Co/Ni/Cu-NH2BDC MOF@natural Egyptian zeolite ore nanocomposite for calcium ion removal in water softening applications.

Water softening is a treatment process required to remove calcium (Ca(II)) and magnesium (Mg(II)) cations from water streams. Nanocomposites can provide solutions for such multiple challenges and have high performance and low application costs. In this work, a multimetallic cobalt, nickel, and copper 2-aminoterephthalic acid metal-organic framework ((Co/Ni/Cu-NH2BDC) MOF) was synthesized by a simple solvothermal technique. This MOF was supported on an Egyptian natural zeolite ore and was used for the adsorption of Ca(II) ions for water-softening applications. The adsorbent was characterized using Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), N2 adsorption-desorption isotherms, and zeta potential measurements. The adsorption isotherm data for the prepared adsorbent toward Ca(II) were best fit using the Redlich-Peterson model and showed a maximum adsorption capacity of 88.1 mg/g. The adsorption kinetics revealed an equilibrium time of 10 min, which was best fit using the Avrami model. The intermolecular interactions of Ca(II) ions with zeolite and MOF were investigated by Monte Carlo simulations, molecular dynamics simulations, and FTIR and XRD analyses. The adsorption sites in the zeolite structure were oxygen atoms, while those in the MOF structure were amine nitrogen atoms. The Ca(II) ions are coordinated with the solvent molecules in both structures. Finally, the in vitro cytotoxicity of this nanocomposite was assessed, revealing viability levels of 74.57 ± 2.1% and 21 ± 2.79% for Vero and African green monkey kidney and human liver (HepG2) cells, respectively. Cytotoxicity assays help assess the environmental impact of these materials, ensuring that they do not harm aquatic organisms or disrupt ecosystems. Thus, this study demonstrated the valorization of MOF/zeolite as a valuable and industry-ready adsorbent that can appropriate Ca(II) contaminants from aqueous streams.

Kinetics of chemical and color changes in wheat and water during atmospheric cooking as affected by the acidity, hardness, and iron content of water.

Color changes in wheat and cooking water, which affect the quality of bulgur and wastewater, are important. Understanding the impacts of cooking water acidity, hardness, and iron content is significant for producing bright-yellow colored bulgur and determining the possible negative effects of cooking water on the environment. Thereby, the gelatinization degree and color (L*, a*, b*, and yellowness index) of wheat cooked with waters at different pH (3, 5, 7, 9, and 11), hardness (soft, hard, and very hard), and iron content (0, 1, and 2 mg/L) were determined every 10 min of cooking. pH, Brix, conductivity, hardness, turbidity, and color of cooking waters were also determined and kinetically modeled. After cooking, it was revealed that cooking with water at pH 3 favored the color of cooked wheat, whereas pH 11 caused darkening. Nevertheless, as the wastewater pH of cooking waters with pH 3 and 11 may be harmful to the environment, it is recommended to use water in the range of pH 5-9 for bulgur production. Cooking with very hard water is also not recommended as it causes some adverse effects such as diminishing the gelatinization rate in wheat, increasing the cooking time, and negatively affecting the color.

The vehicle of administration, feed or water, and prandial state influence the oral bioavailability of amoxicillin in piglets.

Feed and water components may interact with drugs and affect their dissolution and bioavailability. The impact of the vehicle of administration (feed and water) and the prandial condition of weaner piglets on amoxicillin´s oral bioavailability was evaluated. First, amoxicillin's in vitro dissolution and stability in purified, soft, and hard water, as well as release kinetics from feed in simulated gastric and intestinal media were assessed. Then, pharmacokinetic parameters and bioavailability were determined in fasted and fed pigs using soft water, hard water, or feed as vehicles of administration following a balanced incomplete block design. Amoxicillin showed similar dissolution profiles in soft and hard water, distinct from the dissolution profile obtained with purified water. Complete dissolution was only achieved in purified water, and merely reached 50% in soft or hard water. Once dissolved, antibiotic concentrations decreased by around 20% after 24 h in all solutions. Korsmeyer-Peppas model best described amoxicillin release from feed in simulated gastric and intestinal media. Feed considerably reduced antibiotic dissolution in both simulated media. In vivo, amoxicillin exhibited significantly higher bioavailability when delivered via water to fasted than to fed animals, while in-feed administration yielded the lowest values. All treatments showed a similar rate of drug absorption. In conclusion, we demonstrated that water and feed components, as well as feed present in gastrointestinal tract of piglets decrease amoxicillin´s oral bioavailability. Therefore, the use of oral amoxicillin as a broad-spectrum antibiotic to treat systemic infections in pigs should be thoroughly revised.

Lake water chemistry and local adaptation shape NaCl toxicity in Daphnia ambigua.

The increasing application of road deicing agents (e.g., NaCl) has caused widespread salinization of freshwater environments. Chronic exposure to toxic NaCl levels can impact freshwater biota at genome to ecosystem scales, yet the degree of harm caused by road salt pollution is likely to vary among habitats and populations. The background ion chemistry of freshwater environments may strongly impact NaCl toxicity, with greater harm occurring in ion-poor, soft water conditions. In addition, populations exposed to salinization may evolve increased NaCl tolerance. Notably, if organisms are adapted to the water chemistry of their natal environment, toxicity responses may also vary among populations in a given test medium. We examined the potential for this evolutionary and environmental context to interact in shaping NaCl toxicity with a pair of laboratory reciprocal transplant toxicity experiments, using natural populations of the water flea Daphnia ambigua collected from three lakes that vary in ion availability and composition. We observed a strong effect of the lake water environment on NaCl toxicity in both trials. NaCl caused a much greater decline in reproduction and r in lake water from a low-ion/calcium-poor environment (20 µS/cm specific conductance; 1.7 mg/L Ca2+) compared with water from both a Ca2+-rich lake (55 µS/cm; 7.2 mg/L Ca2+) and an ion-rich coastal lake (420 µS/cm; 3.4 mg/L Ca2+). Daphnia from this coastal lake were most robust to the effects of NaCl on reproduction and r. A significant interaction between the population and lake water environment shaped survival in both trials, suggesting that local adaptation to the test waters used may have contributed to toxicity responses. Our findings that the lake water environment, adaptation to that environment, and adaptation to a contaminant of interest may shape toxicity demonstrate the importance of considering environmental and biological complexity in mitigating pollution impacts.

Effects of water quality on palladium-induced olfactory toxicity and bioaccumulation in rainbow trout (Oncorhynchus mykiss).

Through emission processes, palladium (Pd) particulates from industrial sources are introduced into a range of ecosystems including freshwater environments. Despite this, research on Pd-induced bioaccumulation, uptake, and toxicity is limited for freshwater fishes. Unlike other metals, there are currently no regulations or protective guidelines to limit Pd release into aquatic systems, indicating a global absence of measures addressing its environmental impact. To assess the olfactory toxicity potential of Pd, the present study aimed to explore Pd accumulation in olfactory tissues, olfactory disruption, and oxidative stress in rainbow trout (Oncorhynchus mykiss) following waterborne Pd exposure. Olfactory sensitivity, measured by electro-olfactography, demonstrated that Pd inhibits multiple pathways of the olfactory system following 96 h of Pd exposure. In this study, the concentrations of Pd for inhibition of olfactory function by 20% (2.5 µg/L; IC20) and 50% (19 µg/L; IC50) were established. Rainbow trout were then exposed to IC20 and IC50 Pd concentrations in combination with varying exposure conditions, as changes in water quality alter the toxicity of metals. Independent to Pd, increased water hardness resulted in decreased olfactory perception owing to ion competition at the olfactory epithelium. No other environmental parameter in this study significantly influenced Pd-induced olfactory toxicity. Membrane-associated Pd was measured at the olfactory rosette and gill following exposure; however, this accumulation did not translate to oxidative stress as measured by the production of malondialdehyde. Our data suggest that Pd is toxic to rainbow trout via waterborne contamination near field-measured levels. This study further demonstrated Pd bioavailability and uptake at water-adjacent tissues, adding to our collective understanding of the toxicological profile of Pd. Taken together, our results provide novel insights into the olfactory toxicity in fish following Pd exposure. Integr Environ Assess Manag 2024;20:1407-1419. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Profound regional disparities shaping the ecological risk in surface waters: A case study on cadmium across China.

The scientific advancement of water quality criteria (WQC) stands as one of the paramount challenges in ensuring the security of aquatic ecosystem. The region-dependent species distribution and water quality characteristics would impact the toxicity of pollutant, which would further affect the derivation of WQC across regions. Presently, however, numerous countries adhere to singular WQC values. The "One-size-fits-all" WQC value for a given pollutant may lead to either "over-protection" or "under-protection" of organisms in specific region. In this study, we used cadmium(Cd) pollution in surface waters of China as a case study to shed light on this issue. This study evaluated critical water quality parameters and species distribution characteristics to modify WQC for Cd across distinct regions, thus unveiling the geographical variations in ecological risk for Cd throughout China. Notably, regional disparities in ecological risk emerged a substantial correlation with water hardness, while species-related distinctions magnified these regional variations. After considering the aforementioned factors, the variation in long-term WQC among different areas reached 84-fold, while the divergence in risk quotient extended to 280-fold. This study delineated zones of both heightened and diminished ecological susceptibility of Cd, thereby establishing a foundation for regionally differentiated management strategies.

Effect of Water Hardness on Acute Aquatic Toxicity of Fatty Acid Salts.

The acute aquatic toxicity of anionic surfactants, including fatty acid salts, changes depending on water hardness. Generally, the acute aquatic toxicity of Daphnia magna is caused by the adsorption of surfactants and other substances. Despite the low environmental risk, the effect of water hardness on the acute aquatic toxicity of soap should be discussed to improve the assessment accuracy. Previously, we evaluated the effects of water hardness and the presence of an adsorbent on the acute aquatic toxicity of soap by performing an immobility test using D. magna in accordance with Japanese Industrial Standards (JIS) K 0229. Immobility was low at 50 ppm and a higher water hardness was indicated owing to the loss of interfacial activities caused by the formation of insoluble fatty acid calcium or magnesium complexes (soap scum). In the current study, we evaluate the effects of water hardness on the acute aquatic toxicity of C10, C12, C14, C16, and C18 saturated and C18:1 unsaturated fatty acid sodium salts. The EC50 is measured via an immobility test in accordance with JIS K 0229 using D. magna, and the surface tension is measured as an indicator of surface activity. Results show that the EC50 and surface tension curves change with water hardness in single and mixed solutions. C18:1 indicates the least change and the highest surface activity. Moreover, immobility change is not observed when C18:1 is filtered, whereas the immobility of other solutions decreased significantly. This implies the effect of soap scum on immobility, such as the clogging of gills by soap scum. Based on quantitative analysis, the percentage of C18:1 that transformed soap scum to its initial concentration exceeds 80%. This implies that calcium deficiency under 5 and 25 ppm water hardness affects the immobility of larval D. magna. The effects of soap scum clogging and calcium deficiency on D. magna should be considered before assessing the soap.

The Relationship between Mortality from Cardiovascular Diseases and Total Drinking Water Hardness: Systematic Review with Meta-Analysis.

BACKGROUND: Interest in water chemical activity, its content, and its impact on human health has greatly increased throughout the last decade. Some studies suggest that drinking water with high hardness may have preventative effects on cardiovascular diseases. This study aims to investigate the association between drinking water hardness and cardiovascular disease (CVD) mortality. METHODS: The study selection process was designed to find the association between drinking water hardness and CVDs mortality. The search included both qualitative and quantitative research and was performed in three databases: Web of Science (Clarivate Analytics, Ann Arbor, MI, USA), PubMed (National Institute of Health, Bethesda, MA, USA), and Scopus (Elsevier, RELX Group plc, London, UK). The project was registered in the International Prospective Register of Systematic Reviews (PROSPERO), registration number: CRD42020213102. RESULTS: Seventeen studies out of a total of twenty-five studies qualitatively analyzed indicated a significant relation between total water hardness and protection from CVD mortality. The quantitative analysis concluded that high drinking water hardness has a significantly lowering effect on mortality from CVDs, however, the heterogeneity was high. CONCLUSIONS: This systematic literature review shows that total water hardness could affect CVD prevention and mortality. Due to the many confounding factors in the studies, more research is needed.

Membrane Functionalization Approaches toward Per- and Polyfluoroalkyl Substances and Selected Metal Ion Separations.

Adsorption and ion exchange technologies are two of the most widely used approaches to separate pollutants from water; however, their intrinsic diffusion limitations continue to be a challenge. Pore functionalized membranes are a promising technology that can help overcome these challenges, but the extents of their competitive benefits and broad applicability have not been systematically evaluated. Herein, three types of adsorptive/ion exchange (IX) polymers containing strong/weak acid, strong base, and iron-chitosan complex groups were synthesized in the pores and partially on the surface of microfiltration (MF) membranes and tested for the removal of organic and inorganic cations and anions from water, including arsenic, per- and polyfluoroalkyl substances (PFAS), and calcium (hardness). When directly compared with beads (0.5-6 mm) and crushed resins (0.05 mm), adsorptive/IX pore-functionalized membranes demonstrated an increased relative sorption capacity, up to 2 orders of magnitude faster kinetics and the ability to regenerate up to 70-100% of their capacity while concentrating the initial solution concentration up to 12 times. The simple and versatile synthesis approach used to functionalize membranes, notably independent of the polymer type of the MF membrane, utilized pores throughout the entire cross section of the membrane to immobilize the polymers that contain the functional groups. Utilizing the pore volume of commercial membranes (6-112 mL/m2), the scientific weight capacity of the polymer (3.1-11.5 mequiv/g), and the synthesis conditions (e.g., monomer concentration), the theoretical adsorption/IX capacities per area of the membranes were calculated to be as high as 550 mequiv/m2, substantially higher than the 175 mequiv/m2 value needed to compete with commercially available IX resins. This work therefore shows that pore functionalized membranes are a promising path to tackle water contamination challenges, lowering separation diffusion limitations.

The Effect of Water Hardness and pH on the Efficacy of Peracetic Acid and Sodium Hypochlorite against SARS-CoV-2 on Food-Contact Surfaces.

Sodium hypochlorite (NaOCl) and peracetic acid (PAA) are commonly used disinfectants with a maximum recommended concentration of 200 ppm for food-contact surfaces. The objectives of this study were to assess the effect of pH and water hardness on NaOCl and PAA efficacy against SARS-CoV-2 on stainless steel (SS). The two disinfectants were prepared at 200 ppm in water of hardness 150 or 300 ppm with the final pH adjusted to 5, 6, 7, or 8. Disinfectants were applied to virus-contaminated SS for one minute at room temperature following the ASTM E2197 standard assay. SARS-CoV-2 infectivity was quantified using TCID50 assay on Vero-E6 cells. In general, increasingly hard water decreased the efficacy of NaOCl while increasing the efficacy of PAA. Hard water at 300 ppm significantly increased virus log reduction with PAA at pH 8 by ~1.5 log. The maximum virus log reductions were observed at pH 5 for both NaOCl (~1.2 log) and PAA (~2 log) at 150 and 300 ppm hard water, respectively. In conclusion, PAA performed significantly better than NaOCl with harder water. However, both disinfectants at 200 ppm and one minute were not effective (≤3 log) against SARS-CoV-2 on contaminated food-contact surfaces, which may facilitate the role of these surfaces in virus transmission.

Utilization of Computer Classification Methods for Exposure Prediction and Gene Selection in Daphnia magna Toxicogenomics.

Zinc (Zn) is an essential element that influences many cellular functions. Depending on bioavailability, Zn can cause both deficiency and toxicity. Zn bioavailability is influenced by water hardness. Therefore, water quality analysis for health-risk assessment should consider both Zn concentration and water hardness. However, exposure media selection for traditional toxicology tests are set to defined hardness levels and do not represent the diverse water chemistry compositions observed in nature. Moreover, these tests commonly use whole organism endpoints, such as survival and reproduction, which require high numbers of test animals and are labor intensive. Gene expression stands out as a promising alternative to provide insight into molecular events that can be used for risk assessment. In this work, we apply machine learning techniques to classify the Zn concentrations and water hardness from Daphnia magna gene expression by using quantitative PCR. A method for gene ranking was explored using techniques from game theory, namely, Shapley values. The results show that standard machine learning classifiers can classify both Zn concentration and water hardness simultaneously, and that Shapley values are a versatile and useful alternative for gene ranking that can provide insight about the importance of individual genes.

Impact of drinking water hardness on carotid atherosclerosis and arterial stiffness: Insights from the "Corinthia" study.

BACKGROUND: Several investigations have highlighted the role of water quality in cardiovascular health. In the present study, we have investigated the effects of drinking water hardness on atherosclerotic burden in carotid arteries and arterial stiffness. METHODS: "Corinthia" study was conducted in the homonym region in Greece from 2015 to 2017. Carotid atherosclerosis was assessed by intima-media thickness (IMT). Pulse wave velocity (PWV) was used to evaluate arterial stiffness. Tap-water samples were collected from the study area and analyzed for a variety of elements, as well as pH and total hardness. RESULTS: Individuals living in lower drinking water hardness areas (Area 1) versus individuals living in higher water hardness areas (Area 2) had lower max IMT (p = 0.004) and were less susceptible to carotid plaque formation (p = 0.004). Interestingly, individuals over 65 years from Area 1 had lower mean IMT, max IMT, and less plaque formation (p < 0.001 for all). The mean value of PWV in the overall study population was below the 10 m/s cutoff, which defines arterial stiffness (9.15 ± 2.79 m/s). Nevertheless, a marginally higher rate of vascular stiffening was noted in Area 2 vs. Area 1 (16.2% and 12.8%, respectively, p = 0.048). CONCLUSIONS: According to this cross-sectional study's findings, a positive association between extra hard water and carotid atherosclerotic burden was found. However, the association with arterial stiffness is unclear and should be investigated further.

Relationship between Regional Distribution of Centenarians and Drinking Water Hardness in the Amami Islands, Kagoshima Prefecture, Japan.

People who drink naturally hardened water may experience longevity-enhancing effects. In this study, we investigated water hardness and longevity from both geological and epidemiological perspectives in Japan's Amami islands, where drinking water is drawn from coralline or non-coralline bedrock. We investigated drinking water hardness, limestone bedrock occupancy, and the centenarian rate (number per 10,000 population) by municipality across four adjacent islands (Amami-Oshima (non-coralline), Tokunoshima, Okinoerabu, and Yoron (predominantly coralline)). Limestone was strongly correlated with water hardness (r = 0.99; p < 0.01), occupying more than 80% of the bedrock where the water was the hardest (Tokunoshima's Isen municipality: 86.5%; Yoron: 82.9%) and being scarcely detectable in Amami-Oshima (0.0 to 0.2%), where the water was the least hard. The centenarian rate was also strongly correlated with water hardness (r = 0.84, p < 0.01), with the highest figures in Yoron (29.7) and Isen (29.2), and the lowest in Amami-Oshima (0.0 to 12.2). Therefore, we hypothesize a potentially beneficial effect of hard water on longevity when that water is drawn from coralline limestone. Water hardness is determined by the water content of calcium and magnesium and may plausibly influence life expectancy through a preventative effect against cardiovascular disease. Our findings are of interest to current debates about future global access to drinking water and its quality.

Water Hardness Improves the Antioxidant Response of Zinc-Exposed Goldfish (Carassius auratus).

Zinc (Zn), a heavy metal, is an essential element in fish; however, exposure to high concentrations causes oxidative stress. Water hardness reduces oxidative stress reactions caused by heavy metals. To confirm the effect of water hardness on oxidative stress caused by Zn, goldfish were exposed to various Zn concentrations (1.0, 2.0, and 5.0 mg/L) and water hardness (soft (S), hard (H), and very hard (V)). The activity of superoxide dismutase (SOD) and catalase (CAT) in plasma increased with 1.0, 2.0, and 5.0 mg/L of Zn, and decreased with H and V water hardness. The levels of H2O2 and lipid peroxide (LPO) increased with Zn above 1.0 mg/L and decreased with H and V of water hardness. Caspase-9 mRNA expression in the liver increased after 7 and 14 days of Zn exposure and decreased with H and V water hardness. It was confirmed that DNA damage was less dependent on H and V water hardness. Based on the results of this study, at least 1.0 mg/L Zn causes oxidative stress in goldfish, and a high level of apoptosis occurs when exposed for more than 7 days. It appears that the oxidative stress generated by Zn can be alleviated by water hardness of at least 270 mg/L CaCO3. This study provides information on the relationship between the antioxidant response caused by heavy metals and water hardness in fish.

Water quality criteria and ecological risk assessment of lead (Pb) in China considering the total hardness of surface water: A national-scale study.

Site-specific water quality criteria considering hydrochemical conditions are needed for zoning control of environmental risks. However, the differences in water quality parameters between regions have not been fully considered in the current research on water quality criteria and risk assessment of lead. In this study, lead concentration and total hardness (TH) data of surface water in 13 major river basins and 31 administrative regions in China were collected. Based on the normalization of the TH of the toxicity data, the short-term and long-term water quality criteria of lead in China's surface water in the specific TH condition (100 mg/L) were derived using the species sensitivity distribution method, which were 90.7 µg/L and 2.1 µg/L, respectively. Furthermore, this study provided general derivation formulas for the water quality criteria based on the TH of surface water and obtained the site-specific criteria for different regions/basins in China. On this basis, an ecological risk assessment considering the TH was proposed for the first time. The results showed that there was a clear risk of lead in the Pearl River Basin and the rivers in Zhejiang-Fujian. The southern coastal provinces were at an unacceptable risk level, although the lead concentrations in the surface water were medium; the opposite was true in northern China, which meant that a high concentration of lead did not necessarily pose a high ecological risk and about 25 % of the variation in the predicted risk can be explained by the TH in Monte Carlo simulation.

Do sediment-bound nickel and lead affect chironomids life-history? Toxicity assessment under environmentally relevant conditions.

Metal pollution in aquatic ecosystems translates into increased concentrations of sediment-bound metals, representing a risk for benthic species. This risk might be enhanced in soft and moderately hard waters, world widely distributed, due to the protective role of hardness against metal toxicity. As lead (Pb) and nickel (Ni) are amongst the more abundant metals in aquatic systems, and since their combined effects to benthic species have been overlooked, in this study we aimed to investigate the life-cycle toxicity of Pb and Ni (using spiked sediment) to the benthic species Chironomus riparius, considering both single and mixture exposures, in moderately hard water. Environmentally relevant concentrations of each metal were used (25 and 75 mg kg-1, based on a scenario of pollution by runoff waters from burnt forests), following a full factorial design. Effects of the mixture with the highest metal concentrations (Pb 75 mg kg-1 dw + Ni 75 mg kg-1 dw) were also assessed in the second generation. In the first generation, exposure to Pb increased emergence and the weight of males, and decreased time to emergence of both males and females. Conversely, exposure to Ni delayed female emergence and decreased the weight of imagoes. Summarizing, Pb affected more endpoints but showed an apparent positive effect, whereas Ni affected less endpoints but exhibited adverse effects. Reproduction was not affected by these metals. In the second generation, the mixture Pb 75 mg kg-1 + Ni 75 mg kg-1 dw delayed emergence and reduced the emerged female fraction and their weight. These results highlight that Pb and Ni can alter the structure of C. riparius populations at environmentally relevant concentrations, which signals potential repercussions in the dynamics and functioning of freshwater ecosystems under these contamination scenarios. The findings of the present study are relevant not only for metal-polluted environments, in general, but also for fire-affected ecosystems.

Overcoming barriers for nitrate electrochemical reduction: By-passing water hardness.

Water matrix composition impacts water treatment performance. However, matrix composition impacts have rarely been studied for electrochemical water treatment processes, and the correlation between the composition and the treatment efficiency is lacking. This work evaluated the electrochemical reduction of nitrate (ERN) using different complex water matrices: groundwater, brackish water, and reverse osmosis (RO) concentrate/brine. The ERN was conducted using a tin (Sn) cathode because of the high selectivity towards nitrogen evolution reported for Sn electrocatalysts. The co-existence of calcium (Ca2+), magnesium (Mg2+), and carbonate (CO32-) ions in water caused a 4-fold decrease in the nitrate conversion into innocuous nitrogen gas due to inorganic scaling formation on the cathode surface. XRF and XRD analysis of fouled catalyst surfaces detected brucite (Mg(OH)2), calcite (CaCO3), and dolomite (CaMg(CO3)2) mineral scales formed on the cathode surface. Surface scaling created a physical barrier on the electrode that decreased the ERN efficiency. Identifying these main sources of ERN inhibition was key to devising potential fouling mitigation strategies. For this reason, the chemical softening pre-treatment of a real brackish water was conducted and this significantly increased nitrate conversion and faradaic efficiency during subsequent ERN treatment, leading to a lower electric energy consumption per order. Understanding the ionic foulant composition responsible for influencing electrochemically-driven technologies are the first steps that must be taken to move towards niche applications such as decentralized ERN. Thus, we propose either direct ERN implementation in regions facing high nitrate levels in soft waters, or a hybrid softening/nitrate removal system for those regions where high nitrate and high-water hardness appear simultaneously.

Exposure to Sri Lanka's local groundwater in a CKDu prevalent area causes kidney damage in zebrafish.

How local groundwater induces chronic kidney disease of unknown etiology (CKDu) in Sri Lanka is still elusive. This study aims to elucidate the impacts of Sri Lanka's local groundwater in a CKDu prevalent area and reveal the possible pathogenic mechanism of CKDu using zebrafish models. The drinking water from the local underground well in Vavuniya was sampled and the water quality parameters including Na+, Mg2+, K+, Ca2+, Cl-, NO3-, SO42-, and F- were analyzed. Then, local groundwater exposure to zebrafish larvae and 293T cells was performed, and water with high hardness and fluoride was prepared as parallel groups. Our result showed that exposure to Sri Lanka's local groundwater caused developmental toxicity, kidney damage, and pronephric duct obstruction as well as abnormal behavior in zebrafish. Similar results were also found after exposure to water with high hardness and fluoride in zebrafish. Further, the expression levels of marker genes related to renal development and functions (foxj1a, dync2h1, pkd2, gata3, and slc20a1) were significantly altered, which is also confirmed in the 293T cells. Taken together, those results indicated that Sri Lanka's local groundwater in a CKDu prevalent area could cause kidney damage, implying that high water hardness and fluorine might be the inducible environmental factors for the etiological cause of CKDu.

Does the mineral content of tap water correlate with urinary calculus composition?

The association between the mineral content of drinking water and urolithiasis remains elusive. The aim of this study is to investigate whether the mineral composition of tap water correlates with urinary calculus composition. Patients with calculi that underwent biochemical analysis at two urological centres in the North-West of England between November 2015 and December 2020 were included. Calculus composition was reviewed with respect to patient demographics, serum biochemical variables, and water mineral composition data obtained from the local water supply company using patient postcodes. 1711 urinary tract calculi from 1518 patients, living in 87 water supply zones were included. Water sodium concentration was an independent predictor of mixed calcium oxalate/uric acid calculi (OR 1.157, p < 0.001) and a negative independent predictor of calcium oxalate monohydrate (OR 0.896, p = 0.001) and dihydrate (OR 0.742, p = 0.034) calculi. Moreover, the magnesium-to-calcium ratio of tap water was a negative independent predictor of calcium oxalate monohydrate calculi (OR < 0.001, p = < 0.001), while tap water magnesium concentration inversely correlated with the percentage of calcium oxalate within calculi (rs = - 0.054, p = 0.026). Total water hardness did not independently predict calculus type. Many factors are implicated in the formation of urinary calculi. This study is the first to assess calculus composition in relation to tap water mineral content using postcode data on a case-by-case basis. Though total water hardness did not independently predict calculus composition, the interesting findings relating to water sodium and magnesium concentrations are in need of closer scrutiny in larger scale studies.

Water hardness alleviates the stress response caused by waterborne zinc in goldfish Carassius auratus.

In this study, the combined effect of waterborne Zn and water hardness on the stress response in the goldfish Carassius auratus was investigated. Goldfish were exposed to Zn concentrations of 0.5, 1.0, and 3.0 mg/L and water hardness of 90, 270, and 450 mg/L CaCO3 for 1, 3, 7, and 14 d. After exposure, it was determined that higher the Zn concentration, the more obvious the stress response. However, the stress response reduced with increasing water hardness. An increase in the Zn concentration caused stress responses in fish according to the increase in the mRNA expressions of corticotropin-releasing hormone and adrenocorticotropic hormone and cortisol level in the hypothalamus-pituitary-interrenal axis. The expression of these factors was the highest on day 7 and decreased on day 14. Furthermore, to evaluate the stress change in the liver tissue, we analyzed alanine aminotransferase, aspartate aminotransferase, and heat shock protein 70 concentrations to determine the damage caused by Zn and the change in water hardness. Immunohistochemistry staining for Na+/K+-ATPase in the gills showed that the gill activity was inhibited by Zn, and an increase in water hardness could improve Na+/K+-ATPase. In conclusion, we found that increasing water hardness is a successful method to reduce the stress response in goldfish caused by Zn.