Progress in Analytical Methods of Halogenated Disinfection By-Products

Ensuring the health and safety of drinking water is crucial for both nations and their citizens.Since the 20th century,the disinfection of drinking water,effectively controlling pathogens in water sources,has become one of the significant advances in public health.However,the disinfectants used in the process,such as chlorine and chlorine dioxide,react with natural organic matter in the water to produce disinfection by-products(DBPs).Most of these DBPs contain chlorine,and if the source water contains bromine or iodine,brominated or iodinated DBPs,collectively referred to as Halogenated disinfection byproducts(X-DBPs),are formed.Numerous studies have found that X-DBPs pose potential risks to human health and the environment,leading to widespread concern.Mass spectrometry has become an important means of discovering new types of X-DBPs.This paper focuses on the study of methods for analyzing X-DBPs in drinking water using mass spectrometry.

Simultaneous Control of Microorganisms and Disinfection By-products by Sequential Chlorination

Objective To introduce a new sequential chlorination disinfection process in which short-term free chlorine and chloramine are sequentially added. Methods Pilot tests of this sequential chlorination were carried out in a drinking water plant. Results The sequential chlorination disinfection process had the same or better efficiency on microbe （including virus） inactivation compared with the free chlorine disinfection process. There seemed to be some synergetic disinfection effect between free chlorine and monochloramine because they attacked different targets. The sequential chlorination disinfection process resulted in 35.7%-77.0% TTHM formation and 36.6%-54.8% THAA5 formation less than the free chlorination process. The poorer the water quality was, the more advantage the sequential chlorination disinfection had over the free chlorination. Conclusion This process takes advantages of free chlorine＇s quick inactivation of microorganisms and chloramine＇s low disinfection by-product （DBP） yield and long-term residual effect, allowing simultaneous control of microbes and DBPs in an effective and economic way.

Removal of disinfection by-products formation potential by biologically intensified process

The removal of disinfection by-products formation potential(DBPFP) in artificially intensified biological activated carbon(IBAC) process which is developed on the basis of traditional ozone granular activated carbon was evaluated. By IBAC removals of 31% and 68% for THMFP and HAAFP were obtained respectively. Under identical conditions, the removals of the same substances were 4% and 32% respectively only by the granular activated carbon(GAC) process. Compared with GAC, the high removal rates of the two formed potential substances were due to the increasing of bioactivity of the media and the synergistic capabilities of biological degradation cooperating with activated carbon adsorption of organic compounds. A clear linear correlation(R 2=0.9562 and R 2=0.9007) between DOC HAAFP removal rate and Empty Bed Contact Time(EBCT) of IBAC process was observed, while that between THMFP removal rate and EBCT of GAC was R 2=0.9782. In addition certain linear correlations between THMFP, HAAFP and UV 254 (R 2=0.855 and R 2=0.7702) were found for the treated water. For IBAC process there are also more advantages such as long backwashing cycle time, low backwashing intensity and prolonging activated carbon lifetime and so on.

Removal characteristics of disinfection by-products formation potential by bioaugmentation activated carbon process

The high-active bacteria were screened from 8 dominant bacteria obtained from the natural water body,and then the bioaugmentation activated carbon was formed by hydraulic immobilization of the high-active bacteria. Plant-scale studies on removal characteristics of disinfection by-products formation potentials (DBPFP) by bioaugmentation activated carbon process were conducted for micro-polluted raw water treatment. The results show that the bioaugmentation activated carbon process has adopted better purification efficiency to THMFP and HAAFP than traditional biological activated carbon process,and that average removal efficiencies of THMFP and HAAFP can reach 35% and 39.7% during the test period,increasing by more than 10% compared with traditional biological activated carbon process. The removal efficiencies of THMFP and HAAFP are stable because of the biodegradation of the high-active bacteria and the adsorption of active carbon. The biodegradability of CHCl3 formation potential is better as compared with that of CHCl2Br and CHClBr2 formation potentials among THMFP,and high removal efficiency of CHCl3formation potential is obtained by bioaugmentation degradation of the high-active bacteria. The biodegradability of HAAFP is better in comparison with that of THMFP,and the chemical properties of HAAFP are propitious to adsorption of activated carbon. Thus,HAAFP is on predominance during the competitive removal process with THMFP.

Less pressure contributes to gravity-driven membrane ultrafiltration with greater performance:Enhanced driving efficiency and reduced disinfection by-products formation potential

Gravity-driven membrane(GDM)systems have been well developed previously;however,impacts of driving(i.e.,transmembrane)pressure on their performance received little attention,which may infuence GDM performance.In this study,we evaluated 4 GDM systems via altering the transmembrane pressure from 50 mbar to 150 mbar with 2 groups,treating surface water in Beijing,China.Results showed that less driving pressure was more favorable.Specifically,compared to groups(150 mbar),groups under a pressure of 50 mbar were found to have greater normalized permeability and lower total resistance.During the whole operation period,the quality of effuents was gradually improved.For example,the removal efficiency of UV254was significantly improved;particularly,under low driving pressure,the removal efficiency of UV254in PES GDM system increased by 11.91%,as compared to the corresponding system under high driving pressure.This observation was consistent with the reduction on disinfection by-products(DBPs)formation potential;groups under 50 mbar achieved better DBPs potential control,indicating the advantages of lower driving pressure.Biofilms were analyzed and responsible for these differences,and distinct distributions of bacteria communities of two GDM systems under 50 and 150 mbar may be responsible for various humic-like substances removal efficiency.Overall,GDM systems under less pressure should be considered and expected to provide suggestions on the design of GDM systems in real applications.

Degradation of iopamidol in the permanganate/sulfite process:Evolution of iodine species and effect on the subsequent formation of disinfection by-products

Permanganate/sulfite(Mn(VII)/S(IV))process is a promising pre-oxidation technology for sequestering the emerging organic contaminants in drinking water treatment plant.Iopamidol(IPM),a representative of iodinated X-ray contrast media,has been widely detected in water sources and has the risk of forming iodinated disinfection byproducts(I-DBPs)in water treatment system.In this study,we investigated the evolution of iodine species during the IPM degradation by the Mn(VII)/S(IV)process and its effect on the subsequent formation of I-DBPs during chlorination at pH 7.0 and 8.0.IPM could be effectively degraded in the Mn(VII)/S(IV)process at environmentally relevant pH(pH 7.0 and 8.0).The results of quenching and competitive oxidation kinetic experiments revealed that SO^(·-)_(4)was the major reactive oxidizing species contributing to the degradation of IPM whereas the contributions of HO·and reactive manganese species were negligible in the Mn(VII)/S(IV)process.I–and IO–3were generated while no HOI was detected during the degradation of IPM in the Mn(VII)/S(IV)process.The effects of IPM oxidation by Mn(VII)/S(IV)on the subsequent formation of chlorinated disinfection by-products(Cl-DBPs)during chlorination were related to the category of Cl-DBPs.The pre-oxidation of IPM by Mn(VII)/S(IV)resulted in the generation of I-DBPs during the disinfection process although no I-DBPs were detected if no pre-oxidation was applied.The finding of this study suggested that attention should be paid to the toxicity of DBPs when water containing iodinated organic contaminants is treated by Mn(VII)/S(IV)process or other pre-oxidation technologies.

Characteristics of typical dissolved black carbons and their influence on the formation of disinfection by-products in chlor(am)ination

Dissolved black carbon(DBC)released from biochar can be one of the potential disinfection by-products(DBPs)precursors in the dissolved organic matter pool.However,the physiochemical and structural properties of DBC and the effects on the development of DBPs and DBP formation potential(DBPFP)during the disinfection process remain unclear.In this study,the characteristics of two kinds of DBC,namely,animal-derived DBC(poultry litter DBC,PL-DBC)and plant-derived DBC(wheat straw DBC,WS-DBC),were investigated.The effects of different kinds of DBC on the evolution of DBPs and DBPFP in chlorine and chloramine disinfection processes were compared with natural organic matter(NOM).The results showed that the total DBPs concentrations derived from PL-DBC,WS-DBC and NOM were similar during chlorination(i.e.,61.23µg/L,64.59µg/L and 64.66µg/L,respectively)and chloramination(i.e.,44.63µg/L,44.42µg/L and 45.58µg/L,respectively).The lower total DBPs and DBPFP concentrations in chloramination could be attributed to the fact that the introduction of ammonia in chloramine inhibited the breaking of the bond between the disinfectant and the active group of the precursor.Additionally,DBC presented much lower total DBPFP concentrations than NOM in both chlorination and chloramination.However,both kinds of DBC tended to form more monochloroacetic acids and haloacetamides than NOM,which could result from the higher organic strength,higher protein matter,and nitrogen-rich soluble microbial products of DBC.

Removal of organic matter and disinfection by-products precursors in a hybrid process combining ozonation with ceramic membrane ultrafiltration

The performance of an integrated process including coagulation, ozonation, ceramic ultrafiltration （UF） and biologic activated carbon （BAC） filtration was investigated for the removal of organic matter and disinfection by-products （DBPs） precursors from micropolluted surface water. A pilot scale plant with the capacity of 120 m3 per day was set up and operated for the treatment of drinking water. Ceramic membranes were used with the filtration area of 50 m2 and a pore size of 60 nm. Dissolved organic matter was divided into five fractions including hydrophobic acid （HoA）, base （HOB） and neutral （HoN）, weakly hydrophobic acid （WHOA） and hydrophilic matter （HIM） by DAX-8 and XAD-4 resins. The experiment results showed that the removal of organic matter was significantly improved with ozonation in advance. In sum, the integrated process removed 73% of dissolved organic carbon （DOC）, 87% of UV254, 77% of trihalomethane （THMs） precursors, 76% of haloacetic acid （HAAs） precursors, 83%of trichloracetic aldehyde （CH） precursor, 77% of dichloroaeetonitrile （DCAN） precursor, 51% of trichloroacetonitrile （TCAN） precursor, 96% of 1,1,1- trichloroacetone （TCP） precursor and 63% of trichloroni- tromethane （TCNM） precursor. Hydrophobic organic matter was converted into hydrophilic organic matter during ozonation/UF, while the organic matter with molecular weight of 1000-3000 Da was remarkably decreased and converted into lower molecular weight organic matter ranged from 200-500 Da. DOC had a close linear relationship with the formation potential of DBPs.

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,

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.

Identification of key precursors contributing to the formation of CX_(3)R-type disinfection by-products along the typical full-scale drinking water treatment processes

Identification and characterization of disinfection by-product(DBP)precursors could help optimize drinkingwater treatment processes and improve the quality of finishedwater.This study comprehensively investigated the characteristics of dissolved organic matter(DOM),the hydrophilicity and molecule weight(MW)of DBP precursor and DBP-associated toxicity along the typical full-scale treatment processes.The results showed that dissolved organic carbon and dissolved organic nitrogen content,the fluorescence intensity and the SUVA254 value in raw water significantly decreased after the whole treatment processes.Conventional treatment processes were in favor of the removal of high-MW and hydrophobic DOM,which are important precursors of trihalomethane and haloacetic acid.Compared with conventional treatment processes,Ozone integrated with biological activated carbon(O3-BAC)processes enhanced the removal efficiencies of DOM with different MW and hydrophobic fractions,leading to a further decrease in almost all DBP formation potential and DBP-associated toxicity.However,almost 50%of the detected DBP precursors in raw water has not been removed after the coagulation-sedimentation-filtration integrated with O3-BAC advanced treatment processes.These remaining precursors were found to be mainly hydrophilic and low-MW(<1.0 kDa)organics.Moreover,they would largely contribute to the formation of haloacetaldehydes and haloacetonitriles,which dominated the calculated cytotoxicity.Since current drinking water treatment process could not effectively control the highly toxic DBPs,the removal of hydrophilic and low-MW organics in drinking water treatment plants should be focused on in the future.

The impact of iodinated X-ray contrast agents on formation and toxicity of disinfection by-products in drinking water

The presence of iodinated X-ray contrast media（ICM） in source waters is of high concern to public health because of their potential to generate highly toxic disinfection by-products（DBPs）. The objective of this study was to determine the impact of ICM in source waters and the type of disinfectant on the overall toxicity of DBP mixtures and to determine which ICM and reaction conditions give rise to toxic by-products. Source waters collected from Akron,OH were treated with five different ICMs, including iopamidol, iopromide, iohexol,diatrizoate and iomeprol, with or without chlorine or chloramine disinfection. The reaction product mixtures were concentrated with XAD resins and the mammalian cell cytotoxicity and genotoxicity of the reaction mixture concentrates was measured. Water containing iopamidol generated an enhanced level of mammalian cell cytotoxicity and genotoxicity after disinfection. While chlorine disinfection with iopamidol resulted in the highest cytotoxicity overall, the relative iopamidol-mediated increase in toxicity was greater when chloramine was used as the disinfectant compared with chlorine. Four other ICMs（iopromide, iohexol, diatrizoate, and iomeprol） expressed some cytotoxicity over the control without any disinfection, and induced higher cytotoxicity when chlorinated. Only iohexol enhanced genotoxicity compared to the chlorinated source water.

Concentration levels of disinfection by-products in 14 swimming pools of China

Swimming has become a popular exercising and recreational activity in China but little is known about the disinfection by-products （DBPs） concentration levels in the pools. This study was conducted as a survey of the DBPs in China swimming pools, and to establish the correlations between the DBP concentrations and the pool water quality parameters. A total of 14 public indoor and outdoor pools in Beijing were included in the survey. Results showed that the median concentrations for total tfihalomethanes （TTHM）, nine haloacetic acids （HAA9）, chloral hydrate （CH）, four haloacetonitriles （HAN4）, 1,1- dichloropropanone, 1,1,1-trichloropropanone and trichlor- onitromethane were 33.8, 109.1, 30.1, 3.2, 0.3, 0.6 pg＇L-1 and below detection limit, respectively. The TTHM and HAA9 levels were in the same magnitude of that in many regions of the world. The levels of CH and nitrogenous DBPs were greatly higher than and were comparable to that in typical drinking water, respectively. Disinfection by chlorine dioxide or trichloroisocyanuric acid could sub- stantially lower the DBP levels. The outdoor pools had higher TTHM and HAA9 levels, but lower trihaloacetic acids （THAA） levels than the indoor pools. The TTHM and HAA9 concentrations could be moderately correlated with the free chlorine and total chlorine residuals but not with the total organic carbon （TOC） contents. When the DBP concentration levels from other survey studies were also included for statistical analysis, a good correlation could be established between the TTHM levels and the TOC concentration. The influence of chlorine residual on DBP levels could also be significant.

Evaluation of N-acetylcysteine and glutathione as quenching agents for the analysis of halogenated disinfection by-products

Disinfection by-products(DBPs), formed from the reactions of disinfectants with natural organic matter and halides in drinking water, were considered to be cytotoxic and genotoxic, and might trigger various cancers. The relatively low concentration of DBPs in finished water(low μg/L or even ng/L levels) and the interference from water matrix inhibited in situ determination of DBPs. Moreover, the further formation and degradation of DBPs by disinfectants during the holding time(several hours to several days) from sample collection to analysis could adversely affect the determination of DBPs. To obtain accurate, precise and reliable data of DBP occurrence and formation, robust and reliable sample preservation is indispensable. However, the commonly used quenching agents(e.g., sodium sulfite, sodium thiosulfate, and ascorbic acid) for sample preservation can decompose reactive DBPs by reductive dehalogenation. This study evaluated the performance of N-acetylcysteine(NAC) and glutathione(GSH) as quenching agents for the analysis of halogenated DBPs by investigating the stoichiometry of the disinfectant-quenching agent reaction, the formation of DBPs during chlor(am)ination of NAC or GSH, and the effects of NAC or GSH on the stability of 18 individual DBPs and total organic halogen(TOX). Based on the results of this study, NAC and GSH were considered to be ideal quenching agents for the analysis of most DBPs and TOX, except halonitromethanes.

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.

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,

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.

Concentrations of disinfection by-products in swimming pool following modifications of the water treatment process:An exploratory study

The formation and concentration of disinfection by-products（DBPs） in pool water and the ambient air vary according to the type of water treatment process used. This exploratory study was aimed at investigating the short-term impact of modifications of the water treatment process on traditional DBP levels（e.g., trihalomethanes（THMs）, chloramines） and emerging DBPs（e.g., Halonitromethanes, Haloketones, NDMA） in swimming pool water and/or air. A sampling program was carried to understand the impact of the following changes made successively to the standard water treatment process： activation of ultraviolet（UV）photoreactor, halt of air stripping with continuation of air extraction from the buffer tank,halt of air stripping and suppression of air extraction from the buffer tank, suppression of the polyaluminium silicate sulfate（PASS） coagulant. UV caused a high increase of Halonitromethanes（8.4 fold）, Haloketones（2.1 fold）, and THMs in the water（1.7 fold） and, of THMs in the air（1.6 fold） and contributed to reducing the level of chloramines in the air（1.6fold） and NDMA in the water（2.1 fold）. The results highlight the positive impact of air stripping in reducing volatile contaminants. The PASS did not change the presence of DBPs, except for the THMs, which decrease slightly with the use of this coagulant. This study shows that modifications affecting the water treatment process can rapidly produce important and variable impacts on DBP levels in water and air and suggests that implementation of any water treatment process to reduce DBP levels should take into account the specific context of each swimming pool.

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.