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1.
Huan Jing Ke Xue ; 42(4): 1939-1945, 2021 Apr 08.
Artigo em Chinês | MEDLINE | ID: mdl-33742829

RESUMO

In order to study the effects of chlorine dioxide (ClO2) disinfection on the super antibiotic resistance genes (SARGs), the final effluents before and after chlorine dioxide were sampled throughout one year in a wastewater treatment plant (WWTP). The bacteria and extracellular nucleic acid were collected using microporous membrane filtration and nucleic acid adsorption particles, respectively. A total of 9 SARGs was detected through a quantitative real-time polymerase chain reaction (qPCR). The results revealed that both intracellular and extracellular NDM-1, MCR-1, and MEC-A could be positively detected in the samples. Overall, ClO2 disinfection enhanced the relative abundance of the iSARGs (P<0.05), exhibiting a seasonal pattern, and increasing in the spring, summer, and autumn. In spring, it improved the most, up to twice the abundance. No SARGs were detected positive in the winter, either intracellularly or extracellularly. There was no significant variation in the concentrations of eSARGs before and after ClO2 disinfection. Therefore, ClO2 disinfection cannot effectively remove iSARGs and eSARGs in the final effluent from the WWTP.


Assuntos
Compostos Clorados , Desinfetantes , Purificação da Água , Antibacterianos/farmacologia , Cloro , Compostos Clorados/farmacologia , Desinfetantes/farmacologia , Desinfecção , Resistência Microbiana a Medicamentos/genética , Óxidos/farmacologia
2.
Water Res ; 195: 116976, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33706215

RESUMO

Membrane technology has been widely used in the wastewater treatment and seawater desalination. In recent years, the reverse osmosis (RO) membrane represented by polyamide (PA) has made great progress because of its excellent properties. However, the conventional PA RO membranes still have some scientific problems, such as membrane fouling, easy degradation after chlorination, and unclear mechanisms of salt retention and water flux, which seriously impede the widespread use of RO membrane technology. This paper reviews the progress in the research and development of the RO membrane, with key focus on the mechanisms and strategies of the contemporary separation, anti-fouling and chlorine resistance of the PA RO membrane. This review seeks to provide state-of-the-art insights into the mitigation strategies and basic mechanisms for some of the key challenges. Under the guidance of the fundamental understanding of each mechanism, operation and modification strategies are discussed, and reasonable analysis is carried out, which can address some key technical challenges. The last section of the review focuses on the technical issues, challenges, and future perspective of these mechanisms and strategies. Advances in synergistic mechanisms and strategies of the PA RO membranes have been rarely reviewed; thus, this review can serve as a guide for new entrants to the field of membrane water treatment and established researchers.


Assuntos
Cloro , Purificação da Água , Filtração , Membranas Artificiais , Nylons , Osmose
3.
Water Res ; 194: 116964, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33652228

RESUMO

Drinking water treatment plants (DWTPs) produce filter backwash water (FBW) and sedimentation sludge water (SSW) that may be partially recycled to the head of DWTPs. The impacts of key disinfection conditions, water quality parameters (e.g., disinfection times, disinfectant types and doses, and pH values), and bromide concentration on controlling the formation of trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and haloacetamides (HAMs) during disinfection of FBW and SSW were investigated. Concentrations of most disinfection byproducts (DBPs) and associated calculated toxicity increased with extended chlorination for both FBW and SSW. During chlorination of both FBW and SSW, elevated chlorine doses significantly increased THM yields per unit dissolved organic carbon (DOC), but decreased HAN and HAM yields, with minimum effect on HAA yields. Chloramine disinfection effectively inhibited C-DBP formation but promoted N-DBPs yields, which increased with chloramine dose. Calculated toxicities after chloramination increased with chloramine dose, which was opposite to the trend found after free chlorine addition. An examination of pH effects demonstrated that C-DBPs were more readily generated at alkaline pH (pH=8), while acidic conditions (pH=6) favored N-DBP formation. Total DBP concentrations increased at higher pH levels, but calculated DBP toxicity deceased due to lower HAN and HAM concentrations. Addition of bromide markedly increased bromo-THM and bromo-HAN formation, which are more cytotoxic than chlorinated analogues, but had little impact on the formation of HAAs and HAMs. Bromide incorporation factors (BIFs) for THMs and HANs from both water samples all significantly increased as bromide concentrations increased. Overall, high bromide concentrations increased the calculated toxicity values in FBW and SSW after chlorination. Therefore, while currently challenging, technologies capable of removing bromide should be explored as part of a strategy towards controlling cumulative toxicity burden (i.e., hazard) while simultaneously lowering individual DBP concentrations (i.e., exposure) to manage DBP risks in drinking water.


Assuntos
Desinfetantes , Água Potável , Poluentes Químicos da Água , Purificação da Água , Cloro , Desinfetantes/análise , Desinfecção , Halogenação , Esgotos , Trialometanos , Poluentes Químicos da Água/análise
4.
Environ Monit Assess ; 193(4): 202, 2021 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-33745015

RESUMO

Perna viridis Linnaeus (1758) is a major foulant in the cooling water systems of electric power stations located on the East coast of India. Though chlorination is considered an effective fouling control measure, the strategy may fail in the case of bivalve mussels, due to the ability of the mussels to close their shells and still survive for extended periods of time. In a given power station, continuous low dose (exomotive) chlorination (0.2 ± 0.1 mg l-1) is practiced to control biofouling. Laboratory experiments were carried out to assess the mortality and valve movement response of Perna viridis exposed to chlorine, using a Mosselmonitor®. All size groups tested showed progressive reduction in valve opening upon chlorination. However, continuous dosing of chlorine concentration as high as 1.0 mg l-1 was required for sustained and complete valve closure response in this mussel. At lower concentration (0.7 mg l-1), the mussels were able to open their shells and feed. Sustained valve closure resulted in physiological stress to the mussels due to reduced feeding, subsequently leading to death. Time to 100% mortality was dependent on the size of the mussels. At 1.0 mg l-1 chlorine residual, smaller size group (30-50 mm) mussels showed 100% mortality in 79.3 h, while larger groups (50-70 mm and 70-90 mm) took 152 h and 243 h, respectively. Frequency of valve opening was high in smaller size group mussels (30-50 mm), compared with larger groups (70-90 mm). Even though the time taken for killing was size-dependent, frequency of valve opening and time period between successive openings were found to be characteristic of individual mussels. The observations provide new insight into the response of bivalve mussels to continuous chlorination in the context of biofouling control and point to the need to adopt pragmatic strategies to prevent mussel spat settlement rather than killing of adult mussels, thereby reducing environmental burden due to chlorine residuals. Usage of target-specific biocidal strategies (intermittent/pulse dosing) or alternative biocides (chlorine dioxide) may help mitigate green mussel fouling in tropical cooling water systems.


Assuntos
Perna (Organismo) , Animais , Cloro , Monitoramento Ambiental , Halogenação , Índia
5.
Sci Total Environ ; 771: 144885, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33736131

RESUMO

Dissolved nitrogenous organic matter in water can contain precursors of disinfection by-products (DBPs), especially nitrogenous DBPs (N-DBPs). Amino acids are ubiquitous as dissolved nitrogenous organic matter in source water and can pass through drinking water treatment processes to react with disinfectants in finished water and in the distribution system. Phenylalanine (Phe) was selected as a model amino acid precursor to investigate its derived DBPs and their variations during a chlorination regime that simulated water distribution with residue chlorine. The 7-day DBPs formation potential (DBPsFP) test with chlorine revealed chlorination by-products of phenylalanine including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and halonitromethanes (HNMs), but not trichloronitromethane (TCNM) which was a significant N-DBP detected during the first 48 h of chlorine contact. The formation of most carbonaceous DBPs (C-DBPs) increased with chlorination time; however N-DBPs and non-chlorinated byproducts of phenylacetonitrile and phenylacetaldehyde reached their highest concentration after 2 h of reaction, and then gradually decreased until below detection after 7 days. The chlorination influencing factors indicated that light enhanced the peak yield of DBPs; the pH value showed different influences associated with corresponding DBPs; and the presence of bromide ions (Br-) generated a variety of bromine-containing DBPs. The DBPsFP test with chloramine reduced C-DBPs generation to about 1/3 of the level observed for chlorine disinfection and caused an increase in dichloroacetonitrile. Surveillance of DBPs during drinking water distribution to consumers should consider the varying contact times with disinfectants to accurately profile the types and concentrations of C-DBPs and N-DBPs present in drinking water.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Cloro , Desinfecção , Halogenação , Fenilalanina , Trialometanos , Poluentes Químicos da Água/análise
6.
Sci Total Environ ; 768: 144733, 2021 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-33736354

RESUMO

ClO• and BrO• are newly discovered reactive radicals that contribute to the degradation of micropollutants. However, the research on pollutant degradation by ClO• and BrO• is still lacking. Thus, the mechanism, kinetics, and toxicity of caffeine degradation by HO•, ClO•, and BrO• were computationally studied and compared. Results showed that radical adduct formation (RAF) reaction was dominant for HO•, ClO•, and BrO• initiated reactions of caffeine. The main reaction sites were C5 and C8 of caffeine for HO•, while only the RAF reaction on C8 was prominent for ClO• and BrO•. The initiated reaction rate constants of caffeine by HO•, ClO•, and BrO• were in the order of HO• (5.29 × 109 M-1 s-1) > ClO• (1.40 × 109 M-1 s-1) > BrO• (2.17 × 108 M-1 s-1). The kinetic simulation verified that ClO• played a crucial role in the degradation of caffeine by the UV/chlorine process. In addition to HO-adducts, the subsequent reaction mechanisms of ClO- and BrO-adducts have also been investigated. The formation mechanisms of several important products, namely dimethylparabanic acid (P2), di(N-hydroxymethyl) parabanic acid (P5), 1,3,7-trimethyluric acid (P6), and 8-oxocaffeine (P11), were elucidated. Remarkably, stable chlorinated and brominated intermediates or products were not generated in ClO•- and BrO•-mediated subsequent degradations of caffeine. The assessment of aquatic toxicity and health effects showed that caffeine could penetrate the blood-brain barrier (human), and caffeine and its degradation products were potentially harmful to the aquatic environment.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Cafeína , Cloro , Humanos , Cinética , Modelos Teóricos , Oxirredução , Raios Ultravioleta , Poluentes Químicos da Água/análise
7.
Sci Total Environ ; 770: 145356, 2021 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-33736415

RESUMO

This Discussion argues that municipal water utilities may need to consider the health risks of both opportunistic pathogens (OPs) and disinfection by-products (DBPs) while selecting disinfectant residual dosages or levels in engineered water systems. OPs are natural inhabitants in municipal water systems and the leading cause of drinking-water-related disease outbreaks threatening public health. DBPs in water systems are genotoxic/carcinogenic and also significantly affect public health. Disinfectant residuals (such as free chlorine and chloramine residuals) dictate OP (re)growth and DBP formation in engineered water systems. Therefore, regulating the dosages or levels of disinfectant residuals is effective in controlling OP (re)growth and DBP formation. Existing effects assessing optimal disinfectant residual dosages focus solely on minimizing OP (re)growth or solely on DBP formation. However, selecting disinfectant residual dosages aiming to solely limit the formation of DBPs might compromise OP (re)growth control, and vice versa. An optimal disinfectant residual level for DBP formation control or OP (re)growth control might not be optimal for minimizing the overall or combined health effects of OPs and DBPs in drinking water. To better protect public health, water authorities may need to update the current residual disinfection practice and maintain disinfectant residuals in engineered water systems at an optimal level to minimize the overall health risks of OPs and DBPs.


Assuntos
Desinfetantes , Água Potável , Poluentes Químicos da Água , Purificação da Água , Cloro , Desinfetantes/análise , Desinfecção , Água Potável/análise , Poluentes Químicos da Água/análise
8.
Water Res ; 194: 116938, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33636666

RESUMO

The UV/monochloramine (NH2Cl) process is an advanced oxidation process that can effectively remove emerging contaminants (ECs). However, the degradation mechanisms of reactive radicals with ECs are not clear. In this work, we combined theoretical calculations with experimental studies to investigate the kinetics and mechanism of radical-mediated degradation of paracetamol (AAP) in UV/NH2Cl process. The degradation of AAP in UV/NH2Cl process accords with the pseudo first-order kinetics. Impact factors including NH2Cl dose, pH, natural organic matter, HCO3-, and NO3- were evaluated. The reaction mechanisms of AAP with hydroxyl radical (HO·), reactive chlorine species (RCS), and reactive nitrogen species (RNS) were discussed in detail. Specifically, HO· attacked AAP mainly through hydrogen atom transfer (HAT) and radical adduct formation (RAF), while Cl2·- play a certain role through single electron transfer (SET). ·NH2 and Cl· destructed AAP mainly through HAT. Based on the mechanism analysis, the second-order rate constants of AAP reacts with HO·, Cl·, ·NH2, ClO·, Cl2·- and ·NO2 were calculated through transition state theory as 2.66×109 M-1 s-1, 2.61×109 M-1 s-1, 1.02×107 M-1 s-1, 7.74×106 M-1 s-1, 1.32×106 M-1 s-1, 1.48×103 M-1 s-1 respectively. The second-order rate constants were then used to distinguish the contribution of radicals to the degradation of AAP. Thirteen transformation products were identified by high-resolution mass spectrometry. Combined active sites with potential energy surface, the detailed reaction pathways were proposed. Overall, this study provides deep insights into the mechanism of radical-mediated degradation of AAP.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Acetaminofen , Cloro , Cinética , Modelos Teóricos , Oxirredução , Raios Ultravioleta
9.
Water Res ; 194: 116914, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33636667

RESUMO

The UV/monochloramine (UV/NH2Cl) process is an emerging advanced oxidation process (AOP) to remove organic contaminants in water treatment with radicals including hydroxyl radicals (HO•), reactive chlorine species (RCS) and reactive nitrogen species (RNS). This study investigated the formation of nitro(so) and chlorinated products and toxicity alteration during the UV/NH2Cl treatment of phenol. RNS and/or RCS induced the formation of nitro(so), chlorinated and polymeric compounds during phenol transformation by UV/NH2Cl. These compounds dramatically increased the cytotoxicity to Chinese hamster ovary cells after 20 min UV/NH2Cl treatment, which was 10 times higher than that after 24 h chloramination. The increase of cytotoxicity in UV/NH2Cl was primarily attributable to 4-nitrosophenol, and the cytotoxicity followed the order of 4-nitrosophenol >> 4-nitrophenol > 2,4,6-trichlorophenol > 2,4-dichlorophenol > phenol. 4-Nitrosophenol was significantly generated by the combination of •NO and phenoxy radical, where the maximum conversion rates of phenol to 4-nitrosophenol increased from 4.9% to 62.4% when pH increased from 5 to 10. The highest conversion rate was at pH 10 because the •NO concentration increased with increasing pH from 5 to 10 in UV/NH2Cl, as verified by the electron paramagnetic resonance (EPR) analysis. Nitrophenols were also detected at much lower concentrations than 4-nitrosophenol, which were mainly formed by the oxidation of 4-nitrosophenol and the combination of •NO2 with phenoxy radicals. RCS was responsible for the formation of chlorinated products mainly through Cl• addition and the reactions of Cl•/Cl2•- with phenoxy radicals. Also, RCS and RNS significantly enhanced the formation of carbonaceous (i.e., chloroform and chloral hydrate) and nitrogenous disinfection byproducts (i.e., chloropicrin and dichloroacetonitrile) in UV/NH2Cl. This study indicates that the UV/NH2Cl treatment significantly increased toxicity and validates the roles of RNS and RCS in producing toxic nitro(so) and chlorinated products.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Animais , Células CHO , Cloraminas , Cloro , Cricetinae , Cricetulus , Desinfecção , Halogenação , Fenol , Fenóis , Raios Ultravioleta , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade
10.
Water Res ; 193: 116893, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-33582494

RESUMO

Microcystin-LR (MC-LR), a polypeptide toxin generated by cyanobacteria, threatens the safety of drinking water supplies. In this study, fulvic acid (FA) was separated into two molecular weight (MW) ranges to evaluate the effects of FA size on MC-LR degradation in the chlorine/UV process. The rates of MC-LR degradation were significantly reduced in FA-containing water (3.7 × 10-3 s-1 for small MW FA; 4.3 × 10-3 s-1 for large MW FA) as compared with FA free water (4.9 × 10-3 s-1). The contributions of ClO• to MC-LR degradation were dramatically lower in small MW FA water (0.4%) than large MW FA (13.9%) and FA free water (17.4%), suggesting inhibition by lignin-like substances in FA in the transformation of Cl• to ClO• and scavenging ClO•. Monochlorination and hydroxylation occurred in the first step of the MC-LR degradation process. The accumulation of intermediate products in the chlorine/UV process indicated that small MW FA inhibited further degradation of MC-LR. Small MW FA, rather than MC-LR degradation, was the dominant factor in minimizing MC-LR cytotoxicity toward a human intestinal epithelial cell line.


Assuntos
Cloro , Microcistinas , Benzopiranos , Humanos , Toxinas Marinhas , Fotólise
11.
J Environ Sci (China) ; 102: 24-36, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33637249

RESUMO

UV/chlorine process, as an emerging advanced oxidation process (AOP), was effective for removing micro-pollutants via various reactive radicals, but it also led to the changes of natural organic matter (NOM) and formation of disinfection byproducts (DBPs). By using negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS), the transformation of Suwannee River NOM (SRNOM) and the formation of chlorinated DBPs (Cl-DBPs) in the UV/chlorine AOP and subsequent post-chlorination were tracked and compared with dark chlorination. In comparison to dark chlorination, the involvement of ClO•, Cl•, and HO• in the UV/chlorine AOP promoted the transformation of NOM by removing the compounds owning higher aromaticity (AImod) value and DBE (double-bond equivalence)/C ratio and causing the decrease in the proportion of aromatic compounds. Meanwhile, more compounds which contained only C, H, O, N atoms (CHON) were observed after the UV/chlorine AOP compared with dark chlorination via photolysis of organic chloramines or radical reactions. A total of 833 compounds contained C, H, O, Cl atoms (CHOCl) were observed after the UV/chlorine AOP, higher than 789 CHOCl compounds in dark chlorination, and one-chlorine-containing components were the dominant species. The different products from chlorine substitution reactions (SR) and addition reactions (AR) suggested that SR often occurred in the precursors owning higher H/C ratio and AR often occurred in the precursors owning higher aromaticity. Post-chlorination further caused the cleavages of NOM structures into small molecular weight compounds, removed CHON compounds and enhanced the formation of Cl-DBPs. The results provide information about NOM transformation and Cl-DBPs formation at molecular levels in the UV/chlorine AOP.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Cloro/análise , Desinfecção , Halogenação , Espectrometria de Massas , Poluentes Químicos da Água/análise
12.
Bull Environ Contam Toxicol ; 106(4): 560-567, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33629148

RESUMO

Chlorine dioxide (ClO2), an alternative disinfectant to chlorine, has been widely applied in water and wastewater disinfection. This paper aims at presenting an overview of the inactivation kinetics and mechanisms of ClO2 with viruses. The inactivation efficiencies vary greatly among different virus species. The inactivation rates for different serotypes within a family of viruses can differ by over 284%. Generally, to achieve a 4-log removal, the exposure doses, also being referred to as Ct values (mutiplying the concentration of ClO2 and contact time) vary in the range of 0.06-10 mg L-1 min. Inactivation kinetics of viruses show two phases: an initial rapid inactivation phase followed by a tailing phase. Inactivation rates of viruses increase as pH or temperature increases, but show different trends with increasing concentrations of dissolved organic matter (DOM). Both damages in viral proteins and in the 5' noncoding region within the genome contribute to virus inactivation upon ClO2 disinfection.


Assuntos
Compostos Clorados , Desinfetantes , Purificação da Água , Cloro , Compostos Clorados/toxicidade , Desinfetantes/toxicidade , Cinética , Óxidos/toxicidade , Inativação de Vírus , Água
13.
Nat Commun ; 12(1): 150, 2021 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-33420011

RESUMO

Novel bacterial type II topoisomerase inhibitors (NBTIs) stabilize single-strand DNA cleavage breaks by DNA gyrase but their exact mechanism of action has remained hypothetical until now. We have designed a small library of NBTIs with an improved DNA gyrase-binding moiety resulting in low nanomolar inhibition and very potent antibacterial activity. They stabilize single-stranded cleavage complexes and, importantly, we have obtained the crystal structure where an NBTI binds gyrase-DNA in a single conformation lacking apparent static disorder. This directly proves the previously postulated NBTI mechanism of action and shows that they stabilize single-strand cleavage through asymmetric intercalation with a shift of the scissile phosphate. This crystal stucture shows that the chlorine forms a halogen bond with the backbone carbonyls of the two symmetry-related Ala68 residues. To the best of our knowledge, such a so-called symmetrical bifurcated halogen bond has not been identified in a biological system until now.


Assuntos
Antibacterianos/farmacologia , Cloro/metabolismo , DNA Girase/metabolismo , Inibidores da Topoisomerase II/farmacologia , Alanina/química , Alanina/metabolismo , Antibacterianos/química , Cristalografia por Raios X , DNA Girase/química , DNA Topoisomerases Tipo II , DNA de Cadeia Simples/metabolismo , Desenho de Fármacos , Canal de Potássio ERG1/metabolismo , Escherichia coli/efeitos dos fármacos , Escherichia coli/enzimologia , Células Hep G2 , Células Endoteliais da Veia Umbilical Humana , Humanos , Concentração Inibidora 50 , Testes de Sensibilidade Microbiana , Simulação de Acoplamento Molecular , Proteínas de Ligação a Poli-ADP-Ribose/antagonistas & inibidores , Quinolinas/química , Quinolinas/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/enzimologia , Inibidores da Topoisomerase II/química
14.
Environ Sci Pollut Res Int ; 28(7): 7691-7709, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33400105

RESUMO

Chlorine (Cl) in the terrestrial environment is of interest from multiple perspectives, including the use of chloride as a tracer for water flow and contaminant transport, organochlorine pollutants, Cl cycling, radioactive waste (radioecology; 36Cl is of large concern) and plant science (Cl as essential element for living plants). During the past decades, there has been a rapid development towards improved understanding of the terrestrial Cl cycle. There is a ubiquitous and extensive natural chlorination of organic matter in terrestrial ecosystems where naturally formed chlorinated organic compounds (Clorg) in soil frequently exceed the abundance of chloride. Chloride dominates import and export from terrestrial ecosystems while soil Clorg and biomass Cl can dominate the standing stock Cl. This has important implications for Cl transport, as chloride will enter the Cl pools resulting in prolonged residence times. Clearly, these pools must be considered separately in future monitoring programs addressing Cl cycling. Moreover, there are indications that (1) large amounts of Cl can accumulate in biomass, in some cases representing the main Cl pool; (2) emissions of volatile organic chlorines could be a significant export pathway of Cl and (3) that there is a production of Clorg in tissues of, e.g. plants and animals and that Cl can accumulate as, e.g. chlorinated fatty acids in organisms. Yet, data focusing on ecosystem perspectives and combined spatiotemporal variability regarding various Cl pools are still scarce, and the processes and ecological roles of the extensive biological Cl cycling are still poorly understood.


Assuntos
Cloro , Ecossistema , Cloretos/análise , Cloro/análise , Halogenação , Solo
15.
Sci Rep ; 11(1): 2418, 2021 01 28.
Artigo em Inglês | MEDLINE | ID: mdl-33510320

RESUMO

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is currently a global pandemic, and there are limited laboratory studies targeting pathogen resistance. This study aimed to investigate the effect of selected disinfection products and methods on the inactivation of SARS-CoV-2 in the laboratory. We used quantitative suspension testing to evaluate the effectiveness of the disinfectant/method. Available chlorine of 250 mg/L, 500 mg/L, and 1000 mg/L required 20 min, 5 min, and 0.5 min to inactivate SARS-CoV-2, respectively. A 600-fold dilution of 17% concentration of di-N-decyl dimethyl ammonium bromide (283 mg/L) and the same concentration of di-N-decyl dimethyl ammonium chloride required only 0.5 min to inactivate the virus efficiently. At 30% concentration for 1 min and 40% and above for 0.5 min, ethanol could efficiently inactivate SARS-CoV-2. Heat takes approximately 30 min at 56 °C, 10 min above 70 °C, or 5 min above 90 °C to inactivate the virus. The chlorinated disinfectants, Di-N-decyl dimethyl ammonium bromide/chloride, ethanol, and heat could effectively inactivate SARS-CoV-2 in the laboratory test. The response of SARS-CoV-2 to disinfectants is very similar to that of SARS-CoV.


Assuntos
Desinfetantes/farmacologia , Desinfecção/métodos , Inativação de Vírus/efeitos dos fármacos , /prevenção & controle , Cloro/química , Cloro/farmacologia , Desinfetantes/química , Etanol/química , Etanol/farmacologia , Humanos , Pandemias/prevenção & controle , Compostos de Amônio Quaternário/química , Compostos de Amônio Quaternário/farmacologia
16.
Sci Total Environ ; 766: 144424, 2021 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-33421790

RESUMO

Residual free chlorine is not monitored continuously at scale in drinking water distribution systems because existing real-time sensor technologies require frequent maintenance, cleaning, and calibration, which makes these products too costly to be used throughout a distribution system. As a result, current measurement approaches require manual sampling, which is not feasible for the consistent monitoring of free chlorine because chlorine concentrations vary significantly throughout pipeline distribution and over time and space. This research presents an alternative and cost-effective method of predicting free chlorine levels in drinking water using graphite electrodes coated with naturally grown microbial biofilms. This Microbial Potentiometric Sensor (MPS) array was installed in a Continuously Mixed Batch Reactor (CMBR), and drinking water containing variable free chlorine concentrations. The chlorine concentrations were introduced in a controlled manner, and the MPS signals were monitored over time. MPS signals were measured from the change in Open Circuit Potential (OCP) across the MPS array in real-time. An empirically derived relationship between the normalized change in OCP and free chlorine was established by fitting individual and average MPS data to a decaying exponential growth function in order to predict free chlorine levels. The results show that free chlorine can be predicted with reasonable accuracy, with model validation showing an average absolute error of ±0.09 ppm below 1.1 ppm and ±0.30 ppm between 1.1 and 2.7 ppm. However, the accuracy of predictions was reduced at higher free chlorine levels. The researchers conclude that MPS systems may benefit drinking water distribution systems by measuring free chlorine. These advantages of the MPS are especially pronounced in the developing world because this system is inexpensive and does not require routine maintenance or cleaning. The system relies on a naturally forming and regenerating biofilm and an inexpensive potentiometric meter to produce stable measurements.


Assuntos
Água Potável , Purificação da Água , Biofilmes , Cloro/análise , Microbiologia da Água , Abastecimento de Água
17.
Water Res ; 192: 116857, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33517044

RESUMO

Dissolved organic matter (DOM) is a ubiquitous component in effluents, DOM discharged with an effluent can affect the composition and properties of natural DOM in the receiving waters. As the photophysical and photochemical properties of effluent DOM can be changed by wastewater treatment processes, the effect of UV/chlorine treatment on the photophysical and photochemical properties of DOM was investigated using Suwannee River fulvic acid (SRFA) and Suwannee River natural organic matter (SRNOM) as representatives. Results showed that the absorbance of the two DOM was significantly decreased. The evolution trends of three representative photophysical parameters upon increase of chlorine dosages were observed. Also, a decrease in DOM aromaticity, molecular weight and electron-donating capacity was observed upon increasing chlorine dosage. Quantum yields of excited triplet state of DOM (3DOM*), singlet oxygen (1O2) and hydroxyl radicals (·OH) first decreases and then increased in the UV/chlorine systems upon increasing chlorine dosages due to the different reaction pathways of the two DOM. Moreover, 3DOM* can not only be regarded as a "controller" of other reactive intermediates, but also effectively promote the photodegradation of bezafibrate, which is classified as a persistent organic contaminant. This study gives deep insights into effects of UV/chlorine on the photophysical and photochemical properties of DOM, and is helpful for understanding the dynamic roles of DOM in the photodegradation of micropollutants.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Cloro , Radical Hidroxila , Fotólise , Rios
18.
Environ Sci Process Impacts ; 23(1): 48-65, 2021 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-33432313

RESUMO

Drinking water consumption results in exposure to complex mixtures of organic chemicals, including natural and anthropogenic chemicals and compounds formed during drinking water treatment such as disinfection by-products. The complexity of drinking water contaminant mixtures has hindered efforts to assess associated health impacts. Existing approaches focus primarily on individual chemicals and/or the evaluation of mixtures, without providing information about the chemicals causing the toxic effect. Thus, there is a need for the development of novel strategies to evaluate chemical mixtures and provide insights into the species responsible for the observed toxic effects. This critical review introduces the application of a novel approach called Reactivity-Directed Analysis (RDA) to assess and identify organic electrophiles, the largest group of known environmental toxicants. In contrast to existing in vivo and in vitro approaches, RDA utilizes in chemico methodologies that investigate the reaction of organic electrophiles with nucleophilic biomolecules, including proteins and DNA. This review summarizes the existing knowledge about the presence of electrophiles in drinking water, with a particular focus on their formation in oxidative treatment systems with ozone, advanced oxidation processes, and UV light, as well as disinfectants such as chlorine, chloramines and chlorine dioxide. This summary is followed by an overview of existing RDA approaches and their application for the assessment of aqueous environmental matrices, with an emphasis on drinking water. RDA can be applied beyond drinking water, however, to evaluate source waters and wastewater for human and environmental health risks. Finally, future research demands for the detection and identification of electrophiles in drinking water via RDA are outlined.


Assuntos
Desinfetantes , Água Potável , Poluentes Químicos da Água , Purificação da Água , Cloraminas/análise , Cloro , Desinfetantes/análise , Desinfetantes/toxicidade , Desinfecção , Humanos , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade , Abastecimento de Água
19.
Chemosphere ; 270: 129392, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33454557

RESUMO

In this study, the process of decomposition of carbon tetrachloride (CCl4) vapor in oxygen DBD at atmospheric pressure and its kinetic regularities have been studied. In the course of the experiments, it was shown that the efficiency of the decomposition of carbon tetrachloride in DBD can reach 100%. Depending on the conditions of the experiments, the effective rate constants were equal to (0.16-0.59) s-1, and the decomposition energy yields were (0.001-0.012) molecules per 100 eV of the inputed energy. The main decomposition products were CO2 and Cl2 molecules. The formation of a solid on the internal electrode of the reactor was also found. The substance contains atoms of carbon, oxygen, chlorine (C:O:Cl) = 1:0.38:0.01, as well as hydrogen atoms. The substance also contains functional groups -CH, -CH2, -OH and dimers of carboxylic (chlorocarboxylic) acids. Based on the solution of the Boltzmann equation for electrons, it is shown that for the compositions of a gas containing O2 molecules, ССl4, and decay products, the kinetic and transport characteristics of electrons are the same as in a pure oxygen discharge. Using the kinetic characteristics of electrons and the reaction rate constants the mechanisms of reactions leading to the found reaction products are proposed. It was shown that the primary reaction of destruction is the reaction of dissociation of CCl4 by electron impact, leading to the formation of CCl3• and Cl and the reaction with the O (1D) atom, as a result of which CCl3• and ClO• are formed.


Assuntos
Cloro , Oxigênio , Atmosfera , Pressão Atmosférica , Oxirredução
20.
Artigo em Inglês | MEDLINE | ID: mdl-33466624

RESUMO

The benefits of swimming have been extensively assessed. However, swimming pools contain chlorine and other irritating chemicals that may induce contact dermatitis. To evaluate the effect of a swimming training session on transepidermal water loss (TWEL) in swimmers compared to football players, elite swimmers and football players were invited to participate (58 athletes) in the study, where TEWL was measured before, immediately after, and 30 min after a 2 h training session. The probe was held on the dorsum of the hand, volar forearm, and on the antecubital flexure for 1 min. The volar forearm, antecubital flexure, and hand dorsum showed a significant increase in TEWL in swimmers in both measurements after training compared to baseline (p < 0.001). In football players, an increase in TEWL was observed on the hands' dorsum between baseline and after training measurements. The variations on TEWL levels before and immediately after the training session were higher among swimmers on the volar forearm (p = 0.002) and antecubital flexure (p = 0.019). Our findings support the effect of the training environment-swimming pool versus outdoor sports-on the skin barrier function, with an increase of transepidermal water loss immediately after exercise. Exposure to a swimming pool environment in a 2 h training session may lead to changes in skin barrier function.


Assuntos
Piscinas , Natação , Atletas , Cloro , Humanos
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