Atmospheric particulate matter (PM) can be scavenged by rainfall and contribute dissolved organic matter (DOM) to rainwater. Rainwater may serve as a part or the whole of drinking water sources, ...leading to the introduction of PM-derived DOM into drinking water. However, little information is available on the role of PM-derived DOM as a remarkable precursor of CX3R-type disinfection by-products (DBPs) in rainwater. In this study, samples were collected from ten occurrences of rainfall in Shanghai and batch experiments were executed to explore the contribution of PM-derived DOM to CX3R-type DBP formation in rainwater and to further understand some of unknowns regarding its characteristics. Results revealed that a part of PM was scavenged by rainfall and the scavenge performance was better for smaller PM. The formation potentials (FPs) of individual CX3R-type DBP were similar among size-isolated PM. TCM was predominant (around 0.5–4.5 μg-C/mg-C) and TCAA was the secondary (around 0.6–3.2 μg-C/mg-C) among all detectable CX3R-type DBPs. Based on the PM removal data and DBP FP results, the contribution of PM-derived DOM to CX3R-type DBP formation in rainwater was modeled. Furthermore, aromatic proteins and soluble microbial product-like compounds were found to be significant compositions, which were reported to be DBP precursors. And low molecular weight (< 10 kDa) DOM derived from total PM and rainwater exhibited higher CX3R-type DBP FPs. DOM fractions with higher SUVA254 and SUVA285 values gave relatively higher yields of CX3R-type DBPs, indicating that aromatic compounds played an important role in DBP formation.
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•Rainfall decreased PM level and PM contributed DOM to rainwater.•PM-derived DOM contributed to a fraction of CX3R-type DBP formation in rainwater.•Low MW DOM derived from PM and rainwater exhibited higher CX3R-type DBP FPs.•Aromatic compounds in PM can be significant precursors of CX3R-type DBPs.
•Effects of various MW NOM on DBPFP and DBPs in the NF-treated water were investigated.•The medium molecular weight NOM protected NF from fouling.•The medium molecular weight NOM reduced the DBPFP or ...DBPs in the NF treated water.•The medium molecular weight NOM works through forming a layer on the NF membrane.
Nanofiltration (NF) is utilized in water treatment for controlling disinfection by-products formation potential (DBPFP) and disinfection by-products (DBPs). Attention regarding NF-based technology has been paid on membrane fouling of NF and the rejection efficiency of contaminants by NF membranes. Natural organic matter (NOM) presenting in surface waters is one main removal target in drinking water treatment by NF-based technology, and is thereby a contributor to the membrane fouling of NF. In application, pretreatments of other membrane filtration (e.g., microfiltration (MF) and ultrafiltration (UF)) has been taken prior to NF, resulting in the separation of NOM of specific molecular weight. Meanwhile, it is well known that NOM is composed of organic compounds of different molecular weights. However, the effect of NOM of specific molecular weight has been seldom investigated from the aspects of membrane fouling and the resulting DBPFP after membrane filtration. By using combinations of MF and UF (molecular weight cut-off of 100K or 20K) as pretreatment prior to NF, the NOM of various molecular weight on DBPFP and DBPs in the NF-treated water were investigated. The experiments were conducted with two real-world surface water samples and one tap water sample. It was found that medium molecular weight NOM, defined as NOM that passed UF100K but did not pass UF20K in this study, reduced fouling of the NF membrane. This is supported by the excitation and emission matrix (EEM) fluorescence spectra, size exclusion chromatography (SEC) and flux analysis. In addition, the medium molecular weight NOM also reduced the DBPFP in the NF treated water and eventually the DBPs by participating in forming a protective layer on the NF surface, blocking the transfer of small molecular weight NOM into the NF filtrate, thereby reducing the DBPFP of the NF filtrate since small molecular weight NOM was the major contributor to DBPFP in this study.
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•Publications on disinfection byproducts (DBPs) in drinking water were analysed during 1975–2018.•Trihalomethanes, haloacetic acids, and bromate were the main DBPs.•A historical ...review on disinfection byproducts in drinking water was provided.•Research trends of species, detection methods, and removal of DBPs were summarized.
Disinfection is an important part of the drinking water treatment process. Disinfection by-products (DBPs), produced during the disinfection process, can be a threat to human health. Based on the Science Citation Index Expanded from the Web of Science, a total of 3570 publications from 1975 to 2018 on DBPs in drinking water were identified to analyse the present status and tendency. The present review article emphasizes the number of publications, highly cited papers, research areas, authors, leading countries and institutions. The bibliometric review on DBPs in drinking water provides a visual representation of current research focus and future trends. The number of related publications and participating countries has gradually increased each year. The USA is the top productive country with 1405 articles published, followed by China and Canada. These three countries have contributed most of the top 10 productive institutions, and the US EPA was ranked first. Trihalomethanes (THMs), haloacetic acids (HAAs), and bromate are the main DBPs. Disinfection by-product precursors and removal of DBPs are the two issues which are focused on. The main methods of controlling DBPs include coagulation, membrane processes and advanced oxidation. In addition, the overview of current research and the research tendencies on DBPs were analysed and summarized with a timeline. Iodinated, brominated, and nitrogenous DBPs have attracted great attention because of high toxicity. In the following research on DBPs, three aspects should be given special attention: (1) analytical techniques; (2) toxicity and health effects; (3) water quality standards and control methods. The historical review about DBPs in drinking water and a bibliometric analysis of the publications give a global view on future research and identify potential challenges.
Haloacetamides (HAMs), an emerging class of disinfection by-products, have received increasing attention due to their elevated cyto- and genotoxicity. However, only limited information is available ...regarding the iodinated analogues. This study investigated the formation and speciation of iodinated haloacetamides (I-HAMs) and their chlorinated/brominated analogues during the chloramination of bromide and/or iodide-containing waters and a model compound solution over various time periods. The rapid formation of diiodoacetamide (DIAM) was observed during chloramination of three simulated samples, whereas brominated (Br-HAMs) and chlorinated haloacetamides (Cl-HAMs) increased slowly with increasing reaction time. To further understand the differences in the formation of HAMs containing different halogens, experiments with the model compound asparagine in the presence/absence of iodide were conducted. Moreover, iodine utilisation factors and iodine incorporation factors were observed to increase significantly faster and were substantially higher than those of bromine. This implied that, compared with bromide, iodide has substantially greater potential to be transformed to the corresponding HAMs during chloramination, similar to that of other classes of DBPs. That is, I-HAMs formed faster than the other species investigated, including Cl-HAMs and Br-HAMs, in the early reaction stages (0–3 h). The effect of the bromide/iodide ratio (i.e., constant iodide, increasing bromide) on I-HAM formation was also examined. With increasing bromide/iodide ratio, the formation of Br-HAMs increased and dichloroacetamide decreased, but the formation of DIAM was largely unchanged. This was consistent with the constant level of iodide in spite of the increasing bromide. Chlorine and ammonia are applied separately during chloramination in water treatment, so the effect of pre-chlorination (before adding ammonia) on the formation and speciation of I-HAMs during in situ chloramination was also evaluated. Effective mitigation of DIAM formation with in situ chloramination was achieved, and the efficiency improved with increasing pre-chlorination time, where iodide was oxidised to iodate. The HAM-associated cytotoxicity was calculated to determine the change in toxicity at different reaction times, bromide/iodide ratios, and pre-chlorination times. A similar trend as the formation of I-HAMs was observed, which increased rapidly in the first 3 h, but decreased somewhat subsequently. When the bromide/iodide ratio and pre-chlorination time was increased, the calculated toxicity of the HAMs increased (due to more formation of Br-HAMs and less Cl-HAMs) and decreased (due to less DIAM formation), respectively.
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•I-HAMs formed faster than Cl- and Br-HAMs during the early stages of chloramination.•Cl-HAMs shifted to Br-HAMs with increasing bromide, but DIAM was largely unchanged.•Effective mitigation of DIAM formation was achieved by pre-chlorination.•HAM-associated cytotoxicity was mostly driven by the concentration of I-HAMs.
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•IPM could be efficiently degraded by Fe(VI)/sulfite process at pH 6–10.•Sulfate radical was the primary reactive species for IPM decomposition.•Iodine was released from IPM ...degradation.•The released inorganic iodine could be adsorbed by in-situ formed ferric (oxyhydr)oxides.•Fe(VI)/sulfite process reduced the formation of I-DBPs in the subsequent disinfection process.
Iodinated X-ray contrast media (ICM) are widely detected in the aqueous environment, which pose risks of iodinated disinfection by-products (I-DBPs) in the subsequent disinfection treatment. Herein, a novel advanced oxidation process of ferrate(VI) and sulfite (Fe(VI)/sulfite) was employed in removing ICM and controlling I-DBPs formation. The results showed that the Fe(VI)/sulfite process effectively degraded ICM and the removal efficiency of iopamidol (IPM) ranged from 55.4% to 87.7% at pH 6–10 within 120 s. Based on the results of quenching and probing experiments, SO4•- was identified as the predominant oxidant for IPM decomposition at pH 6–10. IPM transformation pathway mainly involved deiodination, hydrogen abstraction, hydroxyl addition, amide hydrolysis, and amino oxidation. The iodine on the benzene ring was released into the solution as I- and then I- was partly oxidized to IO3- during the oxidation of IPM, the concentration of I- and IO3- was 0.34 and 0.13 μM at pH 6, respectively. Then, the formation of I-DBPs in the subsequent disinfection was investigated. It was found that I-DBPs concentration increased with increasing pH and enlarging Fe(VI) dosage as well as slightly increased in the presence of humic acid. Additionally, when solutions were filtered at pH 6 after oxidation, the removal ratios of I- and IO3- were 41.2% and 53.8%, respectively. Because the generated I- and IO3- were adsorbed by in-situ formed ferric (oxyhydr)oxides from Fe(VI) reduction, the yield of I-DBPs was thereby reduced in the subsequent disinfection. Therefore, the Fe(VI)/sulfite process can effectively remove ICM and synchronously control I-DBPs formation in the subsequent disinfection.
The microbial safety of swimming pool waters (SPWs) becomes increasingly important with the popularity of swimming activities. Disinfection aiming at killing microbes in SPWs produces disinfection ...by-products (DBPs), which has attracted considerable public attentions due to their high frequency of occurrence, considerable concentrations and potent toxicity. We reviewed the latest research progress within the last four decades on the regulation, formation, exposure, and treatment of DBPs in the context of SPWs. This paper specifically discussed DBP regulations in different regions, formation mechanisms related with disinfectants, precursors and other various conditions, human exposure assessment reflected by biomarkers or epidemiological evidence, and the control and treatment of DBPs. Compared to drinking water with natural organic matter as the main organic precursor of DBPs, the additional human inputs (i.e., body fluids and personal care products) to SPWs make the water matrix more complicated and lead to the formation of more types and greater concentrations of DBPs. Dermal absorption and inhalation are two main exposure pathways for trihalomethanes while ingestion for haloacetic acids, reflected by DBP occurrence in human matrices including exhaled air, urine, blood, and plasma. Studies show that membrane filtration, advanced oxidation processes, biodegradation, thermal degradation, chemical reduction, and some hybrid processes are the potential DBP treatment technologies. The removal efficiency, possible mechanisms and future challenges of these DBP treatment methods are summarized in this review, which may facilitate their full-scale applications and provide potential directions for further research extension.
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•Body fluid and personal care products are important precursors to DBPs in pool water.•Human exposure to DBPs in swimming pool waters is assessed.•Trihalomethanes are exposed by dermal absorption and inhalation and haloacetic acids by ingestion.•DBP treatment methods, mechanisms and efficiency, and challenges are summarized.
The outbreak of coronavirus infectious disease-2019 (COVID-19) pneumonia raises the concerns of effective deactivation of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in medical ...wastewater by disinfectants. In this study, we evaluated the presence of SARS-CoV-2 viral RNA in septic tanks of Wuchang Cabin Hospital and found a striking high level of (0.5–18.7) × 103 copies/L after disinfection with sodium hypochlorite. Embedded viruses in stool particles might be released in septic tanks, behaving as a secondary source of SARS-CoV-2 and potentially contributing to its spread through drainage pipelines. Current recommended disinfection strategy (free chlorine ≥0.5 mg/L after at least 30 min suggested by World Health Organization; free chlorine above 6.5 mg/L after 1.5-h contact by China Centers for Disease Control and Prevention) needs to be reevaluated to completely remove SARS-CoV-2 viral RNA in non-centralized disinfection system and effectively deactivate SARS-CoV-2. The effluents showed negative results for SARS-CoV-2 viral RNA when overdosed with sodium hypochlorite but had high a level of disinfection by-product residuals, possessing significant ecological risks.
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•First report on disinfection performance for SARS-CoV-2 in medical wastewater•Incomplete removal of SARS-CoV-2 RNA under WHO guideline•High level of DBPs when SARS-CoV-2 is completed removed.
With the development of analytical technology, more emerging disinfection by-products (DBPs) have been identified and detected. Among them, aromatic DBPs, especially heterocyclic DBPs, possess ...relatively high toxicity compared with regulated DBPs, which has been proved by bioassays. Thus, the occurrence of aromatic DBPs is of great concern. This article provides a comprehensive review and summary of the characteristics, occurrence, transformation pathways and control of aromatic DBPs. Aromatic DBPs are frequently detected in drinking water, wastewater and swimming pool water, among which swimming pool water illustrates highest concentration. Considering the relatively high concentration and toxicity, halophenylacetonitriles (HPANs) and halonitrophenols (HNPs) are more likely to be toxicity driver among frequently detected phenyl DBPs. Aromatic DBPs can be viewed as important intermediate products of dissolved organic matter (DOM) during chlor(am)ination. High molecular weight DOM could convert to aromatic DBPs via direct or indirect pathways, and they can further decompose into regulated aliphatic DBPs such as trihalomethanes (THMs) and haloacetic acids (HAAs) by ring opening and side chain cleavage. Even though no single DBPs control strategy is efficient to all aromatic DBPs, the decrease of overall toxicity may be achieved by several methods including absorption, solar radiation and boiling. By systematically considering aromatic DBPs and aliphatic DBPs, a better trade-off can be made to reduce health risk induced by DBPs.
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•Halophenylacetonitriles and halonitrophenols are important potential toxicity drivers among phenyl DBPs.•In vitro and in vivo toxicological bioassays on aromatic DBPs are compared.•DOM from diverse sources forms aromatic DBPs with different characteristics.•Aromatic DBPs convert to aliphatic DBPs through ring opening or side chain cleavage.•N and halogen atoms in aliphatic DBPs originate from both aromatic DBPs and Cl2/NH2Cl.
Halocyclopentadienes (HCPDs) are an emerging class of alicyclic disinfection by-products (DBPs) with high toxicity in disinfected drinking water. However, their potential precursors remain unclear, ...which hinders the understanding of their formation and further development of control strategies. In this study, two HCPDs, 1,2,3,4-tetrachloro-1,3-cyclopentadiene (TCC) and 1,2,3,4,5,5-hexachloro-1,3-cyclopentadiene (HCC), were identified in chlorinated lignin and tannic acid samples for the first time. The chlorination of four lignin-like and two tannic-like phenolic model compounds confirmed that guaiacol and digallic acid can produce HCPDs. According to their structures, ortho-substituents of phenolic compounds were speculated to be crucial for HCPDs formation. The simulated disinfection of catechol, 2-ethoxyphenol (2-EOP), 2-propoxyphenol (2-POP) and 3,4-dihydroxy-5-methoxybenzoic acid (DH-5-MBA) with different ortho-substituents demonstrated that three of these compounds can generate HCPDs, except catechol, which further indicates that ortho-substituents, such as the methoxy, ethoxy and propoxy groups, contribute to HCPDs generation. Guaiacol was the simplest compound for generating HCPDs, and possible formation pathways during chlorination were proposed. Seven hydroxy-chlorocyclopentadienes were tentatively identified and are likely important intermediates of HCPDs formation. Additionally, TCC and HCC were confirmed in tap water and chlorinated SRNOM samples with total concentrations up to 11.07 ng/L and 65.66 ng/L, respectively, further demonstrating the wide existence of HCPDs and their precursors. This study reports the clear precursors of HCPDs and provides a theoretical foundation for controlling HCPDs formation in disinfected drinking water.
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•Tetrachlorocyclopentadiene and hexachlorocyclopentadiene were investigated in chlorinated lignin and tannic acid samples.•Ortho-methoxyphenol is regarded as one of the structural units of halocyclopentadienes precursors.•The ortho-substituents of phenolic compounds are probably beneficial to the formation of halocyclopentadienes.•Formation pathways of halocyclopentadienes were proposed.•Seven hydroxy-chlorocyclopentadienes were tentatively identified in chlorinated guaiacol and SRNOM samples.
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•Ammonia has distinct effects (promote, inhibit, little influence) on NDMA generation;•Ammonia contributed nearly half (46.5%) to NDMA formation during ozonation of HDMS;•Intermediate ...UDMH with higher NDMA yield was the culprit for the increase of NDMA;•55% UDMH dropped off from HDMS, 28.3% from NH2OH, and 16.3% by radical recombination;•NH2OH contributed 38.2% to NDMA formation without ammonia, while 56.3% with ammonia.
Would the widespread ammonia nitrogen (NH4+-N) in surface water provide nitrogen sources for carcinogenic N-nitrosodimethylamine (NDMA) formation during ozonation? What about its influence laws and mechanisms? In this paper, fifteen kinds of typical amines were selected to investigate the effects of ammonia on NDMA generation during ozonation, then the anti-yellowing agent 4,4′-Hexamethylenebis (1,1-dimethylsemicarbazide) (HDMS) was chosen to further probe its influencing factors (oxidation conditions and co-existed components) as well as mechanisms. The results demonstrated that the impacts of ammonia on NDMA formation varied due to distinct structures of precursors. The inorganic ammonia promoted first then inhibited NDMA formation from HDMS with increasing ammonia dosages. No matter with or without ammonia, the increase of O3 concentration (0–4 mg/L) promoted NDMA formation, but the increment of the former (from 0.39 to 96.61 µg/L) was much larger than those of the latter (from 0 to 32.19 µg/L); and the maximum value was achieved at pH 7. Co-existed components bromine (Br−), carbonate (CO32−), sulphate (SO42−) and humic acid (HA) all slightly reduced NDMA production from HDMS during ozonation without ammonia, while nitrite (NO2−) and nitrate (NO3−) significantly increased its production. When ammonia was present, the co-existed components inhibited NDMA production invariably. According to the results of LC-MS/MS, GC–MS, Q-TOF and 15 N isotope labeling experiments, the influencing mechanisms of ammonia on NDMA formation during ozonation of HDMS were proposed. The results of this study would provide reference for NDMA risks control in water matrixes with combined pollution of ammonia and amines.
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