Water

30 pages, 3134 KB

Open AccessArticle

Metformin Mineralization via an Fe-PILC-Catalyzed Photo-Fenton Reaction Driven by UV and Visible Light

by Deysi Amado-Piña, Rubi Romero, Armando Ramírez-Serrano, Sandra Luz Martínez-Vargas, Teresa Torres-Blancas and Reyna Natividad

Water 2025, 17(20), 3028; https://doi.org/10.3390/w17203028 - 21 Oct 2025

Viewed by 396

Abstract

The presence of various drugs in wastewater has generated growing concern about the contamination of water bodies. This requires urgent attention and the development of effective methods for their degradation in aquatic ecosystems. The present study evaluates the efficiency of metformin (MET) degradation [...] Read more.

The presence of various drugs in wastewater has generated growing concern about the contamination of water bodies. This requires urgent attention and the development of effective methods for their degradation in aquatic ecosystems. The present study evaluates the efficiency of metformin (MET) degradation via various photochemical processes—photolysis, H₂O₂ photodecomposition, photocatalysis, and photo-Fenton—using iron-pillared bentonite clays (Fe-PILC) as a catalyst. The influence of radiation wavelength (254 nm and visible light) was investigated, while MET degradation, H₂O₂ consumption, and total organic carbon (TOC) removal were monitored as key response variables. Structural characterization confirmed successful pillaring, increasing the surface area of bentonite from 35 to 246 m²/g, with iron content at 11 wt. % quantified by atomic absorption spectroscopy. Fe₃O₄ and FeO were identified using XPS, and a 2.08 eV band-gap energy was revealed via diffuse reflectance spectroscopy. Experiments were conducted at environmentally relevant MET concentrations (13,000 ng L⁻¹) in a 0.1 L batch photoreactor at 25 °C. The results demonstrate that (i) photo-Fenton was the most efficient process to remove and mineralize MET (100% degradation after 10 min and 83% mineralization after 90 min); (ii) Fe-PILC is effectively activated at λ < 700 nm, enabling 75% mineralization under visible light; (iii) hydroxyl radicals and valence band holes were the primary oxidative species driving MET oxidation; and (iv) cyanoguanidine and carboxylic acids were identified as main oxidation by-products via UHPLC. Pseudo-first-order kinetic constants were determined for all processes, offering insight into their relative efficiencies. Notably, the rate constant for photo-Fenton under visible light (0.406 min⁻¹) was comparable to that under UV -light (0.545 min⁻¹), highlighting the potential of visible light-driven treatments. Therefore, this study demonstrated the metformin degradation capability of iron-pillared clays under both visible and UV light. Full article

(This article belongs to the Special Issue Advanced Design and Synthesis of Novel Photocatalyst Materials for Wastewater Remediation)

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18 pages, 2693 KB

Open AccessArticle

A Geoinformation-Based Approach for Mapping Coastal Vulnerability in Sweden

by Eleni Achmakidou, George P. Petropoulos, Anna Karkani, Niki Evelpidou, Spyridon E. Detsikas and Georgios Nektarios Tselos

Water 2025, 17(20), 3027; https://doi.org/10.3390/w17203027 - 21 Oct 2025

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Abstract

Coastal areas in Arctic and sub-Arctic regions are getting increasingly vulnerable to climate change, particularly due to sea-level rise and changing wave dynamics. This study assesses the coastal vulnerability of Sweden using the Coastal Vulnerability Index (CVI), based on a GIS-based, semi-quantitative approach [...] Read more.

Coastal areas in Arctic and sub-Arctic regions are getting increasingly vulnerable to climate change, particularly due to sea-level rise and changing wave dynamics. This study assesses the coastal vulnerability of Sweden using the Coastal Vulnerability Index (CVI), based on a GIS-based, semi-quantitative approach integrating Earth Observation (EO) and geoinformatics. Six physical parameters were used: coastal geomorphology, coastal slope, shoreline change rate, relative sea-level change, mean tidal range, and significant wave height. CVI scores were derived from openly available national and international datasets, including satellite imagery and historical records. Mean tidal range and relative sea-level change were the most influential variables. The results indicate significant spatial variability: 36.5% of the coastline is classified as having “High” or “Very High” vulnerability, mainly in the south, while over 41% is “Low” or “Very Low,” especially in the Gulf of Bothnia. This assessment offers a harmonized spatial baseline to support sustainable coastal planning and adaptation efforts in Sweden and provides a comparative framework for coastal vulnerability studies across northern Europe. Full article

(This article belongs to the Special Issue Long-Term Coastal Evolution and Morphodynamics: Ecosystem Protection and Coastal Safety)

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11 pages, 1273 KB

Open AccessArticle

A Case Study on Factors Influencing Escherichia coli Concentrations in an Urban River Draining a Fully Sewered Area

by Taro Urase and Saki Goto

Water 2025, 17(20), 3026; https://doi.org/10.3390/w17203026 - 21 Oct 2025

Viewed by 308

Abstract

Escherichia coli is an important indicator microorganism of fecal contamination in water. However, routine government monitoring often fails to capture the actual state of pollution, because E. coli concentrations in urban rivers are highly variable. This study presents a case study on factors [...] Read more.

Escherichia coli is an important indicator microorganism of fecal contamination in water. However, routine government monitoring often fails to capture the actual state of pollution, because E. coli concentrations in urban rivers are highly variable. This study presents a case study on factors influencing E. coli concentrations in an urban river draining a fully sewered area. An approximately 70-fold higher concentration compared with the average dry-weather concentration (1.9 CFU/mL) was observed under wet-weather conditions, probably due to the effects of combined sewer overflows. A very short survival of E. coli (less than one day) was expected in the unfiltered overlying water, due to the contributions of bacteriophages, protozoan predation, and bacterial competition, whereas a longer survival was expected in the sediment. Such a short survival may be a characteristic of the target watershed, where treated wastewater accounted for approximately 75% of the total flow. The highly variable antimicrobial resistance among E. coli populations under dry-weather conditions was possibly caused by the regrowth of a limited number of E. coli individuals in the sediment. Rising temperatures due to global warming are expected to decrease the concentration of E. coli in the target watershed, where E. coli populations are strongly suppressed by predation and competition. Full article

(This article belongs to the Section Water and One Health)

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34 pages, 4359 KB

Open AccessArticle

Groundwater Suitability for Irrigation in the Hennaya Region, Northwest Algeria: A Hydrochemical and GIS-Based Multi-Criteria Assessment

by Abderrahim Badraoui, Chérifa Abdelbaki, Madani Bessedik, Sidi Mohamed Tiar, Yacine Abdelbaset Berrezel, Mahdi Ziane, Amaria Slimani, Ahmed Souafi, Nourredine Boudadi, Bernhard Tischbein and Navneet Kumar

Water 2025, 17(20), 3025; https://doi.org/10.3390/w17203025 - 21 Oct 2025

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Abstract

This study investigated groundwater suitability for irrigation in the Hennaya Irrigated region of Northwest Algeria. The research pursued two primary objectives: first, to establish the hydrochemical origin of the groundwater through comprehensive analyses including hydrochemical parameters, diagrams, and hierarchical clustering; and second, to [...] Read more.

This study investigated groundwater suitability for irrigation in the Hennaya Irrigated region of Northwest Algeria. The research pursued two primary objectives: first, to establish the hydrochemical origin of the groundwater through comprehensive analyses including hydrochemical parameters, diagrams, and hierarchical clustering; and second, to assess its suitability for irrigation based on key criteria such as the Water Quality Index (WQI), Wilcox, and US Salinity diagrams. The analysis revealed a high level of groundwater suitability for irrigation, as indicated by various indices: Sodium Adsorption Ratio (SAR) values ranged from 1.69 to 2.55 (Excellent), Sodium Percentage (Na%) ranged from 24.22% to 36.98% (Good), and the Residual Sodium Carbonate (RSC) was negative, falling between −8.91 to −1.70 meq/L (Safe). Kelly’s Ratio (KR) ranged from 0.32 to 0.59 (Good), and the Permeability Index (PI) was between 62% and 99% (Moderate). Supported by the Analytic Hierarchy Process (AHP) and spatial analysis, the Water Quality Index (WQI) values ranged from 69.25 to 88.71, categorizing the groundwater in the study area as ‘Good’ quality. While suitable for irrigation, the groundwater showed slight salinity (EC 1247–2010 μS/cm) and alkalinity (pH 7.09–8.02), with elevated total dissolved solids (TDSs) ranging from 990 to 1930 mg/L, approaching the permissible limits for optimal agricultural use. The dominant ion concentrations (Ca²⁺ > Na⁺ > Mg²⁺ > K⁺; HCO₃⁻ > Cl⁻ > SO₄²⁻ > NO₃⁻) indicate a mixed hydrochemical facies influenced by both water–rock interactions and evaporative processes. Although these findings are promising, they highlight the necessity for preventive measures. Ongoing proactive management and continuous monitoring are essential to ensure the long-term sustainability and protection of groundwater resources in the region. Full article

(This article belongs to the Special Issue Energy Recovery and Clean Water: Techno-Economic and Environmental Assessment)

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37 pages, 55843 KB

Open AccessArticle

A Data-Driven Framework for Flood Mitigation: Transformer-Based Damage Prediction and Reinforcement Learning for Reservoir Operations

by Soheyla Tofighi, Faruk Gurbuz, Ricardo Mantilla and Shaoping Xiao

Water 2025, 17(20), 3024; https://doi.org/10.3390/w17203024 - 21 Oct 2025

Viewed by 450

Abstract

Floods are among the most destructive natural hazards, with damages expected to intensify under climate change and socio-economic pressures. Effective reservoir operation remains a critical yet challenging strategy for mitigating downstream impacts, as operators must navigate nonlinear system dynamics, uncertain inflow forecasts, and [...] Read more.

Floods are among the most destructive natural hazards, with damages expected to intensify under climate change and socio-economic pressures. Effective reservoir operation remains a critical yet challenging strategy for mitigating downstream impacts, as operators must navigate nonlinear system dynamics, uncertain inflow forecasts, and trade-offs between competing objectives. This study proposes a novel end-to-end data-driven framework that integrates process-based hydraulic simulations, a Transformer-based surrogate model for flood damage prediction, and reinforcement learning (RL) for reservoir gate operation optimization. The framework is demonstrated using the Coralville Reservoir (Iowa, USA) and two major historical flood events (2008 and 2013). Hydraulic and impact simulations with HEC-RAS and HEC-FIA were used to generate training data, enabling the development of a Transformer model that accurately predicts time-varying flood damages. This surrogate is coupled with a Transformer-enhanced Deep Q-Network (DQN) to derive adaptive gate operation strategies. Results show that the RL-derived optimal policy reduces both peak and time-integrated damages compared to expert and zero-opening benchmarks, while maintaining smooth and feasible operations. Comparative analysis with a genetic algorithm (GA) highlights the robustness of the RL framework, particularly its ability to generalize across uncertain inflows and varying initial storage conditions. Importantly, the adaptive RL policy trained on perturbed synthetic inflows transferred effectively to the hydrologically distinct 2013 event, and fine-tuning achieved near-identical performance to the event-specific optimal policy. These findings highlight the capability of the proposed framework to provide adaptive, transferable, and computationally efficient tools for flood-resilient reservoir operation. Full article

(This article belongs to the Special Issue Advances in Flood Hazard and Risk Analysis: Theory, Methods, Numerical Models, Strategies, and Applications)

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17 pages, 2733 KB

Open AccessArticle

Uptake and Effects of Yttrium on the Seaweed Ulva sp.: A Study on the Potential Risks of Rare Earth Elements in Aquatic Environments

by Thainara Viana, João Colónia, Daniela S. Tavares, Madalena Andrade, Nicole Ferreira, Rosa Freitas, Eduarda Pereira and Bruno Henriques

Water 2025, 17(20), 3023; https://doi.org/10.3390/w17203023 - 21 Oct 2025

Viewed by 326

Abstract

Technological proliferation relies on critical elements such as rare earth elements (REEs) and raises environmental problems associated with raw material extraction, industrial manufacturing, and the informal management of the growing e-waste. Algae are good bioindicators of contamination and have shown promise as biosorbents [...] Read more.

Technological proliferation relies on critical elements such as rare earth elements (REEs) and raises environmental problems associated with raw material extraction, industrial manufacturing, and the informal management of the growing e-waste. Algae are good bioindicators of contamination and have shown promise as biosorbents for remediating metal-contaminated environments. However, the effects of REEs on algae are still poorly documented and understood. This study investigated the uptake of yttrium (Y)—one of the most frequently used REEs, particularly in fluorescent lamps—by Ulva sp., as well as its effects on total chlorophyll content, relative growth rate, and biochemical performance. The algae were exposed to Y for 72 h at environmentally relevant concentrations, including levels found in e-waste leachates (0.5, 5.0, 50, and 500 mg/L). Ulva sp. removed 86% of Y within 72 h, with a bioconcentration factor of up to 621. EDTA analysis revealed that over 90% of yttrium was retained on the algal surface. SEM-EDS mapping showed crystal structures on the algae where Y was present. While the relative growth rate was unaffected by the tested Y gradient, photosynthesis was significantly impaired at 500 mg/L. Despite the activation of defence mechanisms, cell damage was observed at most Y concentrations tested, highlighting the potential risks associated with the presence of REEs in aquatic environments. Full article

(This article belongs to the Special Issue Water and Society: Challenges for Freshwater Quality Under a Climate Change Scenario)

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17 pages, 3538 KB

Open AccessArticle

Characterization of Non-Constant Flow in the Recession Process of Pressurized Pipelines with Air Valves

by Shuaihui Sun, Jinyang Ma, Bo Zhang, Jingwen Jia and Jiuwang Li

Water 2025, 17(20), 3022; https://doi.org/10.3390/w17203022 - 21 Oct 2025

Viewed by 274

Abstract

Emptying pressure pipelines is a routine operation during pipeline maintenance. This study investigates the emptying characteristics of pressurized pipelines with air valves under unsteady flow conditions. A mathematical model for the emptying process is developed using the rigid water column theory, exploring the [...] Read more.

Emptying pressure pipelines is a routine operation during pipeline maintenance. This study investigates the emptying characteristics of pressurized pipelines with air valves under unsteady flow conditions. A mathematical model for the emptying process is developed using the rigid water column theory, exploring the influence of drain valve opening, initial air pocket length, and valve opening patterns on the transient flow behavior. The results indicate that, compared with the linear valve opening pattern, a nonlinear power function opening increases the minimum air pocket pressure head by 0.1014 m and delays its occurrence by 0.655 s. The maximum emptying velocity rises by 0.48 m/s when the opening is increased from 10% to 30%, thereby shortening the emptying time by 65.4%. However, the pressure head inside the air pocket decreases accordingly. When the air valve diameter is enlarged from 0.003 mm to 0.008 mm, the pressure recovery time is markedly reduced and the initial pressure fluctuations are attenuated. Numerical simulations based on the Heihe emptying case demonstrate that a well-planned layout of multiple air valves effectively shortens the duration of negative pressure heads. Replacing the first air valve with a 50 cm diameter circular orifice significantly raises the minimum pressure head of the pipeline and dramatically enhances the stability of emptying pressurized pipeline. Full article

(This article belongs to the Special Issue Hydrodynamics in Pressurized Pipe Systems)

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14 pages, 2968 KB

Open AccessArticle

Mineral-Rich Brines from Portuguese Coastal Lagoons: Insights into Their Use in Thalassotherapy and Skin Care

by Lara Almeida, Fernando Rocha and Carla Candeias

Water 2025, 17(20), 3021; https://doi.org/10.3390/w17203021 - 21 Oct 2025

Viewed by 334

Abstract

This study characterized saline waters from traditional and semi-industrial saltpans located in the Ria Formosa and Ria de Aveiro Portuguese coastal lagoons, aiming to evaluate their potential for thalassotherapy and dermatological applications. Five saline water samples were collected and analyzed for physicochemical parameters [...] Read more.

This study characterized saline waters from traditional and semi-industrial saltpans located in the Ria Formosa and Ria de Aveiro Portuguese coastal lagoons, aiming to evaluate their potential for thalassotherapy and dermatological applications. Five saline water samples were collected and analyzed for physicochemical parameters (pH, electrical conductivity, dissolved oxygen, and total dissolved and suspended solids) and chemical composition (major, minor, and trace elements), complemented by SEM-EDS analyses of the suspended solids. All samples exhibited salinities above 70 g/kg, classifying them as mineral-rich brines. Sodium was the dominant element, followed by Mg, K, and Ca, with concentrations significantly higher than those of seawater. Apparent geochemical differences were observed between the two lagoons, with Ria de Aveiro water enriched in Ca, while Ria Formosa showed higher Mg and K contents. Suspended solids were composed mainly of halite, gypsum, K-Mg salts, and biogenic aggregates, reflecting the interaction between evaporitic and microbial processes. These findings highlighted the high therapeutic potential of Portuguese saline waters for skin-related applications, supporting the safe use of natural saline resources in evidence-based wellness and dermatological practices. Full article

(This article belongs to the Special Issue Groundwater for Health and Well-Being)

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20 pages, 7023 KB

Open AccessArticle

Biosorption of Iron-Contaminated Surface Waters Using Tinospora cordifolia Biomass: Insights from the Gostani Velpuru Canal, India

by Penupothula Raju, Fasil Ejigu Eregno, Rajnish Kaur Calay, P. Ramakrishnam Raju and Thokhir Basha Shaik

Water 2025, 17(20), 3020; https://doi.org/10.3390/w17203020 - 21 Oct 2025

Viewed by 339

Abstract

The contamination of water bodies with heavy metals from various anthropogenic sources has become a prominent global issue. New industrial establishments and rapid urbanization have led to heavy metal intrusion into various surface water bodies, deteriorating water quality and causing numerous health issues [...] Read more.

The contamination of water bodies with heavy metals from various anthropogenic sources has become a prominent global issue. New industrial establishments and rapid urbanization have led to heavy metal intrusion into various surface water bodies, deteriorating water quality and causing numerous health issues for people consuming it. Removal of heavy metals from water is a complicated and costly process; hence, researchers are adopting various techniques to remove them naturally. This paper assesses the performance of a biosorption technique to remove heavy metal iron from Gostani Velpuru Canal, India. The techniques involved using biomass of Tinospora cordifolia in the form of green stem (GSB), dry stem (DSB), and extracted powder (PB). The efficiency of iron removal was measured from water samples collected diurnally from the canal. The study focused on the variations of T. cordifolia biomass combinations in iron absorption using static and agitated methods. The results indicated that PB with agitation had the highest mean iron removal efficiency of 72.43%, followed by DSB (41.77%) and GSB (35.32%) in the collected GVC samples. These findings suggest that T. cordifolia, regardless of its form, can be used for diverse water resource applications. Full article

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

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21 pages, 7248 KB

Open AccessArticle

Novel Microwave-Synthesized Bimetallic Ce-Al-MOFs with Efficient Phosphate Removal from Aquaculture Effluent: Synthesis, Characterization and Applications

by Jian Zeng, Jiangnan Zhao, Zhenzhen Cai, Jianshe Hu, Zesheng Zhuo and Xiongping Miao

Water 2025, 17(20), 3019; https://doi.org/10.3390/w17203019 - 21 Oct 2025

Viewed by 320

Abstract

The eutrophication of natural water is a severe environmental risk faced by coastal marine ecosystems, and the excess nitrogen and phosphorus in aquaculture effluent are one of the main sources of environmental pollution. Effectively reducing as well as controlling the phosphorus content in [...] Read more.

The eutrophication of natural water is a severe environmental risk faced by coastal marine ecosystems, and the excess nitrogen and phosphorus in aquaculture effluent are one of the main sources of environmental pollution. Effectively reducing as well as controlling the phosphorus content in aquaculture effluent is of great importance for alleviating eutrophication and the governance of coastal environments. This study focuses on addressing phosphorus pollution by developing novel bimetallic Ce-Al-MOFs adsorbents via the microwave-assisted rapid synthesis method, among which the monomer Ce₃Al₃-BDC₃ exhibits excellent phosphate adsorption capacity (136.99 mg P g⁻¹) and great removal efficiency over a wide pH range (2~10). Batch experiments reveal that the adsorption is followed by pseudo-second-order kinetics and the Langmuir isotherm model, indicating monolayer chemisorption. The MOFs material shows high selectivity for phosphorus even under the interference of co-existing anions, as well as excellent reusability, retaining over 65% removal efficiency after six adsorption–desorption cycles. Field tests in coastal areas and indoor aquaculture systems both achieve over 97% phosphate removal, meeting discharge standards. A series of characterization methods identify ligand exchange, electrostatic interactions and surface complexation as key adsorption mechanisms. The Ce-Al-MOFs present a promising solution for mitigating eutrophication and managing aquaculture wastewater sustainably. Full article

(This article belongs to the Section Water, Agriculture and Aquaculture)

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18 pages, 873 KB

Open AccessReview

From Flood to Drip Irrigation: A Review of Irrigation Modernization Trade-Offs

by Alessandra Santini, Mauro Masiero, Giulia Amato and Davide Matteo Pettenella

Water 2025, 17(20), 3018; https://doi.org/10.3390/w17203018 - 21 Oct 2025

Viewed by 638

Abstract

Water scarcity, climate change, population growth, and rising water demand highlight the urgency of adopting effective water conservation measures. The transition from traditional irrigation systems, such as flood irrigation, to modern ones, like drip irrigation, is often seen as a panacea to improve [...] Read more.

Water scarcity, climate change, population growth, and rising water demand highlight the urgency of adopting effective water conservation measures. The transition from traditional irrigation systems, such as flood irrigation, to modern ones, like drip irrigation, is often seen as a panacea to improve irrigation efficiency and address water shortages. Despite the flourishing literature on the efficiency gains achieved by shifting to drip irrigation, trade-offs associated with replacing traditional irrigation systems with modern irrigation technologies remain unexplored. Building on this gap, this paper provides a systematic literature review to analyze the current state of knowledge and research on the trade-offs associated with this transition. The review analyses not only the possible effects on agricultural productivity and irrigation efficiency at the farm scale, but also the environmental implications and socio–economic consequences that may emerge at a larger scale. We found that while studies conducted at the field-level emphasize clear benefits associated with the adoption of drip irrigation, including higher crop yields and improved water use efficiency, basin-scale analyses reveal drawbacks, including increased consumptive use, reduced return flows for ecosystem processes, and more generally limited real water savings. Overall, our findings stress the need for more holistic, multi-scale, and interdisciplinary approaches to assess the impact of irrigation modernization, along with the need for policy frameworks that balance agricultural productivity gains with sustainable water management. Full article

(This article belongs to the Section Water, Agriculture and Aquaculture)

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18 pages, 2379 KB

Open AccessArticle

Opoka as a Natural Material for Phosphorus Removal: Properties and Applications

by Evelina Svedaite, Kestutis Baltakys and Tadas Dambrauskas

Water 2025, 17(20), 3017; https://doi.org/10.3390/w17203017 - 20 Oct 2025

Viewed by 381

Abstract

This study investigates the adsorption efficiency of thermally activated natural opoka, a siliceous–calcareous sedimentary rock, as a low-cost adsorbent for removing phosphorus from aqueous solutions. Comprehensive characterization using XRF, XRD, and STA revealed that raw opoka is primarily composed of quartz, tridymite, and [...] Read more.

This study investigates the adsorption efficiency of thermally activated natural opoka, a siliceous–calcareous sedimentary rock, as a low-cost adsorbent for removing phosphorus from aqueous solutions. Comprehensive characterization using XRF, XRD, and STA revealed that raw opoka is primarily composed of quartz, tridymite, and calcite, with a CaO/SiO₂ molar ratio of approximately 0.45. After calcination at 850 °C, calcite decomposes and reacts with silica to form wollastonite, enhancing surface reactivity. Adsorption experiments conducted at phosphorus concentrations of 0.2, 2.6, and 5.0 g of P/L demonstrated that the material’s removal efficiency for phosphorus was highest at low concentrations (25.7% at 0.2 g/L) and decreased with an increase in concentration (20.8% at 2.6 g/L and 18.6% at 5.0 g/L). The adsorption process followed pseudo-second-order kinetics (R² > 0.999), indicating that chemisorption is the dominant mechanism. It is assumed that amorphous calcium phosphate forms at low phosphorus concentrations and an alkaline pH, whereas brushite is more prevalent at higher concentrations under acidic conditions. Potassium adsorption was negligible and reversible in all cases. The findings demonstrate that calcined opoka has promising applications as a reactive calcium silicate material for sustainable phosphorus management in decentralized water treatment systems. Full article

(This article belongs to the Section Wastewater Treatment and Reuse)

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22 pages, 2785 KB

Open AccessArticle

A Slope Dynamic Stability Evaluation Method Based on Variable Weight Theory and Trapezoidal Cloud Model

by Delin Li, Zhaohua Zhou, Sailajia Wei, Zongren Li, Zibin Li, Peng Guan and Yi Luo

Water 2025, 17(20), 3016; https://doi.org/10.3390/w17203016 - 20 Oct 2025

Viewed by 246

Abstract

Slope instability may cause severe casualties, property losses, and ecological damage. To accurately evaluate slope stability grades and mitigate geological hazards, a dynamic stability assessment method based on variable weight theory and trapezoidal cloud model is proposed. First, an evaluation index system for [...] Read more.

Slope instability may cause severe casualties, property losses, and ecological damage. To accurately evaluate slope stability grades and mitigate geological hazards, a dynamic stability assessment method based on variable weight theory and trapezoidal cloud model is proposed. First, an evaluation index system for slope stability is established following the principles of uniqueness, purposefulness, and scientific validity. Then, to improve the accuracy of subjective constant weights, the intuitionistic fuzzy analytic hierarchy process (IFAHP) is employed to calculate subjective constant weights. Considering the contrast intensity and conflict among indicators, an improved CRITIC method is applied to determine objective constant weights. To balance subjective and objective factors and avoid constant weight imbalance, the optimal comprehensive constant weights are computed based on game theory, effectively reducing bias caused by single weighting methods. Furthermore, to fully account for the influence of indicator state values on their weights, variable weight theory is introduced to dynamically adjust the comprehensive constant weights. Finally, based on the variable weights of evaluation indicators, a trapezoidal cloud model is utilized to construct the slope stability evaluation model, which is validated through an engineering case study. The results indicate that the stability grade of Stage 1 is assessed as basically stable, while Stages 2 and 3 are evaluated as stable. Numerical simulations show the safety factors of the three stages are 1.36, 1.83, and 2.36, respectively, verifying the correctness of the proposed model. The proposed model demonstrates practical engineering value in slope stability assessment and can be referenced for slope reinforcement and hazard prevention in later stages. Full article

(This article belongs to the Special Issue Slope Stability Analyses and Landslide Risk Assessment Under Hydrodynamic Action)

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22 pages, 18454 KB

Open AccessArticle

Effective Treatment of Wastewater Containing Ni (II) and Pb (II) Using Modified Kaolin: Experimental and Simulation Study

by Zhengtian Yin, Yuxuan Yang, Guanjie Wang and Renzhi Qi

Water 2025, 17(20), 3015; https://doi.org/10.3390/w17203015 - 20 Oct 2025

Viewed by 276

Abstract

With the expansion of industrial production capacity, a substantial volume of hazardous wastewater containing Pb (II) and Ni (II) requires treatment. Kaolin, a low-cost adsorbent with strong adsorption properties, was modified through thermal activation at 750 °C, 850 °C, and 950 °C to [...] Read more.

With the expansion of industrial production capacity, a substantial volume of hazardous wastewater containing Pb (II) and Ni (II) requires treatment. Kaolin, a low-cost adsorbent with strong adsorption properties, was modified through thermal activation at 750 °C, 850 °C, and 950 °C to enhance its adsorption capacity. Following the optimization of pH, reaction time, temperature, heavy metal concentrations, and adsorbent amount, the 850-K was found to have the best removal efficiency, achieving removal rates > 90% for both PbCl₂ and NiCl₂, and the removal efficiency of PbCl₂ was higher compared to NiCl₂. The pseudo-second-order kinetics and Langmuir model could reasonably match the adsorption processes of PbCl₂/NiCl₂. The experimental findings were corroborated through simulations of adsorption distance, variations in bond length/bond angle, adsorption energy, frontier molecular orbital, charge density, and differential charge density. The differences in reactions between adsorbents and PbCl₂/NiCl₂ were primarily due to the electron transfer direction and bonding mechanisms. The O atoms were the main reactive atoms of the adsorbents, capable of forming covalent bonds with both PbCl₂ and NiCl₂, and the Cl atoms could form either ionic or covalent bonds with the adsorbent. Pb could form covalent bonds with the adsorbent, while Ni might be adsorbed through electrostatic interactions. Full article

(This article belongs to the Special Issue Research on Adsorption Technologies in Water Treatment)

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18 pages, 9017 KB

Open AccessArticle

Research on the Influence of Groundwater Level Dynamic Rising Process on Buildings Based on Numerical Simulation

by Hongzhao Li, Mingxu Gu, Ming Zhang, Baiheng Ma, Xiaolong Zhu, Liangyu Gu, Jiaoyang Tai and Lili Chen

Water 2025, 17(20), 3014; https://doi.org/10.3390/w17203014 - 20 Oct 2025

Viewed by 244

Abstract

In the North China region, measures such as restricting groundwater extraction and promoting cross-basin water diversion have effectively alleviated the problem of excessive groundwater exploitation. Nevertheless, the continuous rise in groundwater levels may alter the mechanical properties of foundation soil layers, potentially leading [...] Read more.

In the North China region, measures such as restricting groundwater extraction and promoting cross-basin water diversion have effectively alleviated the problem of excessive groundwater exploitation. Nevertheless, the continuous rise in groundwater levels may alter the mechanical properties of foundation soil layers, potentially leading to geotechnical hazards such as foundation instability and the uneven settlement of structures. This study employs FLAC3D software to simulate the displacement, deformation, and stress–strain behavior of buildings and their surrounding strata during the dynamic recovery of groundwater levels, aiming to assess the impact of this process on structural integrity. Research findings indicate that the maximum building settlement within the study area reaches 54.8 mm, with a maximum inter-column differential settlement of 8.9 mm and a peak settlement rate of 0.16 mm/day. In regions where differential settlement aligns with the interface between the floor slab and walls, tensile stress concentrations are observed. The maximum tensile stress in these zones increases progressively from 1.8 MPa to 2.19 MPa, suggesting a potential risk of tensile cracking in the concrete structures. The influence of groundwater level recovery on buildings exhibits distinct phase characteristics, and the response mechanisms of different lithological strata vary significantly. Therefore, particular attention should be given to the physical properties and mechanical behavior of strata that are highly sensitive to variations in moisture content. These findings hold significant reference value for the sustainable development and utilization of underground space in the North China region. Full article

(This article belongs to the Special Issue Soil and Groundwater Quality and Resources Assessment, 2nd Edition)

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14 pages, 555 KB

Open AccessReview

Impact of Sediment Plume on Benthic Microbial Community in Deep-Sea Mining

by Mei Bai, Fang Dong, Yonggang Jia, Baoyun Qi, Shimin Yu, Shaoyuan Peng, Bingchen Liang, Lei Li, Liwei Yu, Xiuzhan Zhang and Yuanhe Li

Water 2025, 17(20), 3013; https://doi.org/10.3390/w17203013 - 20 Oct 2025

Viewed by 441

Abstract

Deep-sea polymetallic nodule provinces harbor rich benthic microbial communities that underpin biogeochemical cycles and sustain abyssal ecosystem functions. Recent studies have begun to map their abundance, diversity and community structure, emphasizing the role of environmental gradients and spatial heterogeneity. Yet the spatiotemporal dynamics [...] Read more.

Deep-sea polymetallic nodule provinces harbor rich benthic microbial communities that underpin biogeochemical cycles and sustain abyssal ecosystem functions. Recent studies have begun to map their abundance, diversity and community structure, emphasizing the role of environmental gradients and spatial heterogeneity. Yet the spatiotemporal dynamics and assembly mechanisms of these microbes remain largely unresolved. Mining-induced sediment plumes further complicate the picture: they modify microbial biomass, activity and composition, but the trajectories of community succession and the functional consequences of disturbance are still unclear. Thresholds used to gauge plume impacts also differ markedly among studies, hampering consistent risk assessments. In summary, a stark contrast exists between the limited in situ observational data, the widely varying impact thresholds reported across studies, and the pressing need for unified standards in environmental impact assessments for deep-sea mining. It recommends future work that integrates multi-omics, time-series in situ monitoring, cross-regional comparisons and standardized evaluation frameworks to refine microbial indicators and ecological thresholds for deep-sea mining impact assessments. Full article

(This article belongs to the Section Oceans and Coastal Zones)

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21 pages, 8127 KB

Open AccessArticle

Parameter Optimization of Bionic Hydrofoil System and Its Application in Algal Bloom Control in Plain River Networks

by Ertian Hua, Xiaopeng Wu, Yang Lin and Sihan Li

Water 2025, 17(20), 3012; https://doi.org/10.3390/w17203012 - 20 Oct 2025

Viewed by 274

Abstract

The bionic pumping system can effectively improve the hydrodynamic conditions in plain river networks, thereby mitigating the frequent algal blooms in these regions. This study employs numerical simulations to investigate how heave amplitude and chord length affect the hydrodynamic performance of both multi-hydrofoil [...] Read more.

The bionic pumping system can effectively improve the hydrodynamic conditions in plain river networks, thereby mitigating the frequent algal blooms in these regions. This study employs numerical simulations to investigate how heave amplitude and chord length affect the hydrodynamic performance of both multi-hydrofoil and single-hydrofoil systems. The operating frequencies for the two configurations are selected by combining these results with the flow velocity threshold required to suppress algal blooms. The results show that the pumping efficiency of the multi-hydrofoil system increases with chord length and heave amplitude, and the optimal parameter combination is c = 0.18W and h_max = 0.7c. For the single-hydrofoil system, efficiency first rises and then falls, peaking at c = 0.16 W and h_max = 0.6c. Under the algal bloom suppression threshold of 0.15 m/s, the multi-hydrofoil system meets the criterion across the entire cross-section at 0.10 Hz, making it suitable for raising flow velocity throughout the water body and for comprehensive bloom suppression. By contrast, the single-hydrofoil system produces an uneven wake with lower velocities in the upper region, so even at higher operating frequencies, it cannot cover the entire cross-section; it is therefore more appropriate for localized velocity enhancement and localized suppression of algal accumulation. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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17 pages, 1787 KB

Open AccessArticle

In Situ Monitoring of Water Isotopic Composition for Vapor and Precipitation Near-Surface Ground in East Asia Subtropical Monsoon Region

by Xingxian Li, Wenmin Qiu, Ziwei Lin, Changyuan Tang and Yingjie Cao

Water 2025, 17(20), 3011; https://doi.org/10.3390/w17203011 - 20 Oct 2025

Viewed by 304

Abstract

Hydrogen and oxygen isotopes in atmospheric water vapor (δ_v) and precipitation (δ_p or δ_r) were continuously measured using a laser-based water isotope spectrometer in Guangzhou, southeastern China, from March 2016 to February 2018. The measurements were conducted to [...] Read more.

Hydrogen and oxygen isotopes in atmospheric water vapor (δ_v) and precipitation (δ_p or δ_r) were continuously measured using a laser-based water isotope spectrometer in Guangzhou, southeastern China, from March 2016 to February 2018. The measurements were conducted to investigate the variations in water isotopes in the hydrological cycle under the subtropical monsoon climate. The isotopic composition ranged from −24.4‰ to −11.1‰ for δ¹⁸O in water vapor (δ¹⁸O_v) and from −11.5‰ to 2.3‰ for δ¹⁸O in precipitation (δ¹⁸O_r). The values of δ_v and δ_r were enriched during the dry season and depleted during the wet season, exhibiting systematic seasonal variation. A negative correlation was observed between monthly δ_v and precipitation amount, indicating that the values of δ_v exhibits an ‘amount effect’. However, a corresponding amount effect was not observed in the values of δ_r. The mean difference between δ_v and δ_r was −9.7‰ for δ¹⁸O and −76‰ for δD, suggesting that equilibrium fractionation is the dominant process during precipitation. The local meteoric vapor line (LMVL) for Guangzhou (δD = 6.6δ¹⁸O − 6.4) exhibited a slope similar to that of the equilibrium local meteoric vapor line (ELMVL) but with an intercept difference of 8.6. This difference in intercepts can be attributed to the vertical profile of δ_v. The δD-q (q refers to water vapor concentration) relationship is useful for identifying water vapor sources and tracking isotopic changes during atmospheric transport and precipitation. The local water vapor was found to originate primarily from the mixing of oceanic air masses. Data points falling between the oceanic source mixing line and the Rayleigh curve likely reflect post-condensation processes, such as raindrop re-evaporation or mixing with surrounding ambient vapor. Short periods of heavy precipitation were observed to cause severe depletion in δ_v, resulting in values falling below the Rayleigh curve. Full article

(This article belongs to the Special Issue Isotope Hydrology: Tracing Water’s Journey and Water–Rock Interactions in a Changing World)

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16 pages, 6095 KB

Open AccessArticle

Numerical Investigation on the Hydrodynamic Characteristics of the Confluent Channel with Different Tributary Radius-to-Width Ratios

by Yongchao Zou, Haifeng Tian, Lan Yang, Ruichang Hu and Hao Yuan

Water 2025, 17(20), 3010; https://doi.org/10.3390/w17203010 - 20 Oct 2025

Viewed by 312

Abstract

The radius-to-width ratio has an obvious impact on the flow structure within curved channels, which most natural rivers possess, but there are currently few studies on the influence of the radius-to-width ratio of a tributary (R/B) on the hydrodynamic [...] Read more.

The radius-to-width ratio has an obvious impact on the flow structure within curved channels, which most natural rivers possess, but there are currently few studies on the influence of the radius-to-width ratio of a tributary (R/B) on the hydrodynamic characteristics of a confluent channel. In order to contribute to this field of research, this study employed the RNG k-ε turbulence model, which has good applicability and accuracy for confluence, to investigate the effects of the R/B and flow ratios (q*) on the hydraulic characteristics of confluence. The results reveal that the numerical model can effectively simulate the velocity distribution in the confluence. The values of the key errors are all relatively small (e.g., the value of Mean RMSE is 0.05), and the flow patterns near the bed and water surfaces are different. The maximum velocity zone (MVZ) and the scale of the separation zone (SZ) increase as R/B increases; conversely, the MVZ and the scale of the SZ decrease as the q* increases. Upstream of the confluence, turbulent kinetic energy (TKE) increases and decreases as R/B and q* increase, respectively, while TKE downstream of the confluence hardly changes. Furthermore, the size of the SF decreases as R/B increases. The value of

\bar{S_{w}}

peaks downstream of the confluence, increases with the increase in the R/B, and decreases with the increase in the q*. The results of this study will contribute to a better understanding of the hydrodynamic characteristics of confluence and provide valuable insights for the management and ecological restoration of confluent channels. Full article

(This article belongs to the Special Issue Effects of Vegetation on Open Channel Flow and Sediment Transport)

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30 pages, 15268 KB

Open AccessArticle

Multi-Objective Two-Layer Robust Optimisation Model for Water Resource Allocation in the Basin: A Case Study of Yellow River Basin, China

by Danyang Di, Hao Hu, Shikun Duan, Qi Shi, Huiliang Wang and Lizhong Xiao

Water 2025, 17(20), 3009; https://doi.org/10.3390/w17203009 - 20 Oct 2025

Viewed by 343

Abstract

The continuous growth of the social economy and the accelerated urbanisation process have led to a rising increase in the demand for water resources in river basins. The uneven temporal and spatial distribution of water resources has further exacerbated the contradiction between supply [...] Read more.

The continuous growth of the social economy and the accelerated urbanisation process have led to a rising increase in the demand for water resources in river basins. The uneven temporal and spatial distribution of water resources has further exacerbated the contradiction between supply and demand. The traditional extensive water resource allocation model is no longer suitable for the diverse demands of sustainable development in river basins. Therefore, there is an urgent demand to determine how to reconcile the supply and demand of water resources in river basins to achieve a rational allocation. Taking the Yellow River Basin as an example, an optimal water allocation framework based on multi-objective robust optimisation method was proposed in this study. A robust constraint boundary conditions for the industrial, agricultural, construction and service, ecological, and social water demand were selected from the perspective of the economy–society–ecology nexus. Then, Latin hypercube sampling was adopted to modify the Monte Carlo method to improve the dispersion of sampling values for quantifying the uncertainty of water allocation parameters. Furthermore, a multi-dimensional spatial equilibrium optimal allocation combining adjustable robust optimisation and multi-objective optimisation was established. Finally, a multi-objective particle swarm optimisation algorithm based on a crossover operator was constructed to obtain the Pareto-optimal solution for multi-dimensional spatial equilibrium optimal allocation. The primary findings were as follows: (1) Parameter uncertainty had a significant effect on the provincial/regional revenues of water resources but has no obvious effect on basin revenue. (2) The uncertainty in runoff and parameters had a significant influence on decisions for optimal water allocation. The optimal volume of water purchased by different provinces (regions) varied greatly under different scenarios. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

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12 pages, 2598 KB

Open AccessArticle

Impact of pH and PS Concentration on the Thermal Degradation of Brilliant Coomassie Blue G-250: An Experimental and Modeling Approach

by Nassim Kerabchi, Mohamed Larbi Djaballah, Zineb Boutamine, Amani Latreche, Abderrezzaq Benalia, Derbal Kerroum, Antonio Pizzi and Antonio Panico

Water 2025, 17(20), 3008; https://doi.org/10.3390/w17203008 - 20 Oct 2025

Viewed by 377

Abstract

The degradation of Brilliant Coomassie Blue G-250 (BCB) was investigated using the thermally activated persulfate (TAP) process in deionized water. A kinetic model incorporating both hydroxyl (^●OH) and sulfate (SO₄^●–) radicals was developed to predict pseudo-first-order rate constants [...] Read more.

The degradation of Brilliant Coomassie Blue G-250 (BCB) was investigated using the thermally activated persulfate (TAP) process in deionized water. A kinetic model incorporating both hydroxyl (^●OH) and sulfate (SO₄^●–) radicals was developed to predict pseudo-first-order rate constants (kₒ) for the interaction of BCB with these radicals. Experimental results demonstrated efficient BCB degradation under TAP treatment. A parametric study examining the effects of initial conditions such as solution pH, persulfate concentration, initial BCB concentration, and temperature revealed that higher persulfate dosages, lower BCB concentrations, and alkaline pH enhanced degradation performance. Complete removal of BCB was achieved within 20 min under optimal conditions ([BCB]₀ = 10 mg/L, [PS]₀ = 2 mg/L, neutral pH). The kinetic model showed strong agreement with experimental data across a broad range of pH and persulfate concentrations. The rate constants for BCB reactions with ^●OH and SO₄^●– were determined through simulation to be 4.731 × 10⁹ M⁻¹s⁻¹ and 1.07 × 10⁹ M⁻¹s⁻¹, respectively. The selectivity analysis results revealed that SO₄^●– radicals played a dominant role in the degradation process across the various initial persulfate concentration scenarios. The remaining degradation was attributed to the contribution of ^●OH radicals. These findings are linked to the higher reactivity of BCB with SO₄^●– compared to ^●OH. Overall, the results demonstrate that TAP process is an effective method for the removal of emerging contaminants such as BCB from water. Full article

(This article belongs to the Section Wastewater Treatment and Reuse)

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18 pages, 3479 KB

Open AccessArticle

Development of Hydrological Criteria for the Hydraulic Design of Stormwater Pumping Stations

by Alfonso Arrieta-Pastrana, Oscar E. Coronado-Hernández and Vicente S. Fuertes-Miquel

Water 2025, 17(20), 3007; https://doi.org/10.3390/w17203007 - 19 Oct 2025

Viewed by 365

Abstract

For the design of stormwater pumping stations, there is often uncertainty regarding the selection of an appropriate rainfall event to determine the required pumping capacity and temporary storage volume for managing extreme events of a given magnitude. To account for the risk of [...] Read more.

For the design of stormwater pumping stations, there is often uncertainty regarding the selection of an appropriate rainfall event to determine the required pumping capacity and temporary storage volume for managing extreme events of a given magnitude. To account for the risk of system failure, the return period is considered, as recommended based on the size of the catchment’s drainage area or other considerations, depending on the local regulations of a country. This study focused on analysing the direct runoff volume from the catchment, the storage volume required for the operation of the pumping system, and the order of magnitude of the design flow rate. The results indicate that a rainfall event with a duration of at least twice the time of concentration should be used. The design flow rate should range between 50% and 70% of the peak discharge, and designing for flow rates near the peak is not advisable, as it can lead to intermittent pump operation and result in an oversized installed capacity. The methodology developed in this research was applied to the Coastal Protection Project located in the city of Cartagena, Colombia, which includes a 2045.6-m-long box culvert with a cross-sectional area of 2 × 2 m, and three pumping stations, each equipped with three pumps rated at 0.75 m³/s, for a total installed capacity of 6.75 m³/s. Full article

(This article belongs to the Special Issue Sustainable Water Resources Management in a Changing Environment)

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29 pages, 1214 KB

Open AccessSystematic Review

Management of Conventional and Non-Conventional Water Sources: A Systematic Literature Review

by Oleg Dashkevych and Mashor Housh

Water 2025, 17(20), 3006; https://doi.org/10.3390/w17203006 - 19 Oct 2025

Viewed by 547

Abstract

A global transition in water management is currently underway, marked by the declining reliability of conventional sources and the accelerated adoption of non-conventional alternatives. This shift is driven by escalating pressures from climate change, population growth, and freshwater overexploitation. While the literature on [...] Read more.

A global transition in water management is currently underway, marked by the declining reliability of conventional sources and the accelerated adoption of non-conventional alternatives. This shift is driven by escalating pressures from climate change, population growth, and freshwater overexploitation. While the literature on management of water sources (WSs) is extensive, empirical clarity on Hybrid Water Systems Management (HWSM)—the integration of conventional and non-conventional WSs within a single system—remains limited. The present study addresses this gap through a systematic literature review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) approach, which ensures methodological transparency and applicability. From over 9000+ peer-refereed articles retrieved from three major scientific databases (ScienceDirect, Scopus, and Web of Science Core Collections), published between 1999 and 2024, 44 studies were identified as the most relevant and consequently analyzed. The literature review refines the classification of WSs, distinguishing conventional sources, such as groundwater and surface water, from non-conventional alternatives, such as desalinated water, treated wastewater, gray water, and rainwater harvesting. The analysis also indicates that non-conventional WSs are now more prominent in the literature than conventional ones. Overall, the present study demonstrated that modern water management strategies increasingly emphasize optimization and circular reuse. In contrast, earlier approaches tend to focus more on water conservation and economic efficiency. The literature also indicates a gradual shift from traditional supply-dominant models toward integrated, cost-effective, and sustainability-oriented approaches that combine multiple sources and advanced allocation techniques. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

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19 pages, 5014 KB

Open AccessArticle

Environmental Drivers of Macrozoobenthos Structure Along a Discontinuous Tributary of the Oder River (North-Western Poland)

by Nadhira Benhadji, Jarosław Dąbrowski, Adam Brysiewicz, Przemysław Czerniejewski and Łukasz Hałasa

Water 2025, 17(20), 3005; https://doi.org/10.3390/w17203005 - 19 Oct 2025

Viewed by 426

Abstract

The Myśla River, a right-bank tributary of the Oder catchment, was the focus of our study on the impact of environmental parameters on macrozoobenthos diversity and composition. We surveyed 18 sites along the Myśla catchment, from upstream to the outlet, recording environmental features [...] Read more.

The Myśla River, a right-bank tributary of the Oder catchment, was the focus of our study on the impact of environmental parameters on macrozoobenthos diversity and composition. We surveyed 18 sites along the Myśla catchment, from upstream to the outlet, recording environmental features and sampling macrozoobenthos. The taxa composition (31 taxa) was dominated by insect larvae, particularly Diptera Chironomidae, with moderate contributions from mollusc families such as Sphaeriidae, Bithyniidae, and Planorbidae, which are primarily filter-feeders or grazers. Based on environmental affinities, the river was divided into three sections. Sites within lake areas and those with diverse sediment types exhibited the highest biodiversity. Conductivity, flow rate, nitrogen compound levels, dissolved oxygen, suspended particles, and current velocity most strongly influenced biodiversity, while substrate type shaped taxa composition. Lakes heavily disrupt the ecological continuity of the Myśla River, significantly altering natural ecological processes and causing deviations from the River Continuum Concept (RCC), whereas artificial structures exert only minor additional influence. We examined the applicability of the RCC by analyzing macrozoobenthos structure along the upstream-to-downstream gradient. This preliminary study contributes to ongoing regional research, highlighting the role of lakes in shaping the Myśla River ecosystem and assessing the relevance of RCC in unique river systems. Full article

(This article belongs to the Special Issue Advances in Monitoring of Hydrological and Ecological Processes Under Climate Change)

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21 pages, 5705 KB

Open AccessArticle

Research on Internal Flow and Runner Force Characteristics of Francis Turbine

by Jianwen Xu, Peirong Chen, Yanhao Li, Xuelin Yang and An Yu

Water 2025, 17(20), 3004; https://doi.org/10.3390/w17203004 - 19 Oct 2025

Viewed by 306

Abstract

Francis turbines are widely used due to their large capacity and broad head adaptability, placing higher demands on the internal flow characteristics and runner performance of the units. In this paper, numerical simulations of a Francis turbine model were conducted using ANSYS CFX [...] Read more.

Francis turbines are widely used due to their large capacity and broad head adaptability, placing higher demands on the internal flow characteristics and runner performance of the units. In this paper, numerical simulations of a Francis turbine model were conducted using ANSYS CFX 2022 R1. The SST turbulence model, ZGB cavitation model, and VOF multiphase flow model were selected for the calculations. The internal flow characteristics and pressure pulsations in the runner and draft tube under different operating conditions were analyzed, and the variations in normal and tangential forces acting on the runner blades during operation were investigated. The results indicate significant differences in the internal flow within the runner and draft tube under various guide vane opening conditions. The pressure pulsation in the unit is influenced by both the internal flow in the draft tube and the rotation of the runner. The mechanical load on the runner blades is affected by multiple factors, including the wake from upstream fixed guide vanes, rotor–stator interaction, and downstream vortex ropes. Under low-flow conditions, the variation in forces acting on the runner blades is relatively small, whereas under high-flow conditions, the runner blades are prone to abrupt force fluctuations at 0.6–0.8 times the rotational frequency. This is manifested as periodic abrupt force changes in both the X and Y directions of the runner blades under high-flow conditions. The normal force in the Z-direction of the runner blades increases instantaneously and then decreases immediately, while the tangential force decreases instantaneously and then increases promptly. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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17 pages, 5790 KB

Open AccessArticle

Hybrid RSM–ANN Modeling for Optimization of Electrocoagulation Using Aluminum Electrodes (Al–Al) for Hospital Wastewater Treatment

by Khanit Matra, Yanika Lerkmahalikit, Sirilak Prasertkulsak, Amnuaychai Kongdee, Raweeporn Pomthong, Suchira Thongson and Suthida Theepharaksapan

Water 2025, 17(20), 3003; https://doi.org/10.3390/w17203003 - 18 Oct 2025

Viewed by 465

Abstract

Electrocoagulation (EC) employing aluminum–aluminum (Al–Al) electrodes was investigated for hospital wastewater treatment, targeting the removal of turbidity, soluble chemical oxygen demand (sCOD), and total dissolved solids (TDS). A hybrid modeling framework integrating response surface methodology (RSM) and artificial neural networks (ANN) was developed [...] Read more.

Electrocoagulation (EC) employing aluminum–aluminum (Al–Al) electrodes was investigated for hospital wastewater treatment, targeting the removal of turbidity, soluble chemical oxygen demand (sCOD), and total dissolved solids (TDS). A hybrid modeling framework integrating response surface methodology (RSM) and artificial neural networks (ANN) was developed to enhance predictive reliability and identify energy-efficient operating conditions. A Box–Behnken design with 15 experimental runs evaluated the effects of pH, current density, and electrolysis time. Multi-response optimization determined the overall optimal conditions at pH 7.0, current density 20 mA/cm², and electrolysis time 75 min, achieving 94.5% turbidity, 69.8% sCOD, and 19.1% TDS removal with a low energy consumption of 0.34 kWh/m³. The hybrid RSM–ANN model exhibited high predictive accuracy (R² > 97%), outperforming standalone RSM models, with ANN more effectively capturing nonlinear relationships, particularly for TDS. The results confirm that EC with Al–Al electrodes represent a technically promising and energy-efficient approach for decentralized hospital wastewater treatment, and that the hybrid modeling framework provides a reliable optimization and prediction tool to support process scale-up and sustainable water reuse. Full article

(This article belongs to the Special Issue Advanced Treatment Technologies for Emerging Contaminants in Wastewater)

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23 pages, 6511 KB

Open AccessArticle

An Adaptive Management-Oriented Approach to Spatial Planning for Estuary National Parks: A Case Study of the Yangtze River Estuary, China

by Wanting Peng, Ziyu Zhu, Jia Liu, Yunshan Lin, Qin Zhao, Wenhui Yang, Chengzhao Wu and Wenbo Cai

Water 2025, 17(20), 3002; https://doi.org/10.3390/w17203002 - 18 Oct 2025

Viewed by 380

Abstract

Estuaries represent quintessential coupled human–natural systems (CHNS) where the dynamic interplay between ecological processes and anthropogenic pressures (e.g., shipping, water use exploitation) challenges conventional static spatial planning approaches. Focusing on the Yangtze River Estuary—a globally significant yet intensely utilized ecosystem—this study develops an [...] Read more.

Estuaries represent quintessential coupled human–natural systems (CHNS) where the dynamic interplay between ecological processes and anthropogenic pressures (e.g., shipping, water use exploitation) challenges conventional static spatial planning approaches. Focusing on the Yangtze River Estuary—a globally significant yet intensely utilized ecosystem—this study develops an adaptive management (AM)-oriented spatial planning framework for estuarine protected areas. Our methodology integrates systematic identification of optimal zones using multi-criteria assessments of biodiversity indicators (e.g., flagship species habitats), ecological metrics (e.g., ecosystem services), and management considerations; delineation of a three-tier adaptive zoning system (Control–Functional–Seasonal) to address spatiotemporal pressures; and dynamic management strategies to mitigate human-environment conflicts. The proposed phased conservation boundary (Phase I: 664.38 km²; Phase II: 1721.94 km²) effectively balances ecological integrity with socio-economic constraints. Spatial–temporal analysis of shipping activities over five years demonstrates minimal operational interference, confirming the framework’s efficacy in reconciling conservation and development priorities. By incorporating ecological feedback mechanisms into spatial planning, this work advances a transferable model for governing contested seascapes, contributing to CHNS theory through practical tools for adaptive, conflict-sensitive conservation. The framework’s implementation in the Yangtze context provides empirical evidence that science-driven, flexible spatial planning can reduce sectoral conflicts while maintaining ecosystem functionality, offering a replicable pathway for sustainable water management of similarly complex human–natural systems worldwide. Full article

(This article belongs to the Section Oceans and Coastal Zones)

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26 pages, 7464 KB

Open AccessArticle

Quantifying Flood Impacts on Ecosystem Carbon Dynamics Using Remote Sensing and Machine Learning in the Climate-Stressed Landscape of Emilia-Romagna

by Jibran Qadri and Francesca Ceccato

Water 2025, 17(20), 3001; https://doi.org/10.3390/w17203001 - 18 Oct 2025

Viewed by 355

Abstract

Flood events, intensified by climate change, pose significant threats to both human settlements and ecological systems. This study presents an integrated approach to evaluate flood impacts on ecosystem carbon dynamics using remote sensing and machine learning techniques. The case of the Emilia-Romagna region [...] Read more.

Flood events, intensified by climate change, pose significant threats to both human settlements and ecological systems. This study presents an integrated approach to evaluate flood impacts on ecosystem carbon dynamics using remote sensing and machine learning techniques. The case of the Emilia-Romagna region in Italy is presented, which experienced intense flooding in 2023. To understand flood-induced changes in the short term, we quantified the differences in net primary productivity (NPP) and above-ground biomass (AGB) before and after flood events. Short-term analysis of NPP and AGB revealed substantial localized losses within flood-affected areas. NPP showed a net deficit of 7.0 × 10³ g C yr⁻¹, and AGB a net deficit of 0.5 × 10³ Mg C. While the wider region gained NPP (6.7 × 10⁵ g C yr⁻¹), it suffered a major AGB loss (3.3 × 10⁵ Mg C), indicating widespread biomass decline beyond the flood zone. Long-term ecological assessment using the Remote Sensing Ecological Index (RSEI) showed accelerating degradation, with the “Fair” ecological class shrinking from 90% in 2014 to just over 50% in 2024, and the “Poor” class expanding. “Good” and “Very Good” classes nearly disappeared after 2019. High-hazard flood zones were found to contain 9.0 × 10⁶ Mg C in AGB and 1.1 × 10⁷ Mg C in soil organic carbon, highlighting the vulnerability of carbon stocks. This study underscores the importance of integrating flood modeling with ecosystem monitoring to inform climate-adaptive land management and carbon conservation strategies. It represents a clear, quantifiable carbon loss that should be factored into regional carbon budgets and post-flood ecosystem assessments. Full article

(This article belongs to the Special Issue Water-Induced Geo-Disaster Reduction in the Context of Climate Change: Hydrology, Management Strategies, and Ecological Geological Engineering)

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35 pages, 2757 KB

Open AccessReview

Advances in Remote Sensing and Sensor Technologies for Water-Quality Monitoring: A Review

by Huilun Chen, Xilan Gao and Rongfang Yuan

Water 2025, 17(20), 3000; https://doi.org/10.3390/w17203000 - 18 Oct 2025

Viewed by 886

Abstract

Water-quality monitoring plays a vital role in protecting and managing water resources, maintaining ecological balance and safeguarding human health. At present, the traditional monitoring technology is associated with risks of low sampling efficiency, long response time, high economic cost and secondary pollution of [...] Read more.

Water-quality monitoring plays a vital role in protecting and managing water resources, maintaining ecological balance and safeguarding human health. At present, the traditional monitoring technology is associated with risks of low sampling efficiency, long response time, high economic cost and secondary pollution of water samples, and cannot guarantee the accuracy and real-time determination of monitoring data. Remote sensing (RS) technology and sensors are used to automatically realize the real-time monitoring of water quality. In this paper, the principles and composition of remote monitoring systems are systematically summarized. For the RS technology, indicators including chlorophyll-a, turbidity and total suspended matter/solids, colored dissolved organic matter, electrical conductivity (EC), dissolved oxygen (DO), temperature and pH value were considered, and for sensors monitoring, the parameters of pH value, temperature, oxidation reduction potential, DO, turbidity, EC and salinity, and total dissolved solids were analyzed. The practical applications of remote monitoring in surface water, marine water and wastewater are introduced in this context. In addition, the advantages and disadvantages of remote monitoring systems are evaluated, which provides some basis for the selection of remote monitoring systems in the future. Full article

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

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13 pages, 912 KB

Open AccessArticle

Environmental Surveillance of ESKAPE Bacteria in Wastewater and Rivers in the Vhembe District, South Africa: Public Health Risks from a One Health Perspective

by Natasha Potgieter, Mpumelelo Casper Rikhotso, Leonard Owino Kachienga, Rohudzwa Badzhi and Afsatou Ndama Traoré

Water 2025, 17(20), 2999; https://doi.org/10.3390/w17202999 - 18 Oct 2025

Viewed by 336

Abstract

The One Health approach is used to assess health-associated risks resulting from human exposure to antibiotic-resistant bacteria (ARB) that pose a significant public health risk. In this approach, wastewater treatment plants (WWTPs) play an important role in reducing bacteria and antibiotic-resistant genes (ARGs) [...] Read more.

The One Health approach is used to assess health-associated risks resulting from human exposure to antibiotic-resistant bacteria (ARB) that pose a significant public health risk. In this approach, wastewater treatment plants (WWTPs) play an important role in reducing bacteria and antibiotic-resistant genes (ARGs) in the environment. The ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) are of significant concern due to their ability to evade the effects of multiple antibiotics, including last-resort treatments such as carbapenems and glycopeptides. This study aimed to investigate the environmental surveillance of ESKAPE bacteria in wastewater and their adjacent receiving water bodies in Limpopo Province, South Africa. Methodology: Over a period of 6 months, all isolates were identified phenotypically, and genomic DNA was extracted using the QIAamp 96 DNA QIAcube^® HT Kit. Species-specific PCR was performed, followed by Sanger sequencing. The relevant sequences were compared to NCBI GenBank references using BLAST for confirmation and to assess the potential human health-associated risks. Results: ESKAPE organisms identified phenotypically were confirmed using PCR in both WWTP samples. Bacteria such as Acinetobacter baumannii and Enterobacter spp. were not detected in upstream or downstream river samples, particularly during August and September. In December and January, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa were not detected in effluent samples at both sites. Phylogenetic analysis revealed a diverse range of clinically significant genera, including Pseudomonas, Klebsiella, Enterobacter, and Staphylococcus, with strains closely related to global clinical isolates. Many of the isolates were associated with resistance to carbapenems, fluoroquinolones, and aminoglycosides. In addition, some strains clustered with both methicillin-sensitive and methicillin-resistant lineages. Conclusions: The findings emphasise the urgent need for increased genomic surveillance in environmental settings affected by wastewater discharge and highlight the importance of integrated antimicrobial resistance monitoring that connects clinical and environmental health sectors. Full article

(This article belongs to the Section Water and One Health)

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