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Industrial Wastewater Treatment by Coagulation–Flocculation and Advanced Oxidation Processes: A Review
Microvascular Responses in the Dermis and Muscles After Balneotherapy: Results from a Prospective Pilot Histological Study
Simultaneous Heterotrophic Nitrification and Aerobic Denitrification of High C/N Wastewater in a Sequencing Batch Reactor
Urban Geochemical Contamination of Highland Peat Wetlands of Very High Ecological and First Nations Cultural Value
Numerical Study of Turbulent Open-Channel Flow Through Submerged Rigid Vegetation

Journal Description

Water

Water is a peer-reviewed, open access journal on water science and technology, including the ecology and management of water resources, and is published semimonthly online by MDPI. Water collaborates with the Stockholm International Water Institute (SIWI). In addition, the American Institute of Hydrology (AIH), The Polish Limnological Society (PLS) and Japanese Society of Physical Hydrology (JSPH) are affiliated with Water and their members receive a discount on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Ei Compendex, GEOBASE, GeoRef, PubAg, AGRIS, CAPlus / SciFinder, Inspec, and other databases.
Journal Rank: JCR - Q2 (Water Resources) / CiteScore - Q1 (Aquatic Science)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 19.1 days after submission; acceptance to publication is undertaken in 2.6 days (median values for papers published in this journal in the first half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Companion journals for Water include: GeoHazards.
Journal Clusters of Water Resources: Water, Journal of Marine Science and Engineering, Hydrology, Resources, Oceans, Limnological Review, Coasts.

Impact Factor: 3.0 (2024); 5-Year Impact Factor: 3.3 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2073-4441

Latest Articles

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Open AccessArticle

Urban Underground Structures and Karst Groundwater Systems Interactions: The Case of Mazzoccolo Spring in Formia, Central Italy

by Flavia Ferranti, Francesco Maria De Filippi and Giuseppe Sappa

Water 2025, 17(19), 2802; https://doi.org/10.3390/w17192802 - 23 Sep 2025

The construction of underground infrastructure in urban environments can significantly alter groundwater flow dynamics, particularly in karst settings, which are characterized by high permeability, rapid groundwater flow, and strong spatial variability in recharge and discharge processes. Tunneling in a karst system can severely [...] Read more.

The construction of underground infrastructure in urban environments can significantly alter groundwater flow dynamics, particularly in karst settings, which are characterized by high permeability, rapid groundwater flow, and strong spatial variability in recharge and discharge processes. Tunneling in a karst system can severely deplete an aquifer and undermine the sustainability of water resources over the long term. These impacts pose significant challenges for regional water resources management, highlighting the urgent need for strategies that support both sustainable development and the protection of these complex hydrogeological systems. One of the most critical consequences of such construction activities can be tunnel drainage, which can modify the hydrogeological balance of karst aquifers. For this reason, an accurate estimation of groundwater recharge remains a major challenge, yet it is essential for effective groundwater management, particularly in regions that rely heavily on karst groundwater resources. This paper proposes a GIS-based methodological framework to assess the active recharge of the karst aquifer feeding the Mazzoccolo Spring, located in the urban area of Formia (southern Latium Region, Central Italy), which is potentially affected by a planned underground infrastructure. The study focuses on delineating the recharge area and evaluating the potential impacts of tunneling on this complex and sensitive hydrogeological system. Full article

(This article belongs to the Special Issue Advances in Urban Groundwater and Sustainable Water Resources Management and Planning II)

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Open AccessArticle

A Semi-Automated Framework for Flood Ontology Construction with an Application in Risk Communication

by Shenglin Li, Caleb Erickson, Michal Zajac, Xiaoming Guo, Qiuhua Duan and Jiaqi Gong

Water 2025, 17(19), 2801; https://doi.org/10.3390/w17192801 - 23 Sep 2025

Flash floods are increasingly frequent and severe, yet standard risk communication messages are often too generic and lack actionable guidance, causing them to be ignored. This research aims to enhance flood risk communication by first, developing a robust flood ontology using a novel [...] Read more.

Flash floods are increasingly frequent and severe, yet standard risk communication messages are often too generic and lack actionable guidance, causing them to be ignored. This research aims to enhance flood risk communication by first, developing a robust flood ontology using a novel semi-automated approach, and second, demonstrating its potential as a semantic foundation for translating complex data into clear, personalized public alerts. We introduce a semi-automated, human-in-the-loop ontology engineering strategy that integrates expert-defined schemas with Large Language Model (LLM)-driven expansion and refinement from authoritative sources. Evaluation results are twofold: (1) Technical metrics confirm our LLM-constructed ontology achieves superior relationship richness and expressiveness compared with existing disaster ontologies. (2) A proof-of-concept case study demonstrates the ontology’s potential by showing how its specific classes and relations (e.g., `neededForElderly’ relation linking the class `SpecialConsideration’ to `ElderlyCommunityMember’) can be used to generate targeted advice like “check on elderly neighbors”, transforming a generic alert into a clear and actionable message. Consequently, this research delivers two key contributions: a replicable and domain-adaptable methodology for semi-automated ontology construction and a practical demonstration of how such an ontology can bridge the critical gap between flood data and public understanding, empowering communities to respond more effectively. Full article

(This article belongs to the Special Issue Recent Advances in Flood Risk Assessment and Management)

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Open AccessArticle

Analysis of Flood Risk in Ulsan Metropolitan City, South Korea, Considering Urban Development and Changes in Weather Factors

by Changjae Kwak, Junbeom Jo, Jihye Han, Jungsoo Kim and Sungho Lee

Water 2025, 17(19), 2800; https://doi.org/10.3390/w17192800 - 23 Sep 2025

Urban flood damage is increasing globally, particularly in major cities. Factors contributing to flood risk include urban environmental changes, such as watershed development and precipitation variations caused by climate change. Rapid urbanization and weather anomalies further complicate flood management and damage mitigation. Additionally, [...] Read more.

Urban flood damage is increasing globally, particularly in major cities. Factors contributing to flood risk include urban environmental changes, such as watershed development and precipitation variations caused by climate change. Rapid urbanization and weather anomalies further complicate flood management and damage mitigation. Additionally, detailed analyses at small spatial units (e.g., roads, buildings) remain insufficient. Hence, urban flood analysis considering such spatial variations is required. This study analyzed flood risk in Ulsan, Korea, under a severe flood scenario. Land cover changes from the 1980s to 2010s were examined in 10-year intervals, along with the frequency of heavy rainfall and high river water levels that trigger severe floods. Flood risk was structured as a matrix of likelihood and impact. The results revealed that land cover changes, influenced by development policies or regulations, had a minimal impact on urban flood risk, which is likely because effective drainage systems and stringent urban planning regulations mitigated their effects. However, the frequency and intensity of extreme precipitation events had a substantial effect. These findings were validated using a comparative analysis of an inundation damage trace map and flood range simulated by a physical model. The 10 m grid resolution and time-series likelihood-and-impact framework used in this study can inform budget allocation, resource mobilization, disaster prevention planning, and decision-making during disaster response efforts in major cities. Full article

(This article belongs to the Section Urban Water Management)

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Open AccessArticle

Gravity-Driven Operation Mitigates Inorganic Fouling and Enables Low-Pressure Filtration in a Pilot-Scale Dynamic Membrane Bioreactor

by Xuechun Liu, Dezheng Lv, Lugao Jiang and Guoqiang Liu

Water 2025, 17(19), 2799; https://doi.org/10.3390/w17192799 - 23 Sep 2025

The filtration behaviors of dynamic membrane (DM) under gravity-driven and pump-driven modes were investigated in a pilot-scale DM bioreactor (DMBR) for domestic wastewater treatment. After DM formation, both modes achieved effective solid–liquid separation, producing effluent with turbidity below 1 NTU, with the gravity-driven [...] Read more.

The filtration behaviors of dynamic membrane (DM) under gravity-driven and pump-driven modes were investigated in a pilot-scale DM bioreactor (DMBR) for domestic wastewater treatment. After DM formation, both modes achieved effective solid–liquid separation, producing effluent with turbidity below 1 NTU, with the gravity-driven module exhibiting marginally lower turbidity than the pump-driven system. Although the flux in the gravity-driven mode (30–48 L/m²·h) was approximately half that of the pump-driven mode, the transmembrane pressure (TMP) required was only 10–20% of that under the pump-driven operation. The DM formed under pump-driven conditions was thicker and more compact, leading to more frequent and rapid TMP increases. Inorganic content accounted for 85% of the pump-driven DM mass, significantly higher than that in the gravity-driven DM (50%) and activated sludge (15%), indicating a pronounced accumulation of inorganic solids on the mesh filter surface, particularly under the pump-driven operation. This accumulation increased filtration resistance and elevated TMP. Therefore, enhancing the removal of inorganic solids prior to the DMBR can improve system stability and facilitate broader application of the DMBR technology. Full article

(This article belongs to the Special Issue Advances and Innovations in Technologies for Treatment and Toxicity Assessment of Conventional and Emerging Contaminant in Industrial Wastewater)

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Open AccessArticle

Smart Water Conservation: A Behaviourally-Grounded Recommender System for Demand Management Programs

by Md Shamsur Rahim, Khoi Anh Nguyen, Rodney Anthony Stewart, Damien Giurco and Michael Blumenstein

Water 2025, 17(19), 2798; https://doi.org/10.3390/w17192798 - 23 Sep 2025

Water utilities are increasingly turning to digital solutions to promote conservation behaviours among households; however, traditional campaigns often suffer from limited personalisation, low interactivity, and modest long-term impact. Though computer-tailored and recommender systems (RSs) may offer personalisation, these systems lack a generalised framework [...] Read more.

Water utilities are increasingly turning to digital solutions to promote conservation behaviours among households; however, traditional campaigns often suffer from limited personalisation, low interactivity, and modest long-term impact. Though computer-tailored and recommender systems (RSs) may offer personalisation, these systems lack a generalised framework that integrates behavioural theory with system design. This study addresses this research gap by introducing a novel framework that unites behavioural science, user experience (UX) design, and adaptive digital feedback to foster water-conscious practices at the residential level. The model draws on established behavioural theories, including the Theory of Planned Behaviour, the Transtheoretical Model, and Intervention Mapping, to ensure that tailored recommendations align with users’ psychological drivers, behavioural readiness, and daily routines. An industry-first prototype RS was developed and evaluated through an online survey (N = 300), assessing user perceptions of relevance, motivation, ease of use, and likelihood of action. The results reveal strong support for personalised suggestions, with 82% of respondents agreeing that personalised recommendations would help conserve water, and 76% indicating incentives would motivate adoption. This evidence indicates early acceptance and high potential impact. This study also addresses a critical research gap: no generic model previously existed to guide the integration of RSs with behaviour change interventions in water demand management. Broader implications are also discussed for applying the model to other sustainability domains such as energy use, waste reduction, and climate adaptation. Full article

(This article belongs to the Special Issue Artificial Intelligence in Water Science: Opportunities, Prospects, and Concerns)

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Open AccessArticle

A Study on the Use of Copper Ions for Bacterial Inactivation in Water

by Arzu Teksoy and Melis Ece Özyiğit

Water 2025, 17(19), 2797; https://doi.org/10.3390/w17192797 - 23 Sep 2025

This study comprehensively evaluated the antimicrobial performance of copper ions against three bacterial species relevant to water systems: E. coli (ATCC 25922), P. aeruginosa (ATCC 27853), and S. epidermidis (ATCC 12228). Disinfection kinetics were determined at three copper concentrations (0.5, 1.5, and 3.3 [...] Read more.

This study comprehensively evaluated the antimicrobial performance of copper ions against three bacterial species relevant to water systems: E. coli (ATCC 25922), P. aeruginosa (ATCC 27853), and S. epidermidis (ATCC 12228). Disinfection kinetics were determined at three copper concentrations (0.5, 1.5, and 3.3 mg/L) using the Gard model. E. coli exhibited the highest susceptibility, with inactivation rate constants of 0.63, 3.27, and 9.83, achieving complete inactivation at 3.3 mg/L. P. aeruginosa was the most resistant, showing values below 1.0 across all concentrations, while S. epidermidis displayed intermediate responses. Selected experiments further examined the influence of growth phase, temperature, and water chemistry. Exponential-phase cells were more sensitive than stationary-phase cultures, and higher temperatures (37 °C vs. 5 °C) significantly enhanced inactivation. Moderate bicarbonate (50 mg/L) improved bacterial removal by stabilizing soluble Cu²⁺ ions (2.60 lg reduction), whereas elevated calcium and magnesium (Ca²⁺ 100 mg/L, Mg²⁺ 50 mg/L) reduced effectiveness (≤2.10 lg reduction) through competitive interactions. In addition to culture-based methods, adenosine triphosphate (ATP) bioluminescence assays and flow cytometry (FCM) provided complementary insights, confirming early metabolic disruption and membrane damage prior to culturability loss in selected experiments. Full article

(This article belongs to the Section Water Quality and Contamination)

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Open AccessArticle

Assessing the Potential of Drone Remotely Sensed Data in Detecting the Soil Moisture Content and Taro Leaf Chlorophyll Content Across Different Phenological Stages

by Reitumetse Masemola, Mbulisi Sibanda, Onisimo Mutanga, Richard Kunz, Vimbayi G. P. Chimonyo and Tafadzwanashe Mabhaudhi

Water 2025, 17(19), 2796; https://doi.org/10.3390/w17192796 (registering DOI) - 23 Sep 2025

Soil moisture content is an important determinant of crop productivity, especially in agricultural systems that are dependent on rainfall. Climate variability has introduced water management challenges for smallholder farmers in Southern Africa. The emergence of unmanned aerial vehicle (UAV)-borne remote sensing offers modern [...] Read more.

Soil moisture content is an important determinant of crop productivity, especially in agricultural systems that are dependent on rainfall. Climate variability has introduced water management challenges for smallholder farmers in Southern Africa. The emergence of unmanned aerial vehicle (UAV)-borne remote sensing offers modern solutions for monitoring soil moisture, plant health and overall crop productivity in real-time. This study evaluated the utility of UAV-acquired data in conjunction with random forest regression in predicting soil moisture content and chlorophyll across different growth stages of taro. The estimation models achieved R² values up to 0.90 with rRMSE as low as 1.25%, demonstrating the robust performance of random forest in concert with different spectral datasets in estimating soil moisture and chlorophyll. Correlation analysis confirmed the association between these two variables, with the strongest correlation observed during the vegetative stage (r = 0.81, p < 0.05) and the weakest during the late vegetative stage (r = 0.78, p < 0.05). The results showed that UAV bands were crucial in predicting soil moisture and chlorophyll across all stages. These results demonstrate the utility of remote sensing, particularly UAV-borne sensors, in monitoring crop productivity in smallholder farms. By employing UAV-borne sensors, farmers can improve on-farm water management and make better and more informed decisions. Full article

(This article belongs to the Special Issue Advancements in Remote Sensing and UAV Technologies for Water Management in Climate-Smart Agriculture Systems)

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16 pages, 3171 KB

Open AccessArticle

Machine Learning Prediction of Phosphate Adsorption on Red Mud Modified Biochar Beads: Parameter Optimization and Experimental Validation

by Feng Tian, Li Wang, Yiwen Wang, Qichen Wang, Ruyu Sun and Suqing Wu

Water 2025, 17(19), 2795; https://doi.org/10.3390/w17192795 - 23 Sep 2025

Designing phosphate adsorbents is often hindered by trial-and-error optimization that overlooks nonlinear coupling between preparation parameters and operational conditions. Here we present a unified, explainable machine-learning framework that links red mud modified biochar bead (RM/CSBC) preparation (red mud dosage, biomass dosage, and pyrolysis [...] Read more.

Designing phosphate adsorbents is often hindered by trial-and-error optimization that overlooks nonlinear coupling between preparation parameters and operational conditions. Here we present a unified, explainable machine-learning framework that links red mud modified biochar bead (RM/CSBC) preparation (red mud dosage, biomass dosage, and pyrolysis temperature) to operating variables (initial pH, reaction temperature, contact time, and initial phosphate concentration) and directly guides condition selection. Using 95 independent experiments, six regressors were trained and compared. Random Forest (RF) model demonstrated strong prediction accuracy, with R² values of 0.916 for the training set and 0.892 for the test set. Support Vector Regression (SVR) model showed superior performance, achieving R² values of 0.984 and 0.967 for training and test sets, respectively, with low RMSE (0.068 and 0.083) and PBIAS (5.41% and 6.86%). Feature importance analysis revealed red mud and biomass doses positively influenced phosphate adsorption, with surface active sites and phosphate concentration gradient playing significant roles. Experimental verification confirmed RF and SVR models provided accurate predictions under three representative conditions, with deviations between predictions and measurements of +0.66, +0.19, and −0.69 mg·g⁻¹ for SVR and −1.08, −0.79, and −1.15 mg·g⁻¹ for RF, offering reliable guidance for phosphate removal in wastewater using RM/CSBC. This work highlights the potential of using machine learning to optimize waste-based adsorbent materials for wastewater treatment, significantly reducing time and experimental costs. Full article

(This article belongs to the Special Issue Sustainable Water Treatment Systems: Green Infrastructure and Bioremediation, 2nd Edition)

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16 pages, 2952 KB

Open AccessReview

Sediment–Phosphorus Dynamics in the Yellow River Estuary

by Yuan Gao, Kun Liu, Shengpin Li and Wenpeng Li

Water 2025, 17(19), 2794; https://doi.org/10.3390/w17192794 - 23 Sep 2025

The Yellow River, with its extremely high sediment loads, and the Yellow River Estuary (YRE) serve as a vital conduit for material exchange between land and marine environments, where sediment–phosphorus interactions profoundly influence nutrient cycling, ecological health and eutrophication potential. This paper reviews [...] Read more.

The Yellow River, with its extremely high sediment loads, and the Yellow River Estuary (YRE) serve as a vital conduit for material exchange between land and marine environments, where sediment–phosphorus interactions profoundly influence nutrient cycling, ecological health and eutrophication potential. This paper reviews the distribution of phosphorus in overlying water and sediment, the characteristics of phosphorus migration and transformation across the sediment–water interface, and the effecting factors of phosphorus migrate, such as sediment properties and environmental factors in the YRE. Inorganic phosphorus was the dominant form in the overlying water and sediment. Suspended sediment acts as a dynamic reservoir for phosphorus transportation in the YRE. The dynamic estuarine environment promotes sediment deposition, which helps reduce phosphorus levels in the water. Upon entering the Bohai Sea, sediment is transformed into the source of phosphorus. The released phosphorus may increase the nutrient load in shallow Bohai Sea waters. Fine particles demonstrate strong adsorption capacity for reactive phosphorus, acting as the primary carriers for phosphorus migration at the sediment–water interface. The grain size of the suspended sediment in the Yellow River exhibited significant sorting characteristics with varying sediment content, consequently affecting the forms of phosphorus. Likewise, the influence of biogeochemical conditions on the transport and transformation of sediment and phosphorus was further analyzed and the partial least squares-path model of related variables on estuarine phosphorus is constructed to interpret the behavior of sediment and phosphorus in the YRE. Finally, the current situation and indeterminacy of water quality models in the estuary were appraised. The priority of analyzing and revealing the environmental behaviors of phosphorus in a sediment-laden river estuary in the future was further proposed against the present deficiencies. This review holds significant practical importance for enhancing the assessment of ecological environment quality and ecological restoration in the YRE. Full article

(This article belongs to the Section Water Quality and Contamination)

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17 pages, 1980 KB

Open AccessArticle

Occurrence Characteristics and Ecological Risk Assessment of Microplastics in Aquatic Environments of Cascade Reservoirs Along the Middle-Lower Han River

by Ruining Zhang, Ziwei Guo, Li Lin, Xiong Pan, Yu Gao and Yuqiang Liu

Water 2025, 17(19), 2793; https://doi.org/10.3390/w17192793 - 23 Sep 2025

The presence and accumulation of microplastics (MPs) in riverine waters have been widely documented. The sustained operation of cascade reservoirs has altered the retention characteristics of MPs in the Han River basin. In this study, the composition, sources, and ecological risks of MPs [...] Read more.

The presence and accumulation of microplastics (MPs) in riverine waters have been widely documented. The sustained operation of cascade reservoirs has altered the retention characteristics of MPs in the Han River basin. In this study, the composition, sources, and ecological risks of MPs in the water column and sediments of the Han River mainstream across different periods were investigated. Results showed that the MP abundances in the water column and sediments were higher during the flood season than in the non-flood season. Additionally, MPs in the water column exhibited an increasing trend along the operational sequence of cascade reservoirs. During the flood season, polyamide (PA), polyethylene (PE), and polypropylene (PP) were the dominant MP types in the water column, while polycarbonate (PC) and PP prevailed in sediments. In the non-flood season, polyethylene terephthalate (PET) was the dominant MP type in the water column, whereas PC and PET dominated in sediments. Overall, the distribution characteristics of MPs conformed to the “upstream input-reservoir accumulation-downstream output” pattern. The pollution risk of MPs in both the water column and sediments ranged from low to moderate. These findings provide a basis for exploring the impacts of cascade reservoir operation on the characteristics of MP in water and sediments. Future research will focus on migration mechanisms of MP under the joint operation of cascade reservoirs. Full article

(This article belongs to the Section Water Quality and Contamination)

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21 pages, 2466 KB

Open AccessReview

Experimental Modeling of Three-Dimensional (3D) Partial Dam-Break Flows: A Review

by Chuke Meng, Weiyang Zhao, Zhipan Niu and Pengzhi Lin

Water 2025, 17(18), 2792; https://doi.org/10.3390/w17182792 - 22 Sep 2025

The growing threat of dam-break events, fueled by aging infrastructure and climate change, necessitates comprehensive risk management and mitigation strategies. Experimental studies on partial dam-break flows are pivotal for understanding the complex dynamics of these events, particularly in assessing flood risk and refining [...] Read more.

The growing threat of dam-break events, fueled by aging infrastructure and climate change, necessitates comprehensive risk management and mitigation strategies. Experimental studies on partial dam-break flows are pivotal for understanding the complex dynamics of these events, particularly in assessing flood risk and refining predictive models. This review synthesizes current experimental investigations on three-dimensional (3D) partial dam-break flows, with an emphasis on breach dynamics, wave impacts, and the role of urban structures. It highlights the challenges in capturing high-resolution 3D flow characteristics and the advancements in measurement techniques such as particle tracking velocimetry and ultrasonic distance meters. The paper discusses the integration of experimental data with numerical models to validate and improve predictive capabilities, stressing the need for continuous refinement of experimental setups and computational approaches. Gaps in the current literature, including the under-representation of irregular breach geometries and complex terrain, are identified, and future research directions are proposed to address these shortcomings. This work underscores the importance of hybrid measurement techniques and interdisciplinary collaboration to enhance dam-break modeling accuracy and flood risk mitigation. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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24 pages, 6778 KB

Open AccessArticle

Detection of Antibiotic-Resistant Escherichia coli in the Upper Citarum River Using a β-D-Glucuronidase Method

by Siska Widya Dewi Kusumah, Mochinaga Katsuya, Rifky Rizkullah Fahmi, Peni Astrini Notodarmojo, Ahmad Soleh Setiyawan, Hisashi Satoh and Herto Dwi Ariesyady

Water 2025, 17(18), 2791; https://doi.org/10.3390/w17182791 (registering DOI) - 22 Sep 2025

Background: Polluted rivers may become reservoirs of antibiotic-resistant Escherichia coli (AREc), raising concerns about environmental health. While monitoring is crucial for recognizing their incidence and evaluating mitigation solutions, current approaches are limited due to high costs, labor-intensive methods, and a lack of standardized [...] Read more.

Background: Polluted rivers may become reservoirs of antibiotic-resistant Escherichia coli (AREc), raising concerns about environmental health. While monitoring is crucial for recognizing their incidence and evaluating mitigation solutions, current approaches are limited due to high costs, labor-intensive methods, and a lack of standardized indicators. This study aims to identify the priority AREc as the monitoring target and evaluate the applicability of the β-glucuronidase enzyme detection method (MPR Method) as an alternative rapid method for profiling AREc in the Upper Citarum River. Methods: River water sampling was conducted along the river during two periods with varying rainfall levels. Total Escherichia coli (TEc) and twelve types of antibiotic-resistant Escherichia coli (AREc) were measured simultaneously by the Agar Method and the β-D-Glucuronidase detection (MPR Method). Results: Statistical data analyses indicate that Total Escherichia coli (TEc) concentrations in the Upper Citarum River increase during periods of higher rainfall (𝓍 = 2558 ± 360 CFU/mL). Erythromycin-resistant Escherichia coli dominates in both periods (Period I 𝓍 = 57.6 ± 25.9%, Period II 𝓍 = 49.96 ± 29.5%). However, tetracycline-resistant Escherichia coli and Extended-Spectrum β-lactamase-producing Escherichia coli (ESBL-Ec) are the most suitable indicators for AREc concentration due to their consistency and correlation with other AREc types. The MPR method achieved an accuracy of up to 87.2%, a sensitivity of 67.4%, and a specificity of 94%. Conclusion: The MPR Method was considered a better alternative for the AREc screening method, particularly in a high bacterial load aquatic environment. Full article

(This article belongs to the Section Water Quality and Contamination)

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20 pages, 8159 KB

Open AccessArticle

Photoelectrocatalysis as an Effective Treatment for Removing Perfluoroalkyl Substances from Contaminated Groundwaters: The Real Case of the Veneto Region (Italy)

by Alessandro Pietro Tucci, Sapia Murgolo, Cristina De Ceglie, Giuseppe Mascolo, Massimo Carmagnani, Andrea Lucchini Huspek, Massimiliano Bestetti and Silvia Franz

Water 2025, 17(18), 2790; https://doi.org/10.3390/w17182790 - 22 Sep 2025

Per-polyfluoroalkyl substances (PFASs) are a class of persistent organic pollutants that have been detected in several environmental matrices. Photoelectrocatalysis (PEC) was employed to remove PFASs contained in natural groundwater collected in the Veneto region (Italy), where a massive PFAS contamination was present. Nine [...] Read more.

Per-polyfluoroalkyl substances (PFASs) are a class of persistent organic pollutants that have been detected in several environmental matrices. Photoelectrocatalysis (PEC) was employed to remove PFASs contained in natural groundwater collected in the Veneto region (Italy), where a massive PFAS contamination was present. Nine PFASs were detected and monitored throughout the process. By varying the magnitude of the applied cell voltage (no bias and 4, 6, and 8 V) the optimal condition was assessed to be 4 V, resulting in a total PFAS removal of about 87%. The presence of H₂O₂ was ineffective on the reaction kinetic, while NaCl inhibited the oxidation of PFASs. The E_EO (Electrical Energy per Order of Magnitude) analysis revealed that PEC is more energy-efficient than both traditional photolysis and most advanced oxidation techniques discussed in published research. Full article

(This article belongs to the Special Issue The PFAS (Perfluoroalkyl and Polyfluoroalkyl Substances) Challenges: Environmental Impact and Alternative Treatments)

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21 pages, 3697 KB

Open AccessArticle

Heavy Metal Removal from Produced Water Using Waste Materials: A Comparative Study

by Neetu Bansal, Md Maruf Mortula and Sameer Al-Asheh

Water 2025, 17(18), 2789; https://doi.org/10.3390/w17182789 - 22 Sep 2025

Produced water, a typical byproduct of oil and gas extraction, is considered a significant environmental and health problem due to its heavy metals content. The objective of this study is to evaluate and compare the efficiency of seven low-cost, waste-derived adsorbents in removing [...] Read more.

Produced water, a typical byproduct of oil and gas extraction, is considered a significant environmental and health problem due to its heavy metals content. The objective of this study is to evaluate and compare the efficiency of seven low-cost, waste-derived adsorbents in removing Cr³⁺, Cu²⁺, Fe²⁺, Zn²⁺, and Pb²⁺ from simulated produced water. The sorbents include gypsum, neem leaves, mandarin peels, pistachio shells, date seed powder, date seed ash, and activated carbon from date seeds. Adsorption experiments were performed using 2.5 and 5 g/L of the adsorbent. SEM and EDX analyses were used to confirm morphological changes and metal deposition after adsorption. Results showed that date seed ash exhibited the highest efficiency (85–100% across all metals), followed by activated carbon (25–98%), with strong Fe and Cu removal but a lower Pb uptake. Neem leaves, mandarin peels, and date seed powder showed moderate efficiencies (30–97%), while gypsum and pistachio shells were the least effective (0–81%). Lignocellulosic peels also showed good results due to the abundance of –OH and –COOH functional groups. Gypsum performed poorly across most metals. Integrating these waste-based adsorbents into secondary or tertiary treatment stages is an economical and sustainable solution for oil wastewater treatment. The results revealed the potential for valorizing agro-industrial and construction waste for circular economic applications in heavy metal pollution control. Full article

(This article belongs to the Special Issue Adsorption Technologies in Wastewater Treatment Processes—2nd Edition)

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14 pages, 1733 KB

Open AccessArticle

Occurrence and Seasonal Variation of Picoplankton at Saiysad Freshwater in Taif City, Saudi Arabia

by Najwa Al-Otaibi

Water 2025, 17(18), 2788; https://doi.org/10.3390/w17182788 - 22 Sep 2025

A wadi ecosystem, a wetland characterized by seasonal water flow, is a unique freshwater environment typically found in semi-arid and arid regions. This study investigates the seasonal and spatial dynamics of environmental properties and microbial plankton communities at Wadi Saiysad in Taif City, [...] Read more.

A wadi ecosystem, a wetland characterized by seasonal water flow, is a unique freshwater environment typically found in semi-arid and arid regions. This study investigates the seasonal and spatial dynamics of environmental properties and microbial plankton communities at Wadi Saiysad in Taif City, Saudi Arabia. Using flow cytometry, three distinct picoplankton populations were observed: Synechococcus and heterotrophic prokaryotes classified as low (LNA) or high (HNA) nucleic acid content. Surface freshwater samples were collected from three distinct sites, representing habitats with actively flowing water, biodiverse communities, and human-influenced areas. Interestingly, no significant differences among stations were observed, suggesting that the sampled stretch of Wadi Saiysad receives similar nutrient inputs. Seasonal water temperature reached 24.5 ± 0.57 °C in summer and the pH ranged from neutral to slightly alkaline. Nutrient analyses revealed that Wadi Saiysad is eutrophic and limited by phosphorus. Phytoplankton biomass was dominated by nanoplankton, particularly in summer (46.60 ± 5.33%), while Synechococcus increased significantly with a maximum abundance of 1.32 × 10⁴ cells mL⁻¹ during the cooler months. HNA prokaryotes displayed marked seasonal variation (1.95 × 10⁴–1.78 × 10⁵ cells mL⁻¹) compared to LNA prokaryotes (2.05–8.17 × 10⁴ cells mL⁻¹). This study highlights the urgent need for monitoring and managing the nutrient inputs in Wadi Saiysad to protect its biodiversity and support sustainable use. Full article

(This article belongs to the Special Issue Freshwater Ecosystems—Biodiversity and Protection: 2nd Edition)

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21 pages, 10257 KB

Open AccessArticle

Assessing Recent Changes in the Contribution of Rainfall and Air Temperature Effects to Mean Flow and Runoff in Two Slovenian–Croatian Basins Using MLR and MLLR

by Ognjen Bonacci, Ana Žaknić-Ćatović and Tanja Roje-Bonacci

Water 2025, 17(18), 2787; https://doi.org/10.3390/w17182787 - 22 Sep 2025

This study investigates the recent changes in the relationship between annual precipitation, mean annual air temperature, mean annual river discharge, and annual runoff coefficients in two small, neighboring continental catchments in Slovenia and Croatia: the Sutla/Sotla and Krapina River basins. Analyses of discharge, [...] Read more.

This study investigates the recent changes in the relationship between annual precipitation, mean annual air temperature, mean annual river discharge, and annual runoff coefficients in two small, neighboring continental catchments in Slovenia and Croatia: the Sutla/Sotla and Krapina River basins. Analyses of discharge, precipitation, and temperature time series were conducted on an annual scale using simple linear regression, multiple linear regression (MLR), and multiple log-linear regression (MLLR). Despite their geographical proximity and similar climatic conditions, the two basins exhibit markedly different runoff coefficients. Lower values observed in the Krapina River at Kupljenovo likely reflect gentle slopes, permeable soils, dense vegetation, and significant infiltration losses, while higher runoff coefficients at the Sutla River near Rakovec suggest more rapid surface runoff, reduced infiltration, and potentially distinct land use. In both basins, a pronounced rise in mean annual air temperatures has been evident since 1992, followed approximately eight years later by a sharp decline in mean annual flows and annual runoff coefficients. Our results show that the influence of air temperature on both discharge and runoff coefficients has become significantly stronger in recent decades, especially since the year 2000, contributing to a notable decline in mean annual discharges as well as annual runoff coefficients. Mean annual discharges have decreased by 19% in the Sutla and 15% in the Krapina basin, coinciding with temperature increases. Regression analyses confirm that air temperature has become a dominant negative predictor of discharge and runoff, with its influence intensifying over the past two decades. The runoff coefficient declined from 0.483 to 0.394 in the Sutla basin and from 0.325 to 0.270 in the Krapina basin during the same period. These findings highlight the importance of catchment-specific assessments for understanding and managing the localized impacts of climate change on hydrological processes. However, future work should incorporate evaporation as a key variable to better attribute the observed runoff reductions. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Land Use on Water Resources—an Issue of Environmental Global Safety)

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23 pages, 3169 KB

Open AccessArticle

Optimal Water Quality Sensor Placement in Water Distribution Systems: A Computationally Cost-Effective Genetic Algorithm Framework

by Elia Zanelli, Matteo Nicolini and Daniele Goi

Water 2025, 17(18), 2786; https://doi.org/10.3390/w17182786 - 21 Sep 2025

Despite advances in water treatment technologies and monitoring systems, contamination events in drinking water supply systems (DWSSs) still pose a threat to public health. Since timing is crucial in effectively mitigating impacts, the implementation of an early warning system (EWS) represents an optimal [...] Read more.

Despite advances in water treatment technologies and monitoring systems, contamination events in drinking water supply systems (DWSSs) still pose a threat to public health. Since timing is crucial in effectively mitigating impacts, the implementation of an early warning system (EWS) represents an optimal solution for securing the entire network. In this paper, we present a novel multi-objective approach based on the NSGA-II Genetic Algorithm (GA) for solving the sensor placement optimization (SPO) problem, aiming at defining the optimal water quality sensor system (WQSS) design. We start from the original formulation of the objective functions most commonly used in the literature, which aim, on the one hand, to reduce the impact and, on the other, to maximize the network coverage; such objective functions are rewritten in order to enable a comprehensive perspective of all potential contamination scenarios, including those that remain undetected by the WQSS. Furthermore, we address the issue of computational complexity, increasing with the size of the water distribution system (WDS), and we show that the proposed methodology is computationally cost-effective. Finally, we apply the methodology to two well-known benchmarking water distribution networks (WDNs), showcasing the capabilities and potential advantages it offers. Full article

(This article belongs to the Special Issue Monitoring and Assessment of Water Quality in Drinking Water Distribution Systems)

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25 pages, 10729 KB

Open AccessArticle

Water Demand and Water Application for Plants Based on Plant Coefficient Method: Model Development and Verification on Sites of Green Saudi Arabia

by A A Alazba, M.N. Elnesr, Ahmed Elkatoury, Nasser Alrdyan, Farid Radwan and Mahmoud Ezzeldin

Water 2025, 17(18), 2785; https://doi.org/10.3390/w17182785 - 21 Sep 2025

A GIS-based Plant Coefficient Method (PCM), termed the Plant Coefficient Method Tool (PCMT), is presented and validated through this research. It is designed for sustainable irrigation management within arid urban environments, exemplified by Riyadh, Saudi Arabia. The study integrates remote sensing data, including [...] Read more.

A GIS-based Plant Coefficient Method (PCM), termed the Plant Coefficient Method Tool (PCMT), is presented and validated through this research. It is designed for sustainable irrigation management within arid urban environments, exemplified by Riyadh, Saudi Arabia. The study integrates remote sensing data, including Landsat 8 satellite imagery, vegetation indices (NDVI, LAI), and climatic parameters to estimate daily and seasonal plant water demand for diverse landscape species. Results demonstrate that plant-specific coefficients (

K_{p l}

) fluctuate seasonally, ranging from 0.1 to 1.4, with average water demand (

{E T}_{p l}

) reaching up to 25 L per square meter during the summer months and decreasing to around 6 L in winter. It may be found by good management based on PCMT that average daily projected

{E T}_{p l}

rates can be lowered to as low as 3 mm/day, resulting in a significant decrease in water needs, by around 70% to 50%, when compared to higher categories. Validation across three sites (urban trees, date palms, and turf grass), showed strong correlations (R² > 0.8) between satellite-derived vegetation indices and modeled water needs. The volumetric water demand estimates closely aligned with actual irrigation practices, albeit with some over- and under-irrigation episodes. Spatial analysis indicated that high-demand zones predominantly occur in summer, emphasizing the necessity of adaptive irrigation scheduling. Overall, the PCMT presents a scalable, accurate tool for optimizing water use, supporting sustainable landscape management aligned with Saudi Arabia’s green initiatives. Full article

(This article belongs to the Section New Sensors, New Technologies and Machine Learning in Water Sciences)

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18 pages, 8295 KB

Open AccessArticle

Evolution Mechanism of Flow Patterns and Pressure Fluctuations During Runaway Processes of Three Pump–Turbines with Different Blade Lean Angles

by Zhiyan Yang, Jie Fang, Baoyong Zhang, Chengjun Li, Tang Qian and Chunze Zhang

Water 2025, 17(18), 2784; https://doi.org/10.3390/w17182784 - 21 Sep 2025

Pumped storage power stations are effective stabilizers and regulators of the power grids. However, during the transient process, especially the operating point entering the S-shaped region, the internal flow patterns and pressure pulsations in the pump–turbine unit change violently, seriously affecting the safety [...] Read more.

Pumped storage power stations are effective stabilizers and regulators of the power grids. However, during the transient process, especially the operating point entering the S-shaped region, the internal flow patterns and pressure pulsations in the pump–turbine unit change violently, seriously affecting the safety of the power stations, which requires enough optimizations in the design stage of the pump–turbine. In this paper, to explore the key factors which influence the evolutions of flow patterns and pressure pulsations during the runaway process, three pump–turbine runners with different inlet blade lean, including positive angle, no angle and negative angle, were selected to simulate by using the three-dimensional method. The results show that the changes in the inlet blade lean angles have significant effects on the variation periods and maximum values of the macro parameters during the runaway process, and especially the runner with no lean angle results in the smallest oscillation periods and pressure pulsations but enlarges the runner radial forces. In addition, backflows generate from the hub side under the cases with positive or no blade lean angle, while those occur from the shroud side due to the negative angle. The results provide a basic reference for the design of the pump–turbine. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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17 pages, 4314 KB

Open AccessArticle

Oceanography and Culture Shape Morphometric Divergence in Portunus pelagicus: Defining Actionable Management Units for Climate-Resilient Recreational Fisheries in Asia

by Po-Cheng Chen, Chun-Han Shih, Tzong-Der Tzeng, Chi-Hui Huang and Gui-Mei Zhang

Water 2025, 17(18), 2783; https://doi.org/10.3390/w17182783 - 21 Sep 2025

Sustainable management of Portunus pelagicus is hindered by uncertain stock boundaries across rapidly changing marginal seas and culturally diverse markets. We measured 12 size-adjusted morphometrics in 525 adults from five sites (Kyushu, Xiamen, Tainan, Hong Kong, and Singapore). Canonical variate analysis resolved three [...] Read more.

Sustainable management of Portunus pelagicus is hindered by uncertain stock boundaries across rapidly changing marginal seas and culturally diverse markets. We measured 12 size-adjusted morphometrics in 525 adults from five sites (Kyushu, Xiamen, Tainan, Hong Kong, and Singapore). Canonical variate analysis resolved three robust groups that mirror oceanographic regimes: a Kuroshio–China group (Kyushu, Xiamen, and Hong Kong), a Taiwan Strait subgroup (Tainan), and a Southeast Asia group (Singapore). Permutation tests (1000 runs) showed near-zero probabilities of observing the low misclassification rates by chance (p < 0.001). A reproductive trait (female AB3W) displayed group-specific allometric slopes, consistent with local functional demands. We integrate these results with a cultural ecology lens—linking ornamental carapace valuation to selective harvest—to propose morphological management units (MMUs) and region-specific rules that can be implemented immediately and refined with genomics. This work reframes a descriptive morphometric study into a socio-ecological mechanism for climate-ready, actionable fisheries governance. Full article

(This article belongs to the Special Issue Marine Biodiversity and Its Relationship with Climate/Environment)

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