Disinfection Byproducts and Their Precursors in Drinking Water Sources:Origins,Influencing Factors,and Environmental Insights

Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as they tend to be laborious,time-consuming,or technically difficult.Disinfection byproducts(DBPs)are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection treatment.Since DBP precursors have various origins(e.g.,natural,domestic,industrial,and agricultural sources),and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive,we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution origins.After providing a retrospective of the origins of DBPs and DBP precursors,as well as the specific formation patterns of DBPs from different precursors,this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water sources.In practice,the DBPs(i.e.,their concentration and speciation)originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative metrics.When jointly used with other water quality parameters(e.g.,dissolved organic carbon,dissolved organic nitrogen,fluorescence,and molecular weight distribution)and specific contaminants of emerging concern(e.g.,certain pharmaceuticals and personal care products),DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.

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.

Characterization of dissolved organic matter fractions and its relationship with the disinfection by-product formation

Dissolved organic matter （DOM） has been identified as precursor for disinfection by-products （DBPs） formation during chlorination. Recently, it has been demonstrated that the characteristics of DOM influence the DBPs formation mechanism. A study was, therefore, initiated to investigate the effects of DOM fractions on DBPs formation mechanism. In the chlorination process, organic acids are dominant precursors of total thihalomethanes （TTHM） because of the vc-o and unsaturated structures. Furthermore, the TTHM formation of organic acids was affected by pH more greatly. Based on the fluorescence spectroscopy analysis, DOM fractions contained several fluorescence substances. During chlorination, humic acid-like substances were found to exhibit high chlorine reactivity and hydrophobic organics decomposed to smaller molecules faster than hydrophilic organics even at lower chlorine dosages. Unlike hydrophobic fractions, hydrophilic organics showed no toxicity following chlorination, suggesting that the toxic structures in hydrophihc organics showed high chlorine reactivity during chlorination.

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.

Health Risk Assessment of Employees Exposed to Chlorination By-products of Recreational Water in Large Amusement Parks in Shanghai

Objective Chlorination is often used to disinfect recreational water in large amusement parks;however,the health hazards of chlorination disinfection by-products(DBPs)to occupational populations are unknown.This study aimed to assess the exposure status of chlorinated DBPs in recreational water and the health risks to employees of large amusement parks.Methods Exposure parameters of employees of three large amusement parks in Shanghai were investigated using a questionnaire.Seven typical chlorinated DBPs in recreational water and spray samples were quantified by gas chromatography,and the health risks to amusement park employees exposed to chlorinated DBPs were evaluated according to the WHO's risk assessment framework.Results Trichloroacetic acid,dibromochloromethane,bromodichloromethane,and dichloroacetic acid were detected predominantly in recreational water.The carcinogenic and non-carcinogenic risks of the five DBPs did not exceed the risk thresholds.In addition,the carcinogenic and non-carcinogenic risks of mixed exposure to DBPs were within the acceptable risk limits.Conclusion Typical DBPs were widely detected in recreational water collected from three large amusement parks in Shanghai;however,the health risks of DBPs and their mixtures were within acceptable limits.

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.

Waste Water Disinfection During SARS Epidemic for Microbiological and Toxicological Control

Objective To evaluate the disinfection of wastewater in China. Methods During the SARS epidemic occurred in Beijing, a study of different disinfection methods used in the main local wastewater plants including means of chlorine, chlorine dioxide, ozone, and ultraviolet was carried out in our laboratory. The residual coliform, bacteria and trihalomethanes, haloacetic acids were determined after disinfection. Results Chlorine had fairly better efficiency on microorganism inactivation than chlorine dioxide with the same dosage. Formation of THMs and HAAs does not exceed the drinking water standard. UV irradiation had good efficiency on microorganism inactivation and good future of application in China. Organic material and ammonia nitrogen was found to be significant on inactivation and DBPs formation. Conclusion Chlorine disinfection seems to be the best available technology for coliform and bacteria inactivation. And it is of fairly low toxicological hazard due to the transformation of monochloramine.

Disinfection of swimming pools with chlorine and derivatives: formation of organochlorinated and organobrominated compounds and exposure of pool personnel and swimmers

Chlorination of pool water leads to the forma-tion of many by-products, chloroform usually being the most abundant. The paper reports the results of a study evaluating exposure of bath-ers and pool employees to trihalomethanes (chloroform, bromodichloromethane, dibromo-chloromethane, bromoform) in four indoor swimming pools with chlorinated water. Chlo-roform concentrations in environmental air samples when the pool was in use (about 9 h), in the range 1-182 μg/m3, were greater near the pool than in the change rooms, passageways and offices. Chloroform concentrations in per-sonal air samples of pool employees were in the range 18-138 μg/m3. Urinary concentrations of chloroform averaged (geometric means) 0.123 and 0.165 μg/l and 0.404 and 0.342 μg/l prior and at the end of exposure during in water and out of water activities, respectively. The significant increase in urinary excretion of chloroform confirms that the source of the contaminant was pool water. Absorption of chloroform, estimated from airborne and water concentrations, was significantly correlated with delta chloroform (after/before exposure) and urinary concentra-tions of chloroform at the end of exposure. As chloroform is a toxic and possibly carcinogenic substance, these observations pose a problem principally for the general population of pool users.

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.

Alternate disinfection approaches or raise disinfectant dosages for sewage treatment plants to address the COVID-19 pandemic?From disinfection efficiency,DBP formation,and toxicity perspectives

During the COVID-19 pandemic,most sewage treatment plants increased disinfectant dosages to inactivate pathogenic viruses and microorganisms more effectively.However,this approach also led to the production of more disinfection by-products(DBPs).To ensure both disinfection efficiency and a reduction in DBP formation,new disinfection protocols are required.In this study,the disinfection efficiency,DBP amounts,and toxicity changes resulting from ozone(O_(3)),ultraviolet(UV),chlorine(Cl_(2)),and their combined processes were examined.The results demonstrated that the O_(3)/UV/Cl_(2)combination achieved the highest disinfection efficiency.Chlorination produced the most DBPs,whereas UV treatment reduced the formation of trihalomethane(THM),halogenated ketones(HKs),haloacetic acids(HAA),dichloroacetonitrile(DCAN)and N-nitrosodimethylamine(NDMA)by 45.9%,52.6%,82.0%,67.95%,and 47%,respectively.O_(3)also significantly reduced their production by 99.1%,91.1%,99.5%,100%,and 35%.Intracellular organic matter(IOM)was identified as the primary DBP precursors,producing 2.94 times more DBPs than extracellular organic matter(EOM).The increased DBP formation during chlorination was attributed to IOM leakage and cell membrane damage,which was verified using scanning electron microscopy(SEM).The toxicities of DBPs were evaluated for six disinfection methods,revealing inconsistent results.The overall toxicities were assessed using zebrafish embryo experiments.Both evaluations indicated that chlorination alone was the least favorable method.In addition,the toxicities followed a sequence:Cl_(2)≈O_(3)/Cl_(2)>O_(3)>O_(3)/UV/Cl_(2)>UV>UV/Cl_(2).These findings can serve as a reference for sewage treatment plants in selecting appropriate disinfection methods to manage the COVID-19 epidemic from comprehensive perspective.

Impact of ozonation on disinfection byproducts formation from phenylalanine during chlorination

As a strong oxidizing agent,ozone is used in some water treatment facilities for disinfection,taste and odor control,and removal of organic micropollutants.Phenylalanine(Phe)was used as the target amino acid to comprehensively investigate variability of disinfection byproducts(DBPs)formation during chlorine disinfection and residual chlorine conditions subsequent to ozonation.The results showed that subsequent to ozonation,the typical regulated and unregulated DBPs formation potential(DBPsFP),including trichloromethane(TCM),dichloroacetonitrile(DCAN),chloral hydrate(CH),dichloroacetic acid(DCAA),trichloroacetic acid(TCAA),and trichloroacetamide(TCAcAm)increased substantially,by 2.4,3.3,5.6,1.2,2.5,and 6.0 times,respectively,compared with only chlorination.Ozonation also significantly increased the DBPs yield under a 2 day simulated residual chlorine condition that mimicked the water distribution system.DBPs formations followed pseudo first order kinetics.The formation rates of DBPs in the first 6 hr were higher for TCM(0.214 hr^(−1)),DCAN(0.244 hr^(−1)),CH(0.105 hr^(−1)),TCAcAm(0.234 hr^(−1)),DCAA(0.375 hr^(−1))and TCAA(0.190 hr^(−1))than thereafter.The peak DBPsFP of TCM,DCAN,CH,TCAcAm,DCAA,and TCAA were obtained when that ozonation time was set at 5–15 min.Ozonation times>30 min increased the mineralization of Phe and decreased the formation of DBPs upon chlorination.Increasing bromine ion(Br^(−1))concentration increased production of bromine-DBPs and decreased chlorine-DBPs formation by 59.3%–92.2%.Higher ozone dosages and slight alkaline favored to reduce DBP formation and cytotoxicity.The ozonation conditions should be optimized for all application purposes including DBPs reduction.

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.

Genotoxicity Induced by Low Dose and Mixed Exposure to Haloacetaldehydes,an Emerging Class of Drinking Water Disinfection By-products

Haloacetaldehydes(HALs)are the third largest disinfection by-products(DBPs)class by mass in drinking water.Most of them alone in high doses are more cytotoxic and genotoxic than regulated DBPs.However,the toxic effects of mixed exposure to HALs at environmentally relevant levels are still unknown.Given that genotoxicity is critical for risk assessment,we employed multiple genotoxic tests including the Salmonella typhimurium revertant mutation assay(Ames assay),the single cell gel electrophoresis(SCGE)assay,the cytoplasmic blocking micronucleus(CBMN)assay,and theγ-H2AX assay to investigate the genotoxicity of HALs based on the HALs concentrations and components detected in the finished drinking water of Shanghai,China.The results demonstrated the concentrations of HALs were low,ranging from 0.04µg/L to 4.47µg/L,and the total concentration was 10.85µg/L.Although the mutagenicity of HALs was negative even at 1000-fold concentrations in the real world,mixed exposure to 100 and 1000-fold concentrations HALs resulted in DNA and chromosomal damage in human hepotocyte(HepG2)cells.HALs significantly increased the levels of reactive oxygen species(ROS)andγ-H2AX and activated nuclear factor erythroid-derived factor 2-related factor 2(NRF2)pathway-related protein expressions in HepG2 cells.The antioxidant NAC could ameliorate NRF2 pathway-related protein expression and DNA damage caused by HALs,suggesting that the genotoxicity of mixed exposure to HALs involved cellular oxidative stress and NRF2 pathway activation.

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.

Control of Bromate and THM Precursors Using Ozonation Combined System

Objective To investigate the feasibility of reducing THM precursors and controlling bromate taste and odor in drinking water taken from the Yellow River by an ozonation combined system. Methods The appropriate ozone dosage was determined, and then the changes of TOC, UV254 and THM formation potential （THMFP） in the combined system were evaluated. Results One mg/L ozone could effectively remove taste and odor and meet the maximum allowable bromate level in drinking water. The pre-ozonation increased THMFP, but the conventional treatment system could effectively reduce the odor. The bio-ceramic filter could partly reduce CHC13FP, but sometimes might increase CHCl2BrFP and CHClBr2FP. The biological activated carbon （BAC） filter could effectively reduce CHC13FP and CHCl2BrFP, but increase CHClBr2FP. Compared with other filters, the fresh activated carbon （FAC） filter performed better in reducing THMFP and even reduced CHClBr2FP. Conclusion The combined system can effectively reduce taste, odor, CHC13FP, and CHCl2BrFP and also bring bromate under control.

Toxicity effects of disinfection byproduct chloroacetic acid to Microcystis aeruginosa: Cytotoxicity and mechanisms

Chlorine-based disinfectants are widely used for disinfection in wastewater treatment.The mechanism of the effects of chlorinated disinfection by-products on cyanobacteria was unclear.Herein,the physiological effects of chloroacetic acid(CAA)on Microcystis aeruginosa(M.aeruginosa),including acute toxicity,oxidative stress,apoptosis,production of microcystin-LR(MC-LR),and the microcystin transportation-related gene mcyH transcript abundance have been investigated.CAA exposure resulted in a significant change in the cell ultrastructure,including thylakoid damage,disappearance of nucleoid,production of gas vacuoles,increase in starch granule,accumulation of lipid droplets,and disruption of cytoplasm membranes.Meanwhile,the apoptosis rate of M.aeruginosa increased with CAA concentration.The production of MC-LR was affected by CAA,and the transcript abundance of mcyH decreased.Our results suggested that CAA poses acute toxicity to M.aeruginosa,and it could cause oxidative damage,stimulate MC-LR production,and damage cell ultrastructure.This study may provide information about the minimum concentration of CAA in the water environment,which is safe for aquatic organisms,especially during the global coronavirus disease 2019 pandemic period.

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.

Enhanced removal of organic matter and typical disinfection byproduct precursors in combined iron–carbon micro electrolysis-UBAF process for drinking water pre-treatment

The organic matter and two types of disinfection byproduct(DBP) precursors in micropolluted source water were removed using an iron–carbon micro-electrolysis(ICME)combined with up-flow biological aerated filter(UBAF) process. Two pilot-scale experiments(ICME-UBAF and UBAF alone) were used to investigate the effect of the ICME system on the removal of organic matter and DBP precursors. The results showed that ICME pretreatment removed 15.6% of dissolved organic matter(DOM)and significantly improved the removal rate in the subsequent UBAF process. The ICME system removed 31% of trichloromethane(TCM) precursors and 20% of dichloroacetonitrile(DCAN) precursors. The results of measurements of the molecular weight distribution and hydrophilic fractions of DOM and DBP precursors showed that ICME pretreatment played a key role in breaking large-molecular-weight organic matter into low-molecular-weight components, and the hydrophobic fraction into hydrophilic compounds, which was favorable for subsequent biodegradation by UBAF.Three-dimensional fluorescence spectroscopy(3D-EEM) further indicated that the ICME system improved the removal of TCM and DCAN precursors. The biomass analysis indicated the presence of a larger and more diverse microbial community in the ICME-UBAF system than for the UBAF alone. The high-throughput sequencing results revealed that domination of the genera Sphingomonas, Brevundimonas and Sphingorhabdus contributed to the better removal of organic matter and two types of DBP precursors. Also, Nitrosomonas and Pseudomonas were beneficial for ammonia removal.