Drinking Water Disinfection Research Articles

New aspects in deriving health-based guidance values for bromate in swimming pool water

Bromate, classified as a EU CLP 1B carcinogen, is a typical by-product of the disinfection of drinking and swimming pool water. The aim of this study was (a) to provide data on the occurrence of bromate in pool water, (b) to re-evaluate the carcinogenic MOA of bromate in the light of existing data, (c) to assess the possible exposure to bromate via swimming pool water and (d) to inform the derivation of cancer risk-related bromate concentrations in swimming pool water. Measurements from monitoring analysis of 229 samples showed bromate concentrations in seawater pools up to 34 mg/L. A comprehensive non-systematic literature search was done and the quality of the studies on genotoxicity and carcinogenicity was assessed by Klimisch criteria (Klimisch et al., Regul Toxicol Pharmacol 25:1–5, 1997) and SciRAP tool (Beronius et al., J Appl Toxicol, 38:1460–1470, 2018) respectively. Benchmark dose (BMD) modeling was performed using the modeling average mode in BMDS 3.1 and PROAST 66.40, 67 and 69 (human cancer BMDL10; EFSA 2017). For exposure assessment, data from a wide range of sources were evaluated for their reliability. Different target groups (infants/toddlers, children and adults) and exposure scenarios (recreational, sport-active swimmers, top athletes) were considered for oral, inhalation and dermal exposure. Exposure was calculated according to the frequency of swimming events and duration in water. For illustration, cancer risk-related bromate concentrations in pool water were calculated for different target groups, taking into account their exposure using the hBMDL10 and a cancer risk of 1 in 100,000. Convincing evidence was obtained from a multitude of studies that bromate induces oxidative DNA damage and acts as a clastogen in vitro and in vivo. Since statistical modeling of the available genotoxicity data is compatible with both linear as well as non-linear dose–response relationships, bromate should be conservatively considered to be a non-threshold carcinogen. BMD modeling with model averaging for renal cancer studies (Kurokawa et al., J Natl. Cancer Inst, 1983 and 1986a; DeAngelo et al., Toxicol Pathol 26:587–594, 1998) resulted in a median hBMDL10 of 0.65 mg bromate/kg body weight (bw) per day. Evaluation of different age and activity groups revealed that top athletes had the highest exposure, followed by sport-active children, sport-active adults, infants and toddlers, children and adults. The predominant route of exposure was oral (73–98%) by swallowing water, followed by the dermal route (2–27%), while the inhalation route was insignificant (< 0.5%). Accepting the same risk level for all population groups resulted in different guidance values due to the large variation in exposure. For example, for an additional risk of 1 in 100,000, the bromate concentrations would range between 0.011 for top athletes, 0.015 for sport-active children and 2.1 mg/L for adults. In conclusion, the present study shows that health risks due to bromate exposure by swimming pool water cannot be excluded and that large differences in risk exist depending on the individual swimming habits and water concentrations.

Low-Cost ceramic disk filters coated with Graphitic carbon nitride (g-C3N4) for drinking water disinfection and purification

Access to safe drinking water is a challenge in remote and rural areas, where thus urgently need cost-effective household drinking water purification device. In this study, a ceramic disk filter coated with modified g-C3N4 (MCN@CDF) was developed for drinking water disinfection and purification. Factorial analysis results showed that factors including the coating amount of MCN, light intensity, influent humic acid (HA) concentration, influent turbidity, and influent pH had significant positive effects on the E. coli removal efficiency of MCN@CDF. However, the influent turbidity had a significant negative effect on the permeability. The significant 2-factor interaction effects on the performance of MCN@CDF were also discussed. The developed MCN@CDF showed an exceptional performance in bacterial removal, and the log reduction value (LRV) could reach up to 7.14. This could be ascribed to the synergistic effect of physical retention and photocatalytic disinfection. The photocatalytic disinfection was induced by MCN under light irradiation, which produced H2O2 and h+ to inactivate E. coli. These reactive species could attack E. coli cells, causing changes in the cell shape and damage to DNA. The developed MCN@CDF also exhibited excellent practicability during treating realistic ground water, which met the standard of drinking water after purification with MCN@CDF. This study provided a low-cost and safe alternative for household drinking water purification in rural areas.

Associations between drinking water disinfection byproducts and menstrual cycle characteristics: A cross-sectional study among women attending an infertility clinic.

Disinfection byproducts (DBPs) have been shown to alter ovarian steroidogenesis and cause estrous cyclicity disturbance and prolongation in experimental studies, however human studies are lacking. We aimed to evaluate the cross-sectional associations between drinking water DBPs and menstrual cycle characteristics. A total of 1078 women attending an infertility clinic in Wuhan, China were included between December 2018 and January 2020. Characteristics of menstrual cycle were collected by questionnaires. Concentrations of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) were measured in urine as biomarkers of drinking water DBPs. Multivariate logistic and linear regression models were used to evaluate the associations between urinary DCAA and TCAA concentrations and menstrual cycle characteristics. Higher urinary DCAA concentrations were associated with increased odds ratios (ORs) of irregular menstrual cycle (OR=1.80; 95% CI: 0.97, 3.33 for the highest vs. lowest quartile; P for trend=0.05) and long menstrual cycle (OR=1.62; 95% CI: 0.97, 2.70 for the highest vs. lowest quartile; P for trend=0.06), as well as prolonged variation in cycle length (β=1.27 days; 95% CI: -0.11, 2.66 for the highest vs. lowest quartile; P for trend=0.04). Higher urinary TCAA concentrations were associated with prolonged bleeding duration (β=0.23 days; 95% CI: -0.06, 0.51 for the highest vs. lowest quartile; P for trend=0.07). These results suggest that exposure to drinking water DBPs is associated with menstrual cycle disturbances. These findings are warranted to confirm in other studies.

Hybrid of sodium polytungstate polyoxometalate supported by the green substrate for photocatalytic degradation of auramine-O dye.

Nowadays, textile industries have severely polluted the ecosystem and water sources via disposal of highly thermo- and photo-stable dyes within the ecology that require practical strategies to remove them from nature. In studies, the photocatalytic disinfection technique has been shown to have widespread applications in indoor air, environmental health, detection, biological, biomedical, laboratory hospital, pharmaceutical food industry, plant safety, waste water, effluents disposal, and drinking water disinfection. Herein, the sodium polytungstate (SPT) polyoxometalate (POM) was synthesized through a multi-step production procedure and hence modified via employing a green protocol by using tartaric acid, glutamic acid, and kombucha solvent toward efficient and total complete removal of the highly toxic, stable, and carcinogenic auramine-O (AO) dye from aqueous media. In this regard, developed materials were well-characterized, and their photocatalysis performance for photodegradation of AO dye was examined. Achieved results showed that the optimum absorption conditions were achieved at pH of 5.0, 15mg/L of AO concentration, 0.04g of photocatalyst dosage, and 110min irradiation time, where SPT and modified SPT via green protocol showed full desirability (desirability function (DF) index of 1) along with 71.75 and 100% removal percentage, respectively. Obtained results justified the superior photocatalytic role of the SPT POM and its derived nanocluster that can be used for the complete removal of highly stable dyes from aqueous media till reaching the drinking water standard.

Effect of ozone–tea polyphenols as a drinking water disinfection process on antibiotic resistance genes

Abstract In recent years, the wide spread of antibiotic resistance genes (ARGs) has brought tremendous risk to the biological safety of drinking water. With the increasing demand for drinking water quality, ARGs have been regarded as a new pollutant that may cause serious public health problems. A large number of studies have shown that the disinfection process of drinking water treatment plants can remove ARGs. However, the effects of traditional disinfection methods on ARGs have their own disadvantages. Tea polyphenols have attracted more and more researchers’ attention as a green, efficient and non-disinfection by-products disinfectant. The effect of the ozone–tea polyphenols disinfection process on ARGs in filtered effluent of waterworks was analyzed by using metagenomic sequencing. The result shows that the ozone–tea polyphenols disinfection process is suitable for specific raw water containing more tetracycline, sulfonamide, β-lactam, and aminoglycoside resistance genes, and the removal rate of total resistance genes in water is higher than the traditional disinfection process. The effect of the ozone–tea polyphenols disinfection process on ARGs is to reduce the transfer of ARGs by destroying ARGs molecules and inhibiting the proliferation of ARGs host cells. As an assistant disinfectant, tea polyphenols have significance for the ability to remove ARGs during traditional disinfection.

Effects of iodoacetic acid drinking water disinfection byproduct on the gut microbiota and its metabolism in rats

Iodoacetic acid (IAA) is an unregulated disinfection byproduct in drinking water and has been shown to exert cytotoxicity, genotoxicity, tumorigenicity, and reproductive and developmental toxicity. However, the effects of IAA on gut microbiota and its metabolism are still unknown, especially the association between gut microbiota and the metabolism and toxicity of IAA. In this study, female and male Sprague–Dawley rats were exposed to IAA at 0 and 16 mg/kg bw/day daily for 8 weeks by oral gavage. Results of 16S rRNA gene sequencing showed that IAA could alter the diversity, relative abundance and function of gut microbiota in female and male rats. IAA also increased the abundance of genes related to steroid hormone biosynthesis in the gut microbiota of male rats. Moreover, metabolomics profiling revealed that IAA could significantly disturb 6 and 13 metabolites in the feces of female and male rats, respectively. In female rats, the level of androstanediol increased in the IAA treatment group. These results were consistent with our previous findings, where IAA was identified as an androgen disruptor. Additionally, the perturbed gut microbiota and altered metabolites were correlated with each other. The results of this study indicated that IAA could disturb gut microbiota and its metabolism. These changes in gut microbiota and its metabolism were associated with the reproductive and developmental toxicity of IAA.

A Green Approach to Safe Domestic Drinking Water Supply by Using Solar Geyser

Introduction: Accessibility to safe drinking water is an important human health issue, so water reuse and water resources management are critical in arid parts of developing regions. This study aimed to investigate the use of a combined simple designed solar geyser/photocell for drinking water disinfection.&#x0D; Materials and Methods: In this study, a solar geyser with a simple design was combined with a solar cell and its efficiency on the disinfection of contaminated water was investigated. This study was carried out with artificially polluted tap water by a solar geyser joined with a solar photovoltaic cell. The heated water (55°C) was kept for 2 hours using a solenoid valve. The pilot plant was operated and monitored for one year. The volume of the collected effluent was measured every 24 h. The most probably number (MPN) of total coliforms and fecal coliforms in 100 mL of 24-hour composed samples were measured.&#x0D; Results: The mean volume of disinfected water production was calculated as 2095.74 ± 270.28 mL/day. The strongest correlation was found between disinfected water and the maximum daily ambient air temperature with a linear model (R2 = 0.9937). The results showed that by increasing the sunny time, the volume of water outlet increased. Therefore, sunny time and UV radiation have direct effect on volume of disinfected water.&#x0D; Conclusion: The simple designed solar geyser for drinking water disinfection was efficient and recommended for tropical areas, emergency conditions, and farms for agricultural activities.

Toxicological Evaluation of Complex Mixtures: Prediction and interactions – A Review

The evaluation of chemical mixtures is a complex subject and follows several approaches. To strengthen the scientific basis of the toxicology of chemicals mixtures, studies have been carried out to determine the biological concepts and basic formulas of mathematics for the extrapolation of low doses. The extrapolation of these doses should be considered as a key issue in the assessment of potential health risks from exposure to chemical mixtures in the atmosphere, by-products of drinking water disinfection, or in recombinant additives ..., etc. Clearly, the intervention of biologists, biomathematicians and bioengineers in toxicology mixtures is essential for the development of this. Studies on complex mixtures use multidisciplinary knowledge. The risk of complex mixtures remains a challenge. Before the results of the toxicity test can be used to adjust the risk assessment calculations, it is important to assess the chemical composition and to understand the mechanism of chemical interactions observed in animals chronically exposed to low doses of chemical mixtures. The current development of exposure biomarkers allows the assessment of the internal dose of exposure to toxic substances, integrating all the media and pathways of contact, thus allowing a precise assessment of the risk to human health. Finally, it is time to initiate research projects related to this theme, and more particularly to the development of toxicological and eco-toxicological tests, to better study interactions at low doses. This will not only improve scientific knowledge, but also provide essential skills to increase safety against exposure to complex mixtures. A battery of tests seems essential to evaluate the toxic potential of the mixtures, and to better understand the different possible interactions between the substitutes. However, the toxicological and eco-toxicological and risk assessment models appear to be limited by, on the one hand, the non-specificity of the mechanisms of action but at stake, and on the other hand, their lack of representativeness of in vivo effects It would therefore be interesting and desirable for these tests to be better understood, in order to define and interpret the mechanisms of action of the mixtures. This bibliographic review aimed to provide some answers to the central question which is: the nature of the possible interactions between contaminants that can influence their toxicities.

Degradation of 2,6-dichloro-1,4-benzoquinone by UV/H2O2/O3 treatment: Effectiveness, water matrix effects, and degradation mechanism

2,6-dichloro-1,4-benzoquinone (DCBQ), a typical representative of Halobenzoquinones, is an emerging aromatic disinfection by-product (DBP) with high toxicity and carcinogenicity, generated commonly through the chlorination in the drinking water disinfection process while there is still a lack of research on its removal. In this study, the effects of ultraviolet-based advanced oxidation processes (UV-AOPs) on the degradation of DCBQ were evaluated. The results showed that UV-AOPs are effective in degrading DCBQ. The removal of DCBQ by UV/H2O2/O3 was more significant than by UV/H2O2 or UV/O3, achieving a 96.7% removal rate at both the O3 and H2O2 doses of 1 mg/L. The results also indicated the alkaline and weakly acidic environments could facilitate the degradation of DCBQ, inorganic anions could inhibit DCBQ degradation and the degree of inhibition increased as the matrix concentration increased. The degradation of DCBQ was inhibited more by the CO32− than the other matrix components, such as Cl− and NO3−. It was shown by the density functional theory simulations and the ultrahigh-performance liquid chromatography (UPLC) - Orbitrap mass spectra that the electrons in DCBQ are mainly on the chlorine atom connected to the carboatomic ring and that OH• can attack the chlorine atom to cause de-chlorination. The DCBQ degradation pathway may involve the oxidation of DCBQ to 3-hydroxy-2,6-DCBQ (HO–DCBQ) and 3,5-dichloro-1,2,4-pyrogallol, the further degradation of intermediate products by OH• to dechlorinated forms of HO–DCBQ and DCBQ.

The Use of Silver Nanoparticles in Water Treatment, Wastewater Treatment and Recycling

The review paper deals with the use of silver nanoparticles (AgNPs) in water treatment and recycling systems and the presence of AgNPs in wastewater systems. In the water industry, AgNPs can be used in the water treatment process as new filter materials (layers applied to the membranes of various compositions) or as a gentle alternative to the existing drinking water disinfection (solar disinfection in combination with titanium). On the other hand, AgNPs also can be a certain risk to the ecosystem if they are released from such surface-treated materials or preparations into wastewater. The AgNPs, present in the wastewater, then penetrate to the wastewater treatment plants, where they can affect the treatment process itself, especially the sensitive biological nitrification process. Silver ions with antibacterial properties are effectively removed by wastewater treatment plants and no significant negative effect on the treatment process by higher concentrations of silver has been reported so far. With respect to the bioaccumulation capabilities of nanoparticles, it is important to focus primarily on assessing of the longer-term effects of AgNPs in the ecosystem and the aquatic environment.

The effect of chitosan nanoparticles on Escherichia coli viability in drinking water disinfection

Abstract Drinking water disinfection or inactivation of pathogenic microorganisms is an essential step to minimize infection risks and decrease the incidence of waterborne diseases. Recently, chitosan nanoparticles (CNs) have been highlighted as an antimicrobial agent for a wide range of applications due to their natural antimicrobial properties, and low or no toxicity risk for human health. In this study, we generated CNs from three different molecular weight (MW) chitosan (low, medium, high) at various concentrations (0.25, 0.5 and 2% (w/v)). After the CNs preparation and quality assessment, the antimicrobial activity was evaluated by measuring the log reduction of Gram-negative bacteria E. coli as a model microorganism for faecal pollution. The results demonstrated that 0.25% of medium MW CNs are optimal for more than 99.99% reduction of cultivable E. coli and 97% inactivation of metabolically active E. coli. These results indicated that CNs were able to inhibit the growth of cultivable and metabolically active E. coli in tap water and demonstrated the potential use of CNs as an alternative antimicrobial agent in drinking water disinfection.

Cytoprotective effect of taurine against sodium chlorate-induced oxidative damage in human red blood cells: an ex vivo study.

Sodium chlorate (NaClO3) is a common non-selective herbicide that is also used in paper and pulp mills and is produced as a by-product during drinking water disinfection by chlorine dioxide. Here, we report the effect of dietary antioxidant taurine on NaClO3-induced cytotoxicity in human red blood cells (RBC). RBC were treated with 5mM NaClO3, either alone or in presence of 1, 2.5 and 5.0mM taurine. Incubation of RBC with NaClO3 alone caused hemolysis, increased oxidation of lipids and proteins, methemogobin level and decreased total sulfhydryl and glutathione content. It lowered the activities of antioxidant enzymes thioredoxin reductase, glutathione peroxidase, catalase and glutathione reductase, while Cu-Zn superoxide dismutase activity was increased. The antioxidant capacity of RBC was impaired. This strongly suggests that NaClO3 causes the induction of oxidative stress condition in RBC. The specific activities of lactate dehydrogenase, glucose 6-phosphate dehydrogenase and plasma membrane bound enzymes, were also greatly altered. However, prior treatment of RBC with taurine conferred significant protection against NaClO3-induced oxidative damage and also improved the antioxidant defence system of cells. These results were supported by electron microscopy images of RBC. Treatment with NaClO3 alone converted the normal biconcave discoidal RBC to acanthocytes and echinocytes but this transformation was greatly prevented in the presence of taurine. Thus, taurine mitigates the cytotoxicity of NaClO3 in human RBC and can function as an effective chemoprotectant.

Prevalence and Trends of Drinking Water Disinfection Byproducts-Related Cancers in Addis Ababa, Ethiopia

Background:Disinfection byproducts (DBPs) from chlorinated drinking water have been linked to an increased risk of cancer in the bladder, stomach, colon, and rectum. No studies showed the independent trends and prevalence of these cancers in Ethiopia. Therefore, this study aimed to determine the prevalence and trends of disinfection byproducts-related cancers in Addis Ababa, Ethiopia.Methods:Data were collected from the Addis Ababa Cancer Registry. Spatial data sets were produced and classified into households receiving chlorinated surface water and less chlorinated groundwater. The Cochran-Armitage trend test was used to evaluate whether there was a disinfection byproducts-related cancers (DBRCs) trend among communities receiving chlorinated water. Negative binomial regression was used to analyze the incidence rate.Results:A total of 11, 438 cancer cases were registered between 2012 and 2016, and DBRCs accounted for approximately 17%. The majority of the total cancer cases were female; 7,706 (67%). The prevalence of DBRCs was found to be higher in communities supplied with chlorinated water. From 2012 to 2016, the trend of colon cancer increased (β = 10.3, P value = .034); however, esophageal cancer decreased (β = −6.5, P value = .018). Approximately 56% of colorectal cancer patients and 53% of stomach cancer patients are known to be using chlorinated surface water for drinking regularly. In addition, approximately 57.1% and 54% of kidney and bladder cancer patients, respectively, used chlorinated surface water.Conclusion:The prevalence of DBRCs in this study was found to be high. The colon cancer trend increased substantially from 2012 to 2016. The prevalence of DBRCs was higher in communities supplied with chlorinated surface water. Similarly, the prevalence of DBRCs was higher among males than females. Further study is required to validate the association between DBRCs and water chlorination.

Pyrogenic carbon-promoted haloacetic acid decarboxylation to trihalomethanes in drinking water

Drinking water disinfection by chlorination or chloramination can result in the formation of disinfection byproducts (DBPs) such as haloacetic acids (HAAs) and trihalomethanes (THMs). Pyrogenic carbonaceous matter (PCM), such as activated carbon (AC), is commonly used as an ostensibly inert adsorbent to remove HAAs from water. HAA degradation has been mainly attributed to biological factors. This study, for the first time, revealed that abiotic HAA degradation in the presence of PCM could be important under water treatment conditions. Specifically, we observed complete destruction of Br3AA, a model HAA, in the presence of powder AC at pH 7 within 30 min. To understand the role of PCM and the reaction mechanism, we performed a systematic study using a suite of HAAs and various PCM types. We found that PCM significantly accelerated the transformation of three HAAs (Br3AA, BrCl2AA, Br2ClAA) at pH 7. Product characterization indicated an approximately 1:1 HAA molar transformation into their respective THMs following a decarboxylation pathway with PCM. The Br3AA activation energy (Ea) was measured by kinetic experiments at 15–45 °C with and without a model PCM, wherein a significant decrease in Ea from 25.7 ± 3.2 to 13.6 ± 2.2 kcal•mol−1 was observed. We further demonstrated that oxygenated functional groups on PCM (e.g., -COOH) can accelerate HAA decarboxylation using synthesized polymers to resemble PCM. Density functional theory simulations were performed to determine the enthalpy of activation (ΔH‡) for Br3AA decarboxylation with H3O+ and formic acid (HCOOH). The presence of HCOOH significantly lowered the overall ΔH‡ value for Br3AA decarboxylation, supporting the hypothesis that -COOH catalyzes the C-C bond breaking in Br3AA. Overall, our study demonstrated the importance of a previously overlooked abiotic reaction pathway, where HAAs can be quickly converted to THMs with PCM under water treatment relevant conditions. These findings have substantial implications for DBP mitigation in water quality control, particularly for potable water reuse or pre-chlorinated water that allow direct contact between HAAs and AC during filtration as well as PAC fines traveling with finished water in water distribution systems. As such, the volatilization and relative low toxicity of volatile THMs may be considered as a detoxification process to mitigate adverse DBP effects in drinking water, thereby lowering potential health risks to consumers.

Chlorinated cyanurates and potassium salt of peroxymonosulphate as antimicrobial and antibiofilm agents for drinking water disinfection

The understanding of microbial susceptibility to disinfectants is an important step to provide drinking water (DW) of adequate microbiological quality. In drinking water distribution systems (DWDS) the application of disinfectants is the main approach to control microorganisms. Although chlorine has been commonly used for DW treatment, the increase of microbial resistance and the production of harmful disinfection by-products promote the necessity to seek new alternatives. This study evaluated the antimicrobial activity of sodium dichloroisocyanurate (NaDCC), trichloroisocyanuric acid (TCCA), and pentapotassium bis(peroxymonosulphate) bis(sulphate) (OXONE) against two emerging pathogens isolated from DW, Acinetobacter calcoaceticus and Stenotrophomonas maltophilia. Free chlorine from calcium hypochlorite was used for comparison. The dose and time-responses against planktonic bacteria were performed as well as the assessment of the effects on membrane integrity. Moreover, the effects against 48 h-old biofilms formed on polyvinyl chloride and stainless steel were evaluated in terms of biofilm culturability and removal. Minimum bactericidal concentrations of 2.1 and 3.1 mg/L for NaDCC, 2.5 and 3.8 mg/L for TCCA, 340 and 690 mg/L for OXONE, and 0.80 and 1.0 mg/L for free chlorine alone were obtained against S. maltophilia and A. calcoaceticus, respectively. The kinetic modeling revealed that NaDCC and TCCA caused similar inactivation rates and the time for first log reduction by OXONE was less than 10 min, for both bacteria. All the disinfectants triggered significant bacterial cytoplasmic membrane destabilization, even at sub-lethal concentrations. A 30 min treatment with the disinfectants allowed a reduction in the biofilm culturability up to 5 log. OXONE was the disinfectant with the best efficiency against both bacterial biofilms. However, none of the disinfectants caused significant biofilm removal (reduction < 1 log cells/cm2). This study highlights NaDCC, TCCA, and OXONE as promising alternatives to free chlorine for DW disinfection, particularly for planktonic growth control and biofilm culturability reduction.

Haloquinone Chloroimides as Toxic Disinfection Byproducts Identified in Drinking Water.

Haloquinone chloroimides (HQCs) are suspected to be highly toxic contaminants, and their production during drinking water disinfection is predicted. However, HQC disinfection byproducts (DBPs) have not been reported in drinking water to date because of analytical limitations. In this study, we developed an analytical method to detect five HQCs, including 2,6-dichloroquinone-4-chloroimide (2,6-DCQC), 2,6-dibromoquinone-4-chloroimide (2,6-DBQC), 2-chloroquinone-4-chloroimide (2-CQC), 3-chloroquinone-4-chloroimide (3-CQC), and 2,6-dichloroquinone-3-methyl-chloroimide (2,6-DCMQC). This method combined a derivatization reaction of HQCs with phenol in alkaline solutions to produce halogenated indophenols, a solid-phase extraction pretreatment using hydrophilic-lipophilic balanced (HLB) cartridges, and a multiple reaction monitoring (MRM) method for quantification. The method was demonstrated to be sensitive and accurate with recoveries of 71-85% and limits of detection of 0.1-0.2 ng/L for the five tested HQCs. Using this method, five tested HQCs were identified in drinking water samples from nine water treatment plants and water distribution systems as new DBPs at concentrations of up to 23.1 ng/L. The cytotoxicity of the five tested HQCs in HepG2 cells was higher than or comparable to that of 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ), an emerging DBP that was hundreds to thousands of times more toxic than regulated DBPs. This study presents the first analytical method for HQC DBPs in drinking water and the first set of occurrence and cytotoxicity data of HQC DBPs.

Silver nanoparticles on UiO-66 (Zr) metal-organic frameworks for water disinfection application

Drinking water disinfection is an essential process to assure public health all over the world. In this study, silver nanoparticles (AgNPs) on UiO-66 (Zr) Metal-Organic Frameworks (Ag@UiO-66) is proposed as a potential water disinfection strategy. AgNPs are synthesized using polyvinyl pyrrolidone (PVP) as stabilizing agent, and sodium borohydride as reducing agent are subsequently embedded on UiO-66, a high-stability organometallic framework. The effect of premixing time, reaction time and reactant concentration on the loading rate of AgNPs on UiO-66 was investigated. The maximum load rate of AgNPs on UiO-66 could reach 13% when the premixing time is 3h, the reaction time is 45min and the concentration of AgNO3 is 10μg/mL. The formation of AgNPs loaded on UiO-66 was observed and confirmed with ultraviolet and visible spectrophotometry (UV-Vis), scanning electron microscopy (SEM), infrared emission spectroscopy (IES) and X-ray diffraction (XRD) analysis. Ag@UiO-66 exhibited strong antibacterial activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, with minimum inhibitory concentrations (MIC) of 64 and 128μg/mL, respectively. The germicidal efficacy of Ag@UiO-66 enhanced significantly as the temperature rose from 4°C to 37°C. The results indicate that Ag@UiO-66 is potential candidate as a feasible water disinfection material.

Disinfection By-products in Drinking Water and Their Control Strategies: A Review

Disinfection by-products(DBPs) are secondary pollutants generated by the reaction of disinfectants with organic or inorganic precursors during drinking water disinfection. DBPs have received considerable global attention due to their carcinogenic, teratogenic, and mutagenic characteristics. Focusing on drinking water, this paper introduces the main classification and research history of DBPs, and then summarizes the concentration levels of common DBPs in drinking water, and DBPs regulatory compliance in global drinking water standards. Further, the control strategies for DBPs in drinking water, including source control, process control, DBPs removal and integrated control are introduced together with the advantages and disadvantages. Finally, a summary and review of the current level and future trends of DBPs research in China are presented with the proposed control strategies. On the one hand, when evaluating the control effect of a process or technology, the DBPs concentration and comprehensive toxicity should be considered; on the other hand, in order to realize the efficient control of DBPs in drinking water, the focus should be on the integrated methods coupling different DBPs control methods.

The effects of ozone treatments on the agro-physiological parameters of tomato plants and the soil microbial community

Ozone has been applied in many processes (drinking water disinfection and wastewater treatment, among others) based on its high degree of effectiveness as a wide-spectrum disinfectant and its potential for the degradation of pollutants and pesticides. Nevertheless, the effects of irrigation with ozonated water on the soil microbial community and plant physiology and productivity at the field scale are largely unknown. Here, we assessed the impact of irrigation with ozonated water on the microbial community of a Mediterranean soil and on Solanum lycopersicum L. agro-physiology and productivity in a greenhouse experiment. For this purpose, we evaluated: i) soil physicochemical properties, soil enzyme activities, and the biomass (through analysis of microbial fatty acids) and diversity (through 16S rRNA gene and ITS2 amplicon sequencing) of the soil microbial community, and ii) the nutrient content, physiology, yield, and fruit quality of tomato plants. Overall, the soil physicochemical properties were slightly affected by the treatments applied, showing some differences between continuous and intermittent irrigation with ozonated water. Only the soil pH was significantly reduced by continuous irrigation with ozonated water at the end of the assay. Biochemical parameters (enzymatic activities) showed no significant differences between the treatments studied. The biomasses of Gram- bacteria and fungi were decreased by intermittent and continuous irrigation with ozonated water, respectively. However, the diversity, structure, and composition of the soil microbial community were not affected by the ozone treatments. Changes in soil properties slightly affected tomato plant physiology but did not affect yield or fruit quality. The stomatal conductance was reduced and the intrinsic water use efficiency was increased by continuous irrigation with ozonated water. Our results suggest that soil health and fertility were not compromised, however ozonated water treatments should be tailored to individual crop conditions to avoid adverse effects.

The impact of Covid-19 pandemic on water supplies and wastewater sewer system

Besides other issues, the global pandemic caused by SARS CoV-2 also brought a number of water management questions which mainly concern the likelihood of virus spread through drinking water and possible contamination of wastewater. This paper reviews principal data on the virus and the recent course of the pandemics. It shows that there is no risk of the virus spread through drinking water and that drinking water disinfection is sufficiently effective. On the contrary, wastewater was observed for SARS CoV-2 RNA particles. As a result, a number of papers deal with research in the observation of the virus in wastewater, which may become an early-warning tool before an epidemic develops. The monitoring of the virus in wastewaters may also enable researchers to predict the course of Covid-19 illness rates in the future.