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Ultraviolet radiation combined with free chlorine (UV/chlorine) is an attractive alternative to UV or chlorination alone for disinfection. However, •OH and Cl• radicals from UV/chlorine have recently raised increasing concerns about the possible formation of chlorinated products. A significant quantity of alkyl halides was generated from aliphatic carboxylic acids in the UV/chlorine process, in contrast to the absence of any detectable alkyl halides during chlorination alone. During the UV/chlorine process, the formation of CH3Cl, CH3CH2Cl and CH3CH2CH2Cl were was observed from acetic acid, propionic acid and n-butyric acid, respectively. The maximum yield of CH3Cl was up to 54.6 % when acetic acid was treated at a chlorine to precursors (Cl/P) ratio of 4.0. In addition to CH3Cl, CH2Cl2 and CHCl3 were also detected as the products of acetic acid. The presence of bromide ions resulted in a reduction in the yields of chloroalkanes, the formation of bromine byproducts, and an increase in the total amount of halocarbons. Hydroxyl radicals and chlorine radicals were identified as key reactants in the radical quenching experiments. The reactions described in this paper contribute to the understanding of the mechanism of halogenated byproduct formation during the UV/chlorine process. Synopsis: The radicals resulting from UV/chlorine lead to the conversion of carboxylic acids into a significant amount of alkyl halides that would not be generated by chlorination alone.

Disinfection by-products (DBPs) generated from water treatment have serious adverse effects on human health and natural ecosystems. However, research on the mutagenicity of DBPs with different chemical structures is still limited. In the present study, we compared the mutagenicity of 8 typical DBPs in human-hamster hybrid (AL) cells and clarified the mechanisms involved. Our data displayed that the rank order for mutagenicity was as follows: iodoacetamide (IAcAm) > iodoacetonitrile (IAN) > iodoacetic acid (IAA) > bromoacetamide (BAcAm) ≈ bromoacetonitrile (BAN) > bromoacetic acid (BAA), which was confirmed by DNA double strand breaks and oxidative DNA damage. In contrast, bromoform (TBM) and iodoform (TIM) had minimal mutagenicity. The mutation spectrum analysis further revealed that IAN, IAcAm, and IAA could induce multilocus deletions in mammalian cells. Interestingly, nitrogenous DBPs (N-DBPs) and IAA were found to cause varying degrees of iron overload and lipid peroxidation, which was mediated by the activation of the Nrf2/HO-1 signaling pathway. Moreover, the presence of deferoxamine (DFO), an iron ion inhibitor, effectively reduced γ-H2AX and 8-OHdG induced by N-DBPs and IAA. These results indicated that the variations in genotoxicity among DBPs with different structures were associated with their ability to disrupt iron homeostasis. This study provided new insights into the mechanisms underlying the structure-dependent toxicity of DBPs and established a foundation for a more comprehensive understanding and intervention of the health risks associated with DBPs.

Pavement engineers are constantly trying to develop correlations between functional and structural indicators to develop best practices for pavement evaluation and make more informative maintenance and repair (M&R) decisions. This study aims to thoroughly investigate the interaction between the International Roughness Index (IRI), a standard index used to quantify the functional properties of a pavement, and various deflection-based parameters (DBPs) used to detect changes in the structural integrity of pavement. To achieve this goal, long-term pavement performance (LTPP) data from two different Pavements A and B are analyzed. The focus is to diagnose roughness problems detected on pavement surfaces by analyzing the predictability of DBPs based on IRI and pavement layer thickness. It is observed that two IRI values are at least needed to properly reflect the pavement profile condition; a median level and an upper level corresponding to the 90th percentile of a subsection's IRI level. For Pavement A, the median IRI is considered a good predictor, with an R2 value of 0.71, of the Surface Curvature Index that reflects the condition of the asphalt layers, whereas for Pavement B, the upper IRI is considered a good predictor, with a lower R2 value of 0.65, of the deflection index that reflects the pavement's substructure condition (i.e., the condition at higher depths). From a practical perspective, the interaction between roughness and individual DBPs can help engineers and practitioners better identify the potential origin depth of roughness problems and optimize pavement condition assessment strategy. [ABSTRACT FROM AUTHOR]

• NOM, phenolic compound, and algae-derived organic matter could be HBQs precursors. • HBQs concentration increased first and then decreased during chlorination. • Chlorine doses, pH and Br−could impact the generation of HBQs. • The adsorption efficiency of HBQs by activated carbon could reach 80.1%. Halogenated benzoquinones (HBQs) could cause bladder cancer, but there were few related studies on the generation and control. In this study, the impact of different precursors, pH, bromide concentration, and algae-derived organic matters on the formation of HBQs and the removal efficiency by activated carbon were investigated. It was found that the chlorination of bisphenol A produced the most 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ), reaching 14.86 µg/L at 1 hr, followed by tyrosine, 2-chlorophenol, P-hydroxybenzoic acid, trichlorophenol, and N-methylaniline. The production of 2,6-DCBQ increased first and then decreased from 0 to 36 hr (chlorination doses 0-20 mg/L), indicating that HBQs were unstable in water. Trihalomethanes (THMs) were detected during chlorination, and the concentration increased with prolongation of reaction time. 2,6-DCBQ production decreased and 2,6-dibromo-1,4-benzoquinone (2,6-DBBQ) production increased with increment bromide concentration and the bromide promoted the formation of tribromomethane. The production of 2,6-DCBQ decreased with increase of pH, and the maximum production was 141.38 µg/L at pH of 5. Microcystis aeruginosa, Chlorella algae cells, and intracellular organic matters (IOM) could be chlorinated as potential precursors for HBQs. The most amount of 2,6-DCBQ was generated from algae cells of Microcystis aeruginosa, followed by Chlorella algae cells, Microcystis aeruginosa IOM, and Chlorella IOM. This study compared the removal efficiency of HBQs by granular activated carbon (GAC) and columnar activated carbon (CAC) under different carbon doses and initial concentrations of HBQs. It was found that the removal efficiency by GAC (80.1%) was higher than that by CAC (51.8%), indicating that GAC has better control for HBQs. [Display omitted] [ABSTRACT FROM AUTHOR]

Treatment of reuse water sources is critical for achieving proper water quality for the desired end-use. Disinfection is often achieved through chlorination, but this leads to the formation of toxic disinfection byproducts (DBPs). During reuse for agricultural purposes, it is important to reduce the potential for contamination of food crops and thereby minimize DBP production from treatment processes. This study evaluates the DBP formation potential from various reuse water sources under different reaction conditions to determine the implications of chlorination-derived DBPs for agricultural water reuse. Chlorination experiments were conducted on wastewater, stormwater, and farm lagoon water at pH 5, 6, 7, and with Br− addition. DBP concentrations were then evaluated in conjunction with initial concentrations of dissolved organic carbon (DOC), total nitrogen (TN), initial bromide, and specific UV-absorbance (SUVA). The most abundantly formed DBP class for nearly all sources was trihalomethanes (THMs), followed by nitrogenous DBPs (N-DBPs). Despite a high DOC concentration of 37.8 mg/L, lagoon source 2 only formed a total of 4.15 µg/L DBPs, likely due to oxidation of the inorganic nitrogen (54.8 mg/L TN) inhibiting DBP formation. Stormwater sources (DOC range 3.0-15.3 mg/L) had the highest DBP formation potential, with chloroform concentrations reaching up to 92 µg/L. Waters with lower DOC, TN and bromide and at lower pH ranges had less DBP formation potential for the compounds evaluated in this study. While SUVA did not prove to be a strong indicator of DBP formation, with increasing Br/UVA, there was an exponential increase in bromine substitution factor for THMs (R2=0.927, p < 0.0001) across all reuse sources. Toxicity-weighted DBP concentrations were also evaluated for all sources. Waters with higher TN and bromide content produced more toxic N-DBPs, mainly dichloroacetonitrile and dibromoacetonitrile.

Some disinfection by-products (DBPs) in drinking water present a potential safety concern. This study focuses on the elements influencing DBPs formation. A total of 120 water samples were collected from 10 different drinking water facilities spanning 5 counties within Huzhou, Zhejiang Province, China. Concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs) were observed to be 14.5 and 27.4 μg/L, respectively, constituting 34 and 64% of the total DBPs. Seasonal fluctuations demonstrated that HAAs, THMs, halonitromethanes (HNMs), and haloacetonitriles (HANs) followed a similar pattern with higher levels in summer or autumn compared to spring. Importantly, the concentrations of HAAs and THMs were markedly higher in Taihu-sourced water compared to other sources. Geographically, Nanxun exhibited the highest levels of total DBPs, HAAs, and THMs, while Deqing and Changxing demonstrated significantly lower levels. Correlation studies between water quality parameters and DBPs revealed that factors such as chloride content, temperature, and residual chlorine positively influenced DBPs formation, whereas turbidity negatively affected it. Principal component analysis suggested similar formation processes for HANs, haloketones (HKs), HNMs, and THMs. Factors such as temperature, chemical oxygen demand (COD), and residual chlorine were identified as significant contributors to the prevalence of HAAs. HIGHLIGHTS Twenty classes of DBPs and eight kinds of water quality parameters were monitored.; The impacts of water source and season were different between DBP species.; The temperature and COD played important roles in HAAs occurrence.;

Swimming in pools is a popular and healthy recreational activity. However, potential adverse health effects from disinfection byproduct (DBP) exposure in pool water are concerning. This study evaluated how such DBP exposure affects the respiratory system. DBP exposure was simulated with an animal-specific pool environment model. Experimental animals were exposed to DBPs for a specified duration and frequency over 4 weeks. The wet and dry weights of murine lungs were measured, with no significant differences observed. There were no significant differences in interkeukin (IL)-2/4/10, and interferon-γ levels. However, IL-6 expression decreased in the experimental group. To investigate the effects of DBP exposure on immune cell response, various samples, such as bronchoalveolar lavage fluid, lymph nodes, spleen, and thymus, were collected for T-cell isolation and fluorescence-activated cell sorting. Asthma-related blood cell distribution was analyzed using a complete blood count test; no significant differences were found. Thus, DBP exposure through this model did not induce substantial lung tissue damage, major alterations in cytokine expression (besides IL-6), significant immune cell responses, or changes in asthma-associated blood cell distribution. However, considering earlier results, future studies should focus on specific types, intensity, and duration of exercise that could affect DBP exposure-related immune-inflammatory responses. HIGHLIGHTS DBPs have not decoupled the effects of DBP exposure and swimming activities.; A murine DBP exposure model was developed to test the effect of periodic exposure over a 4-week period.; DBP exposure did not cause lung damage in this model.; Inflammatory cytokine levels were unchanged due to DBP exposure, save for IL-6.; There were no significant changes in asthma-related blood cell-type distribution.;

Abstract Disinfectants and preservatives used as biocides may contain or release active substances (a.s.) that can form by-products with the surrounding matrices during their application which may be released into the environment. Over the past 40 years, several hundred of these so-called disinfection by-products (DBPs) have been detected after applications of biocides used for disinfection. Due to intensive research and further development of analytical capabilities, many new DBP classes, such as iodinated DBPs (I-DBPs), halonitromethanes (HNMs), haloacetamides (HaAms), or halomethanesulfonic acids were detected worldwide in various matrices and applications. Due to the possible hazards and risks for humans and the environment, frequently occurring DBP classes, such as trihalomethanes (THM), haloacetic acids (HAA) and nitrosamines (NDMA), have already been included in many legislations and given limit values. In the European Union, biocides are assessed under the Biocidal Products Regulation 528/2012 (BPR) regarding their efficacy, potential hazards, and risks to human health and the environment. However, the available guidance for the environmental risk assessment (ERA) of DBPs remains vague. To identify knowledge gaps and to further develop the assessment scheme for the ERA of DBPs, a literature search on the multiple uses of biocides and their formation potential of DBPs was performed and the existing process for ERA was evaluated. The results show knowledge gaps on the formation of DBP in non-aqueous systems and DBP formation by non-halogen-based biocidal active substances. Based on the literature research on biocides, a possible proposal of grouping a.s. to consider their DBP formation potential is presented to simplify future ERAs. However, this also requires further research. Until then, a pragmatic approach considering the DBPs formation potential of the active substances and the identified knowledge gaps need to be established for the environmental risk assessment of DBPs in the EU. Graphical Abstract

The presence of metal ions in drinking water treatment and distribution systems may affect the disinfection process of organic matter, which had aroused people's concern. L-tyrosine can complex with metal ions through carboxyl, carbonyl, and amino groups and affect its chemical reactions. In this paper, the complexation of L-tyrosine with common metal ions was studied and the influence of complexation on chlorination with different experimental factors was investigated. It was inferred that L-tyrosine complexed with metal ions by single dentate ligand or double dentate chelation in a ratio of 2:1. The degradation of L-tyrosine-metal complex followed the pseudo-first-order reaction kinetic. TCM, DCAA, and TCAA were the main species DBPs in the chlorination of L-tyrosine. Compared with L-tyrosine, the reaction rate constants of complex increased by 5.6%, the formation of trihalomethane production decreased by 21.5% and the formation of haloacetic acids production increased by 26.9% at the state of metal complexation. The effect of metal complexation on chlorination was more obvious than that of metal coexistence. For different metal complexation, the order of inhibition on trihalomethane production was Ca2+> Fe3+> Mn2+ and the order of promotion on haloacetic acids production was Mn2+> Fe3+> Ca2+. Moreover, it was found that alkaline conditions were favorable for the formation of DBPs due to the hydroxyl radical. The combination of ultraviolet and chlorine disinfection promoted L-Tyrosine degradation and DBPs generation, and the promotion efficiency follow the order: UV/Cl2> UV-Cl2> Cl2. [ABSTRACT FROM AUTHOR]

Disinfectants and preservatives used as biocides may contain or release active substances (a.s.) that can form by-products with the surrounding matrices during their application which may be released into the environment. Over the past 40 years, several hundred of these so-called disinfection by-products (DBPs) have been detected after applications of biocides used for disinfection. Due to intensive research and further development of analytical capabilities, many new DBP classes, such as iodinated DBPs (I-DBPs), halonitromethanes (HNMs), haloacetamides (HaAms), or halomethanesulfonic acids were detected worldwide in various matrices and applications. Due to the possible hazards and risks for humans and the environment, frequently occurring DBP classes, such as trihalomethanes (THM), haloacetic acids (HAA) and nitrosamines (NDMA), have already been included in many legislations and given limit values. In the European Union, biocides are assessed under the Biocidal Products Regulation 528/2012 (BPR) regarding their efficacy, potential hazards, and risks to human health and the environment. However, the available guidance for the environmental risk assessment (ERA) of DBPs remains vague. To identify knowledge gaps and to further develop the assessment scheme for the ERA of DBPs, a literature search on the multiple uses of biocides and their formation potential of DBPs was performed and the existing process for ERA was evaluated. The results show knowledge gaps on the formation of DBP in non-aqueous systems and DBP formation by non-halogen-based biocidal active substances. Based on the literature research on biocides, a possible proposal of grouping a.s. to consider their DBP formation potential is presented to simplify future ERAs. However, this also requires further research. Until then, a pragmatic approach considering the DBPs formation potential of the active substances and the identified knowledge gaps need to be established for the environmental risk assessment of DBPs in the EU. [ABSTRACT FROM AUTHOR]

Copyright of Asian Journals of Ecotoxicology is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Biological activated carbon filter backwash water (BAC FBW) removes pollutants from BAC filters in drinking water treatment plants. Characterizing the dissolved organic matter (DOM) in BAC FBW is of great significance for the recycling and treatment of backwash water. DOM pollution was monitored over a year using three-dimensional excitation–emission matrix fluorescence spectra. The dissolved organic carbon (DOC) concentration and fluorescence results showed that the DOC concentration reached the lowest value of 1.95 mg/L in the summer. The relative abundances of fluorescence components had a direct relationship with temperature variations. The soluble microbial products were enhanced greatly during cold seasons, while fulvic-acid-like and humic-acid-like compounds remained constant. Disinfection by-products (DBPs) formation potential and cytotoxicity were evaluated. The total haloacetonitriles (HANs), trihalomethanes (THMs), halonitromethanes (HNMs), and haloacetaldehyde (HALs) formation potentials ranged from 35.5 to 47.3 μg/L, 95.1 to 126 μg/L, 4.95 to 8.06 μg/L, and 43.4 to 53.0 μg/L in BAC FBW, respectively. Among all DBPs included in the calculation, the order of contribution to cytotoxicity was HANs > HALs > THMs > HNMs, respectively. Especially, HANs were much higher than the other DBPs, which should be controlled to avoid the biological risk of effluent quality. HIGHLIGHTS DOC concentration of backwash water reached its lowest value in the summer.; Seasonal variations impacted the composition of DOM due to microbial activity.; THMs were the main DBPs in the backwash water.; The order of contribution to cytotoxicity was HANs > HALS > THMs > HNMs in backwash water.;

• UV/PS and UV/H 2 O 2 pre-oxidation enhances the formation of CNCl during chlorination of river water. • Both pre-oxidation processes can effectively remove glycine and uric acid and decrease the formation of CNCl. • Intermediates formed from pre-oxidation of arginine and histidine may lead to the increasing formation of CNCl and more chlorine consumption. • Pre-oxidation may change precursors of CNCl in water chlorination. Ultraviolet/persulfate (UV/PS) and Ultraviolet/hydrogen peroxide (UV/H 2 O 2) have attracted much attention in recent years as advanced oxidation processes for water treatment. However, it is not all clear how these two methods affect the formation of cyanogen chloride (CNCl) in the subsequent water chlorination process. In this study, it was found that both UV/H 2 O 2 and UV/PS pre-oxidation promoted the formation of CNCl in six actual water samples collected from urban rivers. Glycine, uric acid, arginine and histidine were investigated as the model compounds to explore the effects of different methods on the production of CNCl. The results showed that compared with chlorination alone, pre-oxidation by UV/H 2 O 2 and UV/PS can reduce the production of CNCl for glycine and uric acid by up to 95% during post-chlorination process. However, they can greatly promote the formation of CNCl for arginine and histidine by up to 120-fold. In a more detailed investigation, pre-oxidation of histidine formed highly reactive intermediates to chlorine, leading to increased CNCl formation and chlorine consumption. The results showed that the precursors of CNCl was altered after pre-oxidation, and need to be re-evaluated. [Display omitted] [ABSTRACT FROM AUTHOR]

The hydrophilic substances in natural organic matter (NOM) are the main precursor of disinfection by-products (DBPs) formed during disinfection processes. The fractionation of the components in NOM based on hydrophilicity contributes to elaborating the behavior of NOM during disinfection. However, the traditional NOM fractionation method using two hydrophobic resins of DAX-8 and XAD-4 lays emphasis on the separation of hydrophobic substances, limiting the thorough study of the hydrophilic components in NOM. In this work, the amphiphilic resin NDAM was employed as a replacement of XAD-4 to realize more thorough separation of the hydrophilic substances. Compared with the divinylbenzene (DVB) structure of XAD-4, the NDAM possesses a more hydrophilic skeleton of N-vinylpyrrolidone (NVP) and DVB which favors the adsorption of hydrophilic components in NOM. The two fractionation methods of DAX-8 + XAD-4 and DAX-8 + NDAM were applied to fractionate NOM, and the obtained fractions were characterized via fluorescence spectra, UV spectra, acid–base titration, the partition coefficients of aqueous two-phase systems(ATPs), and 1H nuclear magnetic resonance (1H-NMR). The results showed that the transphilic fractions separated by XAD-4 accounted for 11.09% of NOM, while the proportion increased to 20.33% with the method of NDAM fractionation. Besides, the hydrophilic components enriched by NDAM not only have more π-conjugated systems and more aromatic structure but also contain more oxygen-containing and nitrogen-containing functional groups. In addition, the hydrophilic fractions separated by NDAM contained more DBP precursors. The NDAM separates more NOM which can produce bromine-containing DBPs into HPIA, and the DBP productivity of HPIN is significantly higher than that of XAD-4. In general, the NOM fractionation method proposed in this study utilizing NDAM resin could fractionate the hydrophilic fractions in NOM more thoroughly, showing application potential in the analysis and control of DBPs formed from NOM. [ABSTRACT FROM AUTHOR]

Water treatment plants and disinfection by-products are a worldwide problem in the provision of drinking water with disinfectants. However, in countries like Ethiopia, studies on the condition of water treatment plants and the risks they pose are scarce. Hence, this study was designed to evaluate the drinking water treatment plants of Jimma Town. The WatPro v4 simulation was used to evaluate the performance of the water treatment plant and disinfection. The results show that the treatment efficiency of the study was estimated to be 69.75%, while giardia and virus were reduced by 22.6% and 75.34%, respectively, and did not meet the requirements for surface water treatment. Furthermore, the contact time of the water system did not meet the contact time requirement (it should be great than one), but it was 0.476 for this study, and the current water distribution network and treatment plant of Jimma town were underperforming and did not provide adequate water to the various demand categories. Due to the poor performance of water treatment plants, the health and economic well-being of the majority of the population is seriously affected, and some people refuse to drink it, preferring to treat it at home instead. Disinfection of drinking water (chlorination) causes some to react with naturally occurring organic matter or waterborne diseases, while others exist as free chlorine or residual chlorine, producing the disinfection by-products (DBP), increased risk of bladder cancer and other human health effects. Therefore, the study strongly suggests that DBP and their precursors be removed following chlorination. We believe that the study provided new and updated insights on the treatment condition and DBP risk, which could aid decision-makers, planners and stakeholders in monitoring actions to reduce the health risks associated with DBPs in drinking water.

Disinfection by-products (DBPs) generated from water treatment have serious adverse effects on human health and natural ecosystems. However, research on the mutagenicity of DBPs with different chemical structures is still limited. In the present study, we compared the mutagenicity of 8 typical DBPs in human-hamster hybrid (A L) cells and clarified the mechanisms involved. Our data displayed that the rank order for mutagenicity was as follows: iodoacetamide (IAcAm) > iodoacetonitrile (IAN) > iodoacetic acid (IAA) > bromoacetamide (BAcAm) ≈ bromoacetonitrile (BAN) > bromoacetic acid (BAA), which was confirmed by DNA double strand breaks and oxidative DNA damage. In contrast, bromoform (TBM) and iodoform (TIM) had minimal mutagenicity. The mutation spectrum analysis further revealed that IAN, IAcAm, and IAA could induce multilocus deletions in mammalian cells. Interestingly, nitrogenous DBPs (N-DBPs) and IAA were found to cause varying degrees of iron overload and lipid peroxidation, which was mediated by the activation of the Nrf2/HO-1 signaling pathway. Moreover, the presence of deferoxamine (DFO), an iron ion inhibitor, effectively reduced γ-H2AX and 8-OHdG induced by N-DBPs and IAA. These results indicated that the variations in genotoxicity among DBPs with different structures were associated with their ability to disrupt iron homeostasis. This study provided new insights into the mechanisms underlying the structure-dependent toxicity of DBPs and established a foundation for a more comprehensive understanding and intervention of the health risks associated with DBPs. [Display omitted] • Among 8 typical DBPs, IAN, IAcAm, and IAA were mutagenic to mammalian cells. • IAN, IAcAm, and IAA resulted in multisite deletion mutation in mammalian cells. • Mitochondrial ferrous irons were greatly enhanced by IAN, IAcAm, and IAA. • Iron homeostasis was involved in the mutagenicity induced by IAN, IAcAm, and IAA. • Iron homeostasis was related to the protein expression of Nrf2/HO-1. [ABSTRACT FROM AUTHOR]

Micro/nanoplastics can act as vectors for organic pollutants and enhance their toxicity, which has been attributed to the ingestion by organisms and the "Trojan horse effect". In this study, we disclosed a non-ingestion pathway for the toxicity enhancement effect of nanoplastics. Initially, the combined toxicity of polystyrene microplastics (40 μm) or nanoplastics (50 nm) with three disinfection byproducts (DBPs) to a marine polychaete, Platynereis dumerilii , was investigated. No toxic effect was observed for the micro/nanoplastics alone. The microplastics showed no effect on the toxicity of the three DBPs, whereas the nanoplastics significantly enhanced the toxicity of two aromatic DBPs when the polychaete was in its non-feeding early life stage throughout the exposure period. The microplastics showed no interaction with the P. dumerilii embryos, whereas the nanoplastics agglomerated strongly on the embryonic chorion and fully encapsulated the embryos. This could contribute to higher actual exposure concentrations in the microenvironment around the embryos, as the concentrations of the two aromatic DBPs on the nanoplastics were 1200 and 120 times higher than those in bulk solution. Our findings highlight an important and previously overlooked mechanism by which nanoplastics and organic pollutants, such as DBPs, pose a higher risk to marine species at their vulnerable early life stages. This study may contribute to a broader understanding of the environmental impacts of plastic pollution and underscore the necessity to mitigate their risks associated with DBPs. [Display omitted] • Micro/nanoplastics showed no developmental toxicity on the marine polychaete. • Nanoplastics enhanced the toxicity of DBPs on organisms at the non-feeding stage. • The bioaccumulation of DBPs was enhanced by nanoplastics. • A non-ingestion exposure pathway of DBPs by nanoplastics was proposed. [ABSTRACT FROM AUTHOR]

• The UV/chlorine/Fe(III) process performed best in PNP degradation. • OH and RCSs were the dominant reactive species for PNP degradation. • Fe(III)/Fe(II) cycle worked efficiently to enhance OH and RCSs production. • Reaction mechanisms of PNP degradation were elucidated based on DFT calculation. • The UV/chlorine/Fe(III) process might decrease the yields and toxicity of DBPs. Para-nitrophenol (PNP) enters aquatic environments through wastewater discharge, potentially threatening ecological security and public health. This work investigated the enhanced degradation of PNP in wastewater during the UV/chlorine process with the addition of Fe(III) (UV/chlorine/Fe(III)). The UV/chlorine/Fe(III) process (61.85 %) exhibited higher performance in PNP degradation in 10 min compared to the UV/chlorine process (40.00 %) because the synergistic effect of Fe(III) and free chlorine enhanced hydroxyl radicals (OH) and reactive chlorine species (RCSs) production. Furthermore, OH and RCSs were identified as the primary contributors to degrade PNP during the UV/chlorine/Fe(III) process, and their corresponding contributions accounted for 40.09 % and 37.10 %, respectively. Besides, the degradation efficiencies of PNP were promoted by increasing the dosages of Fe(III) and free chlorine and declined by increasing pH and PNP concentration. Also, Cl− could promote PNP degradation, while SO 4 2− and HCO 3 − inhibited it. Then, the reaction mechanisms of PNP degradation during the UV/chlorine/Fe(III) process were proposed based on the identified transformation products (TPs) and the density functional theory (DFT) calculation. Meanwhile, PNP, TPs, and other possible intermediate products presented different ecotoxicity. Finally, the formation and toxicity of disinfection by-products (DBPs) with different Fe(III) concentrations, chlorine dosages, initial pHs, and PNP concentrations were explored. Overall, the obtained findings can provide deep insights into the mechanisms of PNP degradation and a new approach to enhancing PNP degradation in wastewater. [ABSTRACT FROM AUTHOR]

The presence of microplastics (MPs) products and particles in the environment can significantly impact the human body. Most MPs that enter the environment also enter the water cycle. During sunlight light irradiation (especially ultraviolet (UV) part) or UV disinfection, many of these MPs, particularly those rich in surface functional groups like thermoplastic polyurethanes (TPU), undergo physicochemical changes that can affect the formation of disinfection byproducts (DBPs). This study investigates the physicochemical changes of TPU in water after exposure to UV irradiation and incubation in the dark, as well as the formation of DBPs after chlorination. The results show that TPU undergo chain breakage, oxidation, and cross-linking when exposed to UV irradiation in an aqueous system. This leads to fragmentation into smaller particles, which facilitates the synthesis of DBPs. Subsequent research has demonstrated that the TPU leaching solution produces a significantly higher DBP content than the chlorination of TPU MPs, particularly at high concentrations of CHCl 3. Therefore, it is important to give greater consideration to the soluble DBP precursors released by TPU. [Display omitted] • UV irradiation tends to oxidize MPs, making it less elastic and prone to breakage. • Chlorination of water containing TPU after UV irradiation produces excess DBP. • UV irradiation of TPU enhanced the release of DOM, thereby increased DBP formation. • The precursors of DBP come mainly from released DOM rather than the TPU themselves. [ABSTRACT FROM AUTHOR]

BackgroundExposure to disinfection by-products (DBPs) in drinking water and chlorinated swimming pools are associated with adverse health outcomes, but biological mechanisms remain poorly understood.ObjectivesEvaluate short-term changes in metabolic profiles in response to DBP exposure while swimming in a chlorinated pool.Materials and methodsThe PISCINA-II study (EXPOsOMICS project) includes 60 volunteers swimming 40 min in an indoor pool. Levels of most common DBPs were measured in water and in exhaled breath before and after swimming. Blood samples, collected before and 2 h after swimming, were used for metabolic profiling by liquid-chromatography coupled to high-resolution mass-spectrometry. Metabolome-wide association between DBP exposures and each metabolic feature was evaluated using multivariate normal (MVN) models. Sensitivity analyses and compound annotation were conducted.ResultsExposure levels of all DBPs in exhaled breath were higher after the experiment. A total of 6,471 metabolic features were detected and 293 features were associated with at least one DBP in exhaled breath following Bonferroni correction. A total of 333 metabolic features were associated to at least one DBP measured in water or urine. Uptake of DBPs and physical activity were strongly correlated and mutual adjustment reduced the number of statistically significant associations. From the 293 features, 20 could be identified corresponding to 13 metabolites including compounds in the tryptophan metabolism pathway.ConclusionOur study identified numerous molecular changes following a swim in a chlorinated pool. While we could not explicitly evaluate which experiment-related factors induced these associations, molecular characterization highlighted metabolic features associated with exposure changes during swimming.Highlights•MWAS of exposure to Disinfection By-Products from swimming in a chlorinated pool•6471 metabolic features were detected by UHPLC-QTOF- Mass Spectrometry.•DBP exposures were measured in exhaled breath, urine and in swimming water.•293 metabolic features associated to at least one DPB, and 137 to all exposures•Annotation revealed 13 compounds involved in the tryptophan metabolism pathway.

The generation and dissemination of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) in the environment has become a critical risk to human health. This study is based on a pilot-scale simulated water distribution system to understand the effects of chlorine disinfection treatment (without free chlorine) on ARB and ARGs in biofilms. The hydraulic parameters and pipe materials of the system were simulated based on a drinking water system. The results of the colony counts showed that bacterial multi-antibiotic resistance could be enhanced 13-fold in the biofilms of the pipeline. The use of high-throughput qPCR (HT-qPCR) indicated that the total relative abundance of ARGs in biofilm samples increased significantly (p < 0.05), while the diversity of bacteria was shown to be reduced via taxonomic analysis of the V3–V4 region of 16S rRNA. The prominent types of ARGs were conferred resistance by aminoglycoside and β-lactam after the chlorine disinfection treatment, and antibiotic deactivation was the main mechanism. Phyla Proteobacteria had the highest abundance in both treatment and control groups but decreased from 70.81% (initial biofilm sample) to 26.09% (the sixth-month biofilm sample) in the treatment groups. The results show that the chlorine disinfection plays a role in the risk of development of bacterial antibiotic resistance in pipe networks owing to bacteria in biofilms. This study was the first to investigate the contribution of chlorination without free chlorine to the bacterial community shift and resistome alteration in biofilms at a pilot-test level. HIGHLIGHTS Chlorine disinfection can enhance bacterial multi-antibiotic resistance.; The total relative abundance of ARGs in biofilm samples increased significantly.; The diversity of the treated biofilm bacteria increased.; Antibiotic deactivation was the main mechanism after chlorine disinfection.;

Recently, seven dihalohydroxybenzonitriles (diHHBNs) have been determined as concerning nitrogenous aromatic disinfection byproducts (DBPs) in drinking water. Herein, eight new monohalohydroxybenzonitriles (monoHHBNs), including 3-chloro-2-hydroxybenzonitrile, 5-chloro-2-hydroxybenzonitrile, 3-chloro-4-hydroxybenzonitrile, 3-bromo-2-hydroxybenzonitrile, 5-bromo-2-hydroxybenzonitrile, 3-bromo-4-hydroxybenzonitrile, 5-iodo-2-hydroxybenzonitrile, and 3-iodo-4-hydroxybenzonitrile, were detected and identified in drinking water for the first time. Thereafter, the relative concentration-cytotoxicity contribution of each HHBN was calculated based on the acquired occurrence level and cytotoxicity data in this study, the genome-scale cytotoxicity mechanism was explored, and a quantitative structure-activity relationship (QSAR) model was developed. Results indicated that new monoHHBNs were present in drinking water at concentrations of 0.04-1.83 ng/L and exhibited higher cytotoxicity than some other monohalogenated aromatic DBPs. Notably, monoHHBNs showed concentration - cytotoxicity contribution comparable to diHHBNs, which have been previously identified as potential toxicity drivers in drinking water. Transcriptomic analysis revealed immunotoxicity and genotoxicity as dominant cytotoxicity mechanisms for HHBNs in Chinese hamster ovary (CHO-K1) cells, with potential carcinogenic effects. The QSAR model suggested oxidative stress and cellular uptake efficiency as important factors for their cytotoxicity, highlighting the importance of potential iodinated HHBNs in drinking water, such as 3,5-diiodo-2-hydroxybenzonitrile, for future studies. These findings are meaningful for better understanding the health risk and toxicological significance of HHBNs in drinking water.

Wastewater disinfection is one of the most critical issues in protecting human health against exposure to waterborne pathogenies. Chlorine is among the most commonly used disinfectants in many wastewaters' treatment plants. Nevertheless, disquiets regarding chlorine's disinfection by-products (DBPs) have grown recently. One of the most effective ways to reduce DBPs generation is to reduce chlorine dosage by increasing disinfectant efficiency. Using magnetic field (MF) in wastewater treatment is one of the promising research topics with significant progression. This study aimed to evaluate the efficiency of using a magnetic field and/or sodium hypochlorite (NaClO) disinfection on secondary slaughterhouse wastewater effluent quality and by-products. Three groups of secondary slaughterhouse wastewater effluents were used: G1 was treated with NaClO only at 0, 2, 4, and 6 mg/L; G2 was treated with exposure to MF at 14,500 gausses, and G3 was pretreated with MF, then NaClO at the exact chlorine dosages and MF strength. The results showed an augmented effect when using a magnetic field as a pre-treatment step before NaClO treatment in the remediation of slaughterhouse wastewater over the use of any of them solely. The removal rate of COD and BOD increased by up to 26 and 20%, respectively, when pre-treatment with MF was employed as a mean percentage at all chlorine dosages, while TSS, TDS, and EC increased by 23.5 and 5.5%, respectively. Over and above, the removal rate for each TN and TP increased by 12 and 6.5% as a mean percentage at all chlorine dosages when using a combination of the two. In addition, pre-treatment by MF reduced the required concentration of NaClO from 6 to 4 mg/L, resulting in an 11% increase in the reduction rate of total coliform count, 8% increase in the reduction rate of fecal coliforms, and 10% increase in the reduction rate of E. coli and 5% in Salmonella via increasing the disinfection efficiency of NaClO. Finally, it decreased the concentration of Chloroform produced by more than 77.2% by using the higher concentration of NaClO (6 mg/L). The issue that approved the promising approach of using MF as a pre-treatment step in the treatment of slaughterhouse wastewater provides the advantage of using smaller dosages of disinfection, lowering the cost of the procedure process, and reducing the harmful concentration of DBPs. [ABSTRACT FROM AUTHOR]

Chlorine disinfection of saline wastewater effluents rich in bromide and iodide forms relatively toxic brominated and iodinated disinfection byproducts (DBPs). Ultrasonication is a relatively new water treatment technology, and it is less sensitive to suspended solids in wastewaters. In this study, we examined the effects of ultrasonication (in terms of reactor type and combination mode with chlorination) on the DBP formation and toxicity in chlorinated primary and secondary saline wastewater effluents. Compared with the chlorinated wastewater effluent samples without ultrasonication, ultrasonic horn pretreatment of the wastewater effluent samples reduced the total organic halogen (TOX) levels in chlorination by ∼30%, but ultrasonic bath pretreatment of the wastewater samples did not significantly change the TOX levels in chlorination, which might be attributed to the higher energy utilization and decomposition extent of organic DBP precursors in the ultrasonic horn reactor. Moreover, the TOX levels in the chlorinated samples with ultrasonic horn pretreatment (USH–chlorination), simultaneous treatment (chlorination+USH) and subsequent treatment (chlorination–USH) were also significantly reduced, with the maximum TOX reductions occurring in the samples with ultrasonic horn pretreatment. A toxicity index was calculated by weighting and summing the levels of total organic chlorine, total organic bromine and total organic iodine in each treated sample. The calculated toxicity index values of the chlorinated wastewater effluent samples followed a descending rank order of "chlorination" > "chlorination+USH" > "chlorination–USH" > "USH–chlorination", with the lowest toxicity occurring in the samples with ultrasonic horn pretreatment. Then, a developmental toxicity bioassay was conducted for each treated sample. The measured toxicity index values of the chlorinated wastewater samples followed the same descending rank order. [Display omitted]. [ABSTRACT FROM AUTHOR]

Halogenated disinfection byproducts (DBPs) are an unintended consequence of drinking water disinfection, and can have significant toxicity. XAD resins are commonly used to extract and enrich trace levels of DBPs for comprehensive, nontarget identification of DBPs and also for in vitro toxicity studies. However, XAD resin recoveries for complete classes of halogenated DBPs have not been evaluated, particularly for low, environmentally relevant levels (ng/L to low µg/L). Thus, it is not known whether levels of DBPs or the toxicity of drinking water might be underestimated. In this study, DAX-8/XAD-2 layered resins were evaluated, considering both adsorption and elution from the resins, for extracting 66 DBPs from water. Results demonstrate that among the 7 classes of DBPs investigated, trihalomethanes (THMs), including iodo-THMs, were the most efficiently adsorbed, with recovery of most THMs ranging from 50%-96%, followed by halonitromethanes (40%-90%). The adsorption ability of XAD resins for haloacetonitriles, haloacetamides, and haloacetaldehydes was highly dependent on the individual species. The adsorption capacity of XAD resins for haloacetic acids was lower (5%-48%), even after adjusting to pH 1 before extraction. Recovery efficiency for most DBPs was comparable with their adsorption, as most were eluted effectively from XAD resins by ethyl acetate. DBP polarity and molecular weight were the two most important factors that determine their recovery. Recovery of trichloromethane, iodoacetic acid, chloro- and iodo-acetonitrile, and chloroacetamide were among the lowest, which could lead to underestimation of toxicity, particularly for iodoacetic acid and iodo-acetonitrile, which are highly toxic. [ABSTRACT FROM AUTHOR]

The 10 µm polystyrene and polyethylene-terephthalate microplastics (MPs), prevalent in finished drink water, were employed to investigate the effect of normal dosage UVC-based advanced-oxidation-processes (UVC-AOPs) on the interaction between MPs and their derived disinfection-byproducts (DBPs) during subsequent chlorination-disinfection, in the presence of Br-, for the first time. The results indicated that UVC/H 2 O 2 caused higher leaching of microplastic-derived dissolved-organic-matter (MP-DOM), with smaller and narrower molecular-weight-distribution than UVC and UVC/peroxymonosulfate (UVC/PMS). The trihalomethanes (as dominant DBPs) molar-formation-potentials (THMs-MFPs) for MP-DOM leached in different UVC-AOPs followed the order of UVC/H 2 O 2 >UVC/PMS>UVC. The adsorption of formed THMs, especially Br-THMs, back on MPs was observed in all MPs suspensions with or without UVC-AOPs pre-treatment. The Cl-THMs adsorption by MPs is more sensitive to UVC-AOPs than Br-THMs. The adsorption experiments showed that UVC-AOPs reduce the capacity but increase the rate of THMs adsorption by MPs, suggesting the halogen and hydrogen bonding forces governed the THMs adsorption rate while hydrophobic interaction determines their adsorption capacity. The UVC-AOPs pre-treatment sharply increased the total yield of THMs via both indirectly inducing MP-DOM leaching and directly increasing the THMs-MFPs of MPs by oxidation. 21.36–41.96% of formed THMs adsorbed back on the UVC-AOPs-pretreated MPs, which might increase the toxicity of MPs. [Display omitted] • THMs-MFP for MP-DOM leached in UVC-AOPs followed the order of UVC/H 2 O 2 >UVC/PMS>UVC • UVC-AOPs reduce the capacity but increase the rate of THMs adsorption by MPs • Cl-THMs adsorption is more sensitive to UVC-AOPs than Br-THMs • 21.36-41.96% of formed THMs adsorb back on UVC-AOPs pre-treated MPs [ABSTRACT FROM AUTHOR]

• All tested HPAcAms were cytotoxic than regulated trihalomethanes in HepG2 cells;. • Oxidative stress was an important cytotoxicity mechanism for HPAcAms;. • HPAcAm-SOD interaction could obviously alter the structure and function of SOD. • A QSAR model was developed to predict the cytotoxicity of HPAcAms in HepG2 cells. Halophenylacetamides (HPAcAms) have been identified as a new group of nitrogenous aromatic disinfection byproducts (DBPs) in drinking water, but the toxicity mechanisms associated with HPAcAms remain almost completely unknown. In this work, the cytotoxicity of HPAcAms in human hepatoma (HepG2) cells was evaluated, intracellular oxidative stress/damage levels were analyzed, their binding interactions with antioxidative enzyme were explored, and a quantitative structure-activity relationship (QSAR) model was established. Results indicated that the EC 50 values of HPAcAms ranged from 2353 μ M to 9780 μ M, and the isomeric structure as well as the type and number of halogen substitutions could obviously induce the change in the cytotoxicity of HPAcAms. Upon exposure to 2-(3,4-dichlorophenyl)acetamide (3,4-DCPAcAm), various important biomarkers linked to oxidative stress and damage, such as reactive oxygen species, 8‑hydroxy-2-deoxyguanosine, and cell apoptosis, exhibited a significant increase in a dose-dependent manner. Moreover, 3,4-DCPAcAm could directly bind with Cu/Zn-superoxide dismutase and induce the alterations in the structure and activity, and the formation of complexes was predominantly influenced by the van der Waals force and hydrogen bonding. The QSAR model supported that the nucleophilic reactivity as well as the molecular compactness might be highly important in their cytotoxicity mechanisms in HepG2 cells, and 2-(2,4-dibromophenyl)acetamide and 2-(3,4-dibromophenyl)acetamide deserved particular attention in future studies due to the relatively higher predicted cytotoxicity. This study provided the first comprehensive investigation on the cytotoxicity mechanisms of HPAcAm DBPs. [Display omitted] [ABSTRACT FROM AUTHOR]

The feasibility of on-site generated chlorine (OSG chlorine) as an alternative disinfectant to chlorine gas was evaluated in terms of total organic carbon (TOC) removal, disinfection efficiency, biofilm control, disinfection by-products (DBPs) formation, chlorine decay rate, and volatility. Chlorine gas decreased the pH of the treated water by -0.1 per mg/L of free available chlorine (FAC) while OSG chlorine increased the pH by + 0.06 per mg/L. OSG chlorine with more hypochlorite ion (OCl-) at higher pH was less effective in the inactivation of suspended bacteria and TOC removal but remained in the distribution system longer and controlled biofilm formation more effectively than chlorine gas. The DBPs formation by OSG chlorine was not significantly different from that by chlorine gas except for the reduction of Haloacetonitriles. Hypochlorous acid (HOCl) was more volatile than OCl-, indicating the lower volatility of FAC in the OSG chlorine-treated water. Two types of OSG systems, "Mixed oxidants" and OSG hypochlorite, did not show any significant difference in disinfection, DBPs formation, and chlorine decay rate (paired t-test, p = 0.40, 0.11 ~ 0.70, > 0.42). A significant synergy effect by oxidants other than FAC cannot be expected in the use of "mixed oxidants" at a water treatment plant. [ABSTRACT FROM AUTHOR]

Previous studies have shown that algal-derived dissolved organic matter (DOM) has a strong influence on the formation of disinfection byproducts (DBPs) during the treatment of drinking water. In the summer of 2010, we evaluated the role of nitrogen and phosphorus loading and phytoplankton abundance as drivers of the concentrations and quality of DOM and the associated DBP formation in 30 reservoirs in the mountains and plains of the State of Colorado. Optical properties such as Specific Ultraviolet Absorbance at 254 nm (SUVA254) and fluorescence spectroscopy were used to characterize DOM quality. Nutrient concentrations such as total nitrogen were also assessed and were associated with high concentrations of chlorophyll a (Chl-a). In turn, high total organic carbon (TOC) concentrations were associated with high concentrations of Chl-a, and the DOM in these reservoirs had a fluorescence signature indicative of contributions from phytoplankton growth. The reservoirs with TOC concentrations above 4 mgC/L were predominantly located in the plains and many are impacted by agricultural runoff and wastewater discharges, rather than in the mountains and are characterized by warm water conditions and shallow depths. For a subset of fourteen reservoirs, we characterized the composition of the phytoplankton using a rapid imaging microscopy technique and observed a dominance by filamentous Cyanobacteria in reservoirs with TOC concentrations above 4 mgC/L. The combination of high TOC concentrations with microbial characteristics resulted in high potential for production of two major classes of regulated DBPs, trihalomethanes and haloacetic acids. While fluorescence spectroscopy was useful in confirming the contribution of phytoplankton growth to high TOC concentrations, evaluation of predictive models for DBP yields found that all equally predictive models included SUVA254 and some of these models also included fluorescence indices or logTOC. These findings provide a limnological context in support of the recent guidelines that have been implemented for protection of high-quality drinking water supplies in the State of Colorado.

As highly toxic nitrogenous disinfection byproducts (DBPs), monohaloacetamides (monoHAcAms) generally exhibited a cytotoxic rank order of iodoacetamide ˃ bromoacetamide ˃ chloroacetamide. However, the mechanisms underlying the halogen-dependent cytotoxic pattern remain largely veiled as yet. In this work, oxidative stress/damage levels in monoHAcAm-treated Chinese hamster ovary cells were thoroughly analyzed, and binding interactions between monoHAcAms and antioxidative enzyme Cu/Zn-superoxide dismutase (Cu/Zn-SOD) were investigated by multiple spectroscopic techniques and molecular docking. Upon exposure to monoHAcAms, the intracellular levels of key biomarkers associated with oxidative stress/damage, including reactive oxygen species, malondialdehyde, lactate dehydrogenase, 8-hydroxy-2-deoxyguanosine, cell apoptosis, and G 1 cell cycle arrest, were all significantly increased in a dose-response manner with the same halogen-dependent rank order as their cytotoxicity. Moreover, this rank order was also determined to be applicable to the monoHAcAm-induced alterations in the conformation, secondary structure, and activity of Cu/Zn-SOD, the microenvironment surrounding aromatic amino acid residues in Cu/Zn-SOD, as well as the predicted binding energy of SOD-monoHAcAm interactions. Our results revealed that the halogen-dependent cytotoxic pattern of monoHAcAms was attributed to their differential capacity to induce oxidative stress/damage and their interaction with antioxidative enzyme, which contribute to a better understanding of the halogenated DBP-induced toxicological mechanisms. [Display omitted] • MonoHAcAms showed a cytotoxic rank order of IAcAm ˃ BAcAm ˃ CAcAm in CHO-K1 cells. • Oxidative stress played an important role in monoHAcAms-induced cytotoxicity. • The cytotoxic pattern was related to the capacity to induce oxidative stress/damage. • SOD-monoHAcAm interaction altered the structure/function of SOD with the same order. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are ubiquitously present in source water and undergo ultraviolet (UV) aging in aquatic environments before entering drinking water treatment plants. The presence of MPs in drinking water can impact the formation of halogenated disinfection byproducts (DBPs) during chlorine disinfection, yet the exact effect of MPs on DBP formation remain unclear. In this study, we conducted an investigation into the influence of non-aged and UV-aged MPs on halogenated DBP formation in drinking water and unveiled the underlying mechanisms. In comparison to source water samples devoid of MPs, the total organic halogen concentration was reduced by 19%–43% and 4%–13% in the drinking water samples containing non-aged and aged MPs, respectively. The differing effects on halogenated DBP formation can be attributed to the alternation in physical and chemical characteristics of MPs following UV aging. Aged MPs exhibited larger surface area with signs of wear and tear, heightened hydrophilicity, surface oxidation, increased oxygen-containing functional groups and dechlorination during the UV aging process. Both non-aged and aged MPs possess the capability to adsorb natural organic matter, leading to a reduction in the concentration of DBP precursors in the source water. However, the release of organic compounds from aged MPs outweighed the adsorption of organics. Furthermore, as a result of the surface activation of MPs through the UV aging process, the aged MPs themselves can also serve as DBP precursors. Consequently, the presence of halogenated DBP precursors in source water increased, contributing to a higher level of DBP formation compared to source water containing non-aged MPs. Overall, this study illuminates the intricate relationship among MPs, UV aging, and DBP formation in drinking water. It highlights the potential risks posed by aged MPs in influencing DBP formation and offers valuable insights for optimizing water treatment processes. [Display omitted] • MPs in source water led to varying degrees of reduction in DBP formation. • Aged MPs showed larger surface areas, heightened hydrophilicity, surface oxidation and dechlorination. • Mechanisms elucidating the influence of MPs on DBP formation were proposed. • Both organic release and activated surfaces of aged MPs elevated DBP precursor levels. [ABSTRACT FROM AUTHOR]

Drinking water disinfection by‐products (DBPs), including the ubiquitous trihalomethanes (THMs), are formed during the treatment of water with disinfectants (e.g., chlorine, chloramines) to produce and distribute potable water. Brominated THMs (Br‐THMs) are activated to mutagens via glutathione S‐transferase theta 1 (GSTT1); however, iodinated THMs (I‐THMs) have never been evaluated for activation by GSTT1. Among the I‐THMs, only triiodomethane (iodoform) has been tested previously for mutagenicity in Salmonella and was positive (in the absence of GSTT1) in three strains (TA98, TA100, and BA13), all of which have error‐prone DNA repair (pKM101). We evaluated five I‐THMs (chlorodiiodomethane, dichloroiodomethane, dibromoiodomethane, bromochloroiodomethane, and triiodomethane) for mutagenicity in Salmonella strain RSJ100, which expresses GSTT1, and its homologue TPT100, which does not; neither strain has pKM101. We also evaluated chlorodiiodo‐, dichloroiodo‐, and dibromoiodo‐methanes in strain TA100 +/− rat liver S9 mix; TA100 has pKM101. None was mutagenic in any of the strains. The I‐THMs were generally more cytotoxic than their brominated and chlorinated analogues but less cytotoxic than analogous trihalonitromethanes tested previously. All five I‐THMs showed similar thresholds for cytotoxicity at ~2.5 μmoles/plate, possibly due to release of iodine, a well‐known antimicrobial. Although none of these I‐THMs was activated by GSTT1, iodoform appears to be the only I‐THM that is mutagenic in Salmonella, only in strains deficient in nucleotide excision repair (uvrB) and having pKM101. Given that only iodoform is mutagenic among the I‐THMs and is generally present at low concentrations in drinking water, the I‐THMs likely play little role in the mutagenicity of drinking water. [ABSTRACT FROM AUTHOR]

Increased concentrations of natural organic matter (NOM), a complex mixture of organic substances found in most surface waters, have recently emerged as a substantial environmental issue. NOM has a significant variety of molecular and chemical properties, which in combination with its varying concentrations both geographically and seasonally, introduce the opportunity for an array of interactions with the environment. Due to an observable increase in amounts of NOM in water treatment supply sources, an improved effort to remove naturally-occurring organics from drinking water supplies, as well as from municipal wastewater effluents, is required to continue the development of highly efficient and versatile water treatment technologies. Photocatalysis has received increasing interest from around the world, especially during the last decade, as several investigated processes have been regularly reported to be amongst the best performing water treatment technologies to remove NOM from drinking water supplies and mitigate the formation of disinfection by products. Consequently, this overview highlights recent research and developments on the application of photocatalysis to degrade NOM by means of TiO2-based heterogeneous and homogeneous photocatalysts. Analytical techniques to quantify NOM in water and hybrid photocatalytic processes are also reviewed and discussed. [ABSTRACT FROM AUTHOR]

Periodic chemical cleaning with sodium hypochlorite (NaClO) is essential to restore the membrane permeability in a membrane bioreactor (MBR). However, the chlorination of membrane foulants results in the formation of disinfection by-products (DBPs), which will cause the deterioration of the MBR effluent and increase the antibiotic resistance in bacteria in the MBR tank. In this study, the formation of 14 DBPs during chemical cleaning offouled MBR membrane modules was investigated. Together with the effects of biofilm extracellular polymeric substances (EPS), influences of reaction time, NaClO dosage, initial pH, and cleaning temperature on the DBP formation were investigated. Haloacetic acids (HAAs) and trichloromethane (TCM), composed over 90% of the DBPs, were increasingly accumulated as the NaClO cleaning time extended. By increasing the chlorine dosage, temperature, and pH, the yield of TCM and dichloroacetic acid (DCAA) was increased by up to a factor of 1–14, whereas the yields of haloacetonitriles (HANs) and haloketones (HKs) were decreased. Either decreasing in the chlorine dosage and cleaning temperature or adjusting the pH of cleaning reagents toward acidic or alkaline could effectively reduce the toxic risks caused by DBPs. After the EPS extraction pretreatment, the formation of DBPs was accelerated in the first 12 h due to the damage of biofilm structure. Confocal laser scanning microscopy (CLSM) images showed that EPS, particularly polysaccharides, were highly resistant to chlorine and might be able to protect the cells exposed to chlorination. [ABSTRACT FROM AUTHOR]

Abstract The Bureau of Indian Standard (BIS, New Delhi) has framed a set of standards for drinking water description (IS 10500:1991-http://www.indiawaterportal.org), which has specifications drawn up in 1983 with the most current amendment (July, 2010), and the US Environmental Protection Agency (USEPA 2003) has also developed policy for different drinking water disinfection by-products (DBPs). This study examined the quality of metropolitan drinking water by monitoring the physicochemical parameters, and DBPs study such as the effects of halide ions, natural organic matter, and drinking water characterization were investigated. The sampled water had halo phenols DBPs as a result of disinfection, during chlorination. The water was alkaline in nature, and the water temperature varied from 33 to 37 °C. The major ions, namely bromate, iodate, chlorite, chromate, sulfate and phosphate, have been investigated in the municipality drinking water, Tiruchirappalli and Srirangam in Tamil Nadu, India. Here, three solvents such as hexane, petroleum ether and pentane were used for the liquid–liquid extraction of target compounds. The gas chromatographs equipped with capillary columns (DB-WAX) were employed for the determination of DBPs and 2-bromo-4-chlorophenol was predominantly identified.

This study investigated the occurrence of disinfection by-products (DBPs) (trihalomethanes (THMs), haloacetic acids (HAAs), halonitriles (HANs), halonitromethane (TCNM) and haloketones (HKs)) in different type of swimming pools in the area of Thessaloniki, northern Greece by employing the EPA methods 551.1 and 552.3. Moreover, general water quality parameters (pH, residual chlorine, dissolved organic carbon, UV254 absorption, total nitrogen, alkalinity and conductivity) were also measured. The concentrations of DBPs showed great variability among swimming pools as well as within the same pool between sampling campaigns. HAAs exhibited the highest concentrations followed by THMs, HANs, TCNM and HKs. Exposure doses for four age groups (3–

Measurements of the UV–Vis absorbance (Abs) and intensity of fluorescence emission (Fluor), as well as of concentrations of total or dissolved organic carbon (OC) in aqueous samples are commonly used to estimate the potential for disinfection byproducts (DBPs) formation during water chlorination. In this work, based on 574 linear associations collected from 70 experimental research papers published over the period of 1997–2019, the strengths of the correlations of Abs, Fluor, and OC with DBPs concentrations are compared. The correlations were expressed as approximately normally distributed Z-scores using Fisher variance-stabilizing transformation. The effects of specific prediction method, chlorination agent, water source, and DBPs type, with consideration of possible effects due to the presence of bromide, are examined against Z-scores by ANOVA, testing main effects and some variables interactions. The performed analysis is a first attempt to expose differences and patterns in correlation strengths associated with DBPs formation, based on systematically covered broad existing literature. Abs and OC concentration of water samples tend to demonstrate the strongest correlations with DBPs formation as compared with specific UV absorbance (SUVA) or intensity of fluorescence emission. Correlations of DBPs formation during chloramination demonstrated weaker strengths as compared with other chlorination agents, suggesting more caution in predicting DBPs concentrations, based on simple descriptors such as Abs, OC, and Fluor. In a series of different water types, the correlations with DBPs formation are expected to be enhanced, when wastewater is chlorinated. Non-fluorescent matter may be an important contributor to DBPs formation during water chlorination. When fluorescence intensity is considered as a predicting tool, choosing humic-like rather than proteinaceous fluorescence may enhance the strengths of the correlations with DBPs formation. Different performances of Abs, OC, and Fluor in correlating with DBPs formation may be beneficial for their concurrent use helping to optimize removal of different DBPs precursors. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) are a class of solvents increasingly used as "green chemicals." Widespread applications of ILs have led to concerns about their accidental entry to the environment. ILs have been assessed for some environmental impacts; however, little has been done to characterize their potential impacts on drinking water if ILs accidentally enter surface water. IL cations are often aromatic or alkyl quaternary amines that resemble structures of previously confirmed N -nitrosamine (NA) precursors. Therefore, this study has evaluated two common ILs, 1-ethyl-3-methylimidazolium bromide (EMImBr) and 1-ethyl-1-methylpyrrolidinium bromide (EMPyrBr), for their NA formation potential. Each IL species was reacted with pre-formed monochloramine under various laboratory conditions. The reaction mixtures were extracted using liquid–liquid extraction and analyzed for NAs using high performance liquid chromatography tandem mass spectrometry. At low concentration of IL (250 μmol/L), the yields of NAs (NMEA or NPyr) increased with increasing doses of monochloramine from both IL species. The total NA yield was as high as 2.5 ± 0.3 ng/mg from EMImBr, and as high as 8.6 ± 0.8 ng/mg from EMPyrBr. At high concentration of IL (5 mmol/L), the NA yield reached a maximum at 2.5 mmol/L NH 2 Cl, and then decreased with subsequent increases in the reactant concentrations, demonstrating ILs' solvent effects. This study re-emphasizes the importance of preventing discharge of ILs to water bodies to prevent secondary impacts on drinking water. Unlabelled Image [ABSTRACT FROM AUTHOR]

In the present study, a meta‐analysis was carried out to clarify the association between disinfection byproducts (DBPs) in drinking water and human cancer risk worldwide. Kidney, colorectal, esophagus, urinary bladder, brain, breast, leukemia, lung, and rectum cancers were selected to perform this analysis. According to preferred reporting items for systematic review and meta‐analysis protocol (PRISMA) guidelines, the relevant studies were identified and selection criteria (inclusion and exclusion criteria) were applied. Next, effective subgroups in these studies (gender, type of drinking water source, and type of DBPs) were analyzed. The quality of the studies was evaluated using the Newcastle‐Ottawa Scale. In addition, this overall study included analyses of 16 case–control and 3 cohort studies. The overall odds ratio (OR) with 95% confidence intervals (CI) between DBPs and cancer risk was 1.01 (95% CI, 0.94–1.09). The summary ORs of cancer risk were 1.04 (95% CI, 0.89–1.19) for kidney; 0.98 (95% CI, 0.87–1.09) for colorectal; 1.07 (95% CI, 0.84–1.29) for esophagus; 0.93 (95% CI, 0.80–1.06) for pancreatic; 1.00 (95% CI, 0.83–1.18) for brain; 1.13 (95% CI, 0.99–1.26) for breast; 0.93 (95% CI, 0.72–1.13) for leukemia; and 1.18 (95% CI, 1–1.36) for lung cancers. The results of this meta‐analysis suggested that there is not a significant association between DBPs in water and cancer risk. In addition, subgroup analysis shows a positive association with colorectal and kidney cancer risk in men, as well as colon and breast cancers in females. Studies of both genders have shown a significant association between lung and pancreatic cancers. Moreover, this study finds a significant relationship between cancer rate and consumers of city water and bottled water sources. In analyzing different types of DBPs in water, chlorine and trichloromethane show a significant association in increasing cancer risk. [ABSTRACT FROM AUTHOR]

• City dust can react directly with chlorine-based disinfectants to produce DBPs. • Organic content within city dust determines the quantity of generated DBPs. • A significant portion of the generated DBPs consist of brominated compounds. • Unknown DBPs were analysed with the employment of GC-qTOF-MS. • The generated DBPs could have impacts on both human health and ecological environment. Chlorine-based disinfectants, such as sodium hypochlorite, are extensively used in our daily lives. In particular, during the recent Covid-19 pandemic and post-pandemic period, excessive amounts of chlorine-based disinfectants were used both indoors and outdoors to interrupt virus transmission. However, the interaction between disinfectants and city dust during the disinfection process has not been sufficiently evaluated. In this study, we conducted a comprehensive investigation into the intrinsic characteristics (e.g. morphology, size, elemental composition, and organic content, etc.) of dust collected from various indoor and outdoor areas. The results showed that the organic carbon content of indoor dust reached 6.14 %, with a corresponding measured dissolved organic carbon value of 4.17 ± 0.23 mg/g (normalized to the dust weight). Concentrations of regulated DBPs, resulting from the interaction between dust and NaClO, ranged from 57.78 ± 2.72 to 102.80 ± 22.63 µg/g for THMs and from 119.18 ± 6.50 to 285.14 ± 36.95 µg/g for HAAs (normalized to the dust weight). More significantly, using non-target analysis through gas chromatography quadrupole time-of-flight mass spectrometry (GC-qTOF-MS), we identified a total of 68, 89, and 87 types of halogenated DBPs from three typical indoor and outdoor sites (R-QH, C-JS, and W-BR, respectively). These unknown DBPs included compounds with higher toxicity compared to regulated DBPs. These findings highlight that city dust is a significant source of DBP generation during chlorine-based disinfection, posing potential harm to both the ecological environment and human health. [Display omitted] [ABSTRACT FROM AUTHOR]

Ozone‒chlor(am)ine is a commonly used combination of disinfectants in drinking water treatment. Although there are quite a few studies on the formation of some individual DBPs in the ozone‒chlor(am)ine disinfection, an overall picture of the DBP formation in the combined disinfection is largely unavailable. In this study, the effects of ozone dose on the formation and speciation of organic brominated disinfection byproducts (DBPs) in subsequent chlorination, chloramination, or chlorination‒chloramination of simulated drinking water were investigated. High-molecular-weight, aliphatic, alicyclic and aromatic brominated DBPs were selectively detected and studied using a powerful precursor ion scan method with ultra performance liquid chromatography/electrospray ionization triple quadrupole mass spectrometry (UPLC/ESI-tqMS). Two groups of unregulated yet relatively toxic DBPs, dihalonitromethanes and dihaloacetaldehydes, were detected by the UPLC/ESI-tqMS for the first time. With increasing ozone dose, the levels of high-molecular-weight (m/z 300-500) and alicyclic and aromatic brominated DBPs generally decreased, the levels of brominated aliphatic acids were slightly affected, and the levels of dihalonitromethanes and dihaloacetaldehydes generally increased in the subsequent disinfection processes. Despite different molecular compositions of the detected DBPs, increasing ozone dose generally shifted the formation of DBPs from chlorinated ones to brominated analogues in the subsequent disinfection processes. This study provided a comprehensive analysis of the impact of ozone dose on the DBP formation and speciation in subsequent chlor(am)ine disinfection., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Disinfection byproducts (DBPs) are ubiquitous environmental contaminants, which are present in virtually all drinking water and linked to detrimental health effects. Iodinated-DBPs are more cytotoxic and genotoxic than chloro- and bromo-DBPs and are formed during disinfection of iodide-containing source water. Liquid-liquid extraction (LLE) paired with gas chromatography (GC)-mass spectrometry (MS) has been the method of choice in the study of low molecular weight iodinated-DBPs; however, this method is laborious and time-consuming and struggles with complex matrices. We developed an environmentally friendly method utilizing headspace solid phase extraction with the application of vacuum to measure six iodinated-trihalomethanes (I-THMs) in drinking water and urine. Vacuum-assisted sorbent extraction (VASE) has the ability to exhaustively and rapidly extract volatile and semivolatile compounds from liquid matrices without the use of solvent. Using VASE with GC-MS/MS provides improved analyte recovery and reduced matrix interference compared to LLE. Additionally, VASE enables extraction of 30 samples simultaneously with minimal sample handling and improved method reproducibility. Using VASE with GC-MS/MS, we achieved quantification limits of 3-4 ng/L. This technique was demonstrated on drinking water from four cities, where five I-THMs were quantified at levels 10-33 times below comparable LLE methods with 10 times lower volumes of sample (10 mL vs 100 mL).

An emerging class of unregulated disinfection byproducts, halobenzoquinones (HBQs), has gained recent interest following suggestions of enhanced toxicity compared to regulated disinfection byproducts. While the kinetics of HBQ hydrolysis in water have been well characterized, the stability of HBQs in cell culture media, a critical parameter when evaluating toxicity in vitro, has been overlooked. The objective of this study was: (1) to contrast the stability of a prevalent HBQ, 2,6-dichloro-1,4-benzoquinone (DCBQ), in cell culture media and water, and (2) to evaluate the cytotoxicity of parent and transformed DCBQ compounds as well as the ability of these compounds to generate intracellular reactive oxygen species (ROS) in normal human colon cells (CCD 841 CoN ) and human liver cancer cells (HepG2). The half-life of DCBQ in cell media was found to be less than 40 min, compared to 7.2 h in water at pH 7. DCBQ induced a concentration-dependent decrease in cell viability and increase in ROS production in both cell lines. The parent DCBQ compound was found to induce significantly greater cytotoxicity compared to transformed DCBQ products. We demonstrate that the study design used by most published studies (i.e. , extended exposure periods) has led to a potential underestimation of the cytotoxicity of HBQs by evaluating the toxicological profile primarily of transformed HBQs, rather than corresponding parent compounds. Future in vitro toxicological studies should account for HBQ stability in media to evaluate the acute cytotoxicity of parent HBQs. • The half-life of DCBQ, a prevalent HBQ, is shorter in culture media than water. • Water- and media-transformed DCBQ compounds induce cytotoxicity and generate ROS. • Media-transformed DCBQs induce decreased cytotoxicity vs the parent DCBQ compound. • In vitro studies with extended exposures may have underestimated DCBQ cytotoxicity. [ABSTRACT FROM AUTHOR]