Adsorption of typical NDMA precursors by superfine powdered activated carbon: Critical role of particle size reduction.

Control of N-nitrosodimethylamine (NDMA) in drinking water could be achieved by removing its precursors as one practical way. Herein, superfine powdered activated carbons with a diameter of about 1 µm (SPACs) were successfully prepared by grinding powdered activated carbon (PAC, D50=24.3 µm) and applied to remove model NDMA precursors, i.e. ranitidine (RAN) and nizatidine (NIZ). Results from grain diameter experiments demonstrated that the absorption velocity increased dramatically with decreasing particle size, and the maximum increase in k2 was 26.8-folds for RAN and 33.4-folds for NIZ. Moreover, kinetic experiments explained that rapid absorption could be attributed to the acceleration of intraparticle diffusion due to the shortening of the diffusion path. Furthermore, performance comparison experiments suggested that the removal of RAN and NIZ (C0=0.5 mg/L) could reach 61.3% and 60%, respectively, within 5 min, when the dosage of SAPC-1.1 (D50=1.1 µm) was merely 5 mg/L, while PAC-24.3 could only eliminate 17.5% and 18.6%. The adsorption isotherm was well defined by Langmuir isotherm model, indicating that the adsorption of RAN/NIZ was a monolayer coverage process. The adsorption of RAN or NIZ by SAPC-1.1 and PAC-24.3 was strongly pH dependent, and high adsorption capacity could be observed under the condition of pH > pka+1. The coexistence of humic acid (HA) had no significant effect on the adsorption performance because RAN/NIZ may be coupled with HA and removed simultaneously. The coexistence of anions had little effect on the adsorption also. This study is expected to provide an alternative strategy for drinking water safety triggered by NDMA.

A Comparative Analysis of Drinking Water Provision and Hepatitis A Incidence in Uzbekistan in 2010-2023.

Objective This study aims to analyze the relationship between access to safe drinking water and the incidence of hepatitis A in Uzbekistan from 2010 to 2023 to inform public health strategies for disease prevention. Methods We utilized hepatitis A incidence data from the Sanitary and Epidemiological Well-Being and Public Health Authority and drinking water provision data from the Government Statistics Agency of Uzbekistan. A linear regression analysis was performed using R 4.3.2 to investigate the correlation between these variables. The study examined hepatitis A cases per 100,000 population and the percentage of households with access to safe drinking water. Results Hepatitis A incidence fluctuated significantly over the study period, with a notable spike to 162 cases per 100,000 population in 2023, despite relatively stable access to safe drinking water (ranging from 67.4% to 77% of households). The analysis revealed a complex relationship between water access and hepatitis A incidence. The linear regression coefficient was 3.89 (adjusted R-squared: 0.3021, P-value: 0.02), indicating that each growing percent of water supply is raising the incidence of hepatitis 3.89 cases of hepatitis infection. Conclusion The reverse effect of water supply percentage and the incidence of hepatitis A incidence in Uzbekistan suggests that other factors play significant roles in disease transmission. These may include sanitation practices, hygiene behaviors, and vaccination coverage. The findings emphasize the need for a multifaceted approach to hepatitis A prevention, incorporating improved water infrastructure, enhanced sanitation, public education, and comprehensive vaccination programs. Further research is needed to identify specific determinants of hepatitis A transmission in Uzbekistan to guide targeted interventions and public health policies.

Mitigating harmful cyanobacterial blooms in drinking water reservoirs through in-situ sediment resuspension.

Mitigating harmful cyanobacterial blooms is a global challenge, particularly crucial for safeguarding source water. Given the limitations of current technologies for application in drinking water reservoirs, we propose an innovative strategy based on in-situ sediment resuspension (SR). This method's effectiveness in cyanobacterial control and its potential impacts on water quality were assessed through laboratory culture experiments and further validated via field applications in five drinking water reservoirs. The results revealed that SR could significantly mitigate cyanobacterial growth, evidenced by the treated sets (removal rate: 3.82×106 cells L-1d-1) compared to the control set (growth rate: 2.22×107 cells L-1d-1) according to the laboratory experiments. The underlying mechanisms identified included underwater light reduction (2.38× increase in extinction coefficient) and flocculation and entrainment of cells by resuspended particles (30 % reduction per operation). Additional contributions were noted in the reduction of bioavailable phosphate and remediation of anaerobic sediment characterized by increased redox potential. This facilitated the oxidation of iron, which in turn promoted the co-precipitation of phosphate (removal rate: 46 µg L-1d-1) and inhibited its release from the sediment. The SR operation, devoid of importing extra substances, represents a safe and economical technology for controlling harmful cyanobacteria in drinking water reservoirs.

Applying a novel mechanistic framework for drinking water management to mitigate emerging contaminants.

A novel framework has been developed which summarizes the efficacy of treatment technologies for emerging contaminants (ECs) based on the general mitigation mechanisms of Removal, Inactivation/Degradation, and Destruction (i.e., RIDD). The RIDD framework allows for a concise critical evaluation of the efficacy of treatment processes for their mitigation potential, and provides an efficient methodology for drinking water system managers to identify knowledge gaps related to the management of ECs in water treatment with respect to current technologies available in practice. Additionally, the RIDD framework provides an understanding of the treatment processes which provide: (1) broad spectrum treatment, (2) effective mitigation for certain categories of contaminants or under certain circumstances, or (3) little or no mitigation of ECs. In the proposed format, this information is intended to assist water managers to make more informed treatment decisions. Four categories of ECs noted in recent literature as presently concerning to drinking water utilities, including both anthropogenic and microbial contaminants, were used in this study to provide examples of RIDD framework application. In many cases, broad-spectrum treatment barriers (e.g., high-pressure membranes) are expected to provide cost-effective management of a suite of ECs, which then can be compared to the costs and practicality of additional treatment barriers for individual ECs (e.g., selective ion exchange resins or tailored biological processes). Additionally, understanding the typical performance of existing treatment processes can help assist with capital planning for alternative treatment processes or upgrades, or for developing novel treatment approaches at the watershed scale such as integrated urban water management and One Water frameworks.

Influence of tailing dust contamination in drinking water on the health status of goats in subtropical Regions.

The contamination of river systems by tailing dust remains a constraint to goat productivity in communal farming systems. A cross-sectional study was conducted to investigate how resource-limited households in subtropical regions assessed the effects of tailing dust contamination in drinking water on the health status of goats. In a study conducted in the Ba-Phalaborwa Local Municipality, 200 households from two villages were randomly selected and interviewed using a questionnaire. Forty-eight percent (n = 96) of the households were located in contaminated areas, while 52% (n = 104) were from uncontaminated areas. The study found that poor water quality, caused by tailing dust contamination, as well as a high incidence of diseases, were key factors affecting goat productivity. Water contamination was most severe during the hot and cool dry seasons. It was also noted that goats rely on freshwater as their primary source of supplemental water during dry seasons. Urine colour, oedema of the eyelids, and kid survival were indicators for assessing the health status of goats. Nominal binary logistic regression revealed that water contamination was 2.96 more likely to be reported by youth compared to elderly members. Farmers who received informal education were 37 times more likely to report contamination than those who received formal education. High kid mortality as a health status indicator was 50 times less likely to be reported in uncontaminated areas. Intervention strategies for reducing the adverse health effects of tailing dust in contaminated areas should focus primarily on the health of goats during dry seasons.

Pipe material and natural organic matter impact drinking water biofilm microbial community, pathogen profiles and antibiotic resistome deciphered by metagenomics assembly.

Biofilms in drinking water distribution systems (DWDSs) are a determinant to drinking water biosafety. Yet, how and why pipe material and natural organic matter (NOM) affect biofilm microbial community, pathogen composition and antibiotic resistome remain unclear. We characterized the biofilms' activity, microbial community, antibiotic resistance genes (ARGs), mobile genetic elements (MGEs) and pathogenic ARG hosts in Centers for Disease Control and Prevention (CDC) reactors with different NOM dosages and pipe materials based on metagenomics assembly. Biofilms in cast iron (CI) pipes exhibited higher activity than those in polyethylene (PE) pipes. NOM addition significantly decreased biofilm activity in CI pipes but increased it in PE pipes. Pipe material exerted more profound effects on microbial community structure than NOM. Azospira was significantly enriched in CI pipes and Sphingopyxis was selected in PE pipes, while pathogen (Ralstonia pickettii) increased considerably in NOM-added reactors. Microbial community network in CI pipes showed more edges (CI 13520, PE 7841) and positive correlation proportions (CI 72.35%, PE 61.69%) than those in PE pipes. Stochastic processes drove assembly of both microbial community and antibiotic resistome in DWDS biofilms based on neutral community model. Bacitracin, fosmidomycin and multidrug ARGs were predominant in both PE and CI pipes. Both pipe materials and NOM regulated the biofilm antibiotic resistome. Plasmid was the major MGE co-existing with ARGs, facilitating ARG horizontal transfer. Pathogens (Achromobacter xylosoxidans and Ralstonia pickettii) carried multiple ARGs (qacEdelta1, OXA-22 and aadA) and MGEs (integrase, plasmid and transposase), which deserved more attention. Microbial community contributed more to ARG change than MGEs. Structure equation model (SEM) demonstrated that turbidity and ammonia affected ARGs by directly mediating Shannon diversity and MGEs. These findings might provide a technical guidance for controlling pathogens and ARGs from the point of pipe material and NOM in drinking water.

Selenium and concomitant anions removal in a fixed bed bioreactor to satisfy drinking water regulations and subsequent stability check of selenium-laden biosludge.

This is the first successful report on selenium bio-attenuation to satisfy drinking water regulations as per Indian Standards (10 µg/L) in the presence of concomitant nitrate and sulfate from water sources utilizing a fixed bed bioreactor. The bioreactor was immunized with blended microbial culture and worked in downflow mode under anoxic conditions at 30 ± 2 °C for around 190 days under varying influent selenate (100-500 µg/L as selenium), nitrate (50 mg/L), sulfate concentrations (as per selenium removal) and necessary dose of acetic acid (as COD, a carbon source) in synthetic groundwater, operated at an empty bed contact time (EBCT) of 45-120 min. After supplying an adequate dosage of sulfate and alteration of EBCT, selenium was found to comply with drinking water regulations and nitrate was completely removed. X-ray diffraction and transmission electron microscopy analyses depicted nanocrystalline selenium sulfides (SeS and SeS2) formation as the possible mechanisms of selenium removal. Extended toxicity characteristic leaching procedure (TCLP) extractions confirmed a maximum selenium leaching of 52 and 282 µg/L during anoxic and oxic extractions, respectively. Long-term column leaching (>3-month equilibration) under aerobic conditions at pH 7 confirmed the produced precipitate to be essentially stable (∼0.14% Se leaching). This work exhibits the synchronous bioremoval of selenium and its co-anions from contaminated water complying with drinking water standards, and leaving a stable and non-hazardous selenium-laden biosludge.

Too early to add lithium to drinking water? No association between lithium and suicides in a pre-registered Swiss study.

BACKGROUND: Suicide remains a significant public health concern worldwide. Ecological studies reported decreased suicide rates with higher levels of trace lithium levels in drinking water, leading to suggestions of adding lithium to drinking water as a preventative anti-suicide strategy. However, the evidence remains inconclusive, and thus more data are needed. METHODS: This pre-registered study analyzed the association between lithium concentrations in drinking water and suicide rates across 1043 municipalities in Switzerland between 1981 and 2021. We used bivariate correlation analysis, ordinary regression models, and spatial regression models, while accounting for potential confounding variables. RESULTS: There were no significant associations between lithium levels in drinking water and suicide rates, as determined by correlation analysis (r = -0.03, 95 % CI -0.09-0.03, p = 0.33), and by multivariable ordinary and spatial regression models. LIMITATIONS: The correlation between levels of lithium in tap water and the serum of individuals is unknown and ecological studies are inherently limited to establish a causal association. CONCLUSIONS: The null finding in our study adds to the ongoing debate on the effectiveness of trace lithium in drinking water as a public health intervention for suicide prevention, indicating that calls for lithium supplementation are still premature. These findings highlight the need for further research with transparent and replicable methodologies to clarify the potential role of lithium in suicide prevention.

Disparities in access to water, sanitation, and hygiene (WASH) services and the status of SDG-6 implementation across districts and states in India.

Introduction: Access to affordable and improved Water, Sanitation, and Hygiene (WASH) facilities is essential for people's daily lives, and it is the primary goal of Sustainable Development Goal 6 (SDG-6). However, achieving this goal is a significant challenge for many countries, including India. The aim of this study is to assess the progress made towards achieving SDG-6 targets in Indian districts, states, and Union Territories (UTs) and to identify clusters by measuring spatial inequality of WASH coverage in India. Aim and objective: The primary objective of this study is to measure the progress made towards achieving the SDG-6 targets for WASH facilities in Indian districts, states, and UTs. To fulfill this objective, the study used the household data of the National Family Health Survey-5 (NFHS-5) conducted from 2019 to 21. Data and methods: The study used the household data of NFHS-5, which is a nationally representative survey that provides information on household and individual-level characteristics related to health and nutrition. The study identified the variables associated with WASH and created a composite index to measure WASH coverage separately and combined. The study used Gini coefficient to show WASH inequality, and Moran's statistics were used to show spatial dependency. Result: The study found that the inequality of improved water coverage sources in Indian districts was high. Western and northeastern districts need to catch up in terms of achieving the SDG-6 targets. The value of the Gini coefficient (0.29) indicates that inequality in sanitation coverage is also high. All states have reached close to SDG-6 achievement in hygiene indicators. Goa, Sikkim, Andaman & Nicobar Islands, and Lakshadweep are close to the overall WASH coverage achievements of SDG-6. However, Jharkhand, Orissa, Tripura, Assam, and Rajasthan are behind in meeting the goal of SDG-6. Conclusion: The study suggests that more government initiatives and investments are needed to increase the availability, accessibility, and affordability of WASH facilities to improve WASH conditions in western and northeastern Indian districts. The localization or bottom-up approach by giving responsibility to rural and urban local bodies can also help enforce the achievement of SDG-6. The findings of this study can be used to guide policymakers in developing targeted interventions to improve WASH conditions and reduce inequality in India.

Antibiotic-resistant bacteria and resistance-genes in drinking water source in north Shoa zone, Amhara region, Ethiopia.

Background: The growing number of antimicrobial-resistant bacteria in a range of environments poses a serious challenge to infectious disease prevention. Good water quality is critical to human health and has a direct impact on a country's socio-economic growth. Therefore, assessing the bacteriological quality of drinking water provides benchmark data and provides insight into the development of further protection and treatment measures. Methods: A cross-sectional study was conducted from February 1, 2022, to September 31, 2023, in the diarrhea hotspot areas of North Shewa Zone (Minjar-Shenkora and Mojana-Wedera districts). Water samples were collected from drinking water sources (hand-pumps, boreholes, wells, spring water and ponds) to assess the quality following WHO guidelines. The collected water samples were processed for bacterial isolation, antimicrobial susceptibility testing, and detection of antimicrobial resistance genes. Data were entered and analyzed using the Statistical Package for the Social Sciences (SPSS) version 25. Results: A total of (49/138, 35.5%) bacteria were isolated from 138 drinking water samples, with a positive rate of (41/138, 29.7%). Among the isolates, (16/138, 11.6%) were Staphylococcus aureus while (33/138, 23.9%) were members of Enterobacteriaceae. Relatively high resistance rate among all isolates were observed for the most prescribed antibiotics in Ethiopia, including erythromycin, cotrimoxazole, doxycycline, ceftriaxone, gentamicin, and chloramphenicol. However, a low resistance was observed for early introduced antibiotics such as ciprofloxacin and recently introduced antibiotics such as cefotaxime, ceftazidime, imipenem, and meropenem. Among the 49 bacteria isolates, (32/49, 65.3%) were multidrug-resistant (MDR) pathogens while (12/49, 24.5%) were ESßL producers. Different ESßL genes were detected in most bacterial isolates. The predominant ESßL genes were blaCTX-M-gp8/25 (6/33, 18.2%), blaCTX-M-gp9 (5/33, 15.2%), and blaCTX-M-gp1 (5/33, 15.2%). Conclusion: The result of this study suggests that most water sources in the study area were contaminated by various bacterial species that are resistant to different antibiotics. Various ESßL resistance genes have also been detected. Therefore, regular sanitary inspection and bacteriological analysis should be mandatory to protect drinking water sources from contamination and the persistence of resistant bacteria.

Aging of drinking water transmission pipes during long-term operation as a potential source of nano- and microplastics.

Microplastics (MPs) and nanoplastics (NPs) released into drinking water from transmission pipes can pose a potential health risk to consumers. This paper presents the results of a comprehensive study of PE and PVC pipes after long-term operation in drinking water distribution networks, which confirmed that degradable polymers can be a significant source of MPs. Both plastics age relatively quickly, and the degree of damage to the pipe surface depends on the time and operating conditions. During aging, polymer chains deteriorate, leading to a weakening of the structure and increased amorphousness of the plastics. As a result, the surfaces of PE and PVC crack and peel, resulting in the formation of particles with sizes corresponding to NP and MP with high potential for release into water. The magnitude of the phenomenon increases as the diameter of the pipes decreases, indicating that the most vulnerable customers are those at the ends of the network to which drinking water is supplied through small-diameter pipes. Aging PE and PVC pipes should be considered a real and very important source of MPs and NPs in drinking water, and water quality in this aspect should be monitored by manufacturers.

Tracing pesticide dynamics: High resolution offers new insights to karst groundwater quality.

Generally, karst aquifers and springs are highly susceptible to contamination due to the high permeability and, therefore, groundwater flow velocities. The often thin soil cover, accompanied by dolines, can lead to fast infiltration of precipitation water loaded with mobilized contaminants such as pesticides and their transformation products. To date, continuous, temporally highly resolved in-situ monitoring to decipher concentration dynamics for a broad range of pesticides is missing. Therefore, a transportable HPLC-HRMS/MS system (MS2field) was positioned at two karst study sites in the Swiss Jura. Water samples were collected and analyzed for pesticides and their transformation products in-situ every 20 min for 6 weeks in 2021 and 8 weeks in 2022. During the spraying season in 2021, six rain events at site 1 and three at site 2 in 2022 were captured. Concurrently, the water quality parameters electrical conductivity, pH, nitrate, turbidity, and water level, were monitored continuously at high temporal resolution. Further, bacterial cell counts were monitored via online flow cytometry. In 2021, several pesticides and pesticide transformation products were detected in peak concentrations after rain events, of which metamitron showed the highest concentration of up to 1000 ng/L. In one rain event, the Swiss federal and EU drinking water limit of 100 ng/L was exceeded for up to 38 h. Compared with highly frequent MS2field samples collected every 20 min, 42-hours composite samples severely underestimated peak concentrations for all compounds, especially for labile ones. Therefore, it was demonstrated that exceedences of the regulatory limit would have been missed if just composite sampling would have been conducted. Peak concentrations of pesticides coincided with peaks in nitrate concentration and bacterial cell counts following rain events. The correlation analysis showed strong correlations between the three analyzed contaminants (pesticides, nitrate and bacteria), and the proxy parameters electrical conductivity, and pH. The investigation of a second spring revealed similar dynamics indicating that these can be expected in other karst aquifers as well.

[Distribution and health risk assessment of pesticide pollution in raw water and drinking water within key river basins in China in 2022].

OBJECTIVE: To investigate the distribution and exposure levels of pesticides in raw water and drinking water in China, as well as to assess the potential health risks associated with long-term consumption. METHODS: A total of 83 typical water plants were selected in key river basins in China to collected samples of the raw water, finished water, and tap water. The online-solid phase extraction coupled with liquid chromatography-tandem mass spectrometry method was used to determine 13 pesticides, including acetochlor, atrazine, dimethoate, malathion, carbofuran, dichlorvos, chlorpyrifos, parathion, trifluralin, isoprothiolane, simetryn, methyl parathion, and metalaxyl, as well as 6 environmental metabolites, including carbendazim, malaoxon, 3-hydroxycarbofuran, deethyl atrazine, deisopropyl atrazine and hydroxy atrazine. The carcinogenic and non-carcinogenic risks of these pesticides were assessed. RESULTS: The concentrations of total amount of pesticides in the samples ranged from 0.1 ng/L to 1299.4 ng/L, with a median value of 64.7 ng/L. The detection rates of 5 pesticides or their metabolites exceeds 80%, namely acetochlor, atrazine, hydroxyl atrazine, deethyl atrazine, and metalaxyl. More than 6 pesticides or their metabolites were detected in 77.7% of the total 498 samples. The total concentration of pesticides during the wet season ranged from 1.1 ng/L to 1299.4 ng/L, with a median of 69.2 ng/L and a median average daily dose of 2.3 ng/(kg·d). The total concentration of pesticides in the dry season samples ranged from 0.1 ng/L to 543.5 ng/L, with a median of 60.2 ng/L and a median average daily dose of 2.0 ng/(kg·d). Among the 498 samples, the maximum carcinogenic risk of dichlorvos was 2.0×10~(-7), and the maximum carcinogenic risk of trifluralin was 1.1×10~(-10). The non-carcinogenic HI of 19 pesticides and metabolites pesticides was ≤6.0×10~(-3). Among them, the maximum HI of the middle route of the South to North Water Diversion Project, the lower reaches of the Yellow River, the eastern route of the South to North Water Diversion Project, the Liaohe River, and the Songhua River basin was 2.0×10~(-3)-6.0×10~(-3), while the HI of other basins was less than 1.0×10~(-3). CONCLUSION: Different concentrations of pesticides have been detected in raw water, finished water, and tap water of key river basins in China, with the highest total concentration of detected reaching 1299.4 ng/L. The carcinogenic risk was lower than 10~(-6) and the non-carcinogenic hazard index of 19 pesticides was less than 1, and both below the acceptable level. Because of the universality and diverse occurrence of these pesticides in drinking water, long-term exposure to pesticides is still a concern.

[Distribution of 21 organic ophospesters and their metabolites in drinking water in Dongcheng District of Beijing and their health hazard assessment in 2023].

OBJECTIVE: To investigate the pollution of organophosphate esters(OPEs) and their metabolites in drinking water in Dongcheng District of Beijing, and to assess the exposure risk of adults in drinking water. METHODS: The contents of 14 OPEs and 7 metabolites in drinking water were determined by automatic solid phase extraction, isotope dilution and liquid chromatography tandem mass spectrometry. The average daily potential dose(ADD) were calculated based on the recommended intake of drinking water. RESULTS: Seventeen pieces of tap water and 30 pieces of packaged drinking water collected by supermarket were measured. OPEs and di-OPEs were widely detected in drinking water(11 kinds of OPEs and 6 kinds of di-OPEs with the detection rate of more than 50%). The ΣOPEs range was 16.8 to 177ng/L, and the Σdi-OPEs range was 0.328 to 16.3 ng/L. The average daily dose of adult population was calculated: the ADD of 14 kinds of ΣOPEs in male and female were 3.15 and 3.10 ng/(kg·BW·d), and the P95 exposure was 6.95 and 7.00 ng/(kg·BW·d), respectively. The ADD of the seven Σdi-OPEs in male and female were 0.150 and 0.147 ng/(kg·BW·d), and the P95 exposure was 0.330 and 0.332 ng/(kg·BW·d), respectively. The hazard quotient(HQ) of exposure to OPEs through drinking water, calculated using the EPA's oral reference dose assessment, was much less than 1. CONCLUSION: The current exposure of OPEs via drinking water poses a low health risk to adult residents in Dongcheng District. However, due to the lack of Health-based guidance values for the metabolites of OPEs, the exposure risk may be underestimated.

Prevalence of antibiotic resistance genes in different drinking water treatment processes in a northwest Chinese city.

Antibiotic resistance genes (ARGs) are an emerging issue which are receiving increasing concerns in drinking water safety. However, the factors (e.g. treatment processes and water quality) affecting the removal efficiency of ARGs in the drinking water treatment plants (DWTPs) is still unclear. This work investigated the ARG profiles in each treatment process of two DWTPs located in a northwest Chinese city. The results showed that tetracycline and sulfonamide resistance genes were predominant among the 14 targeted ARGs. After the treatment, the Z water treatment plant which demonstrated a higher removal rate of ARGs (ranging from 50 to 80%), compared to the S plant (50-75%). And the average removal rate of tetracycline resistance genes (tetA, tetG, tetQ, tetX) was about 49.18% (S plant) and 67.50% (Z plant), as well as the removal rate of 64.2% and 72.9% for sulfonamide resistance (sul1 and sul2) at S and Z water plants, respectively. It was found that the relative abundance of main microbial communities (such as Bacteroidota, Actinobacteria, Verrucomicrobiota, Roseomonas), α-diversity index, as well as the abundance of pathogenic bacteria were all significantly reduced after different treatment processes. Network co-occurrence analysis revealed that Methylocystis possibly was the potential host for most ARGs, and sul1 was found across a broad spectrum of microorganisms in the drinking water environment. Adonis analysis showed that heavy metals and microbial communities explain solely 44.1% and 35.7% of variances of ARGs within DWTPs. This study provides insights into the contamination status and removal efficiencies of ARGs in DWTPs, offering valuable references for future studies on ARG removal, propagation, and diffusion patterns in drinking water treatment.

Crouching bacteria, hidden tetA genes in natural waters: Intracellular damage via double persulfate activation (UVA/Fe2+/PDS) effectively alleviates the spread of antibiotic resistance.

In this study, we elucidated the chemical and biological inactivation mechanisms of peroxydisulfate (PDS) activated by UVA and Fe2+ (UVA/Fe2+/PDS) in wild-type antibiotic-resistant bacteria (ARB) isolated from a river in Inner Mongolia. Among the screened wild-type ARB, the relative abundance of unidentified Enterobacteriaceae, Stenotrophomonas, and Ralstonia was high. A ratio of 1:1 for Fe2+ and PDS under 18 W·m-2 UVA radiation (sunny days) completely inactivated the environmental ARB isolates. In the macro view of the inactivation process, Fe2+ first activates PDS rapidly, and later the UVA energy accumulated starts to activate PDS; HO• then becomes the main active species at a rate-limiting step. From a micro perspective, damage to the cell wall, intracellular proteins, inactivation of antioxidant enzymes, and genetic material degradation are the inactivation series of events by UVA/Fe2+/PDS, contributing to the 97.8 % inactivation of ARB at the initial stage. No regrowth of sublethal ARBs was observed. The transfer of tetracycline resistance genes from ARB to lab E. coli was evaluated by horizontal gene transfer (HGT), in which no HGT occurred when ARB was eliminated by UVA/Fe2+/PDS. Moreover, the sulfate and iron residuals in the effluents of treated water were lower than the drinking water standards. In summary, PDS, UVA, and Fe2+ activation effectively inactivated wild ARB with a low concentration of reagents, while inhibiting their regrowth and spread of resistance due to the contribution of intracellular inactivation pathways.

Diagnostic screening of private well water using gas chromatography with high resolution mass spectrometry to support well water management.

In the US, private well users are responsible for their own water quality testing, but local health officials are often uncertain what tests to recommend, particularly for regulated organic chemical contaminants. This study evaluated the utility of suspect and non-target screening (NTS) high resolution mass spectrometry (HRMS) as a tool to identify a wide range of organic chemicals of emerging concern in private well water and to inform well water management decisions. Qualitative NTS, which detects chemicals without providing concentrations, was used to analyze 25 private well water samples from Wake County, North Carolina. Using the NIST 20 mass spectral database (M1), NTS tentatively identified 106 unique organic chemicals across the 25 samples and an average of 11 organic chemicals per sample. At least one USEPA ToxCast chemical was identified in each private well water sample. Private well water users were interviewed prior to and after their sample's NTS results were reported back; four county groundwater managers were interviewed after aggregated results for all 25 water samples were reported back. All but one well user participant chose to participate in the reporting-back post-interview. The 24 private well users found NTS results useful and valued the contextualization of their results using NTS results for other well users and a local municipal water sample. Most private well users (67%) were surprised by their well water results, especially regarding the number of tentatively identified organic chemicals detected. All the groundwater managers believed the NTS results were useful and could help improve their testing recommendations to private well users. Even with qualitative limitations, NTS results can be an effective and valuable tool to inform the public and governance stakeholders in decisions around groundwater quality management.

Neglected contributors to the transmission of bacterial antibiotic resistance in drinking water: Extracellular antibiotic resistance genes and the natural transformation.

Antibiotic resistance genes (ARGs) have increasingly gained recognition as an "emerging contaminant" that poses a threat to the biosafety of drinking water. However, previous researches have primarily focused on the intracellular state of ARGs and rarely investigated the ecological characteristics (e.g., distribution and origin), environmental behavior (spread), and risks of extracellular form (eARGs) within drinking water systems. Therefore, this review evaluated isolation strategies and extraction methods for recovering eARGs from drinking water, elucidated the distribution characteristics of eARGs, and examined their impact on the antibiotic resistome from source water to tap water. We emphasized that chlorination and biological treatments significantly contribute to the prevalence and persistence of eARGs in drinking water. Moreover, we highlighted the role of biological reactors (e.g., biofilter, biological activated carbon) and drinking water distribution systems in facilitating the natural transformation of eARGs while significantly contributing to bacterial antibiotic resistance (BAR) propagation. Finally, we summarized the current risk assessment systems for ARGs and critically address remaining challenging questions necessary for better forecasting health risks associated with eARGs in drinking water environments. Collectively, this review enhances the understanding of ecological characteristics and environmental behavior of eARGs in drinking water while providing important implications for controlling and reducing BAR contamination not only in drinking water but also in other aquatic environments.

Per- and polyfluoroalkyl substances (PFAS) in drinking water in Southeast Los Angeles: Industrial legacy and environmental justice.

Per- and polyfluoroalkyl substances (PFAS) are persistent chemicals of increasing concern to human health. PFAS contamination in water systems has been linked to a variety of sources including hydrocarbon fire suppression activities, industrial and military land uses, agricultural applications of biosolids, and consumer products. To assess PFAS in California tap water, we collected 60 water samples from inside homes in four different geographic regions, both urban and rural. We selected mostly small water systems with known history of industrial chemical or pesticide contamination and that served socioeconomically disadvantaged communities. Thirty percent of the tap water samples (18) had a detection of at least one of the 32 targeted PFAS and most detections (89 %) occurred in heavily industrialized Southeast Los Angeles (SELA). The residents of SELA are predominately Latino and low-income. Concentrations of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) ranged from 6.8 to 13.6 ng/L and 9.4-17.8 ng/L, respectively in SELA and were higher than State (PFOA: 0.007 ng/L; PFOS: 1.0 ng/L) and national health-based goals (zero). To look for geographic patterns, we mapped potential sources of PFAS contamination, such as chrome plating facilities, airports, landfills, and refineries, located near the SELA water systems; consistent with the multiple potential sources in the area, no clear spatial associations were observed. The results indicate the importance of systematic testing of PFAS in tap water, continued development of PFAS regulatory standards and advisories for a greater number of compounds, improved drinking-water treatments to mitigate potential health threats to communities, especially in socioeconomically disadvantaged and industrialized areas.

Microplastics in the urban water cycle: A critical analysis of issues and of possible (needed?) solutions.

Microplastic (MP) contamination is a problem that affects even remote, scarcely populated regions of the world. This topic has recently been the subject of many published studies, however, these often adopt hyperbolic statements and do not actually provide definitive evidence that MPs are a cause of environmental risk in actual environmental conditions. New technologies to remove MPs from supply and waste water are being investigated, but they are able to intercept a minimal fraction of the MPs circulating in all environmental media. Recently, several pieces of legislation were introduced to reduce plastic production, use, and disposal, but it is not clear how such measures could achieve a significant environmental MP reduction. This paper addresses the MP issue within the urban water cycle, examining recent current literature on MP presence in drinking and waste water, and overviewing available recent treatment technologies for their removal. The ensuing discussion attempts to holistically assess the actual relevance of the issue in the light of the current scientific evidence.