Potentiometric electrodes for total dissolved solids: Universal ion response from crosslinked polymer membranes.

Enhancing the accuracy of seawater intrusion vulnerability assessment using a hybrid GALDIT framework in tropical low-lying coastal settings.

Produced water (PW) is a complex effluent characterized by high salinity, recalcitrant organic compounds, metals, and dispersed hydrocarbons. These properties challenge conventional separation technologies. Microemulsions (MEs) offer thermodynamic stability, ultralow interfacial tension, and the ability to extract hydrophobic and ionic contaminants simultaneously. However, the literature remains fragmented and dominated by studies using synthetic produced water (SPW), while investigations involving real produced water (RPW) represent approximately 30% of publications. This imbalance limits mechanistic interpretation and restricts the direct extrapolation of laboratory-scale data to industrial conditions. This review consolidates current knowledge on the phase behavior, interfacial mechanisms, and solubilization performance of MEs in both SPW and RPW systems. The analysis highlights the influence of salinity, divalent ions, naturally occurring surfactants, and temperature on shifting Winsor transitions and controlling stability. Reported ME systems remove up to 100% of oils and greases and achieve more than 95% removal of benzene, toluene, ethylbenzene, and xylenes ( BTEX). Some systems also reduce salinity by up to 47% and achieve metal recovery efficiencies above 98%. Despite these advances, relevant gaps persist regarding ME regeneration, stability in high–salinity and high–total dissolved solids (TDS) matrices, and offshore scalability. This review critically synthesizes available knowledge on the phase behavior, interfacial mechanisms, and solubilization performance of MEs in SPW and RPW systems, while highlighting key industrial constraints.

Hydrogen is a valuable commodity due to its high energy density and properties as a flexible energy carrier. It is possible to store hydrogen by blending it with methane and utilizing existing natural gas infrastructure. However, adapting current methane storage strategies to withstand the expected biogeochemical processes caused by H2 injection has not been fully explored. In this study, a series of experiments were designed to identify potential geochemical and microbial challenges of storing hydrogen/methane gas blends in existing methane reservoirs. First, fluid samples were collected from two methane reservoirs located in the western United States. The geochemical composition, microbial taxonomy, and metabolic potential of each fluid sample were characterized by utilizing ion chromatography (IC), inductively coupled plasma optical emission spectroscopy (ICP-OES), a Total Organic Carbon (TOC) analyzer, 16S rRNA gene amplicon sequencing, and metagenomic sequencing. Next, fluid samples from one field site (Site 2) were used to complete a series of short-term reactor experiments at reservoir conditions (80 °C and ∼1000 psi) for natural gas (100% CH4) and hydrogen blend (80% CH4/20% H2) storage environments. Both biotic and abiotic (sterilized) measurements were conducted to accurately understand and decouple abiotic and microbially driven processes, with the goal of linking these processes to storage impacts. Overall, the two reservoirs had a high, but variable, total dissolved solids (TDS) concentration, with various organic acids including acetate and propionate. The field sample was characterized by a diverse microbial community with the metabolic capacity for sulfur reduction, iron reduction, and acetogenesis. Across these reactors, there was minimal change in the fluid geochemistry and a minimal (0-5%) decrease of hydrogen gas during the initial storage event (days 1-3). This work contributes to the understanding of the complexities of hydrogen storage and demonstrates the need for additional research.

Influence of hydrodynamics on dissolved and particulate organic carbon release from sediments in vegetated flows.

In cold arid regions, the relationships between dissolved organic matter (DOM) characteristics and heavy metal distributions across ice, water, and sediment interfaces remain insufficiently resolved. This study characterized DOM spectral features and examined their associations with measured metal distributions in a typical frozen eutrophic lake using excitation-emission matrices coupled with parallel factor analysis (EEMs-PARAFAC), ultraviolet-visible absorption spectroscopy (UV-Vis), and Fourier-transform infrared spectroscopy (FTIR). Protein-like substances dominated ice DOM, whereas water and sediment-derived DOM contained more humified fluorescent components. Fluorescence indices confirmed a primarily biological origin across all media, with ice showing the highest autochthonous microbial contribution (BIX = 1.23) but the lowest humification (HIX = 0.26), suggesting a greater contribution of recently produced protein-like fluorescent DOM in the ice samples. Water DOM showed the highest average HIX (1.88), followed by sediment-derived DOM (0.61) and ice DOM (0.26). The measured hydrochemical conditions, including weak alkalinity, elevated total dissolved solids (TDS), and locally low dissolved oxygen, provide environmental context for differences in metal distributions. Exploratory Spearman analysis at 17 matched water stations identified the strongest DOM-metal associations for HIX-As (rho = 0.474, p = 0.054) and FI-Zn (rho = 0.471, p = 0.056), indicating that DOM optical properties provide testable indicators of metal-distribution patterns but should be combined with direct binding and speciation measurements for mechanistic confirmation. Because ice was collected in January 2021, whereas water and sediment were collected in October 2020, cross-medium differences are interpreted as between-campaign associations rather than synchronous partitioning. These findings provide a basis for targeted winter monitoring and future binding, speciation, and freeze-concentration experiments in shallow eutrophic lakes.

ABSTRACT This study evaluated the spatio-temporal water quality of the Ismailia Canal, the primary drinking water source for the Suez Canal governorates, which is significantly impacted by surrounding agricultural (63%) and urban (27%) land use. The research aimed to assess the formation of carcinogenic Trihalomethanes (THMs) during pre-chlorination to help optimize disinfection protocols. Physicochemical parameters including Total Organic Carbon (TOC), heavy metals (Fe, Mn, Pb), and THMs, were analyzed in 32 raw and treated water samples collected from eight water treatment plants (WTPs) during the 2024 winter and summer seasons. GIS-based land-use mapping and multivariate statistical analysis (Pearson correlation and HCA) were employed to identify pollution drivers. Results indicate a spatial decline in raw water quality, with Total Dissolved Solids (TDS) increasing downstream due to cumulative pollution. Raw water Iron (Fe) concentrations consistently exceeded the 0.3 mg/L Egyptian standard. Treated water THM levels ranged from 40.50–82.10 μg/L in winter and 24.50–68.22 μg/L in summer. While the cumulative non-carcinogenic Hazard Index (HI) remained below 1.0, the lifetime incremental cancer risk (CRtotal) exceeded the 10–4 benchmark at several downstream WTPs, driven by dermal and inhalation exposure. Statistical analysis revealed strong associations between heavy metals, TOC, and turbidity, especially in summer, indicating that higher temperatures and agricultural runoff accelerate the formation of halogenated by-products through metal-organic complexation. These findings highlight the urgent need for stringent source water protection and the optimization of disinfection processes. Implementing advanced pre-treatment and evaluating alternative disinfectants are essential to mitigate public health risks associated with chlorinated by-products.

Genotoxic evaluation and gene expression in Mus musculus exposed to landfill soil simulated leachates.

ABSTRACT The object of the study was a stream, characterised by high nutrient concentrations in water. The water quality subindex (WQSI) values calculated for nutrients were used for the identification of pollution events, the positive matrix factorisation (PMF) model was used for source apportionment, and total dissolved solids (TDS) concentrations were used as the proxies of direct flow/base flow ratios in stream flow. As the result of PMF analysis, three sources were apportioned. It was found that contributions of one source were positively correlated with TDS, contributions of the second source were negatively correlated with TDS, and the contributions of the third source were uncorrelated with TDS. It was suggested that these sources were deep groundwater, shallow groundwater, and wastewater, respectively. According to the PMF results, deep groundwater was likely the source of phosphates and nitrates, and wastewater was likely the source of ammonium and nitrites. However, the verification of results of PMF analysis by establishing the correlation between PMF-derived source contributions and WQSI values calculated for PO4 3- showed that wastewater may also be a significant source of phosphates. Shallow groundwater, apparently, did not contribute significantly to the concentration of any nutrient ion in stream water.

This study investigated the potential of microbial-assisted phytoremediation using Eichhornia crassipes (water hyacinth) to reduce heavy metal and salinity pollution in produced water collected from Aadi Oil Field in Gujar Khan, Pakistan. Produced water was analyzed for physicochemical parameters and heavy metal content using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) to establish baseline data. E. crassipes plants augmented with indigenous, contaminant-tolerant microbial isolates were employed in a 15-day laboratory experiment. The results showed a resilient growth response, with plant height increasing to approximately 11-15 cm and root length extending up to 10-13 cm across treatments. Biomass also improved, with wet weights reaching 21-24 g from an initial 20 g. The treatment effectively reduced key physicochemical parameters: pH was stabilized from an initial alkaline value of 9.14 to near-neutral values (7.0-7.5), and total dissolved solids (TDSs) were reduced by approximately 50%. Heavy metal removal rates varied, with the highest efficiency of 79.2% for Silver (Ag) and the lowest (18.5%) for Mercury (Hg) This study demonstrates that E. crassipes actively participated in phytoremediation by absorbing and accumulating heavy metals and reducing salinity. The association with contaminant-tolerant microbes appeared to enhance the plant's tolerance and overall treatment efficacy, indicating that plant-microbe interactions offer a sustainable strategy for the treatment of produced water.

ABSTRACT This study presents groundwater quality and associated non-carcinogenic health risks in Jaipur district of western India, based on the 274 analytical hydrochemical data in May 2021 retrieved from the Department of Ground Water, Rajasthan. Hydrochemical parameters (pH, electrical conductivity (EC), total dissolved solids (TDS), major ions, nitrate and fluoride) were assessed, and water suitability was examined using arithmetic weighted water quality index (AWWQI), entropy weighted water quality index (EWWQI) and total chronic hazard index (TCHI). TDS ranged from 195 mg/L to 6780 mg/L, with 62% of samples exceeding the Bureau of Indian Standards (BIS) limit, indicating salinity enrichment. Nitrate in 27% and fluoride in 15% samples surpassed safe thresholds, mainly in agricultural and discharge areas. Hydrochemical facies were dominated by Na-Cl and Na-HCO3 water types, controlled by rock-water interaction and evaporation. Multivariate analysis revealed anthropogenic influences. AWWQI and EWWQI classified 44% and 30% of the samples as poor to unfit, while TCHI (>1.0) indicated significant health risks, especially to children. This integrated approach supports the SDG-3 and SDG-6 for groundwater management.

Sustainable leather processing: A critical review of emerging green technologies and practices

Synthesis and physical properties characterization of artificial seawater samples.

• Algal-infused biochar discs removed 71.06% TDS from RO reject water • Adsorption was spontaneous with ΔG° ranging from -3742 to -4377 J/mol • Enthalpy of +35.42 J/mol indicated endothermic process • Entropy of -13.88 J/K·mol proposed the disorder at the solid-liquid interface • Composite discs enable low-cost desalination with 498.9 mg/g sorption capacity The increasing salinization of groundwater due to desalination reject streams poses a significant challenge to water sustainability. This study explores the potential of algal-infused biochar discs for effective salinity reduction, emphasizing their thermodynamic behavior. Biochar derived from groundnut shells was surface-modified and infused with algal biomass to enhance ion removal capacity. The adsorption process was evaluated through batch experiments, assessing key parameters such as initial total dissolved solids (TDS) concentration (1676 mg/L to 8728 mg/L), temperature (25°C to 55°C), and disc dosage (2 to 6 discs). Thermodynamic analysis revealed that the adsorption process was spontaneous, with Gibbs free energy (ΔG°) values decreasing from -3742 J/mol to -4377 J/mol, confirming favorable ion uptake. Enthalpy (ΔH°) was determined as 35.42 J/mol revealing an endothermic nature, while entropy (ΔS°) showed a value of -13.88 J/K·mol, indicating reduced randomness at the solid-liquid interface. Characterization studies, including Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), and Thermogravimetric Analysis (TGA), demonstrated changes in porosity, surface chemistry, and thermal stability post-salinity rduction, with BET surface area decreasing from 18.98 m²/g to 16.08 m²/g, indicating salt deposition within the biochar matrix. This study examined the ionic salinity reduction performance of algal biochar discs under optimal conditions of 25°C temperature, 6-disc dosage, and 150 minutes contact time across varying initial TDS levels. Removal efficiency of 71.06 % was achieved for an initial TDS concentration of 1676 mg/L, whereas a maximum sorption capacity was 498.9 mg/g was observed for an initial TDS concentration of 8728 mg/L. This study underscores the salinity reduction potential of biochar-algal discs as a sustainable approach for addressing salinity challenges.

Influence of seasonal environmental conditions on 222Rn concentration in the surface water of the River Nile.

The dynamic relationship between water quantity and quality has been neglected in water resources models. This study dynamically integrated simple water quality processes into Pywr to allow water quality to inform water allocation. To demonstrate, Pywr-WQ is applied to the highly human-modified Grootdraai Dam catchment in southern Africa. Pywr-WQ simulations of Total Dissolved Solids (TDS) and various nutrients were generally representative of variations in observed water quality in the Grootdraai Dam. Water quality thresholds for water abstraction were applied to the Grootdraai Dam, with the results showing that Pywr-WQ dynamically ‘switched off’ the abstraction when these thresholds were exceeded. This study confirms the viability of dynamically adding water quality simulation to Pywr. This can aid in more realistic estimations of water yield considering water quality constraints. Given the flexibility of Pywr, more complex rules between water quantity and quality can be implemented. • Simple water quality processes were dynamically integrated into Pywr (Pywr-WQ) • Pywr-WQ was applied to the highly modified Grootdraai Catchment • Water quality simulations were representative of monitoring data • Water abstractions were dynamically turned off by setting water quality thresholds • Opportunities for representing more complex water quantity-quality dynamics

In this study, pine-cone and pine-needle forestry wastes were used to produce activated carbons for the purification of dye contaminated textile effluents. The characterization of the adsorbents conducted through SEM (Scanning Electron Microscopy), N 2 porosimetry and FTIR (Fourier Transform Infrared Spectroscopy) before and after adsorption to provide insights on the adsorption mechanism. For PCAC5 S BET was 1305 m 2 /g, while for PNAC5 was 743.9 m 2 /g. FTIR confirmed the successful binding of textile wastewater through various mechanisms. Preliminary adsorption experiments performed for the removal of Methylene Violet (MV), Reactive Black 5 (RB5) and Reactive Red 120 (RR120) in single- and multi-component solutions. Optimal removal occurred at pH 3 for anionic dyes (RB5: 99.6% PCAC5, 98.2% PNAC5; RR120: 70.2% PCAC5, 94.8% PNAC5) and at pH 9 for MV (99.9% PCAC5, 99.5% PNAC5). The maximum adsorption capacities were 1198, 287 and 70.7 mg/L for MV, RB5 and RR120 removal, respectively. Kinetics followed pseudo-second order (PSO) kinetic model, suggesting that chemisorption was governing adsorption. Multi-component dye mixtures studies revealed the synergistic effect occurring between cationic and anionic species. Regeneration studies conducted for four consecutive cycles. Experiments with real textile wastewater demonstrated that a single-step adsorption approach can enhance the removal efficiency of multi-component contaminated solutions and reduce total dissolved solids (TDS) by 77% on average compared to the samples received after industrial chemical treatment. All the above suggest that pine-waste activated carbons can enhance water quality, decrease secondary environmental pollution and reduce the overall cost of wastewater treatment through a single-step green and sustainable approach. • Sustainable activated carbons were produced from pine-cones and pine-needles forestry waste for textile wastewater treatment. • High adsorption capacities were achieved for cationic and anionic dyes in single- and multi-component systems. • Binary dye mixtures showed synergistic adsorption between cationic and anionic species. • Real textile wastewater treatment confirmed the effectiveness of pine-waste activated carbons.

Laboratory microcosm evidence for denitrification-driven iodine mobilization in coastal groundwater systems: Implications for salinity and redox control

This research aimed to assess the bioindicator potential of bacterial coliforms and benthic macroinvertebrates of the Ndongo stream, an urban stream on the southeast slope of Mount Cameroon. For this purpose, macroinvertebrates were collected monthly from November 2021 to May 2022 at three sampling stations of the Ndongo stream. At each sampling station, temperature, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), salinity, pH, flow velocity, flow rate and total coliforms were measured. Results revealed that there was a significant fluctuation in water hydrological, physico-chemical and microbiological parameters across stations (p < 0.05). Furthermore, a total of 917 macroinvertebrates were collected at the 3 stations, but their community structure differed across sampling sites. The values of the Shannon–Weaver index indicated a less diversified community with the dominance of a few species. The bacterial coliform count was above the WHO maximum acceptable concentration (i.e. 0 CFU per 100 ml) in all the sampling stations, hence compromising the use of the stream for domestic purposes. Water abiotic variables had less effect on total coliform count (R2 = 0.54; F = 1.42, df = 11, p = 0.29). Macroinvertebrate families such as Planariidae, Gerridae, Dytiscidae, Veliidae, Nepidae, Pseudostigmatidae, Dipterocarpaceae had strong association with water abiotic variables. The study confirmed the potential use of benthic macroinvertebrates as bioindicators of water abiotic variables in tropical freshwater ecosystems.

Access to safe and clean water is essential for sustainable development, particularly in rural areas where infrastructural deficits and sanitation challenges are pronounced. This study evaluated groundwater quality in 32 rural communities across 10 local government areas (LGAs) of Osun State, Nigeria, in relation to Sustainable Development Goal (SDG) Target 6.3, which aims to improve water quality by reducing pollution and eliminating hazardous discharges. Water samples were analysed for physico-chemical parameters—pH, temperature, total alkalinity, total dissolved solids (TDS), electrical conductivity (EC), total hardness, nitrates, phosphates, sulphates, chlorides, and turbidity—and microbiological indicators, including total coliforms and Escherichia coli (E. coli). Results indicate that most physico-chemical parameters complied with World Health Organization (WHO) and Nigerian standards, suggesting minimal chemical degradation of groundwater. In contrast, widespread microbiological contamination was observed, with elevated coliform counts and E. coli presence in 14 communities, identifying faecal contamination as the primary factor undermining SDG 6.3 compliance. Water Quality Index (WQI) analysis further revealed substantial spatial variation: several villages scored “excellent” or “good,” whereas others, including Owu-Ile, Masifa, and Alaasan, were classified as “very poor” or “unsuitable” for drinking. Hotspots of microbial non-compliance were concentrated in Ejigbo and Ede North LGAs, while temperature and minor alkalinity deviations were observed in select communities.The findings highlight that failures in rural water quality are predominantly driven by inadequate sanitation and hygiene practices rather than chemical contamination. Achieving SDG 6.3 in Osun State therefore requires targeted interventions, including strengthened rural sanitation infrastructure, routine microbial monitoring, community-based water governance, and spatially prioritised resource allocation. The integration of WQI provides a practical tool for synthesising multi-parameter water quality data, enabling policymakers to identify high-risk communities and design evidence-based strategies for sustainable rural water management in Nigeria.