Reaction of ortho-methoxybenzoic acid with the water disinfecting agents ozone, chlorine and sodium hypochlorite

Ozone, chlorine and sodium hypochlorite are commonly used as disinfecting agents for drinking water production. The reaction pathways of ozonation and chlorination of o-methoxybenzoic acid in aqueous solution were studied using gas chromatography-mass spectrometry (GC-MS) and high pressure liquid chromatography (HPLC). The results show that less than 1% of o-methoxybenzoic acid remains in reaction. The final major products using ozone oxidation are oxalic and glyoxalic acids. Phenols appear only at insufficient ozone levels. Sodium hypochlorite leads to higher levels of primary products. Molecular chlorine leads to the formation of higher amounts of polychlorinated derivatives. Model experiments allow to propose schemes of o-methoxybenzoic acid transformation under the conditions simulating water treatment processes.     

管道分质供水消毒副产物及其安全性评价

消毒副产物是饮用水中应主要控制的毒害物。然而，管道分质供水中消毒副产物特征及污染水平很少研究。以某一管道分质供水工程为例，对其中消毒副产物进行了详细研究。研究结果表明，管道分质供水消毒副产物在量与质上与其源水自来水存在很大差别。在管道分质供水中消毒副产物量少，一般不到自来水的1／10，且主要是一些毒性较低、与供水管材有关的溶出物。据此计算出管道分质供水由消毒副产物引起的致癌风险性一般不到其源水的1／10，其安全性大大提高。     

美国自来水行业消毒现状和展望

为了了解美国自来水行业消毒现状,在查阅了相关外文文献的基础上,对相关资料进行总结和分析.结果表明:氯气虽然仍是最广泛使用的消毒方式,但出于人们对健康安全的关注和许多饮用水法规的实施,使用氯气的水厂数量在不断减少.     

Trihalomethane Formation Potential and Concentration Changes During Water Treatment at Mumbai (India)

The treated water at the outlet oftreatment plants and representative servicereservoirs of Mumbai city have been evaluatedfor trihalomethane formation potential in1995–1996. Chloroform, dichlorobromomethane,chlorodibromomethane and bromoform have beenmonitored during monsoon, winter and summer.The levels of chloroform are found above theregulated WHO guideline value of 200 g L^-1 in final water during postmonsoon atGhatkopar (226 g L^-1), Malbar (210.3 g L^-1) and Tulsi (231.26 g L^-1).     

Nontargeted identification of peptides and disinfection byproducts in water

A broad range of organic compounds are known to exist in drinking water sources and serve as precursors of disinfection byproducts(DBPs).Epidemiological findings of an association of increased risk of bladder cancer with the consumption of chlorinated water has resulted in health concerns about DBPs.Peptides are thought to be an important category of DBP precursors in water.However,little is known about the actual presence of peptides and their DBPs in drinking water because of their high sample complexity and low concentrations.To address this challenge and identify peptides and non-chlorinated/chlorinated peptide DBPs from large sets of organic compounds in water,we developed a novel high throughput analysis strategy,which integrated multiple solid phase extraction(SPE),high performance liquid chromatography(HPLC)separation,and non-target identification using precursor ion exclusion(PIE)high resolution mass spectrometry(MS).After MS analysis,structures of candidate compounds,particularly peptides,were obtained by searching against the Human Metabolome Database(HMDB).Using this strategy,we successfully detected 625 peptides(out of 17,205 putative compounds)and 617 peptides(out of 13,297)respectively in source and finished water samples.The source and finished water samples had 501 peptides and amino acids in common.The remaining 116 peptides and amino acids were unique to the finished water.From a subset of 30 putative compounds for which standards were available,25 were confirmed using HPLC-MS analysis.By analyzing the peptides identified in source and finished water,we successfully confirmed three disinfection reaction pathways that convert peptides into toxic DBPs.     

A new technique helps to uncover unknown peptides and disinfection by-products in water

正Environmental water samples can be extremely complex,with potentially thousands of molecules that can derive from natural organic matter(NOM)and thousands that derive from anthropogenic contaminants.As complex as these samples are,drinking water can be even more complex.Due to disinfectants that are used to treat drinking water(e.g.,chlorine,chloramines,     

Investigation of nuclear enzyme topoisomerase as a putative molecular target of monohaloacetonitrile disinfection by-products

Disinfection by-products occur widely as the unintended effect of water disinfection and are associated with toxicity and adverse human health effects. Yet the molecular mechanisms of their toxicity are not well understood. To investigate the molecular basis of hyperploidy induction by monohaloacetonitriles, the interaction of monohaloacetonitriles with topoisomerase Ⅱ in Chinese hamster ovary cells was examined. We showed a concentration-dependent inhibition of DNA decatenation activity of topoisomerase under acellular conditions while in vitro monohaloacetonitrile treatment expressed mixed results. The working hypothesis, that topoisomerase Ⅱ is a molecular target of monohaloacetonitriles, was only partially supported.Nevertheless, this research serves as a starting point toward molecular mechanisms of toxic action of monohaloacetonitriles.     

Genotoxicity of drinking water treated with different disinfectants and effects of disinfection conditions detected by umu-test

The genotoxicity of drinking water treated with 6 disinfection methods and the effects of disinfection conditions were investigated using the umu-test. The pretreatment procedure of samples for the umu-test was optimized for drinking water analysis. The results of the umu-test were in good correlation with those of the Ames-test. The genotoxicity and production of haloacetic acids (HAAs) were the highest for chlorinated samples. UV + chloramination is the safest disinfection method from the aspects of genotoxicity, HAA production and inactivation effects. For chloramination, the effects of the mass ratio of Cl₂ to N of chloramine on genotoxicity were also studied. The changes of genotoxicity were different from those of HAA production, which implied that HAA production cannot represent the genotoxic potential of water. The genotoxicity per chlorine decay of chlorination and chloramination had similar trends, indicating that the reaction of organic matters and chlorine made a great contribution to the genotoxicity. The results of this study are of engineering significance for optimizing the operation of waterworks.     

Exploration of reaction rates of chlorine dioxide with tryptophan residue in oligopeptides and proteins

Chlorine dioxide (ClO₂), an alternative disinfectant to chlorine, has a superior ability to inactivate microorganisms, in which protein damage has been considered as the main inactivation mechanism. However, the reactivity of ClO₂ with amino acid residues in oligopeptides and proteins remains poorly investigated. In this research, we studied the reaction rate constants of ClO₂ with tryptophan residues in five heptapeptides and four proteins using stopped-flow or competition kinetic method. Each heptapeptide and protein contain only one tryptophan residue and the reactivity of tryptophan residue with ClO₂ was lower than that of free tryptophan (3.88 × 10⁴ (mol/L)^?1sec^?1 at pH 7.0). The neighboring amino acid residues affected the reaction rates through promoting inter-peptide aggregation, changing electron density, shifting pK_a values or inducing electron transfer via redox reactions. A single amino acid residue difference in oligopeptides can make the reaction rate constants differ by over 60% (e.g. 3.01 × 10⁴ (mol/L)^?1sec^?1 for DDDWNDD and 1.85 × 10⁴ (mol/L)^?1sec^?1 for DDDWDDD at pH 7.0 (D: aspartic acid, W: tryptophan, N: asparagine)). The reaction rates of tryptophan-containing oligopeptides were also highly pH-dependent with higher reactivity for deprotonated tryptophan than the neutral specie. Tryptophan residues in proteins spanned a 4-fold range reactivity toward ClO₂ (i.e. 0.84 × 10⁴ (mol/L)^?1sec^?1 for ribonuclease T1 and 3.21 × 10⁴ (mol/L)^?1sec^?1 for melittin at pH 7.0) with accessibility to the oxidant as the determinating factor. The local environment surrounding the tryptophan residue in proteins can also accelerate the reaction rates by increasing the electron density of the indole ring of tryptophan or inhibit the reaction rates by inducing electron transfer reactions. The results are of significance in advancing understanding of ClO₂ oxidative reactions with proteins and microbial inactivation mechanisms.     

Research progress of disinfection and disinfection by-products in China

Disinfection is an indispensable water treatment process for killing harmful pathogens and protecting human health. However, the disinfection has caused significant public concern due to the formation of toxic disinfection by-products(DBPs). Lots of studies on disinfection and DBPs have been performed in the world since 1974. Although related studies in China started in1980 s, a great progress has been achieved during the last three decades. Therefore, this review summarized the main achievements on disinfection and DPBs studies in China, which included:(1) the occurrence of DBPs in water of China,(2) the identification and detection methods of DBPs,(3) the formation mechanisms of DBPs during disinfection process,(4) the toxicological effects and epidemiological surveys of DBPs,(5) the control and management countermeasures of DBPs in water disinfection, and(6) the challenges and chances of DBPs studies in future. It is expected that this review would provide useful information and reference for optimizing disinfection process, reducing DBPs formation and protecting human health.