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Water, Volume 17, Issue 17 (September-1 2025) – 160 articles

Cover Story (view full-size image): The use of seawater in public swimming pools is emerging as a sustainable alternative in response to freshwater scarcity and climate changes. However, regulatory frameworks across Europe remain fragmented, with inconsistent guidelines on microbiological and chemical safety, permitted disinfection methods, and limits for disinfection by-products. The review of regulatory landscape of 23 coastal European countries highlights both opportunities and challenges for public health. The findings emphasize the need for a harmonized policy to ensure sustainable seawater utilization while safeguarding human health and aquatic environments. View this paper
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22 pages, 2718 KB  
Article
Prediction of Time Variation of Local Scour Depth at Bridge Abutments: Comparative Analysis of Machine Learning
by Yusuf Uzun and Şerife Yurdagül Kumcu
Water 2025, 17(17), 2657; https://doi.org/10.3390/w17172657 - 8 Sep 2025
Viewed by 566
Abstract
Computing the temporal variation in clearwater scour depth around abutments is important for bridge foundation design. To reach the equilibrium scour depth at bridge abutments takes a very long time. However, the corresponding times under prototype conditions can yield values significantly greater than [...] Read more.
Computing the temporal variation in clearwater scour depth around abutments is important for bridge foundation design. To reach the equilibrium scour depth at bridge abutments takes a very long time. However, the corresponding times under prototype conditions can yield values significantly greater than the time to reach the design flood peak. Therefore, estimating the temporal variation in scour depth is necessary. This study evaluates multiple machine learning (ML) models to identify the most accurate method for predicting scour depth (Ds) over time using experimental data. The dataset of 3275 records, including flow depth (Y), abutment length (L), channel width (B), velocity (V), time (t), sediment size (d50), and Ds, was used to train and test Linear Regression (LR), Random Forest Regressor (RFR), Support Vector Regression (SVR), Gradient Boosting (GBR), XGBoost, LightGBM, and KNN models. Results demonstrated the superior performance of AI-based models over conventional regression. The RFR model achieved the highest accuracy (R2 = 0.9956, Accuracy = 99.73%), followed by KNN and GBR. In contrast, the conventional LR model performed poorly (R2 = 0.4547, Accuracy = 57.39%). This study confirms the significant potential of ML, particularly ensemble methods, to provide highly reliable scour predictions, offering a robust tool for enhancing bridge design and safety. Full article
(This article belongs to the Special Issue Advances in AI, Numerical, and Experimental Approaches for Water Resources Applications)
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20 pages, 3151 KB  
Article
Removal of Ciprofloxacin from Pharmaceutical Wastewater Using Untreated and Treated Eggshells as Biosorbents
by Maryam Bin Hammad, Sameer Al-Asheh and Mohamed Abouleish
Water 2025, 17(17), 2656; https://doi.org/10.3390/w17172656 - 8 Sep 2025
Viewed by 552
Abstract
Pharmaceutical wastewater contains high levels of organic matter, salts, and toxic compounds that are resistant to conventional treatment methods. Even after secondary treatment, traces of dissolved organics and suspended solids often remain, contributing to environmental concerns such as increased microbial resistance and harm [...] Read more.
Pharmaceutical wastewater contains high levels of organic matter, salts, and toxic compounds that are resistant to conventional treatment methods. Even after secondary treatment, traces of dissolved organics and suspended solids often remain, contributing to environmental concerns such as increased microbial resistance and harm to aquatic life. This study introduces a sustainable “waste-to-treat-waste” approach that utilizes discarded white chicken eggshells as a low-cost biosorbent for removing ciprofloxacin, a common antibiotic. Unlike previous eggshell-based adsorption studies that primarily targeted dyes or heavy metals, this work demonstrates the first comprehensive evaluation of both untreated and chemically/thermally modified eggshells for antibiotic removal from real pharmaceutical wastewater. Batch adsorption experiments under optimized conditions showed removal efficiencies of 85% for raw eggshells, 91% after HCl activation, and 96% after thermal conversion to CaO. Batch adsorption experiments under optimized conditions (pH 7, 25 °C, 625 µm particle size, 3 g/100 mL dose, 90 min contact time) showed maximum adsorption capacities of 23.75 mg/g for untreated ES, 4.08 mg/g after HCl activation, and 1.82 mg/g after thermal conversion to CaO, with removal efficiencies of 85%, 91%, and 96%, respectively. The simplicity of preparation, use of an abundant waste material, and high removal efficiency highlight the potential for scalable cost-effective applications in industrial wastewater treatment systems. Full article
(This article belongs to the Special Issue Adsorption Technologies in Wastewater Treatment Processes—2nd Edition)
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18 pages, 2463 KB  
Review
Mapping the Research Landscape of Stormwater Quality Improvement Devices: Trends, Influencers, and Thematic Evolution (1992–2024)
by Sesugh Yua, Gokhan Yildirim, Mohammad Ataul Morshed, Monisha Anindita, Mohammad A. Alim and Ataur Rahman
Water 2025, 17(17), 2655; https://doi.org/10.3390/w17172655 - 8 Sep 2025
Viewed by 733
Abstract
This study presents a comprehensive bibliometric analysis of the research landscape on Stormwater Quality Improvement Devices (SQIDs) covering 1992–2024. Using data from the Web of Science (WoS) and utilizing Bibliometrix R-package 5.1.0 and VOSviewer 1.6.20, this study identifies key trends, influential contributors, and [...] Read more.
This study presents a comprehensive bibliometric analysis of the research landscape on Stormwater Quality Improvement Devices (SQIDs) covering 1992–2024. Using data from the Web of Science (WoS) and utilizing Bibliometrix R-package 5.1.0 and VOSviewer 1.6.20, this study identifies key trends, influential contributors, and the thematic evolution within SQIDs research. The findings reveal distinct growth phases driven by policy shifts, scientific advancements, and an increasing global emphasis on sustainability. Keyword analysis highlights a significant thematic transition post-2015, with terms like performance, runoff, and management (Keyword Plus), and stormwater management, green infrastructure, and stormwater (Author Keywords) indicating a strong shift toward sustainable, nature-based solutions. Bioretention system has emerged as the most researched SQIDs, reflecting widespread academic and practical interest. The most prolific countries in SQIDs research are the USA, China, and Australia, while prominent thought leaders include Fletcher (Monash University), Wang (Guangzhou University), Shuster (US EPA), and Deletic (UNSW). Leading publication outlets include the Journal of Environmental Management, Science of the Total Environment, Journal of Hydrology, and Water. Overall, this study underscores the field’s maturation toward policy-relevant and interdisciplinary innovations, long-term performances and smart SQIDs using artificial intelligence positioning SQIDs as vital tools in addressing urban stormwater management challenges globally. Full article
(This article belongs to the Section Urban Water Management)
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24 pages, 4146 KB  
Article
Investigation of the Adsorption Capacity of H3PO4-Activated Biochar from Eucalyptus Harvest Waste for the Efficient Removal of Paracetamol in Water
by Lúcia Allebrandt da Silva Ries, Joyce Helena da Silveira Chies, Luamar de Mattos Soares, Edilson Valmir Benvenutti and Fabiano Perin Gasparin
Water 2025, 17(17), 2654; https://doi.org/10.3390/w17172654 - 8 Sep 2025
Viewed by 525
Abstract
The present study showed that it is possible add value to eucalyptus harvest waste, obtained in large quantities, from the cellulose industries, without known economic use, for the production of an activated biochar. The biochar, produced from the impregnation of eucalyptus harvest waste [...] Read more.
The present study showed that it is possible add value to eucalyptus harvest waste, obtained in large quantities, from the cellulose industries, without known economic use, for the production of an activated biochar. The biochar, produced from the impregnation of eucalyptus harvest waste with H3PO4, and subsequently pyrolyzed at 600 °C for 1 h, was successfully used as a bioadsorbent in the removal of paracetamol, an emerging pollutant present in wastewater. The biochar showed a high specific surface area with micro- and mesopores and functionalized surface. The optimal conditions for the removal of paracetamol achieve an efficiency around 88–93%. The Langmuir and the pseudo-first-order models best fit the experimental data, with a maximum adsorption capacity of approximately 27.8 mg g−1, at 25 °C. The thermodynamic showed that adsorption occurred spontaneously, endothermally and randomly at the solid–liquid interface. In addition, the bioadsorbent showed excellent reusability and no significant difference in adsorption capacity was observed in more complex aqueous matrices. Thus, the activated biochar produced in this study proved to be an efficient, low-cost and environmentally friendly bioadsorbent, capable of removing paracetamol from contaminated water, with great potential for use in water treatment plants, on a large scale and economically, contributing to the improvement of water quality and minimizing residual biomass in the environment. Full article
(This article belongs to the Special Issue Sustainable Water Treatment Systems: Green Infrastructure and Bioremediation, 2nd Edition)
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18 pages, 532 KB  
Article
Multi-Agentic Water Health Surveillance
by Vasileios Alevizos, Zongliang Yue, Sabrina Edralin, Clark Xu, Nikitas Gerolimos and George A. Papakostas
Water 2025, 17(17), 2653; https://doi.org/10.3390/w17172653 - 8 Sep 2025
Viewed by 606
Abstract
Clean water security demands autonomous systems that sense, reason, and act at scale. We introduce AquaSurveil, a unified multi-agent platform coupling mobile robots, fixed IoT nodes, and privacy-preserving machine learning for continent-scale water health surveillance. The architecture blends Gaussian-process mapping with distributed particle [...] Read more.
Clean water security demands autonomous systems that sense, reason, and act at scale. We introduce AquaSurveil, a unified multi-agent platform coupling mobile robots, fixed IoT nodes, and privacy-preserving machine learning for continent-scale water health surveillance. The architecture blends Gaussian-process mapping with distributed particle filtering, multi-agent deep-reinforcement Voronoi coverage, GAN/LSTM anomaly detection, and sheaf-theoretic data fusion; components are tuned by Bayesian optimization and governed by Age-of-Information-aware power control. Evaluated on a 2.82-million-record dataset (1940–2023; five countries), AquaSurveil achieves up to 96% spatial-coverage efficiency, an ROC-AUC of 0.96 for anomaly detection, ≈95% state-estimation accuracy, and reduced energy consumption versus randomized patrols. These results demonstrate scalable, robust, and energy-aware water quality surveillance that unifies robotics, the IoT, and modern AI. Full article
(This article belongs to the Special Issue NBS for Watershed Management: From Ecological Health Assessment to Ecosystem Restoration)
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27 pages, 3704 KB  
Review
Radionuclide Tracing in Global Soil Erosion Studies: A Bibliometric and Systematic Review
by Yinhong Huang, Yong Yuan, Yang Xue, Jinjin Guo, Wen Zeng, Yajuan Chen and Kun Chen
Water 2025, 17(17), 2652; https://doi.org/10.3390/w17172652 - 8 Sep 2025
Viewed by 658
Abstract
Radionuclide tracer technology, as a state-of-the-art tool for quantifying and monitoring soil erosion processes, has attracted much attention in global sustainable land management research in recent years. However, existing studies are fragmented in methodological applications, lack systematic knowledge integration and interdisciplinary perspectives, and [...] Read more.
Radionuclide tracer technology, as a state-of-the-art tool for quantifying and monitoring soil erosion processes, has attracted much attention in global sustainable land management research in recent years. However, existing studies are fragmented in methodological applications, lack systematic knowledge integration and interdisciplinary perspectives, and lack global research trends and dynamic evolution of key themes. This study integrates Bibliometrix, VOSviewer, and CiteSpace to conduct bibliometric and knowledge mapping analysis of 1692 documents (2000–2023) in the Web of Science Core Collection, focusing on the overall developmental trends, thematic evolution, and progress of convergence and innovation. The main findings of the study are as follows: (1) China, the United States, and the United Kingdom are in a “three-legged race” at the national level, with China focusing on technological application innovation, the United States on theoretical breakthroughs, and the United Kingdom contributing significantly to methodological research; (2) “soil erosion” and “137Cs” continue to be the core themes, while “climate change” and “human impact” on soil erosion and its reflection in radionuclide tracing became the focus of attention; and (3) multi-scale radionuclide tracing (watershed, slope), multi-method synergy (radionuclide tracing combined with RS, GIS, AI), and the integration of advanced measurement and control technologies (PGS, ARS) have become cutting-edge trends in soil erosion monitoring and control. This study provides three prospective research directions—the construction of a global soil erosion database, the policy transformation mechanism of the SDG interface, and the iterative optimization of multi-radionuclide tracer technology, which will provide scientific guidance for the realization of the sustainable management of soil erosion and the goal of zero growth of land degradation globally. Full article
(This article belongs to the Special Issue Soil Erosion and Soil and Water Conservation, 2nd Edition)
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19 pages, 3219 KB  
Article
Spatial Targeting and Budget-Adaptive Optimization of Best Management Practices for Cost-Effective Nitrogen Reduction
by Yunkai Fan, Huazhi Zhang, Bing Yu, Ming Cong and Zhuohang Xin
Water 2025, 17(17), 2651; https://doi.org/10.3390/w17172651 - 8 Sep 2025
Viewed by 497
Abstract
This study developed a Soil and Water Assessment Tool (SWAT) model for the Fuzhou River Basin in China to quantify the spatial distribution, sources, and reduction potential of total nitrogen (TN) load. We comprehensively evaluated the effectiveness of eight Best Management Practices (BMPs) [...] Read more.
This study developed a Soil and Water Assessment Tool (SWAT) model for the Fuzhou River Basin in China to quantify the spatial distribution, sources, and reduction potential of total nitrogen (TN) load. We comprehensively evaluated the effectiveness of eight Best Management Practices (BMPs) and 186 combinations thereof in reducing TN load. Our analysis demonstrated that adding more BMPs did not yield proportionally additive benefits but instead led to reduced cost-effectiveness (CE) once the number of BMPs exceeded three. Targeting BMPs to Critical Source Areas (CSAs) increased CE by an average of 15.6% compared to watershed-wide application, although the environmental benefit (EB) was lower (22.0% versus 32.8% on average). We identified a critical budget threshold of 70 million CNY. Below this threshold, CSA-targeting optimized BMPs delivered the most cost-effective TN reductions (123.0 kg/104 CNY per year). However, with a sufficient budget exceeding this threshold, our findings support implementing BMPs throughout the entire watershed, which maximized the TN reduction rate to over 40%. Overall, our findings highlight that spatial targeting and budget-adaptive implementation of BMPs are essential for maximizing both economic efficiency and environmental benefits, providing a practical decision approach for nutrient management in river basins. Full article
(This article belongs to the Section Water Quality and Contamination)
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16 pages, 3050 KB  
Article
Hot-Point Ice Thermal Drills: Design Parameters, Recommendations, and Examples
by Mikhail A. Sysoev, Pavel G. Talalay, Xiaopeng Fan, Nan Zhang, Da Gong, Jialin Hong, Yang Yang and Ting Wang
Water 2025, 17(17), 2650; https://doi.org/10.3390/w17172650 - 8 Sep 2025
Viewed by 655
Abstract
Hot-point thermal drills are among the simplest and most compact tools for drilling boreholes in ice by melting. They are widely used in glaciological and geophysical research, including subsurface access on Earth and planetary missions. This study focuses on electrically heated hot-point drills. [...] Read more.
Hot-point thermal drills are among the simplest and most compact tools for drilling boreholes in ice by melting. They are widely used in glaciological and geophysical research, including subsurface access on Earth and planetary missions. This study focuses on electrically heated hot-point drills. It presents a comparative review of four analytical models commonly used to describe thermal penetration into ice. Our theoretical processing and computation allow for the analysis and optimization of the drilling performance of thermal drill heads. The predictive accuracy of the adapted model was evaluated through comparison with experimental data obtained using the RECAS-200 thermal sonde. Based on the analysis of various sources and calculations using the modified model, a set of recommendations is proposed for early-stage estimation of drilling parameters and assessment of thermal drilling efficiency in the design of hot-point drills for autonomous and resource-constrained missions. Full article
(This article belongs to the Section Oceans and Coastal Zones)
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27 pages, 8062 KB  
Article
Comparative Study of RANS Models for Simulating Turbulent Flow and Heat Transfer in Corrugated Pipes
by Ting-Ting Tang, Fang-Qiu Li, Guang-Yao Wang, Jun Yan and Zhao-Kuan Lu
Water 2025, 17(17), 2649; https://doi.org/10.3390/w17172649 - 8 Sep 2025
Viewed by 685
Abstract
Corrugated pipes are extensively used in engineering applications that require flexibility and enhanced heat exchange, such as drainage and compact heat exchangers, and recently as inner layers in cryogenic flexible hoses for offshore liquid ship-to-ship transfer. The great flexibility of these hoses makes [...] Read more.
Corrugated pipes are extensively used in engineering applications that require flexibility and enhanced heat exchange, such as drainage and compact heat exchangers, and recently as inner layers in cryogenic flexible hoses for offshore liquid ship-to-ship transfer. The great flexibility of these hoses makes them well-suited for deployment in dynamic and harsh marine environments. However, the corrugated geometry also induces flow separation, elevated turbulence, and intricate heat transfer behaviors. This study focuses on the flow and heat transfer characteristics in corrugated pipes with various geometries, addressing the current lack of systematic comparative studies on the performance of different Reynolds-Averaged Navier–Stokes (RANS) models in such configurations. Despite their limitations in accuracy compared to high-fidelity methods, RANS models remain the workhorse for engineering analysis due to their computational efficiency. This study employs several RANS models to simulate flow and heat transfer in three corrugated pipe geometries—sinusoidal (Sin), C-type, and U-type—over a Reynolds number range of O(104) to O(105) and assesses their performance against high-fidelity Large Eddy Simulation benchmarks. The results show that prediction accuracy decreases with increasing corrugation depth, with the most significant errors in trough regions where reverse flow dominates, and that the choice of turbulence model has a strong influence on the predicted flow and heat transfer behavior. Among all models, the k−ϵ models overall provide the most consistent and accurate predictions for friction factor, velocity distribution, and Nusselt number, while the k−ω models perform the worst. The Reynolds Stress Model improves friction factor prediction accuracy at high Reynolds numbers and provides marginally better accuracy in mean Nusselt number prediction, but its advantages are limited relative to its substantially higher computational cost. The Standard k−ϵ model with Enhanced Wall Treatment demonstrates robust and balanced performance across geometries and flow regimes, making it a practical choice for engineering use. This work provides engineers and researchers guidance for choosing RANS models that balance accuracy and computational efficiency in simulations of LNG ship-to-ship transfer, compact heat exchangers, and other industrial systems that employ corrugated pipes. Full article
(This article belongs to the Special Issue Ship and Ocean Engineering)
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1 pages, 126 KB  
Correction
Correction: Pearson et al. Transforming Water Research Through Human Rights-Based Approaches: A Framework for Implementation. Water 2025, 17, 1418
by Leonie J. Pearson, Vachararutai Boontinand and Phan Thanh Thanh
Water 2025, 17(17), 2648; https://doi.org/10.3390/w17172648 - 8 Sep 2025
Viewed by 424
Abstract
There were errors in the original publication [...] Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
20 pages, 14858 KB  
Article
Hydrochemistry and Geothermal Potential of Żary Pericline (SW Poland)
by Barbara Kiełczawa
Water 2025, 17(17), 2647; https://doi.org/10.3390/w17172647 - 7 Sep 2025
Viewed by 1442
Abstract
The mineralization of groundwater within the Żary pericline exhibits a broad range, from 0.2 to 0.3 g/L up to 401 g/L, with the majority classified as brines. These waters are predominantly chloride-rich, characterized by variable concentrations of cations such as Na+, [...] Read more.
The mineralization of groundwater within the Żary pericline exhibits a broad range, from 0.2 to 0.3 g/L up to 401 g/L, with the majority classified as brines. These waters are predominantly chloride-rich, characterized by variable concentrations of cations such as Na+, K+, Ca2+, and Mg2+. Their chemical composition varies by geological formation: Na-Cl and Mg-Cl types dominate in the Triassic strata, while more complex mixtures are observed in the Zechstein and Rotliegend formations. Brine formation and evolution are primarily influenced by evaporation and ion exchange processes, particularly Na+/Ca2+ exchange. These brines represent residual evaporative fluids that migrate through the subsurface during sediment compaction and tectonic deformation. The observed variability in mineral content suggests the occurrence of hydrochemical inversion within the geological layers. Groundwater temperatures range from 20 °C to 55 °C at depths between 490 and 1525 meters below ground level. The geothermal gradient spans from 3.55 °C/100 m to 4 °C/100 m, with the highest values recorded in the western and northwestern sectors of the pericline. These thermal conditions indicate promising potential for geothermal energy development in the region. Full article
(This article belongs to the Section Hydrogeology)
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25 pages, 4156 KB  
Article
Preserving Denitrification in High-Dissolved-Oxygen Environments: A Novel Sulfur–Polycaprolactone–Polyurethane Sponge Composite Carrier with Multi-Omics Insights
by Junjie Wang, Zuan Yang, Zhang Xu, Qihang Cen, Yuxin Shi and Yongchao Zhou
Water 2025, 17(17), 2646; https://doi.org/10.3390/w17172646 - 7 Sep 2025
Cited by 1 | Viewed by 851
Abstract
To address the denitrification challenges in the high-dissolved-oxygen (DO) aquatic environment system caused by the secondary effluent of wastewater treatment plants, this study innovatively developed a sulfur–polycaprolactone (S0-PCL) dual-electron donor composite carrier embedded in polyurethane sponge to mitigate high DO stress. [...] Read more.
To address the denitrification challenges in the high-dissolved-oxygen (DO) aquatic environment system caused by the secondary effluent of wastewater treatment plants, this study innovatively developed a sulfur–polycaprolactone (S0-PCL) dual-electron donor composite carrier embedded in polyurethane sponge to mitigate high DO stress. The system demonstrated remarkable resilience, with a denitrification efficiency decline of only 11.3% under a DO gradient (0–6.5 mg/L), significantly outperforming previously reported efficiency losses exceeding 90%. Metatranscriptomic analysis revealed that the millimeter-scale pores in the sponge created potential anoxic microzones, providing a microenvironment conducive to maintaining key denitrification gene expression. The anoxic stage was dominated by the sulfur-autotrophic denitrification (SAD) microorganism Sulfurovum (abundance 68.1%, expression 55.1%). In high-DO conditions, Alicycliphilus (55.3, 41.1%) and Paracoccus (31.6%, 31.8%) synergistically drove denitrification, while Hyphomonas (8.7%, 24.1%) assisted in DO and organics consumption. Gene expression data further revealed that Alicycliphilus hydrolyzed PCL to enter the tricarboxylic acid cycle, while Paracoccus simultaneously utilized S0 for SAD, establishing a dual-electron donor transfer pathway to sustain denitrification activity. The S0-PCL–polyurethane sponge provided resilience via oxygen isolation, sustained carbon release, and metabolic diversification, enabling microbial and functional gene reconfiguration. This study provides a novel technological pathway for deep nitrogen removal in oxygen-rich environments. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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31 pages, 515 KB  
Article
Forecasting Water Consumption for Sustainable Development in Saudi Arabia: A Copula-Based Approach
by Amwaj Falah AL-Rashidi, Dalia Kamal Alnagar and Hussein Eledum
Water 2025, 17(17), 2645; https://doi.org/10.3390/w17172645 - 7 Sep 2025
Viewed by 925
Abstract
Effective water resource planning is essential for Saudi Arabia, where limited freshwater availability is challenged by rapid population growth, economic development, and climate variability. This study introduces a copula-based modeling framework for forecasting water demand across the country’s urban, industrial, and agricultural sectors. [...] Read more.
Effective water resource planning is essential for Saudi Arabia, where limited freshwater availability is challenged by rapid population growth, economic development, and climate variability. This study introduces a copula-based modeling framework for forecasting water demand across the country’s urban, industrial, and agricultural sectors. Copulas, compared to traditional models, effectively capture nonlinear and asymmetric relationships among essential variables, including population, temperature, GDP, and sectoral water consumption. Multivariate copula models (Gaussian, Clayton, Gumbel, Frank, t-Copula, and Vine structures) were fitted and evaluated using historical data from 2008 to 2024, obtained from national authorities, including the Ministry of Environment, Water, and Agriculture, the General Authority for Statistics, and the National Center for Meteorology. The 4D normal copula was developed as the most efficient method across all sectors, with MAPE values of 6.37% for urban, 17.51% for industrial, and 23.20% for agricultural consumption. Scenario-based forecasts, which include baseline, high-growth, and sustainability-focused trajectories, indicate that the sustainability scenario yields the best results, resulting in significant demand reductions (21.7% urban, 20.4% industrial, and 8.2% agricultural) with minimal climate impact (+0.4 °C) and the lowest risk levels. The study demonstrates the successful decoupling of water demand from population and economic growth through proper policy interventions, with conditional risk analysis offering actionable early warning capabilities for proactive management. These findings provide a valuable foundation for enhancing national water strategy planning in Saudi Arabia under Vision 2030 and contribute to methodological improvements applicable to water-scarce regions internationally. Full article
(This article belongs to the Section Water Use and Scarcity)
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23 pages, 5538 KB  
Article
The TAM-xLSTM Model for Hourly River Flow Forecasting: A Case Study of Qiandongnan, Guizhou Province, China
by Renfeng Liu, Dingdong Wang, Liangyi Wang, Chi Cheng, Xiaoling Xia and Ziheng Yang
Water 2025, 17(17), 2644; https://doi.org/10.3390/w17172644 - 7 Sep 2025
Viewed by 742
Abstract
Accurate river flow forecasting is vital for flood warning and water resource management, yet hourly-scale prediction in small catchments remains underexplored despite its importance for rapid response flood control. To address this gap, this study proposes an enhanced temporal attention module xLSTM (TAM-xLSTM) [...] Read more.
Accurate river flow forecasting is vital for flood warning and water resource management, yet hourly-scale prediction in small catchments remains underexplored despite its importance for rapid response flood control. To address this gap, this study proposes an enhanced temporal attention module xLSTM (TAM-xLSTM) model that combines temporal feature extraction with timestep-level attention to better capture dynamic variations and dependencies. Case studies in the Qiandongnan region demonstrate that TAM-xLSTM substantially outperforms baseline models during wet season forecasting at Panghai Station, reducing RMSE by 9.6%, MAE by 24.1%, and Theil’s U by 6.6%, while increasing NSE by 4.8%. These results highlight the model’s ability to improve short-term river flow prediction in complex mountainous terrain and its potential to support effective flood warning and water resource management. Full article
(This article belongs to the Topic Advances in Earth Observation Technologies to Support Water-Related Sustainable Development Goals (SDGs))
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15 pages, 4299 KB  
Article
A Comparison of Characteristics of Infilling Sediments in Three Mud-Capped Dredge Pits on the Louisiana Continental Shelf
by Wenqiang Zhang, Kehui Xu, Chaochen Jia, Adam Gartelman, Omar Alawneh, Navid Jafari, Colin Herke, Madison Liotta and Samuel J. Bentley
Water 2025, 17(17), 2643; https://doi.org/10.3390/w17172643 - 7 Sep 2025
Viewed by 667
Abstract
Due to high sedimentation rate up to ~1 m/year, mud-capped dredge pits (MCDP) are often considered natural laboratories for studying sedimentary processes, slope stability and the impacts of dredging activities on marine environments. Although many studies have been performed on the Louisiana shelf, [...] Read more.
Due to high sedimentation rate up to ~1 m/year, mud-capped dredge pits (MCDP) are often considered natural laboratories for studying sedimentary processes, slope stability and the impacts of dredging activities on marine environments. Although many studies have been performed on the Louisiana shelf, there is a lack of high spatial resolution research covering the eastern, central and western Louisiana shelf to comprehensively investigate sediment infilling. Eighteen vibracores were collected from the Peveto Channel dredge pit (PC), Raccoon Island dredge pit (RI) and Sandy Point dredge pit (SP), and more than 1300 samples were analyzed to study the spatial variation in surficial sediment using statistical analyses. Our results indicate that the inner Louisiana continental shelf is silt-dominated, and there was no consistent grain size variation when comparing the sediment within the pits with that outside the pits. Skewness emerged as a prominent factor in the RI and SP, while standard deviation was the most influential in the PC. Our analysis shows also that two principal components are confirmed and account for more than 95% of the total grain size variance. Full article
(This article belongs to the Special Issue New Insights into Sea Level Dynamics and Coastal Erosion)
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22 pages, 2756 KB  
Article
Integrating Ecotoxicological Assessment to Evaluate Agricultural Impacts on Aquatic Ecosystems: A Case Study of the Lage Reservoir (Mediterranean Region)
by Adriana Catarino, Clarisse Mourinha, Mariana Custódio, Pedro Anastácio and Patrícia Palma
Water 2025, 17(17), 2642; https://doi.org/10.3390/w17172642 - 6 Sep 2025
Viewed by 953
Abstract
This study analyzed the use of a toolbox to evaluate the impact of agricultural activity on the water quality/status classification of a hydro-agricultural reservoir (Lage reservoir, Southern Portugal). The framework integrated the quantification of a group of 51 pesticides and ecotoxicological endpoints with [...] Read more.
This study analyzed the use of a toolbox to evaluate the impact of agricultural activity on the water quality/status classification of a hydro-agricultural reservoir (Lage reservoir, Southern Portugal). The framework integrated the quantification of a group of 51 pesticides and ecotoxicological endpoints with organisms from different trophic categories (the bacterium Aliivibrio fischeri, the microalga Pseudokirchneriella subcapitata, and the crustaceans Daphnia magna and Thamnocephalus platyurus) at two sampling points in the reservoir (Lage (L) and Lage S (LS)) between 2018 and 2020. Over the three-year study, we quantified 36 of the 51 pesticides analyzed in the Lage reservoir. Total concentrations increased successively from 0.95 µg L−1 to 1.99 and 2.66 µg L−1. Among these, the pesticides most frequently detected were terbuthylazine (100% of detection) and metolachlor (83% of detection), with maximum concentrations of 115.6 and 85.5 µg L−1, respectively. Samples from the LS site showed higher toxicity, where A. fischeri presented 30 min EC50 values of 39–51%. Microalgae growth was consistently inhibited, correlating with agricultural activity, mainly the application of herbicides and insecticides, while D. magna feeding rates revealed no inhibitory effects in the Lage samples. The results highlight that although the detected pesticide levels were below regulatory limits, they still induced toxic effects in the tested organisms. The potential ecological status of the reservoir was classified as moderate, and the integration of the proposal toolbox allowed refinement of the classification of water status. The results demonstrated that this integrated approach, combining multiple assessment methods, establishes a more robust water quality evaluation methodology, allowing it to be used as a tool complementary to the WFD methodology. This proposal not only identified existing pollution impacts but also enabled (1) early detection of the toxic effects of emerging contaminants to prevent ecological damage; (2) proactive management through specific actions to restore water status; and (3) improved sustainable water use. Full article
(This article belongs to the Special Issue Pesticides in Water and Health)
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26 pages, 8705 KB  
Article
Hydrochemical Characteristics and Formation Mechanism of Neogene Geothermal Water in the Zhangye–Minle Basin
by Zhen Zhang, Yang Hu, Tao Ren, Xiaodong Han and Xue Wu
Water 2025, 17(17), 2641; https://doi.org/10.3390/w17172641 - 6 Sep 2025
Viewed by 1025
Abstract
Geothermal resources in arid inland basins are important for clean energy development, yet their circulation and geochemical mechanisms remain insufficiently understood. This study investigates the hydrochemical characteristics and formation mechanisms of geothermal water in the Zhangye–Minle Basin, an arid inland region in northwestern [...] Read more.
Geothermal resources in arid inland basins are important for clean energy development, yet their circulation and geochemical mechanisms remain insufficiently understood. This study investigates the hydrochemical characteristics and formation mechanisms of geothermal water in the Zhangye–Minle Basin, an arid inland region in northwestern China. A total of nine geothermal water samples were analyzed using major ion chemistry, stable isotopes (δ2H, δ18O), tritium (3H), and radiocarbon (14C) to determine recharge sources, flow paths, and geochemical evolution. The waters were predominantly of the Cl–Na and Cl·SO4–Na types, with total dissolved solids ranging from 3432.00 to 5810.00 mg/L. Isotopic data indicated that recharge originated from atmospheric precipitation and snowmelt in the Qilian Mountains, with recharge altitudes between 2497 and 5799 m. Tritium and 14C results suggested that most samples were recharged before 1953, with maximum ages exceeding 40,000 years. Gibbs diagrams and ion ratio plots demonstrated that water–rock interaction was the primary geochemical process, while cation exchange was weak. Na+ was mainly derived from halite, albite, and mirabilite, while SO42− originated largely from gypsum. The calculated reservoir temperatures using cation geothermometers ranged from 57 °C to 148 °C. The deep circulation of geothermal water was closely related to NNW-trending fault zones that facilitated infiltration and heat accumulation. These findings provide new insights into the recharge sources, circulation patterns, and geochemical processes of geothermal systems in fault-controlled basins, offering a scientific basis for their sustainable exploration and development. Full article
(This article belongs to the Special Issue Dynamic Response of Water and Soil Resources in the Context of Climate Change and Human Activities)
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20 pages, 12005 KB  
Article
Reactivation Mechanism of Ancient Accumulation Landslides Synergistically Triggered by Excavation Disturbance and Critical Rainfall Infiltration
by Jiayong Zhang, Jinhong Chen, Yigen Qin, Xiaotong Xu, Wenlong Gou and Kunpeng Lu
Water 2025, 17(17), 2640; https://doi.org/10.3390/w17172640 - 6 Sep 2025
Viewed by 690
Abstract
The reactivation of the Longdongpo ancient colluvial landslide in Sinan County, Guizhou Province represents a typical multi-factor coupled failure. Based on detailed geological investigations and FLAC3D fluid–solid coupling numerical simulations, this study reveals its complex reactivation mechanisms. The analysis demonstrates that long-term [...] Read more.
The reactivation of the Longdongpo ancient colluvial landslide in Sinan County, Guizhou Province represents a typical multi-factor coupled failure. Based on detailed geological investigations and FLAC3D fluid–solid coupling numerical simulations, this study reveals its complex reactivation mechanisms. The analysis demonstrates that long-term groundwater action has significantly weakened the slip zone at the soil–bedrock interface, causing strength degradation and inducing prolonged quasi-stable creep deformation of the slope. The artificial cut slopes formed in the middle-to-lower sections disrupted the original stress field and induced localized plastic deformation. Crucially, the numerical simulation identified a 5 m rainfall infiltration depth as the threshold triggering abrupt instability; when exceeding this critical value (simulated as 10 m and 16 m infiltration depths), pore water pressure surged (>2.7 MPa) and displacement dramatically increased (>2.2 m), reducing shear strength along the potential failure surface to critical levels. This process culminated in the full connection of the shear surface and the landslide’s catastrophic reactivation. This work quantitatively elucidates the chain-reaction mechanism of “long-term groundwater weakening → engineering disturbance initiation → critical-depth rainfall infiltration triggering”, providing vital quantitative evidence for regional ancient landslide risk prevention. Full article
(This article belongs to the Special Issue Rainfall-Induced Landslides: Influencing, Modelling and Hazard Assessment: 2nd Edition)
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57 pages, 11196 KB  
Review
Continuous Electrocoagulation Processes for Industrial Inorganic Pollutants Removal: A Critical Review of Performance and Applications
by Zakaria Al-Qodah, Maha Mohammad AL-Rajabi, Enshirah Da’na, Mohammad Al-Shannag, Khalid Bani-Melhem and Eman Assirey
Water 2025, 17(17), 2639; https://doi.org/10.3390/w17172639 - 6 Sep 2025
Viewed by 1049
Abstract
This review provides a critical and technically grounded assessment of continuous electrocoagulation processes (CEPs) for the treatment of industrial inorganic pollutants, emphasizing recent innovations, methodological developments, and practical outcomes. A comprehensive literature survey indicates that 53 studies published over the past 25 years [...] Read more.
This review provides a critical and technically grounded assessment of continuous electrocoagulation processes (CEPs) for the treatment of industrial inorganic pollutants, emphasizing recent innovations, methodological developments, and practical outcomes. A comprehensive literature survey indicates that 53 studies published over the past 25 years have investigated CEPs for inorganic contaminant removal, with 36 focusing on standalone electrocoagulation systems and 17 exploring integrated CEPs approaches. Recent advancements in reactor design, such as enhanced internal mixing, optimized electrode geometry, and modular configurations, have significantly improved treatment efficiency, scalability, and operational stability. Evidence indicates that CEPs can achieve high removal efficiencies for a wide range of inorganic contaminants, including fluoride, arsenic, heavy metals (e.g., chromium, lead, nickel, iron), nitrates, and phosphates, particularly under optimized operating conditions. Compared to conventional treatment methods, CEPs offer several advantages, such as simplified operation, reduced chemical consumption, lower sludge generation, and compatibility with renewable energy sources and complementary processes like membrane filtration, flotation, and advanced oxidation. Despite these promising outcomes, industrial-scale implementation remains constrained by non-standardized reactor designs, variable operational parameters, electrode passivation, high energy requirements, and limited long-term field data. Furthermore, few studies have addressed the modeling and optimization of integrated CEPs systems, highlighting critical research gaps for process enhancement and reliable scale-up. In conclusion, CEPs emerge as a novel, adaptable, and potentially sustainable approach to industrial inorganic wastewater treatment. Its future deployment will rely on continued technological refinement, standardization, validation under real-world conditions, and alignment with regulatory and economic frameworks. Full article
(This article belongs to the Special Issue Advanced Technologies in Water and Wastewater Treatment)
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16 pages, 3525 KB  
Article
A Decade of Change in the Floodplain Lake: Does Zooplankton Yield or Resist?
by Anita Galir, Filip Stević, Karla Čmelar, Dubravka Špoljarić Maronić, Tanja Žuna Pfeiffer and Nikolina Bek
Water 2025, 17(17), 2638; https://doi.org/10.3390/w17172638 - 6 Sep 2025
Cited by 1 | Viewed by 750
Abstract
Natural ecosystems, especially those regulated by floods, are sensitive to prolonged temperature fluctuations that affect hydrology and the lateral connection between the river and its floodplain. Here, we analyzed a series of zooplankton data collected monthly from 2007 to 2016 during the ice-free [...] Read more.
Natural ecosystems, especially those regulated by floods, are sensitive to prolonged temperature fluctuations that affect hydrology and the lateral connection between the river and its floodplain. Here, we analyzed a series of zooplankton data collected monthly from 2007 to 2016 during the ice-free period in Kopački Rit Nature Park in the Middle Danube, an area important as a food source and nursery area for fish stocks in the Danube. The aim was to find out how the long-term change in temperature and fluctuating environmental parameters affect the succession of zooplankton in the warmer (from April to September) and colder parts of the year (from October to March). Throughout the decade, total nitrogen concentrations showed significant differences between years, with an increase since 2012. Despite the increase in nitrogen levels and the expected increase in primary production, the higher nitrogen levels were accompanied by lower zooplankton biomass. A significant difference was found between the values of the zooplankton geometric mean index, with 73% of the variance explained by the difference between groups. In general, a trend toward a significant decrease in zooplankton biomass, with a simultaneous increase in the number of species and high turnover rates, was observed throughout the decade. Full article
(This article belongs to the Special Issue Freshwater Ecosystems—Biodiversity and Protection: 2nd Edition)
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19 pages, 2281 KB  
Article
Impact of Water pH and Cultivar on Lettuce Growth, Water Use Efficiency, and Nutrient Use Efficiency in Deep Water Culture Systems
by Xinhua Jia, Alexander Speck, Xiaoyu Feng and Chiwon W. Lee
Water 2025, 17(17), 2637; https://doi.org/10.3390/w17172637 - 6 Sep 2025
Viewed by 1113
Abstract
Maintaining optimal pH in hydroponic systems typically requires continuous pH adjustment, increasing both labor and production costs. In regions with alkaline water sources, this challenge is especially critical. Identifying lettuce cultivars tolerant to high pH conditions offers a cost-effective and sustainable alternative to [...] Read more.
Maintaining optimal pH in hydroponic systems typically requires continuous pH adjustment, increasing both labor and production costs. In regions with alkaline water sources, this challenge is especially critical. Identifying lettuce cultivars tolerant to high pH conditions offers a cost-effective and sustainable alternative to frequent pH buffering. This study evaluated the impact of water pH on growth, water use efficiency (WUE), and nutrient use efficiency (NUE) of lettuce (Lactuca sativa L.) in deep water culture (DWC) hydroponics. A greenhouse experiment was conducted from June to July 2024 using a completely randomized design with four pH treatments: T1 (unbuffered control), T2 (pH 6.3), T3 (pH 7.0), and T4 (pH 8.3). Three lettuce cultivars—Tacitus (L1), Rex (L2), and Rutilai (L3)—were tested, with three replicates per treatment. Results showed that fresh yield was significantly affected by cultivar but not by pH treatment. Rex produced the highest yield, reaching 132 g/plant at pH 7.0, compared to 127 g/plant for Tacitus and 98 g/plant for Rutilai. WUE differed strongly among cultivars, with Rex achieving 68.7 g/L at pH 7.0, which is nearly double that of Rutilai (37.2 g/L). Nitrogen uptake was unaffected by treatment; however, nitrogen NUE differed significantly, with Rutilai recording 12.8 mg N/g fresh weight at pH 8.3, compared to 8.3 mg N/g fresh weight for Rex and 6.7 mg N/g fresh weight for Tacitus. Calcium uptake and NUE were significantly influenced by both pH and cultivar, ranging from 3.2 to 10.7 mg Ca/g fresh weight. These findings suggest that selecting pH-tolerant cultivars plays a more critical role than pH adjustment in determining yield and efficiency in hydroponic lettuce. Choosing pH-tolerant cultivars such as Rex can reduce dependence on chemical buffering, offering a cost-effective strategy for sustainable hydroponic lettuce production in regions with alkaline water sources. Full article
(This article belongs to the Section Water, Agriculture and Aquaculture)
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30 pages, 2870 KB  
Article
Hybrid Explainable AI Framework for Predictive Maintenance of Aeration Systems in Wastewater Treatment Plants
by Daniel Voipan, Andreea Elena Voipan and Marian Barbu
Water 2025, 17(17), 2636; https://doi.org/10.3390/w17172636 - 6 Sep 2025
Viewed by 940
Abstract
Aeration systems are among the most energy-intensive components of wastewater treatment plants (WWTPs), consuming up to 75% of total electricity while being prone to performance degradation caused by diffuser fouling and pressure losses. Traditional maintenance strategies are largely reactive or preventive, leading to [...] Read more.
Aeration systems are among the most energy-intensive components of wastewater treatment plants (WWTPs), consuming up to 75% of total electricity while being prone to performance degradation caused by diffuser fouling and pressure losses. Traditional maintenance strategies are largely reactive or preventive, leading to inefficient interventions, higher operational costs, and limited fault anticipation. This study addresses the need for an advanced predictive maintenance framework capable of early detection and differentiation of multiple aeration system faults. Using the Benchmark Simulation Model No. 2 (BSM2), two representative degradation scenarios—acute airflow pressure loss and chronic diffuser fouling—were simulated to generate a labeled dataset. A hybrid machine learning approach was developed, combining Random Forest-based feature selection with Long Short-Term Memory (LSTM) neural networks for temporal, multi-label fault classification. To enhance interpretability and operator trust, SHapley Additive exPlanations (SHAP) were applied to quantify feature contributions and provide transparent model predictions. The results show that the proposed framework achieves over 94% detection accuracy and provides early warnings compared to static threshold-based methods. The integration of explainable AI ensures actionable insights for maintenance planning. This approach supports more energy-efficient, reliable, and sustainable operation of WWTP aeration systems and offers a benchmark methodology for future predictive maintenance research. Full article
(This article belongs to the Special Issue AI, Machine Learning and Digital Twin Applications in Water)
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24 pages, 2718 KB  
Article
Composition of Dinoflagellate Resting Cyst Assemblages and Its Monthly Variability in a Shallow Mediterranean Lagoon (Santa Giusta Lagoon, Sardinia, Italy)
by Cecilia Teodora Satta, Bachisio Mario Padedda, Silvia Pulina, Nicola Fois and Antonella Lugliè
Water 2025, 17(17), 2635; https://doi.org/10.3390/w17172635 - 6 Sep 2025
Viewed by 767
Abstract
The present study identifies and quantifies the dinoflagellate resting cysts along an annual cycle from a shallow Mediterranean lagoon. Sediment samples were collected and analyzed for the determination of the dinoflagellate cyst density and composition at four sampling stations in Santa Giusta Lagoon [...] Read more.
The present study identifies and quantifies the dinoflagellate resting cysts along an annual cycle from a shallow Mediterranean lagoon. Sediment samples were collected and analyzed for the determination of the dinoflagellate cyst density and composition at four sampling stations in Santa Giusta Lagoon (Oristano Gulf) from March 2015 to February 2016. At the same time, selected physicochemical variables and the cell densities of the dinoflagellate species in the water column were measured and determined. The group of Peridiniales dominated the cyst assemblages at spatial and temporal scales, with an almost total prevalence of the autotrophic–mixotrophic taxa. Heterotrophic Peridiniales showed occasional importance, especially in the stations closest to the sea connections, as well as the group of Gonyaulacales and Gymnodiniales. The composition in morphotypes revealed the dominance of Ensiculifera tyrrhenica and Scrippsiella kirschiae in correspondence with the maximum cyst densities in the inner sampling stations. Cysts of Margalefidinium cf polykrikoides reached high density values following an intense summer bloom. Salinity, ammonia, and total nitrogen were the environmental variables more strongly correlated with the multivariate cyst assemblage structure. The monthly time-scale offered a more accurate focus on cyst assemblages changes in respect to the usual single seasonal sampling in Santa Giusta Lagoon. The obtained data provided further knowledge on the relation among cyst assemblage variability, environmental conditions, and dinoflagellate motile stages in the water column relevant for comparisons with similar ecosystems in the Mediterranean and worldwide. Full article
(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)
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22 pages, 2881 KB  
Review
Water, Sanitation, and Hygiene in Urban Areas: A Review
by Gabriela Souza, Cristina Santos and Érico Lisboa
Water 2025, 17(17), 2634; https://doi.org/10.3390/w17172634 - 6 Sep 2025
Viewed by 1023
Abstract
This paper provides a comprehensive bibliographic and bibliometric review of water, sanitation, and hygiene (WASH) in global urban areas, employing the Proknow-C methodology. The study categorizes WASH into four main themes: sustainability, urban areas, indicators and index, and urban planning, allowing for a [...] Read more.
This paper provides a comprehensive bibliographic and bibliometric review of water, sanitation, and hygiene (WASH) in global urban areas, employing the Proknow-C methodology. The study categorizes WASH into four main themes: sustainability, urban areas, indicators and index, and urban planning, allowing for a detailed analysis of several multidimensional aspects. The review underscores the importance of providing basic infrastructure to adopt an integrated, sustainable, and socially inclusive approach, showcasing the resilience and adaptability of the WASH sector in tackling the dynamic challenges of urbanization. It is noticeable that the WASH area has undergone significant development, moving from a focus primarily on infrastructure to a more holistic approach. In general, the WASH framework is globally characterized by high irregularity/inequality in provision and access. The relationship between urban vulnerabilities and WASH is very clear, but also multifaceted and complex, and there is a crucial need to combine behavior change with infrastructure development while addressing economic challenges and prioritizing investments in WASH. The improvement of WASH conditions in urban areas should focus the interplay between urban development policies and the provision of WASH services, while focusing also on the role of multi-sectoral collaboration, stakeholder engagement, and policy implementation in overcoming barriers to effective WASH delivery. Full article
(This article belongs to the Section Water and One Health)
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9 pages, 1517 KB  
Communication
Toxic Potential and Long-Term Dynamics of Cyanobacterial Blooms in the Gulf of Gdańsk (Southern Baltic Sea)
by Agata Błaszczyk and Justyna Kobos
Water 2025, 17(17), 2633; https://doi.org/10.3390/w17172633 - 6 Sep 2025
Viewed by 858
Abstract
Over the past 15 years, Nodularia spumigena blooms in the Gulf of Gdańsk (southern Baltic Sea) have reached exceptional intensity, accounting for up to 90% of phytoplankton biomass during peak summer periods. Our long-term observations revealed oscillations in blooms intensity, with peak nodularin [...] Read more.
Over the past 15 years, Nodularia spumigena blooms in the Gulf of Gdańsk (southern Baltic Sea) have reached exceptional intensity, accounting for up to 90% of phytoplankton biomass during peak summer periods. Our long-term observations revealed oscillations in blooms intensity, with peak nodularin concentrations (up to 45,000 μg/L) recorded in 2012, 2015, and 2018—the highest levels of this toxin documented to date in both the Baltic Sea and worldwide. An extreme cyanobacterial bloom in 2018, caused by unusually high air and water temperatures, covered almost the whole surface of the Gulf of Gdańsk, causing multi-day closures of bathing areas. During this bloom, high levels of microcystins (up to 6640 μg/L MC-LR) were also detected, as well as the presence of 42 cyanopeptides, mainly anabaenopeptides and spumigins, which were present at concentrations 5–10 times higher than hepatotoxins. Full article
(This article belongs to the Section Oceans and Coastal Zones)
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19 pages, 6706 KB  
Article
Preparation and Characterization of Polyferric Sulfate Derived from Iron Sludge in De-Ironing Water Plants and Its Utilization in Water Treatment
by Huiping Zeng, Simin Li, Xiao Sun, Chengbo Liu, Jie Zhang and Dong Li
Water 2025, 17(17), 2632; https://doi.org/10.3390/w17172632 - 5 Sep 2025
Viewed by 820
Abstract
Resource utilization of water treatment residuals (WTRs) has emerged as a significant focus in environmental engineering research. In this study, waste iron sludge from a groundwater de-ironing plant was used as the raw material. Ferric salts were recovered via sulfuric acid leaching and [...] Read more.
Resource utilization of water treatment residuals (WTRs) has emerged as a significant focus in environmental engineering research. In this study, waste iron sludge from a groundwater de-ironing plant was used as the raw material. Ferric salts were recovered via sulfuric acid leaching and subsequently polymerized into polyferric sulfate (PFS) with varying basicity (B = 0.1–0.4) using the alkalization–aging method. The optimal leaching conditions were determined as a liquid–solid ratio of 10:1, a sulfuric acid concentration of 3 mol·L−1, a reaction temperature of 70 °C, and a reaction time of 30 min, yielding a ferric leaching amount of 0.45 g Fe/g dry sludge. Characterization results revealed that the synthesized PFS exhibited similar ferric polymer species, functional group structures, and polymeric crystal structures to those of commercial PFS (CPFS). Coagulation performance tests demonstrated that at a dosage of 30 mg Fe/L, the prepared PFS achieved turbidity and UV254 removal efficiencies of 96.88% and 81.87%, respectively, outperforming CPFS. In domestic wastewater treatment, combining the synthesized PFS with magnetic nanoparticles Fe3O4@C yielded a magnetic coagulant that further enhanced the removal of turbidity, chemical oxygen demand (COD), and total phosphorus (TP) to maximum efficiencies of 94.66%, 81.97%, and 98.08%, respectively. This study confirms the technical feasibility and environmental–economic benefits of preparing magnetic PFS coagulants from waste iron sludge for wastewater treatment. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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18 pages, 1655 KB  
Article
Pilot-Scale Evaluation of a Filter Prototype for Bacterial Inactivation in Agro-Food Processing Wastewater
by Piotr Kanarek, Barbara Breza-Boruta and Wojciech Poćwiardowski
Water 2025, 17(17), 2631; https://doi.org/10.3390/w17172631 - 5 Sep 2025
Viewed by 920
Abstract
The processing of freshly cut fruits and vegetables represents an important niche for implementing circular economy principles, particularly through the reuse of washing water. This is especially relevant as post-wash water is often treated as wastewater and discarded without reuse. One promising research [...] Read more.
The processing of freshly cut fruits and vegetables represents an important niche for implementing circular economy principles, particularly through the reuse of washing water. This is especially relevant as post-wash water is often treated as wastewater and discarded without reuse. One promising research avenue is the use of plant-derived extracts in water sanitation processes. Their antimicrobial properties offer a natural alternative to conventional disinfectants while reducing the formation of harmful disinfection by-products. The aim of this study was to evaluate the effectiveness of different filter bed configurations in removing pathogens from water. These configurations included a hydrogel saturated with natural plant extracts, an ion exchange resin layer, and an activated carbon layer. The most effective composite was also tested using real process water from a fruit washing line. The test materials included concentrated extracts from oak bark (Quercus robur), willow (Salix alba), birch (Betula pendula), raspberry shoots (Rubus idaeus), tea leaves (Camellia sinensis), and linden flowers (Tilia cordata), all immobilized in hydrogel, along with activated carbon and ion-exchange resin. Water samples were artificially inoculated with six opportunistic pathogens and collected process water was also used. Samples were analyzed microbiologically at six time intervals. The composite filter (hydrogel–resin–carbon) achieved a reduction of over 2 log10 in heavily inoculated water (~108 CFU mL−1) and maintained at least a 1 log10 reduction in real process effluents. The proposed solution supports blue water footprint reduction strategies (as the system aims to decrease the demand for freshwater resources through the reuse of treated wastewater) and aligns with the principles of green processing. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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25 pages, 9748 KB  
Article
Physical Drivers of Salinity in a Southern Baltic Coastal Lagoon: A Selective Modeling Approach
by Weronika Sowińska, Aleksandra Dudkowska, Maciej Matciak, Wojciech Brodziński and Marta Małgorzata Misiewicz
Water 2025, 17(17), 2630; https://doi.org/10.3390/w17172630 - 5 Sep 2025
Viewed by 937
Abstract
Coastal lagoons provide vital ecological functions, supporting diverse flora and fauna while being highly sensitive to environmental changes. In the southern Baltic Sea, the Puck Lagoon is a hydrologically distinct subregion of the Gulf of Gdańsk characterized by variable exchange of water with [...] Read more.
Coastal lagoons provide vital ecological functions, supporting diverse flora and fauna while being highly sensitive to environmental changes. In the southern Baltic Sea, the Puck Lagoon is a hydrologically distinct subregion of the Gulf of Gdańsk characterized by variable exchange of water with the outer bay and substantial freshwater inflows. Its benthic communities are particularly sensitive to salinity, yet the processes shaping this parameter remain insufficiently understood. In situ measurements in summer 2020 revealed relatively high salinity in the lagoon (up to 7.7 PSU) compared to the adjacent outer bay (7.2–7.4 PSU), with localized reductions near the Kuźnica Passage and the Reda River mouth. As a first step toward explaining the hydrodynamic processes responsible for these anomalies, we applied a high-resolution, two-dimensional model focused on three fundamental physical drivers: river inflows, open-boundary exchange, and wind forcing. These processes represent the primary controls on salinity in shallow lagoons and provide a basis for evaluating additional mechanisms. The model reproduced observed patterns with a mean absolute error of 0.15 PSU, confirming that this selective framework captures the key features of salinity variability and establishes a baseline for future three-dimensional modeling that will incorporate further processes such as vertical mixing, precipitation, and evaporation. Full article
(This article belongs to the Special Issue Application of Numerical Modeling in Estuarine and Coastal Dynamics)
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12 pages, 9058 KB  
Article
Water Masses and Circulation in the Chain Fracture Zone (Equatorial Atlantic)
by Alexander Demidov, Kseniya Artamonova and Sergey Dobrolyubov
Water 2025, 17(17), 2629; https://doi.org/10.3390/w17172629 - 5 Sep 2025
Viewed by 768
Abstract
In this study, we discuss the water masses and their transport in the Chain fracture zone (CFZ), which is a poorly studied part of the Equatorial Atlantic. Our study is based on measurements carried out during the 63rd cruise of R/V “Akademik Ioffe” [...] Read more.
In this study, we discuss the water masses and their transport in the Chain fracture zone (CFZ), which is a poorly studied part of the Equatorial Atlantic. Our study is based on measurements carried out during the 63rd cruise of R/V “Akademik Ioffe” in 2022. We identified water masses in the CFZ, determined their physical and chemical properties, localized their boundaries and components of the North Atlantic Deep Water (NADW), and calculated the transport of water masses. A four-layer structure of the NADW was identified with two components of middle NADW, which are defined by minimal and maximal oxygen concentrations. The upper boundary of the Antarctic Bottom Water (AABW) corresponds approximately to the isotherm θ = 1.5 °C. The assessed proportion of AABW in the bottom layer at the western entrance to the CFZ is 50%, and not higher than 33% at the eastern exit from the CFZ. For the first time, instrumental observations were carried out at the exit of the CFZ and in its western part. They showed that the AABW flux has an intensity of about 0.02–0.5 Sv depending on the upper boundary of AABW and moves through a passage in the northern wall (at 13° W), and not through the main sill. Full article
(This article belongs to the Section Oceans and Coastal Zones)
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23 pages, 4980 KB  
Article
A Study on the Removal of Phosphate from Water Environments by Synthesizing New Sodium-Type Zeolite from Coal Gangue
by Yiou Wang, Qiang Li, Muyuan Ma, Zekun Xu and Tianhui Zhao
Water 2025, 17(17), 2628; https://doi.org/10.3390/w17172628 - 5 Sep 2025
Viewed by 936
Abstract
Excessive phosphorus emissions are a significant driver of severe eutrophication in water bodies, and developing an efficient and cost-effective adsorbent for phosphorus removal is imperative. In this study, a Na-type zeolite was synthesized from coal gangue sourced from an open-pit mine in Xinjiang [...] Read more.
Excessive phosphorus emissions are a significant driver of severe eutrophication in water bodies, and developing an efficient and cost-effective adsorbent for phosphorus removal is imperative. In this study, a Na-type zeolite was synthesized from coal gangue sourced from an open-pit mine in Xinjiang province, China. The synthesis process involved drying, crushing, alkali activation, aging, hydrothermal crystallization, and Na+ ion exchange. Orthogonal design identified the optimal synthesis parameters: an alkali-to-ash ratio of 1:1, aging at 20 °C for 12 h, and crystallization at 130 °C for 12 h. Aging time exerted the greatest influence on the phosphate removal efficiency. The optimized zeolite exhibited excellent phosphate adsorption performance, achieving a removal efficiency of up to 96% and a capacity of 16 mg/g. The adsorption kinetics followed both pseudo-first-order and pseudo-second-order models, indicating processes governed by combined physical and chemical mechanisms. Isotherm data fitting with Freundlich and Langmuir models suggested the presence of both homogeneous and heterogeneous active sites. Thermodynamic studies confirmed a spontaneous and endothermic process, increasingly favorable at higher temperatures. Characterizations via scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of Na-type zeolite and revealed structural and compositional changes following phosphate adsorption. Aluminum and calcium binding played key roles in the chemical adsorption mechanisms. This work not only offers a high-efficiency, low-cost solution for phosphorus removal from wastewater but also provides a sustainable pathway for the valorization of coal gangue in the Zhundong area of Xinjiang, China. Full article
(This article belongs to the Special Issue Emerging Contaminants in Natural and Engineered Water Environments: Environmental Behavior, Ecological Effects and Control Strategies, 2nd Edition)
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