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1.
Artigo em Inglês | MEDLINE | ID: mdl-35409686

RESUMO

Nitrification is a major challenge in chloraminated drinking water systems, resulting in undesirable loss of disinfectant residual. Consequently, heterotrophic bacteria growth is increased, which adversely affects the water quality, causing taste, odour, and health issues. Regular monitoring of various water quality parameters at susceptible areas of the water distribution system (WDS) helps to detect nitrification at an earlier stage and allows sufficient time to take corrective actions to control it. Strategies to monitor nitrification in a WDS require conducting various microbiological tests or assessing surrogate parameters that are affected by microbiological activities. Additionally, microbial decay factor (Fm) is used by water utilities to monitor the status of nitrification. In contrast, approaches to manage nitrification in a WDS include controlling various factors that affect monochloramine decay rate and ammonium substrate availability, and that can inhibit nitrification. However, some of these control strategies may increase the regulated disinfection-by-products level, which may be a potential health concern. In this paper, various strategies to monitor and control nitrification in a WDS are critically examined. The key findings are: (i) the applicability of some methods require further validation using real WDS, as the original studies were conducted on laboratory or pilot systems; (ii) there is no linkage/formula found to relate the surrogate parameters to the concentration of nitrifying bacteria, which possibly improve nitrification monitoring performance; (iii) improved methods/monitoring tools are required to detect nitrification at an earlier stage; (iv) further studies are required to understand the effect of soluble microbial products on the change of surrogate parameters. Based on the current review, we recommend that the successful outcome using many of these methods is often site-specific, hence, water utilities should decide based on their regular experiences when considering economic and sustainability aspects.


Assuntos
Desinfetantes , Água Potável , Amônia , Bactérias , Cloraminas , Desinfecção , Nitrificação , Abastecimento de Água
2.
Anal Chem ; 94(16): 6216-6224, 2022 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-35420783

RESUMO

Specific locations of carbon-carbon double bonds (C═C) in lipids often play an essential role in biological processes, and there has been a booming development in C═C composition analysis by mass spectrometry. However, a universal derivatization and fragmentation pattern for the annotation of C═C positions in lipids is still challenging and attractive. To expand this field in lipidomics, a flexible and convenient N-tosylaziridination method was developed, with high derivatization efficiency, sensitivity, and specificity. The derivatization was very fast (15 s), and C═C numbers as well as locations could be pinpointed specifically in tandem mass spectra. By qualitative and quantitative studies of paratumor and tumor thyroid tissues of human beings, the total content of unsaturated fatty acids was suggested to be increased in tumor tissues, and good correlations in and between lysophosphatidylcholines and phosphatidylcholines were revealed by Spearman analysis. Further studies of C═C isomers showed that n-6/n-3 ratios were closely associated with human thyroid tumorigenesis, and high ratios of n-6/n-3 isomers seemed to suffer a high risk of carcinogenesis. Other isomers were not very representative; however, C═C in n-9/n-7 could also be significant for oncology research. Generally, it is supposed that both total amounts and C═C isomer ratios were related to cancer, and N-tosylaziridine derivatization could provide an alternative strategy for the C═C isomer study of disease models.


Assuntos
Fosfatidilcolinas , Glândula Tireoide , Carbono , Cloraminas , Ácidos Graxos Insaturados/análise , Humanos , Espectrometria de Massas em Tandem/métodos , Compostos de Tosil
3.
Water Res ; 216: 118278, 2022 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-35366494

RESUMO

Cethyltrimethylammonium chloride (CTMA) is one of the most used quaternary ammonium compounds (QACs) in consumer products. CTMA and other QACs are only partially eliminated in municipal wastewater treatment and they can interact with bacteria in biological processes. Currently, there is only limited information on the antimicrobial efficiency of CTMA in matrices other than standard growth media and if and how CTMA influences conventional chemical disinfection. The results obtained in this study showed that the susceptibility of E. coli to CTMA was significantly enhanced in phosphate-buffered saline, lake water and wastewater compared to broth. In broth, a minimum inhibitory concentration (MIC) of CTMA of 20 mgL-1 was observed for E. coli, whereas a 4-log inactivation occurred for CTMA concentrations of about 4 mgL-1 in buffered ultra-purified water, a lake water and wastewater effluent. The impacts of the pre-exposure and the presence of CTMA on inactivation by ozone and monochloramine were tested with three different E. coli strains: AG100 with the efflux pump acrAB intact, AG100A with it deleted and AG100tet with it overexpressed. Pre-exposure of E. coli AG100 to CTMA led to an increased susceptibility for ozone with second-order inactivation rate constants (∼ 106 M-1s-1) increasing by a factor of about 1.5. An opposite trend was observed for monochloramine with second-order inactivation rate constants (∼ 103 M-1s-1) decreasing by a factor of about 2. For E. coli AG100tet, the second-order inactivation rate constant decreased by a factor of almost 2 and increased by a factor of about 1.5 for ozone and monochloramine, respectively, relative to the strain AG100. The simultaneous presence of CTMA and ozone enhanced the second-order inactivation rate constants for CTMA concentrations of 2.5 mgL-1 by a factor of about 3. For monochloramine also an enhancement of the inactivation was observed, which was at least additive but might also be synergistic. Enhancement by factors from about 2 to 4.5 were observed for CTMA concentrations > 2.5 mgL-1.


Assuntos
Ozônio , Purificação da Água , Compostos de Bis-Trimetilamônio , Cetrimônio/farmacologia , Cloraminas , Desinfecção/métodos , Escherichia coli , Cinética , Ozônio/química , Águas Residuárias , Água/farmacologia , Purificação da Água/métodos
4.
Vet Parasitol ; 303: 109667, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35124292

RESUMO

Trichodinids are problematic ectoparasites for intensive arapaima fish farming, which can make their breeding costly and unprofitable. The search for effective and safe therapeutic molecules is constant, and chloramine-T has stood out as an effective biocide to treat various pathogens in aquaculture. Here we investigated the acute toxicity (LC50-4h) of chloramine-T and its behavioural, morphological, histological, physiological, and antiparasitic effects on the control of trichodinids in arapaima juveniles. Initially arapaima were exposed to chloramine-T (0, 10, 20, 40, 50, 60, 80, 100 mg L-1) for 4 h. During this period, behavioural, morphological, and mortality changes were recorded. Immediately after a toxicity test, gills were collected for the histological analysis. The LC50-4h was calculated at 23.8 mg L-1 of chloramine-T. Behavioural changes like erratic swimming, loss of balance, gasping at the water surface, excessive mucus, jumping at the water surface, lethargy and gill hyperventilation, and morphological changes like loss of scales, ocular opacity, and skin darkening, were considered mild in arapaima exposed to 10 and 20 mg L-1 of chloramine-T for 4 h. The arapaima gills exposed to 10, 20 and, 40 mg L-1 of chloramine-T presented epithelial hyperplasia, dilated venous sinus and eosinophilic infiltrate, but they were reversible and of a low pathological degree. Based on the acute toxicity test (LC50-4h) results, concentrations were defined for the in vivo efficacy test, during which arapaima were exposed to 0, 10, 15, and 20 mg L-1 of chloramine-T for 1 h. After a therapeutic bath, physiological and parasitological analyses were performed. The use of 20 mg L-1 of chloramine-T significantly reduced (p < 0.05) parasitism by Trichodina sp. with an efficacy of 50.27 % and 53.23 % in gills and on the body surface, respectively. Chloramine-T did not change haematological parameters (erythrogram and thrombogram) or the biochemical parameters of arapaima after 1 h of exposure. However, monocytosis and neutrophilia were noted at slightly higher concentrations (15 and 20 mg L-1), but changes in fish homeostasis were not characterised. Thus, we demonstrate that the application of a therapeutic bath with 20 mg L-1 of chloramine-T for 1 h reduces parasitism by trichodinids and does not affect general arapaima juvenile health.


Assuntos
Peixes , Brânquias , Animais , Aquicultura , Cloraminas , Peixes/anatomia & histologia , Peixes/fisiologia , Brânquias/parasitologia , Compostos de Tosil
5.
Chemistry ; 28(16): e202200060, 2022 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-35133031

RESUMO

We report a method for the synthesis of chiral vicinal chloroamines via asymmetric protonation of catalytically generated prochiral chloroenamines using chiral Brønsted acids. The process is highly enantioselective, with the origin of asymmetry and catalyst substituent effects elucidated by DFT calculations. We show the utility of the method as an approach to the synthesis of a broad range of heterocycle-substituted aziridines by treatment of the chloroamines with base in a one-pot process, as well as the utility of the process to allow access to vicinal diamines.


Assuntos
Aziridinas , Catálise , Cloraminas , Ciclização , Estereoisomerismo
6.
J Hazard Mater ; 429: 128370, 2022 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-35121291

RESUMO

Iodinated trihalomethanes (I-THMs) have drawn increasing concerns due to their higher toxicity than those of their chlorinated and brominated analogues. In this study, I-THM formation was firstly evaluated for three treatment scenarios - (i) chlorine alone, (ii) chloramine alone, and (iii) mixed chlorine/chloramine - in the presence and absence of UV irradiation for the iodide-containing humic acid solution or natural water. The results indicated that I-THM formation decreased in the order of mixed chlorination/chloramination > chloramination > > chlorination, which fitted the trend of toxicity evaluation results using Chinese hamster ovary cells. Conversely, total organic halide concentration decreased in the order of chlorination > > chloramination ≈ mixed chlorination/chloramination. Besides, I-THM formation can be efficiently controlled in a UV-activated mixed chlorine/chloramine system. Influencing factors including pH values and Br-/I- molar ratios were also systematically investigated in a mixed chlorine/chloramine system. Enhanced I-THM formation was observed with increasing pH values (6.0-8.0) and Br-/I- molar ratios (1: 1-10: 1). The results obtained in this study can provide new insights into the increasing risk of I-THM formation in a mixed chlorine/chloramine system and the effective control of I-THMs in the iodide-containing water using UV irradiation.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Animais , Células CHO , Cloraminas , Cloro , Cricetinae , Cricetulus , Desinfecção/métodos , Halogenação , Trialometanos , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade , Purificação da Água/métodos
7.
Water Res ; 210: 117990, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-34974344

RESUMO

Amino acids (AAs) are a major group of odorous disinfection by-product (O-DBP) precursors. O-DBPs formations during free chlorine disinfection has been previously investigated. However, knowledge regarding the O-DBP formation mechanism and kinetics under chloramination of AAs is very limited. In this study, the generation of odorous isovaleraldehyde, isovaleronitrile and N-chloroisovaleraldimine from leucine (Leu), a typical and abundant AA in many drinking water sources, in its free and combined forms during chloramination under several typical addition schemes of disinfectants was investigated. Free Leu and glycylleucine (Gly-Leu) were chosen as model compounds since they have been indicated to be O-DBP precursors during chlorination. Intermediate product analysis and kinetics studies were conducted to study the reaction mechanisms. Impacts of disinfectants dosages and pH were also investigated in experiments and simulations. The results indicated that comparing with chlorination, chloramination of Leu has its uniqueness by participating in reacting with isovaleraldehyde to form N-chloroisovaleraldimine. And all the three O-DBPs formations from free Leu and Gly-Leu during chloramination (with preformed NH2Cl) were less than those during chlorination, indicating that using NH2Cl for disinfection ensures control over the off-flavor problems to some degree. When chloramination was realized by adding chlorine and ammonia separately, a longer pre-chlorination time led to greater yields of the O-DBPs from both precursors, whereas adding ammonia before chlorine promoted more isovaleraldehyde formation from free Leu. Under alkaline conditions, more isovaleronitrile and N-chloroisovaleraldimine were produced, and acidic conditions led to more isovaleraldehyde formation during chloramination. Notably, O-DBPs yields from free Leu were approximately 1000 times greater than those from Gly-Leu during chloramination under all the schemes. In addition, chlor(am)ination experiments with real water from Taihu Lake (the third largest freshwater lake and water source for twenty million people in China) indicated the formation of N-chloroisovaleraldimine and isovaleraldehyde was highly likely to cause odorous problems in drinking water. This study facilitates further understanding of the causes of off-flavor issues in drinking water and can help control the odorous problems by optimizing the operating parameters of drinking water treatment plants.


Assuntos
Cloraminas , Poluentes Químicos da Água , Aldeídos , Humanos , Leucina , Nitrilas
8.
Water Res ; 211: 118049, 2022 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-35032872

RESUMO

Bromate, a regulated disinfection byproduct, forms during the ozonation of bromide through reactions with both ozone and hydroxyl radical. In this study, preformed monochloramine was evaluated for use as a bromate suppression method in pilot testing of wastewater reuse with an average bromide concentration of 422±20 µg/L. A dose of 3 mg/L NH2Cl-Cl2 decreased bromate formation by an average of 82% and was sufficient to keep bromate below the MCL at ozone doses up to 8.6 mg/L (1.2 O3:TOC). Removal of 1,4-dioxane through ozonation decreased with increasing NH2Cl dose, confirming that monochloramine suppresses bromate formation, at least in part, by acting as a hydroxyl radical scavenger. This may negatively impact oxidation objectives of ozonation in reuse applications. Increasing monochloramine contact time did not improve bromate suppression, indicating that monochloramine probably did not mask bromide as NHBrCl or other haloamines prior to ozonation. However, NHBrCl and NH2Br may be formed from reactions between HOBr and NH2Cl and excess free ammonia during ozonation. NDMA was formed by ozonation at concentrations up to 79 ng/L and was not enhanced by NH2Cl addition.


Assuntos
Ozônio , Poluentes Químicos da Água , Purificação da Água , Bromatos , Cloraminas , Poluentes Químicos da Água/análise
9.
J Hazard Mater ; 424(Pt B): 127341, 2022 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-34634702

RESUMO

The need in using reclaimed water increased significantly to address the water shortage and its continuing quality deterioration in sustaining societal development. Degrading micropollutants in wastewater treatment plant effluents is one of the most important tasks in supplying safe drinking water, which is often achieved by full advanced treatment technologies (FATs), including reverse osmosis (RO) and the UV-based advanced oxidation process (AOP). As an emerging AOP, UV/chloramine process shows many noteworthy advantages in the scenario of potable water reuse, including membrane biological fouling control by chloramine, producing highly reactive radicals (e.g., Cl•, HO•, Cl2•-, and reactive nitrogen-containing species) to degrade the RO permeated pollutants, and acting as long-lasting disinfectant in the potable water distribution system. In addition, chloramine is often designedly produced by taking advantage of the ammonia in source. Thus, UV/chloramine processes gather much attention from researcher and published papers on UV/chloramine process have drastically increased since 2016, which were thoroughly reviewed in this paper. The fundamentals of chloramine photolysis, including the photolysis kinetics, the quantum yield, the generation and transformation of radicals and the final products, were scrutinized. Further, the impacts of reaction conditions such as pH, chloramine dosage and water matrix on the degradation of micropollutants by the UV/chloramine process are discussed. Moreover, the formation potential of disinfection by-products is debated. The opportunity of application of the UV/chloramine process in real-world practice is also presented, emphasizing the need for extensive efforts to remove currently prevalent knowledge roadblocks.


Assuntos
Água Potável , Poluentes Químicos da Água , Purificação da Água , Cloraminas , Peróxido de Hidrogênio , Oxirredução , Raios Ultravioleta , Águas Residuárias/análise
10.
Sci Total Environ ; 806(Pt 4): 151372, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34728210

RESUMO

Monochloramine (NH2Cl) oxidant combined with a Ultraviolet (UV)-Light-emitting-diode (LED) light source forms a new advanced oxidation process (AOP), which can achieve high-efficiency degradation of carbamazepine (CBZ). The degradation of CBZ displayed pseudo-first-order reaction kinetics (R2 > 0.98, kCBZ = 0.0043 cm2 mJ-1 at pH 7). The degradation of CBZ was dependent on UV-LED wavelength, with maximum degradation efficiency observed at 265 nm since it was the lowest wavelength studied among UV-LEDs. Variation in pH across the range, which might be expected under normal environmental conditions (pH 6-8), and the presence of Cl- had no significant effect on the degradation efficiency of CBZ, while the presence of HCO3- and natural organic matter (NOM) inhibited degradation. Electron paramagnetic resonance (EPR) experiments detected OH in the system. Probe compounds were used to distinguish the contribution of reactive chlorine species (RCS). It was proved that OH and Cl played major roles and OH was responsible for around 50% of the observed degradation of CBZ. Eight transformative products (TPs) in the degradation process of CBZ were identified, with a generally decreasing toxicity. The concentration of disinfection by-products (DBPs) formed during CBZ degradation was all within limits of WHO and China standard for drinking water. Although the concentration of nitrogen-containing DBPs (N-DBPs) was the lowest, N-DBPs were the main contributors to toxicity, and these would require more attention in practical applications. UV-LED/NH2Cl AOP was identified as an effective way to degrade pharmaceutically active compounds.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Carbamazepina/toxicidade , Cloraminas , Cloro , Desinfecção , Halogenação , Cinética , Oxirredução , Raios Ultravioleta , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade
11.
Sci Total Environ ; 806(Pt 3): 151322, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34743887

RESUMO

The two most commonly adopted strategies, rechlorination (addition of chlorine) and rechloramination (addition of chlorine and ammonia), to recover and stabilise chloramine from nitrification were comprehensively evaluated in laboratory- and full-scale systems. Laboratory-scale batch experiments were conducted in a nitrifying sample (~0.05 mg-N/L). In the full-scale service reservoir, repeated rechlorination was ineffective in suppressing nitrification and microbial chloramine decay during warmer months (>20 °C), even when rechlorination was started at nitrite <0.005 mg-N/L. Measurement of decay rates through microbial chloramine decay factor method provides a deeper understanding of a water sample than traditional nitrification indicators. The method has the ability to provide an early warning (one month in advance), show the presence of microbial chloramine decay in non-nitrified water and that of chloramine decaying proteins in any samples. In the batch sample, nitrification and the production of chloramine-decaying proteins and bacterial regrowth had to be suppressed to recover chloramine. Rechloramination (~2.5 mg/L) outperformed rechlorination, as it maintained a relatively higher chloramine concentration. Microbes were killed within 30 min of dosing chlor(am)ine, likely due to shock or compounds formed during chloramine formation reactions; however, microbes regrew (or survive) to a different degree in all samples despite the prolonged presence of chloramine (large CxT), defying the CxT concept. The key to the recovery of chloramine appears to be consistently maintaining chloramine >1.7 mg/L and shocking with a high chloramine dose. The findings will assist water utilities in designing and assessing the effectiveness of nitrification remediation strategies in chloraminated water supply systems.


Assuntos
Cloraminas , Nitrificação , Amônia , Bactérias , Nitritos
12.
Chemosphere ; 286(Pt 2): 131747, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34358893

RESUMO

Pyrimidine and purine bases (adenine, cytosine, guanine and thymine) are important precursors of organic chloramines (OC) and disinfection by-products (DBPs) during chlor(am)ination. In this study, OC and DBP formation derived from pyrimidine and purine bases during chlor(am)ination, post-chlor(am)ination after pretreated by UV alone and UV/chlorination were systematically investigated with ultraviolet light-emitting diodes (UV-LEDs, 265 and 275 nm) and low pressure mercury lamp (LPUV, 254 nm). The results revealed that higher OC formation was observed during chlorination than that during chloramination of pyrimidine and purine bases. The degradation of pyrimidine and purine bases followed the pseudo-first-order kinetics. Both solution pH and UV wavelength played vital influence on the degradation of pyrimidine and purine bases. In terms of fluence-based rate constants (kobs), the degradation rates of pyrimidine and purine bases decreased in the order of 275 nm > 265 nm > 254 nm in alkaline conditions. The synergistic effects of kobs, chlorine,kobs, •OH and kobs, RCS contributed to the differences of pyrimidine and purine bases degradation at different pH values and UV wavelengths. A vital suppression of OC formation was observed during post-chlorination after pretreated by 275 nm UV-LED/chlorination. In addition, compared with LPUV (254 nm), less DBP formation was observed at UV-LED (275 nm), especially during the UV/chlorine process. The phenomena obtained in this study indicated that 275 nm UV-LED combined with chlorine could be a preferred method to promote pyrimidine and purine bases degradation and control OC and DBP formation in practical water treatment.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Cloraminas , Cloro , Desinfecção , Halogenação , Purinas , Pirimidinas , Poluentes Químicos da Água/análise
13.
J Hazard Mater ; 421: 126459, 2022 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-34365233

RESUMO

Organic chloramines of little disinfection efficacy commonly exist in disinfection process (chlor(am)ination) due to the wide presence of organic amines in water, of which N-chlorodimethylamine (CDMA) is a typical one. For the first time, UV photolysis for the activation of CDMA was investigated. UV photolysis caused the cleavage of N-Cl bond in CDMA to form Cl• and subsequently HO•, both of which are dominant contributors to the destruction of model contaminant bisphenol A (BPA). Typical spectra of HO• were detected by electron paramagnetic resonance (EPR) experiments, while spectra of reactive nitrogen species (RNS) were not detected during UV photolysis of CDMA. The increase of pH (6.0-8.0), HCO3-/CO32-, Cl- and nature organic matter inhibited the degradation of BPA. We proposed pathways of CDMA and BPA degradation based on the identified transformation products. UV photolysis of CDMA and BPA reduced the formation of N-nitrosodimethylamine (NDMA) at pH 8.0, but increased the formation of trichloronitromethane (TCNM) at pH 7.0 and 8.0. The increasing toxicity and the formation of TCNM and NDMA gave us a hint that formation of organic chloramines should be concerned.


Assuntos
Cloraminas , Purificação da Água , Desinfecção , Fotólise , Raios Ultravioleta
14.
J Hazard Mater ; 422: 126813, 2022 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-34399222

RESUMO

This study systematically investigates the formation of trichloronitromethane (TCNM) from 2 natural waters, 6 humic substances and 16 phenolic compounds during UV/monochloramine (UV/NH2Cl) followed by post-chloramination. Using 15N-NH2Cl as an isotope tracer, we found that 15N-TCNM accounted for 70.7-76.5% of total TCNM during UV/NH2Cl treated 2 natural waters, which was significantly higher than the proportion of 15N-TCNM in chloramination (NH2Cl alone). This is a direct evidence that NH2Cl, rather than the nitrogenous matters in waters, was the predominant nitrogen source of TCNM during UV/NH2Cl treatment. Phenol derivatives with meta-substituents and with electron-withdrawing groups facilitated the formation of TCNM precursors during UV/NH2Cl treatment. Significant correlations were found between Hammett constants (σ) of substituents and TCNM formation potentials. The formation mechanisms of TCNM were revealed using resorcinol as a representative phenolic compound. During UV/NH2Cl treatment, HO•, reactive chlorine species and reactive nitrogen species contributed to 28.1%, 29.0% and 19.4% of resorcinol degradation. Five nitro(so)-intermediates were identified as the main TCNM precursors. The formation pathways of TCNM were proposed. Alkaline pH was recommended to reduce the formation of TCNM precursors during UV/NH2Cl treatment.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Cloraminas , Cloro , Desinfecção , Halogenação , Hidrocarbonetos Clorados , Poluentes Químicos da Água/análise
15.
Water Res ; 207: 117795, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34736003

RESUMO

Due to the wide-presence of organic amines in natural waters, organic chloramines are commonly formed during (pre-)chlorination. With the increasing application of UV disinfection in water treatment, both the activation mechanism of organic chloramine by UV photolysis and its subsequent impact on water quality are not clear. Using sarcosine (Sar) as an amine group-containing compound, it was found that organic chloramines (i.e., Cl-Sar) would be firstly formed during chlorination even in the presence of natural organic matter. Compared with self-decay of Cl-Sar, UV photolysis accelerated Cl-Sar decomposition and induced NCl bond cleavage. Using metoprolol (MTP) as a model micro-pollutant, UV-activated Cl-Sar (UV/Cl-Sar) can accelerate micro-pollutant degradation, attributed to reactive radicals formation. HO• and Cl• were important contributors, with a total contribution of 45%‒64%. Moreover, the degradation rate of MTP by UV/Cl-Sar was pH-dependent, which monotonically increased from 0.044 to 0.065 min‒1 under pHs 5.5‒8.5. Although the activation of organic chloramine by UV could accelerate micro-pollutant degradation, UV/Cl-Sar treatment could also enhance disinfection by-products formation. Trichloromethane (TCM) formation was observed during MTP degradation by UV/Cl-Sar. After post-chlorination, TCM, 1,1-dichloropropanone, 1,1,1-trichloropropanone, and dichloroacetonitrile were detected. Their individual and total concentrations were all positively proportional to UV/Cl-Sar treatment time. The total concentration with 30 min treatment (66.93 µg L‒1) was about 2.3 times that with 1 min treatment (28.76 µg L‒1). Finally, the accelerated effect was verified with Cl-glycine and Cl-alanine. It is expected to unravel the non-negligible role of organic chloramine on water quality during UV disinfection.


Assuntos
Poluentes Ambientais , Poluentes Químicos da Água , Purificação da Água , Cloraminas , Cloro , Desinfecção , Halogenação , Oxidantes , Fotólise , Raios Ultravioleta
16.
Environ Sci Technol ; 55(21): 14876-14885, 2021 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-34652150

RESUMO

The increasing use of chlorine- or chloramine-containing irrigation waters to minimize foodborne pathogens is raising concerns about the formation and uptake of disinfection byproducts into irrigated produce. Chlorate has received particular attention in the European Union. While previous research demonstrated the formation of chlorate from dark disproportionation reactions of free chlorine and uptake of chlorate into produce from roots, this study evaluated chlorate formation from solar irradiation of chlorine- and chloramine-containing irrigation droplets and uptake through produce surfaces. Sunlight photolysis of 50 µM (3.6 mg/L as Cl2) chlorine significantly enhanced the formation of chlorate, with a 7.2% molar yield relative to chlorine. Chlorate formation was much less significant in sunlit chloramine solutions. In chlorinated solutions containing 270 µg/L bromide, sunlight also induced the conversion of bromide to 280 µg/L bromate. Droplet evaporation and the resulting increase in chlorine concentrations approximately doubled sunlight-induced chlorate formation relative to that in the bulk solutions in which evaporation is negligible. When vegetables (broccoli, cabbage, chicory, lettuce, and spinach) were sprayed with chlorine-containing irrigation water in a sunlit field, sunlight promoted chlorate formation and uptake through vegetable surfaces to concentrations above maximum residue levels in the European Union. Spraying with chloramine-containing waters in the dark minimized chlorate formation and uptake into the vegetables.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Cloraminas , Cloratos , Cloro , Desinfecção , Luz Solar , Água
17.
Water Res ; 206: 117746, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34678699

RESUMO

Release of algal organic matter (AOM) from algae poses great threats to drinking water safety. As organic nitrogen in AOM is relatively higher compared to natural organic matter (NOM), the organic chloramine formation during chlorination cause overestimation of effective chlorine, which may lead to a biological risk. This study compared the organic chloramine formation from AOM and NOM, and confirmed that AOM tend to form more organic chloramines during chlorination. Furthermore, it was found that hydrophilic fraction and high molecular weight (>100 kDa) fraction of AOM generated major organic chloramines due to a high content of protein. Based on the results of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), Spearman's rank correlation was used to analyze the relationship between molecular composition of AOM and organic chloramine formation. Notably, molecules with high correlation to organic chloramine formation located in a triangle region of van Krevelen diagram, which is a typical area of peptides. Therefore, it indicates that the precursors of organic chloramine in AOM are mainly proteins/peptides, and appropriate treatment processes (e.g., biological treatment or membrane filtration) should be addressed to effectively remove the precursors before chlorination.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Cloraminas , Cloro/análise , Ciclotrons , Desinfecção , Análise de Fourier , Halogenação , Espectrometria de Massas , Poluentes Químicos da Água/análise
18.
Water Res ; 205: 117689, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34607086

RESUMO

Chloramine is a secondary disinfectant used to maintain microbial control throughout public water distribution systems. This study investigated the relationship between chloramine concentration, heterotrophic bacteria, and specific Mycobacterium species. Sixty-four water samples were collected at four locations within the utility's distribution network on four occasions. Water samples were analyzed for total chlorine and monochloramine. Traditional culture methods were applied for heterotrophic bacteria and nontuberculous mycobacteria (NTM), and specific quantitative polymerase chain reaction (qPCR) assays were used to detect and quantify Mycobacterium avium, M. intracellulare, and M. abscessus. Total chlorine and monochloramine concentrations decreased between the distribution entry point (4.7 mg/L and 3.4 mg/L as Cl2, respectively) to the maximum residence time location (1.7 mg/L and 1.1 mg/L as Cl2, respectively). Results showed that heterotrophic bacteria and NTM counts increased by two logs as the water reached the average residence time (ART) location. Microbiological detection frequencies among all samples were: 86% NTMs, 66% heterotrophic bacteria, 64% M. abscessus, 48% M. intracellulare, and 2% M. avium. This study shows that heterotrophic bacteria and NTM are weakly correlated with disinfectant residual concentration, R2=0.18 and R2=0.04, respectively. Considering that specific NTMs have significant human health effects, these data fill a critical knowledge gap regarding chloramine's impact on heterotrophic bacteria and Mycobacterial species survival within public drinking water distribution systems.


Assuntos
Água Potável , Mycobacterium , Cloraminas , Desinfecção , Humanos
19.
Microbiol Spectr ; 9(2): e0030121, 2021 10 31.
Artigo em Inglês | MEDLINE | ID: mdl-34549994

RESUMO

Intervening proteins, or inteins, are mobile genetic elements that are translated within host polypeptides and removed at the protein level by splicing. In protein splicing, a self-mediated reaction removes the intein, leaving a peptide bond in place. While protein splicing can proceed in the absence of external cofactors, several examples of conditional protein splicing (CPS) have emerged. In CPS, the rate and accuracy of splicing are highly dependent on environmental conditions. Because the activity of the intein-containing host protein is compromised prior to splicing and inteins are highly abundant in the microbial world, CPS represents an emerging form of posttranslational regulation that is potentially widespread in microbes. Reactive chlorine species (RCS) are highly potent oxidants encountered by bacteria in a variety of natural environments, including within cells of the mammalian innate immune system. Here, we demonstrate that two naturally occurring RCS, namely, hypochlorous acid (the active compound in bleach) and N-chlorotaurine, can reversibly block splicing of DnaB inteins from Mycobacterium leprae and Mycobacterium smegmatis in vitro. Further, using a reporter that monitors DnaB intein activity within M. smegmatis, we show that DnaB protein splicing is inhibited by RCS in the native host. DnaB, an essential replicative helicase, is the most common intein-housing protein in bacteria. These results add to the growing list of environmental conditions that are relevant to the survival of the intein-containing host and influence protein splicing, as well as suggesting a novel mycobacterial response to RCS. We propose a model in which DnaB splicing, and therefore replication, is paused when these mycobacteria encounter RCS. IMPORTANCE Inteins are both widespread and abundant in microbes, including within several bacterial and fungal pathogens. Inteins are domains translated within host proteins and removed at the protein level by splicing. Traditionally considered molecular parasites, some inteins have emerged in recent years as adaptive posttranslational regulatory elements. Several studies have demonstrated CPS, in which the rate and accuracy of protein splicing, and thus host protein functions, are responsive to environmental conditions relevant to the intein-containing organism. In this work, we demonstrate that two naturally occurring RCS, including the active compound in household bleach, reversibly inhibit protein splicing of Mycobacterium leprae and Mycobacterium smegmatis DnaB inteins. In addition to describing a new physiologically relevant condition that can temporarily inhibit protein splicing, this study suggests a novel stress response in Mycobacterium, a bacterial genus of tremendous importance to humans.


Assuntos
Cloro/farmacologia , DnaB Helicases/antagonistas & inibidores , Inteínas/genética , Mycobacterium leprae/genética , Mycobacterium smegmatis/genética , Processamento de Proteína/efeitos dos fármacos , Cloraminas/farmacologia , Cloro/química , Replicação do DNA/efeitos dos fármacos , Replicação do DNA/genética , DnaB Helicases/genética , DnaB Helicases/metabolismo , Regulação Bacteriana da Expressão Gênica/genética , Ácido Hipocloroso/farmacologia , Mycobacterium leprae/metabolismo , Mycobacterium smegmatis/metabolismo , Oxidantes/farmacologia , Oxirredução , Processamento de Proteína/fisiologia , Espécies Reativas de Oxigênio/metabolismo , Taurina/análogos & derivados , Taurina/farmacologia
20.
Water Res ; 204: 117570, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34464745

RESUMO

Organic chloramines have attracted considerable attention because of their potential toxicity and reactivity. However, the lack of suitable and effective analytical methods has limited the study of organic chloramines due to their volatile and unstable properties. In this study, membrane introduction mass spectrometry (MIMS) combined with DPD/FAS titration was used to monitor the formation of organic chloramines. N-chlorodimethylamine [(CH3)2NCl] and N-chlorodiethylamine [(C2H5)2NCl] were detected and identified as the dominant volatile DBPs during chlorination of 18 organic compounds with dimethylamine or diethylamine functional groups, with yields ranging from 0.3% to 51.1% at a chlorine to precursor (Cl/P) molar ratio of 8.0. (CH3)2NBr was formed in the presence of bromide, while the formation of (CH3)2NCl was decreased. The reaction of phenol with (CH3)2NCl combined with theoretical calculations confirmed that the reactivity of (CH3)2NCl was similar to that of monochloramine. Moreover, (CH3)2NCl and (C2H5)2NCl were observed at the ppb level during chlorination of actual water samples collected from different areas. The results suggest that (CH3)2NCl and (C2H5)2NCl are important organic chloramines during chlorination, which may lead to the occurrence of further oxidation reactions and promote the formation of other disinfection byproducts simultaneously and should be of concern.


Assuntos
Desinfetantes , Poluentes Químicos da Água , Purificação da Água , Cloraminas , Cloro/análise , Desinfecção , Halogenação , Poluentes Químicos da Água/análise
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