecular structure. Both ferric and ferrous iron had substantial effects on the DBP formation of surrogates (citric acid and catechol in particular), which implied that the catalytic effects of ferric and ferrous iron mainly depended on molecular weight. The catalytic effect of cupric ions was also observed on natural water samples, while the effects of calcium, ferrous and ferric ions on natural water samples were not evident.
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effects of ozonation on Disinfection Byproduct formation and speciation during subsequent chlorination
Chemosphere, 2014Co-Authors: Yuqin Mao, Xiaomao Wang, Hongwei Yang, Haoyu Wang, Yuefeng F XieAbstract:Ozone has been widely used for drinking water treatment recently. This study was conducted to inves- tigate the effect of dosing ozone on the formation potentials and speciation of Disinfection by-products (DBPs, brominated DBPs in particular) during subsequent chlorination. Trihalomethanes (THMs), trihalo- acetic acids (THAAs), dihaloacetic acids (DHAAs), dihaloacetonitriles (DHANs), chloral hydrate (CH) and trichloronitromethane (TCNM) were included. The results showed that the yields of THMs, THAAs and DHAAs reached the maxima at 1.83, 0.65 and 0.56 lM, respectively, corresponding to an ozone dose approximately at 2 mg L � 1 . The formation potentials of CH and TCNM increased, while that of DHAN decreased, with the increase of ozone dose up to 6 mg L � 1 . The bromide incorporation factor values of THMs, THAAs, DHAAs and DHANs increased from 0.62, 0.37, 0.45 and 0.39 at O3 = 0 mg L � 1 to 0.89, 0.65, 0.62 and 0.89 at O3 = 6 mg L � 1 , respectively. It indicated that the use of ozone as a primary disinfec- tant may cause a shift to more brominated DBPs during subsequent chlorination, and the shift may be more evident with increased ozone dose. The total percentage of brominated DBPs (as bromide) reached the maximum value of 55% at 2 mg L � 1 ozone dose.
Po Keung Wong - One of the best experts on this subject based on the ideXlab platform.
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Disinfection Byproduct formation from chlorination of pure bacterial cells and pipeline biofilms
Water Research, 2013Co-Authors: Junjian Wang, Alex T. Chow, Po Keung Wong, Xin Liu, Jiewen XiaoAbstract:Disinfection Byproduct (DBP) formation is commonly attributed to the reaction between natural organic matters and disinfectants, yet few have considered the contribution from disinfecting bacterial materials – the essential process of water Disinfection. Here, we explored the DBP formation from chlorination and chloramination of Escherichia coli and found that most selected DBPs were detectable, including trihalomethanes, haloacetonitriles, chloral hydrate, chloropicrin, and 1,1,1-trichloro-2-propanone. A positive correlation (P = 0.08–0.09) between DBP formation and the log reduction of E. coli implied that breaking down of bacterial cells released precursors for DBP formation. As Pseudomonas aeruginosa is a dominant bacterial species in pipeline biofilms, the DBP formation potentials (DBPFPs) from its planktonic cells and biofilms were characterized. Planktonic cells formed 7–11 times greater trihalomethanes per carbon of those from biofilms but significantly lower (P < 0.05) chloral hydrate, highlighting the bacterial phenotype's impact on the bacteria-derived DBPFP. Pipe material appeared to affect the DBPFP of bacteria, with 4–28% lower bromine incorporation factor for biofilms on polyvinyl chloride compared to that on galvanized zinc. This study revealed both the in situ Disinfection of bacterial planktonic cells in source water and ex situ reaction between biofilms and residual chlorine in pipeline networks as hitherto unknown DBP sources in drinking water.
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Effect of constructed wetlands receiving agricultural return flows on Disinfection Byproduct precursors
Water research, 2009Co-Authors: Francisco J. Díaz, Alex T. Chow, Anthony T. O'geen, Randy A. Dahlgren, Po Keung WongAbstract:Abstract The effects of wetland treatment on Disinfection Byproduct precursors were evaluated for six constructed wetlands receiving agricultural return flows in the Central Valley of California. Wetlands varied in size, age, vegetation, hydrologic residence time (0.9–20 days) and water management (continuous flow vs. flood pulse). The effects of wetland treatment were determined by analyzing input and outflow waters for dissolved organic carbon concentration and quality, bromide concentration, and formation potentials for nine Disinfection Byproduct species, including trihalomethanes, haloacetronitriles, chloral hydrate, and haloketones. We hypothesized that hydraulic residence time was a key factor governing differences in Disinfection Byproduct precursors. Small wetlands ( 100 ha) with long hydraulic residence times (>10 days) resulted in higher dissolved organic carbon and bromide levels, increasing Disinfection Byproduct formation by factors ranging between 1.7 and 10.2 compared to agricultural return flows. Results from this study provide important information for optimizing the design and management of constructed wetlands to effectively combine control of Disinfection Byproduct precursors with other water quality parameters.
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restored wetlands as a source of Disinfection Byproduct precursors
Environmental Science & Technology, 2008Co-Authors: Francisco J. Díaz, Alex T. Chow, Anthony T. O'geen, Randy A. Dahlgren, Po Keung WongAbstract:The effects of a restored wetland system in the Sacramento Valley, California on the production of dissolved organic carbon (DOC) and nitrogen (DON) and the formation potential of common disinfecti...