Silver nanoparticles on UiO-66(Zr)metal-organic frameworks for water disinfection application

Drinking water disinfection is an essential process to assure public health all over the world.In this study,silver nanoparticles(AgNPs)on UiO-66(Zr)Metal-Organic Frameworks(Ag@UiO-66)is proposed as a potential water disinfection strategy.AgNPs are synthesized using polyvinyl pyrrolidone(PVP)as stabilizing agent,and sodium borohydride as reducing agent are subsequently embedded on UiO-66,a high-stability organometallic framework.The effect of premixing time,reaction time and reactant concentration on the loading rate of AgNPs on UiO-66 was investigated.The maximum load rate of AgNPs on UiO-66 could reach 13%when the premixing time is 3 h,the reaction time is 45 min and the concentration of AgNO_(3) is10μg/mL.The formation of AgNPs loaded on UiO-66 was observed and confirmed with ultraviolet and visible spectrophotometry(UV-Vis),scanning electron microscopy(SEM),infrared emission spectroscopy(IES)and X-ray diffraction(XRD)analysis.Ag@UiO-66 exhibited strong antibacterial activity against both Gramnegative Escherichia coli and Gram-positive Staphylococcus aureus,with minimum inhibitory concentrations(MIC)of 64 and 128μg/mL,respectively.The germicidal efficacy of Ag@UiO-66 enhanced significantly as the temperature rose from 4℃to 37℃.The results indicate that Ag@UiO-66 is potential candidate as a feasible water disinfection material.

News:The 595^(th) Session of the Xiangshan Science Conferences focused on water disinfection by-products

The 595th session of the Xiangshan Science Conferences was recently held in Fragrant Hill Hotel,Beijing,on May 22-23,2017.The theme of this highly successful session was on＂Health Risk ad Control of Disinfection By-products（DBPs）in China＂.More than fifty prominent scientists from Australia,Canada,China,and the United States actively participated in the two-day meeting and engaged in lively discussions.

News: JES well represented at the recent Gordon Research Conference on Drinking Water Disinfection By-products

The Gordon Research Conference （GRC） on Drinking Water Disinfection By-products （DBPs） was recently held in Mount Holyoke College, South Hadley, Massachusetts, United States, on July 30-August 4, 2017. The theme of this year＇s GRC on DBPs was ＂Disinfection 2100： Linking Engineering, Chemistry, Toxicology, and Epidemiology to Reduce Exposure to Toxicity Drivers while Curtailing Pathogens＂ （GRC, 2017）. More than one hundred and fifty scientists from around the world actively participated in the week-long conference.

Solar-Driven Water Treatment: New Technologies, Challenges, and Futures

In this review, the new solar water treatment technologies, including solar water desalination in two direct and indirect methods, are comprehensively presented. Recent advances and applications of five major solar desalination technologies include solar-powered humidification–dehumidification, multi-stage flash desalination, multi-effect desalination, RO, and solar stills. Each technology’s productivity, energy consumption, and water production costs are presented. Also, common methods of solar water disinfection have been reviewed as one of the common and low-cost methods of water treatment, especially in areas with no access to drinking water. However, although desalination technologies have many social, economic, and public health benefits, they are energy-intensive and negatively affect the environment. In addition, the disposal of brine from the desalination processes is one of the most challenging and costly issues. In this regard, the environmental effects of desalination technologies are presented and discussed. Among direct solar water desalination technologies, solar still technology is a low-cost, low-tech, and low-investment method suitable for remote areas, especially in developing countries with low financial support and access to skilled workers. Indirect solar-driven water desalination technologies, including thermal and membrane technologies, are more reliable and technically more mature. Recently, RO technology has received particular attention thanks to its lower energy demand, lower cost, and available solutions to increase membrane durability. Disposal of brines can account for much of the water cost and potentially negatively affect the environment. Therefore, in addition to efforts to improve the efficiency and reduce the cost of solar technologies and water treatment processes, future research studies should consider developing new solutions to this issue.

Intensifying electrified flow-through water treatment technologies via local environment modification

Removing high-risk and persistent contaminants from water is challenging,because they typically exist at low concentrations in complex water matrices.Electrified flow-through technologies are viable to overcome the limitations induced by mass transport for efficient contaminant removal.Modifying the local environment of the flow-through electrodes offers opportunities to further improve the reaction kinetics and selectivity for achieving near-complete removal of these contaminants from water.Here,we present state-of-the-art local environment modification approaches that can be incorporated into electrified flow-through technologies to intensify water treatment.We first show methods of nanospace incorporation,local geometry adjustment,and microporous structure optimization that can induce spatial confinement,enhanced local electric field,and microperiodic vortex,respectively,for local environment modification.We then discuss why local environment modification can complement the flow-through electrodes for improving the reaction rate and selectivity.Finally,we outline appropriate scenarios of intensifying electrified flow-through technologies through local environment modification for fit-for-purpose water treatment applications.

Bacteria inactivation by sulfate radical:progress and non-negligible disinfection by-products

Sulfate radicals have been increasingly used for the pathogen inactivation due to their strong redox ability and high selectivity for electron-rich species in the last decade.The application of sulfate radicals in water disinfection has become a very promising technology.However,there is currently a lack of reviews of sulfate radicals inactivated pathogenic microorganisms.At the same time,less attention has been paid to disinfection by-products produced by the use of sulfate radicals to inactivate microorganisms.This paper begins with a brief overview of sulfate radicals’properties.Then,the progress in water disinfection by sulfate radicals is summarized.The mechanism and inactivation kinetics of inactivating microorganisms are briefly described.After that,the disinfection by-products produced by reactions of sulfate radicals with chlorine,bromine,iodide ions and organic halogens in water are also discussed.In response to these possible challenges,this article concludes with some specific solutions and future research directions.

Regulating crystallinity in linear conjugated polymer to boost the internal electric field for remarkable visible-light-driven disinfection

Conjugated linear polymers are promising metal-free photocatalysts for visible-light-driven photocatalytic water disinfection,but it was still bottlenecked by the insufficient photogenerated charge separation and transport(CST)process.Herein,we obtained the highly crystalline imine-linked conjugated linear poly-mer(ODA-BPAH)with a greatly enhanced CST process.The highly crystalline ODA-BPAH exhibited excel-lent broad-spectrum water disinfection efficiency up to 99.99999%in 1 h,which is among the reported highest of state-of-the-art photocatalysts.The crystallinity of ODA-BPAH was regulated by simply turn-ing the solvent and the experiment results revealed that the ODA-BPAH with high crystallinity exhibited higher internal electric field strength and photocatalytic performance than that with low crystallinity,which indicates that higher crystallinity in linear conjugated polymers contributes to superior CST ef-ficiency as well as the generation of reactive oxygen species.This work highlights the impact of poly-mer crystallinity on the internal electric field and proves that linear poly-imine could be a new type of promising metal-free photocatalyst for water treatment.

Formation and control of disinfection byproducts and toxicity during reclaimed water chlorination： A review

Chlorination is essential to the safety of reclaimed water; however, this process leads to concern regarding the formation of disinfection byproducts（DBPs） and toxicity. This study reviewed the formation and control strategies for DBPs and toxicity in reclaimed water during chlorination.Both regulated and emerging DBPs have been frequently detected in reclaimed water during chlorination at a higher level than those in drinking water, indicating they pose a greater risk to humans. Luminescent bacteria and Daphnia magna acute toxicity, anti-estrogenic activity and cytotoxicity generally increased after chlorination because of the formation of DBPs. Genotoxicity by umu-test and estrogenic activity were decreased after chlorination because of destruction of toxic chemicals. During chlorination, water quality significantly impacted changes in toxicity.Ammonium tended to attenuate toxicity changes by reacting with chlorine to form chloramine,while bromide tended to aggravate toxicity changes by forming hypobromous acid. During pretreatment by ozonation and coagulation, disinfection byproduct formation potential（DBPFP）and toxicity formation potential（TFP） occasionally increase, which is accompanied by DOC removal; thus, the decrease of DOC was limited to indicate the decrease of DBPFP and TFP. It is more important to eliminate the key fraction of precursors such as hydrophobic acid and hydrophilic neutrals. During chlorination, toxicities can increase with the increasing chlorine dose and contact time. To control the excessive toxicity formation, a relatively low chlorine dose and short contact time were required. Quenching chlorine residual with reductive reagents also effectively abated the formation of toxic compounds.

Impact of disinfection on drinking water biofilm bacterial community

Disinfectants are commonly applied to control the growth of microorganisms in drinking water distribution systems. However, the effect of disinfection on drinking water microbial community remains poorly understood. The present study investigated the impacts of different disinfectants（chlorine and chloramine） and dosages on biofilm bacterial community in bench-scale pipe section reactors. Illumina MiS eq sequencing illustrated that disinfection strategy could affect both bacterial diversity and community structure of drinking water biofilm. Proteobacteria tended to predominate in chloraminated drinking water biofilms, while Firmicutes in chlorinated and unchlorinated biofilms. The major proteobacterial groups were influenced by both disinfectant type and dosage. In addition, chloramination had a more profound impact on bacterial community than chlorination.

Disinfection By-Products in Drinking Water, Recycled Water and Wastewater： Formation, Detection, Toxicity and Health Effects： Preface

The disinfection of drinking water was an outstanding（and perhaps the most important）public health achievement of the 20^（th） century.According to the United Nations World Health Organization,

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

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,

E. coli and bacteriophage MS2 disinfection by UV, ozone and the combined UV and ozone processes

The combination of low-dose ozone with ultraviolet （UV） irradiation should be an option to give benefit to disinfection and reduce drawbacks of UV and ozone disinfection. However, less is known about the disinfection performance of UV and ozone （UV/ozone） coexposure and sequential UV-followed-by-ozone （UV- ozone） and ozone-followed-by-UV （ozone-UV） expo- sures. In this study, inactivation of E. coli and bacterioph- age MS2 by UV, ozone, UV/ozone coexposure, and sequential UV-ozone and ozone-UV exposures was investigated and compared. Synergistic effects of 0.5-0.9 log kill on E. coli inactivation, including increases in the rate and efficiency, were observed after the UV/ozone coexposure at ozone concentrations as low as 0.05 mg-L-1 in ultrapure water. The coexposure with 0.02-mg.L-1 ozone did not enhance the inactivation but repressed E. coli photoreactivation. Little enhancement on E. coli inactivation was found after the sequential UV-ozone or ozone-UV exposures. The synergistic effect on MS2 inactivation was less significant after the UV/ozone coexposure, and more significant after the sequential ozone-UV and UV-ozone exposures, which was 0.2 log kill for the former and 0.8 log kill for the latter two processes, at ozone dose of 0.1 mg. t-1 and UV dose of 8.55 mJ. cm 2 in ultrapure water. The synergistic effects on disinfection were also observed in tap water. These results show that the combination of UV and low-dose ozone is a promising technology for securing microbiological quality of water.

New methods for identification of disinfection byproducts of toxicological relevance: Progress and future directions

Disinfection byproducts(DBPs)represent a ubiquitous source of chemical exposure in disinfected water.While over 700 DBPs have been identified,the drivers of toxicity remain poorly understood.Additionally,ever evolving water treatment practices have led to a continually growing list of DBPs.Advancement of analytical technologies have enabled the identification of new classes of DBPs and the quantification of these chemically diverse sets of DBPs.Here we summarize advances in new workflows for DBP analysis,including sample preparation,chromatographic separation with mass spectrometry(MS)detection,and data processing.To aid in the selection of techniques for future studies,we discuss necessary considerations for each step in the strategy.This review focuses on how each step of a workflow can be optimized to capture diverse classes of DBPs within a single method.Additionally,we highlight new MS-based approaches that can be powerful for identifying novel DBPs of toxicological relevance.We discuss current challenges and provide perspectives on future research directions with respect to studying new DBPs of toxicological relevance.As analytical technologies continue to advance,new strategies will be increasingly used to analyze complex DBPs produced in different treatment processes with the aim to identify potential drivers of toxicity.

Inactivation effect of pressurized carbon dioxide on bacteriophage Qβ and ΦX174 as a novel disinfectant for water treatment

The inactivation effects of pressurized CO2 against bacteriophage Qβ and ФX 174 were investigated under the pressure of 0.3-0.9 MPa, initial concentration of 107-109 PFU/mL, and temperature of 17.8℃-27.2℃. The optimum conditions were found to be 0.7 MPa and an exposure time of 25 min. Under identical treatment conditions, a greater than 3.3-log reduction in bacteriophage Qβ was achieved by CO2, while a nearly 3.0 log reduction was observed for phage ФX174. The viricidal effects of N2O （an inactivation gas with similar characteristics to CO2）, normal acid （HC1）, and CO2 treatment with phosphate buffered saline affirmed the chemical nature of CO2 treatment. The pumping cycle, depressurization rate, and release of intracellular substances caused by CO2 were its viricidal mechanisms. The results indicate that CO2 has the potential for use as a disinfectant without forming disinfection by-products.

Method to assess component contribution to toxicity of complex mixtures： Assessment of puberty acquisition in rats exposed to disinfection byproducts

A method based on regression modeling was developed to discern the contribution of component chemicals to the toxicity of highly complex, environmentally realistic mixtures of disinfection byproducts（DBPs）. Chemical disinfection of drinking water forms DBP mixtures.Because of concerns about possible reproductive and developmental toxicity, a whole mixture（WM） of DBPs produced by chlorination of a water concentrate was administered as drinking water to Sprague–Dawley（S–D） rats in a multigenerational study. Age of puberty acquisition,i.e., preputial separation（PPS） and vaginal opening（VO）, was examined in male and female offspring, respectively. When compared to controls, a slight, but statistically significant delay in puberty acquisition was observed in females but not in males. WM-induced differences in the age at puberty acquisition were compared to those reported in S–D rats administered either a defined mixture（DM） of nine regulated DBPs or individual DBPs. Regression models were developed using individual animal data on age at PPS or VO from the DM study. Puberty acquisition data reported in the WM and individual DBP studies were then compared with the DM models. The delay in puberty acquisition observed in the WM-treated female rats could not be distinguished from delays predicted by the DM regression model, suggesting that the nine regulated DBPs in the DM might account for much of the delay observed in the WM. This method is applicable to mixtures of other types of chemicals and other endpoints.

Occurrence and formation of disinfection by-products in the swimming pool environment： A critical review

Disinfection of water for human use is essential to protect against microbial disease;however, disinfection also leads to formation of disinfection by-products（DBPs）, some of which are of health concern. From a chemical perspective, swimming pools are a complex matrix, with continual addition of a wide range of natural and anthropogenic chemicals via filling waters, disinfectant addition, pharmaceuticals and personal care products and human body excretions. Natural organic matter, trace amounts of DBPs and chlorine or chloramines may be introduced by the filling water, which is commonly disinfected distributed drinking water. Chlorine and/or bromine is continually introduced via the addition of chemical disinfectants to the pool. Human body excretions（sweat, urine and saliva） and pharmaceuticals and personal care products（sunscreens, cosmetics, hair products and lotions） are introduced by swimmers. High addition of disinfectant leads to a high formation of DBPs from reaction of some of the chemicals with the disinfectant.Swimming pool air is also of concern as volatile DBPs partition into the air above the pool.The presence of bromine leads to the formation of a wide range of bromo-and bromo/chloro-DBPs, and Br-DBPs are more toxic than their chlorinated analogues. This is particularly important for seawater-filled pools or pools using a bromine-based disinfectant.This review summarises chemical contaminants and DBPs in swimming pool waters, as well as in the air above pools. Factors that have been found to affect DBP formation in pools are discussed. The impact of the swimming pool environment on human health is reviewed.

Organic chloramines in chlorine-based disinfected water systems： A critical review

This paper is a critical review of current knowledge of organic chloramines in water systems,including their formation, stability, toxicity, analytical methods for detection, and their impact on drinking water treatment and quality. The term organic chloramines may refer to any halogenated organic compounds measured as part of combined chlorine（the difference between the measured free and total chlorine concentrations）, and may include N-chloramines,N-chloramino acids, N-chloraldimines and N-chloramides. Organic chloramines can form when dissolved organic nitrogen or dissolved organic carbon react with either free chlorine or inorganic chloramines. They are potentially harmful to humans and may exist as an intermediate for other disinfection by-products. However, little information is available on the formation or occurrence of organic chloramines in water due to a number of challenges. One of the biggest challenges for the identification and quantification of organic chloramines in water systems is the lack of appropriate analytical methods. In addition, many of the organic chloramines that form during disinfection are unstable, which results in difficulties in sampling and detection. To date research has focussed on the study of organic monochloramines.However, given that breakpoint chlorination is commonly undertaken in water treatment systems, the formation of organic dichloramines should also be considered. Organic chloramines can be formed from many different precursors and pathways. Therefore, studying the occurrence of their precursors in water systems would enable better prediction and management of their formation.

Formation of iodo-trihalomethanes, iodo-haloacetic acids, and haloacetaldehydes during chlorination and chloramination of iodine containing waters in laboratory controlled reactions

Iodine containing disinfection by-products（I-DBPs） and haloacetaldehydes（HALs） are emerging disinfection by-product（DBP） classes of concern. The former due to its increased potential toxicity and the latter because it was found to be the third most relevant DBP class in mass in a U.S. nationwide drinking water study. These DBP classes have been scarcely investigated, and this work was performed to further explore their formation in drinking water under chlorination and chloramination scenarios. In order to do this, iodo-trihalomethanes（I-THMs）,iodo-haloacetic acids（I-HAAs） and selected HALs（mono-HALs and di-HALs species, including iodoacetaldehyde） were investigated in DBP mixtures generated after chlorination and chloramination of different water matrices containing different levels of bromide and iodide in laboratory controlled reactions. Results confirmed the enhancement of I-DBP formation in the presence of monochloramine. While I-THMs and I-HAAs contributed almost equally to total I-DBP concentrations in chlorinated water, I-THMs contributed the most to total I-DBP levels in the case of chloraminated water. The most abundant and common I-THM species generated were bromochloroiodomethane, dichloroiodomethane, and chlorodiiodomethane. Iodoacetic acid and chloroiodoacetic acid contributed the most to the total I-HAA concentrations measured in the investigated disinfected water. As for the studied HALs, dihalogenated species were the compounds that predominantly formed under both investigated treatments.

UV light tolerance and reactivation potential of tetracycline-resistant bacteria from secondary effluents of a wastewater treatment plant

Tetracycline-resistant bacteria（TRB） are of concern as emerging microbial contaminants in reclaimed water.To understand the effects of UV disinfection on TRB,both inactivation and reactivation profiles of TRB,as well as 16 tetracycline-resistant isolates from secondary effluent,were characterized in this study.The inactivation ratio of TRB was significantly lower（3.0-log） than that of heterotrophic bacteria（〉4.0-log） in the secondary effluent.Additionally,the proportion of TRB significantly increased from 1.65%to 15.51%under20 mJ/cm^2 ultraviolet（UV） exposure.The inactivation rates of tetracycline-resistant isolates ranged from 0.57/s to 1.04/s,of which tetracycline-resistant Enterobacter-1 was the most tolerant to UV light.The reactivation of TRB,tetracycline-resistant isolated strains,as well as heterotrophic bacteria commonly occurred in the secondary effluent even after20 mJ/cm^2 UV exposure.The colony forming ability of TRB and heterotrophic bacteria reached 3.2-log and 3.0-log under 20 mJ/cm^2 UV exposure after 22 hr incubation.The final inactivation ratio of tetracycline-resistant Enterobacter-1 was 1.18-log under 20 mJ/cm^2 UV exposure after 22 hr incubation,which is similar to those of TRB（1.18-log） and heterotrophic bacteria（1.19-log）.The increased proportion of TRB and the reactivation of tetracycline-resistant enterobacteria in reclaimed water could induce a microbial health risk during wastewater reuse.