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Water, Volume 17, Issue 16 (August-2 2025) – 141 articles

Cover Story (view full-size image): This study presents a six-year multi-matrix assessment (2018–2023) of heavy metal contamination in the Romanian Black Sea, integrating seawater, sediments, and benthic mollusks. The results highlight elevated nearshore pressures linked to Danube inputs, ports, and coastal activity, contrasted with generally lower offshore levels but occasional episodic anomalies. The combination of bioconcentration and bioaccumulation factors underscores cadmium as a key contaminant of concern. The study demonstrates the importance of integrated monitoring approaches to better understand ecological risks and to guide the long-term management of semi-enclosed seas. View this paper
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18 pages, 1211 KB  
Article
Sustainable Greywater Treatment in Jordan: The Role of Constructed Wetlands as Nature-Based Solutions
by Ahmed M. N. Masoud, Amani Alfarra, Alham W. Al-Shurafat and Sabrina Sorlini
Water 2025, 17(16), 2497; https://doi.org/10.3390/w17162497 - 21 Aug 2025
Viewed by 449
Abstract
Water scarcity in Jordan is intensifying, creating an urgent need for innovative approaches to maximize the use of nonconventional water resources, such as greywater treatment and reuse. This study presents a detailed analysis of the suitability of nature-based solutions (NbSs) for greywater treatment, [...] Read more.
Water scarcity in Jordan is intensifying, creating an urgent need for innovative approaches to maximize the use of nonconventional water resources, such as greywater treatment and reuse. This study presents a detailed analysis of the suitability of nature-based solutions (NbSs) for greywater treatment, with a focus on the application of horizontal flow constructed wetlands (HFCWs). Two systems were implemented to treat greywater generated from mosques located in Az-Zarqa Governorate, a dry region in Jordan. Following several months of operation, monitoring, and evaluation, the systems demonstrated high removal efficiencies: turbidity (>87%), total suspended solids (TSS) (>96%), chemical oxygen demand (COD) (>91%), and five-day biological oxygen demand (BOD5) (>85%). The eight-square-meter HFCW units successfully produced one cubic meter of treated greywater per day, meeting Jordanian standards for reclaimed greywater (JS 1776:2013) for use in irrigating food crops, including those consumed raw. The system achieved a 70% reduction in water consumption compared to the same period in the year prior to its implementation. These results demonstrate the potential of constructed wetlands (CWs) as effective, low-cost, and sustainable NbSs for decentralized greywater treatment and reuse in water-scarce regions. Full article
(This article belongs to the Special Issue Impacts of Climate Change & Human Activities on Wetland Ecosystems)
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21 pages, 16313 KB  
Article
An Interpretable Deep Learning Framework for River Water Quality Prediction—A Case Study of the Poyang Lake Basin
by Ying Yuan, Chunjin Zhou, Jingwen Wu, Fuliang Deng, Wei Liu, Mei Sun and Lanhui Li
Water 2025, 17(16), 2496; https://doi.org/10.3390/w17162496 - 21 Aug 2025
Viewed by 583
Abstract
Accurate prediction of water quality involves early identification of future pollutant concentrations and water quality indicators, which is an important prerequisite for optimizing water environment management. Although deep learning algorithms have demonstrated considerable potential in predicting water quality parameters, their broader adoption remains [...] Read more.
Accurate prediction of water quality involves early identification of future pollutant concentrations and water quality indicators, which is an important prerequisite for optimizing water environment management. Although deep learning algorithms have demonstrated considerable potential in predicting water quality parameters, their broader adoption remains hindered by limited interpretability. This study proposes an interpretable deep learning framework integrating an artificial neural network (ANN) model with Shapley additive explanations (SHAP) analysis to predict spatiotemporal variations in water quality and identify key influencing factors. A case study was conducted in the Poyang Lake Basin, utilizing multi-dimensional datasets encompassing topographic, meteorological, socioeconomic, and land use variables. Results indicated that the ANN model exhibited strong predictive performance for dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP), permanganate index (CODMn), ammonia nitrogen (NH3N), and turbidity (Turb), achieving R2 values ranging from 0.47 to 0.77. Incorporating land use and socioeconomic factors enhanced prediction accuracy by 37.8–246.7% compared to models using only meteorological data. SHAP analysis revealed differences in the dominant factors influencing various water quality parameters. Specifically, cropland area, forest cover, air temperature, and slope in each sub-basin were identified as the most important variables affecting water quality parameters in the case area. These findings provide scientific support for the intelligent management of the regional water environment. Full article
(This article belongs to the Section Water Quality and Contamination)
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17 pages, 4548 KB  
Article
Ultrasonic-Cavitation-Enhanced Biodegradation of Ciprofloxacin: Mechanisms and Efficiency
by Qianheng Wen, Qiwei Peng, ThuThi Pham and Xiwei He
Water 2025, 17(16), 2495; https://doi.org/10.3390/w17162495 - 21 Aug 2025
Viewed by 442
Abstract
Ciprofloxacin (CIP), a persistent fluoroquinolone antibiotic, poses serious environmental concerns due to its low biodegradability and widespread presence in aquatic ecosystems. This study investigates the synergistic application of low-frequency ultrasonic cavitation and biological treatment to enhance CIP removal efficiency. Experiments have shown that [...] Read more.
Ciprofloxacin (CIP), a persistent fluoroquinolone antibiotic, poses serious environmental concerns due to its low biodegradability and widespread presence in aquatic ecosystems. This study investigates the synergistic application of low-frequency ultrasonic cavitation and biological treatment to enhance CIP removal efficiency. Experiments have shown that under the optimal biological treatment conditions (6 g/L sludge concentration, pH 8), single biological treatment for 48 h can only remove 41.9% CIP and 24.9% total organic carbon (TOC). Ultrasonic pretreatment was conducted under varying frequencies and pH conditions to determine optimal cavitation parameters, while biodegradation performance was evaluated at different sludge concentrations and pH levels. Results indicated that in 10 mg/L CIP wastewater under alkaline conditions (pH 9.0), CIP and TOC removal efficiencies reached 58.9% and 35.2%, respectively, within 30 min using 15 kHz ultrasound irradiation. When ultrasonic pretreatment was followed by biological treatment, overall removal rates increased to 96.3% for CIP and 90.4% for TOC, significantly outperforming either method alone. LC-MS analysis identified several degradation intermediates during ultrasonic pretreatment, revealing key transformation pathways such as piperazine ring cleavage, hydroxylation, and defluorination. Furthermore, toxicity evaluation using the T.E.S.T. model confirmed a substantial reduction in ecological risk after ultrasonic treatment. Overall, the combined ultrasonic–biological process offers a cost-effective and environmentally sustainable strategy for the efficient removal of fluoroquinolone antibiotics from wastewater. Full article
(This article belongs to the Special Issue Application of Microbial Technology in Wastewater Treatment)
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22 pages, 1058 KB  
Review
Recent Advances in Organic Pollutant Removal Technologies for High-Salinity Wastewater
by Jun Dai, Yun Gao, Kinjal J. Shah and Yongjun Sun
Water 2025, 17(16), 2494; https://doi.org/10.3390/w17162494 - 21 Aug 2025
Viewed by 474
Abstract
Industrial processes like farming, food processing, petroleum refinery, and leather manufacturing produce a lot of high-salinity wastewater. This wastewater presents serious environmental risks, such as soil degradation, eutrophication, and water salinization, if it is released without adequate treatment. The sources and features of [...] Read more.
Industrial processes like farming, food processing, petroleum refinery, and leather manufacturing produce a lot of high-salinity wastewater. This wastewater presents serious environmental risks, such as soil degradation, eutrophication, and water salinization, if it is released without adequate treatment. The sources and features of high-salinity wastewater are outlined in this review, along with the main methods for removing organic pollutants, such as physicochemical, biological, and combined treatment approaches. Membrane separation, coagulation–flocculation, and advanced oxidation processes are the primary physicochemical techniques. Anaerobic and aerobic technologies are the two categories into which biological treatments fall. Physicochemical–biological combinations and the fusion of several physicochemical techniques are examples of integrated technologies. In order to achieve sustainable and effective treatment and resource recovery of high-salinity wastewater, this review compares the effectiveness and drawbacks of each method and recommends that future research concentrate on the development of salt-tolerant catalysts, anti-fouling membrane materials, halophilic microbial consortia, and optimized hybrid treatment systems. Full article
(This article belongs to the Special Issue Advanced Wastewater Treatment Technologies with the Potential to Achieve Resource Recycling)
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21 pages, 8981 KB  
Article
The Influence of the Sediment and Water Transported by the Yellow River on the Subaqueous Delta Without Water and Sediment Regulation
by Junyao Song, Bowen Li, Kaifei He and Xuerong Cui
Water 2025, 17(16), 2493; https://doi.org/10.3390/w17162493 - 21 Aug 2025
Viewed by 425
Abstract
Globally, sediment transport from rivers and the morphological evolution of deltas are strongly shaped by human activities. The Yellow River Delta is a typical representative of this. In this paper, Delft 3D v4.01.00 software was used to simulate the sediment diffusion in the [...] Read more.
Globally, sediment transport from rivers and the morphological evolution of deltas are strongly shaped by human activities. The Yellow River Delta is a typical representative of this. In this paper, Delft 3D v4.01.00 software was used to simulate the sediment diffusion in the subaqueous delta of the Yellow River in 2017 so as to explore the influence of the sediment and water transported by the Yellow River on the subaqueous delta without water and sediment regulation. The results reveal the occurrence of a low–high–low suspended sediment concentration distribution from the coastlines to the far shore. The main accumulation areas shifted from the coasts of Bohai Bay and Laizhou Bay in the dry season to the estuary in the wet season. The sediments entering the sea formed deposition zones along the coastline, and erosion zones were formed outside these deposition zones, with a maximum depth of about 5 m. In 2017, the impact of the sediment inflow into the Yellow River on its subaqueous delta generally resulted in the erosion being greater than the sedimentation, and the erosion/deposition volume in 2017 was −1.28 × 108 m3, and the estimated critical value of the sediment inflow balance was 2.13 × 108 tons. Full article
(This article belongs to the Section Water Erosion and Sediment Transport)
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23 pages, 5651 KB  
Article
Creep Tests and Fractional Creep Damage Model of Saturated Frozen Sandstone
by Yao Wei and Hui Peng
Water 2025, 17(16), 2492; https://doi.org/10.3390/w17162492 - 21 Aug 2025
Viewed by 354
Abstract
The rock strata traversed by frozen shafts in coal mines located in western regions are predominantly composed of weakly cemented, water-rich sandstones of the Cretaceous system. Investigating the rheological damage behavior of saturated sandstone under frozen conditions is essential for evaluating the safety [...] Read more.
The rock strata traversed by frozen shafts in coal mines located in western regions are predominantly composed of weakly cemented, water-rich sandstones of the Cretaceous system. Investigating the rheological damage behavior of saturated sandstone under frozen conditions is essential for evaluating the safety and stability of these frozen shafts. To explore the damage evolution and creep characteristics of Cretaceous sandstone under the coupled influence of low temperature and in situ stress, a series of triaxial creep tests were conducted at a constant temperature of −10 °C, under varying confining pressures (0, 2, 4, and 6 MPa). Simultaneously, acoustic emission (AE) energy monitoring was employed to characterize the damage behavior of saturated frozen sandstone under stepwise loading conditions. Based on the experimental findings, a fractional-order creep constitutive model incorporating damage evolution was developed to capture the time-dependent deformation behavior. The sensitivity of model parameters to temperature and confining pressure was also analyzed. The main findings are as follows: (1) Creep deformation progressively increases with higher confining pressure, and nonlinear accelerated creep is observed during the final loading stage. (2) A fractional-order nonlinear creep model accounting for the coupled effects of low temperature, stress, and damage was successfully established based on the test data. (3) Model parameters were identified using the least squares fitting method across different temperature and pressure conditions. The predicted curves closely match the experimental results, validating the accuracy and applicability of the proposed model. These findings provide a theoretical foundation for understanding deformation mechanisms and ensuring the structural integrity of frozen shafts in Cretaceous sandstone formations of western coal mines. Full article
(This article belongs to the Special Issue Freeze–Thaw Dynamics and Water Pathways: Vulnerability of Infrastructures and Disasters in Mines in Cold Regions)
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16 pages, 2080 KB  
Article
Methane Emissions from Wetlands on the Tibetan Plateau over the Past 40 Years
by Tingting Sun, Zehua Jia, Yiming Zhang, Mengxin Ying, Mengxin Shen and Guanting Lyu
Water 2025, 17(16), 2491; https://doi.org/10.3390/w17162491 - 21 Aug 2025
Viewed by 418
Abstract
Methane (CH4) emissions from the wetlands of the Tibetan Plateau (TP) remain poorly quantified, particularly regarding their historical dynamics, spatial heterogeneity, and response to climate change. This study provides the high-resolution, observation-driven reconstruction of TP wetland CH4 emissions over the [...] Read more.
Methane (CH4) emissions from the wetlands of the Tibetan Plateau (TP) remain poorly quantified, particularly regarding their historical dynamics, spatial heterogeneity, and response to climate change. This study provides the high-resolution, observation-driven reconstruction of TP wetland CH4 emissions over the past four decades, integrating a machine learning model with 108 flux measurements from 67 sites. This unique combination of field-based data and fine-scale mapping enables unprecedented accuracy in quantifying both emission intensity and long-term trends. We show that current TP wetlands emit 5.87 ± 1.43 g CH4 m−2 yr−1, totaling 97.3 Gg CH4 yr−1, equivalent to 7.8% of East Asia’s annual wetland emissions. Despite a climate-driven increase in per-unit-area CH4 fluxes, a 19.8% (8432.9 km2) loss of wetland area since the 1980s has reduced total emissions by 15%, counteracting the enhancement from warming and moisture increases. Our comparative analysis demonstrates that existing land surface models (LSMs) substantially underestimate TP wetland CH4 emissions, largely due to the inadequate representation of TP wetlands and their dynamics. Projections under future climate scenarios indicate a potential 8.5–21.2% increase in emissions by 2100, underscoring the importance of integrating high-quality, region-specific observational datasets into Earth system models. By bridging the gap between field observations and large-scale modeling, this work advances understanding of alpine wetland–climate feedback, and provides a robust foundation for improving regional carbon budget assessments in one of the most climate-sensitive regions on Earth. Full article
(This article belongs to the Section Water and Climate Change)
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38 pages, 3980 KB  
Review
Current State of Research on the Three-Dimensional Particle Electrode System for Treating Organic Pollutants from Wastewater Streams: Particle Electrode, Degradation Mechanism, and Synergy Effects
by Guene L. Razack, Jiayi Wang, Xian Zhao, Worou Chabi Noel, Hanjun Sun, Jiwei Pang, Jie Ding, Wenshuo Wang, Xiaoyin Yang, Chenhao Cui, Yani Zang, Yuqian Wang, Geng Luo, Nanqi Ren and Shanshan Yang
Water 2025, 17(16), 2490; https://doi.org/10.3390/w17162490 - 21 Aug 2025
Viewed by 409
Abstract
As the demand for effective wastewater treatment continues to rise, the application of three-dimensional (3D) electrochemical particle electrodes for the removal of organic compounds from industrial wastewater has emerged as a promising solution. This approach offers significant advantages, including high treatment efficiency, operational [...] Read more.
As the demand for effective wastewater treatment continues to rise, the application of three-dimensional (3D) electrochemical particle electrodes for the removal of organic compounds from industrial wastewater has emerged as a promising solution. This approach offers significant advantages, including high treatment efficiency, operational flexibility, high current efficiency, low energy consumption, and the ability to degrade non-biodegradable organic pollutants, ultimately mineralizing them. This review provides a comprehensive and systematic exploration of the research and development of particle electrodes for use in 3D electrochemical reactors in wastewater treatment. The pivotal role of particle electrodes in removing organic contaminants from wastewater was highlighted, with most materials used as particle electrodes characterized by a specific surface area and well-defined porous structure, both of which were thoroughly discussed. Through the synergistic mechanism of adsorption, the particle electrode aids in the breakdown of organic contaminants, demonstrating the 3D particle electrode’s effectiveness in facilitating multiple oxidation mechanisms for organic wastewater treatment. Furthermore, this review categorized various particle electrode types used in 3D electrochemical wastewater treatment based on their primary components or carriers and the presence or absence of catalysts. Finally, the current status and prospects for the development and enhancement of 3D electrode particles were presented. This review offers valuable insights into the application of the 3D electrode process for environmental water treatment. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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25 pages, 3665 KB  
Article
Quantifying the Comprehensive Water Resources and Environment Carrying Capacity in Wuhan City Based on the “Human-Water-City” Framework
by Huiyuan Liu, Yi Dong, Jun Xia, Guoqing Wang and Jun Ma
Water 2025, 17(16), 2489; https://doi.org/10.3390/w17162489 - 21 Aug 2025
Viewed by 536
Abstract
In recent years, China’s rapid economic growth and urbanization have heightened the conflict between economic development and resource sustainability, leading to severe urban water challenges, including scarcity and environmental degradation. This study proposes a quantitative model that integrates the “Human-Water-City” (HWC) feedback mechanisms [...] Read more.
In recent years, China’s rapid economic growth and urbanization have heightened the conflict between economic development and resource sustainability, leading to severe urban water challenges, including scarcity and environmental degradation. This study proposes a quantitative model that integrates the “Human-Water-City” (HWC) feedback mechanisms to assess and measure urban comprehensive water resources and environmental carrying capacity (CWRECC), aimed at addressing urban water sustainability challenges. The CWRECC integrates water quantity and quality dimensions following the principles of the “Cannikin Law”—selecting the lower envelope between water resources and water environment carrying capacities, which emphasizes the importance of weaknesses in enhancing the overall system. The maximum sustainable population and Gross Domestic Product (GDP) under the CWRECC constraints can be obtained using this quantitative method. A case study was conducted in Wuhan City. The results show that Wuhan has abundant water resources. From 2013 to 2020, if only considering the water quantity aspect, the water resources carrying capacity could support a population ranging from 22.63 to 61.17 million and a GDP between 1946.6 and 7988.9 billion yuan, maintaining a sustainable state throughout the period. However, when considering both water quantity and quality, the CWRECC revealed an overloaded state in 2013, 2014, 2018, and 2019, primarily attributable to significant water environmental issues. In 2013, 2014, 2018, and 2019, the quantified CWRECC could sustain populations of 9.88 million, 10.01 million, 10.33 million, and 10.57 million people, and support a GDP of 849.5 billion, 976.5 billion, 1402.9 billion, and 1538.9 billion yuan, respectively. Both the population and GDP capacities fell short of the actual recorded values for those years. The findings demonstrate that Wuhan needs to make greater efforts in water environmental protection to sustain the harmonious development within the HWC. This empirical study highlights the model’s potential to provide a scientific foundation for urban water resources management and environmental protection strategies. Full article
(This article belongs to the Section Water Use and Scarcity)
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22 pages, 1130 KB  
Review
Spectroscopy-Based Methods for Water Quality Assessment: A Comprehensive Review and Potential Applications in Livestock Farming
by Aikaterini-Artemis Agiomavriti, Thomas Bartzanas, Nikos Chorianopoulos and Athanasios I. Gelasakis
Water 2025, 17(16), 2488; https://doi.org/10.3390/w17162488 - 21 Aug 2025
Viewed by 505
Abstract
Water quality monitoring and evaluation are essential across multiple sectors, including public health, environmental protection, agriculture and livestock management, industrial processes, and broader sustainability efforts. Conventional water analysis techniques, although accurate, are often constrained by their labor-intensive nature, extended processing times, and limited [...] Read more.
Water quality monitoring and evaluation are essential across multiple sectors, including public health, environmental protection, agriculture and livestock management, industrial processes, and broader sustainability efforts. Conventional water analysis techniques, although accurate, are often constrained by their labor-intensive nature, extended processing times, and limited applicability for in situ, real-time monitoring. In recent years, spectroscopy-based methods have gained prominence as alternatives for water quality assessment, particularly when combined with chemometric analyses and advanced technological systems. This review provides an overview of the current advancements of spectroscopy-based water monitoring, with a focus on spectroscopy techniques operating within ultraviolet–visible (UV–Vis) and infrared (IR) spectral regions, which are currently applied for the assessment of a broad range of physicochemical and biological parameters relevant to livestock water management, including chemical oxygen demand (COD), dissolved organic carbon (DOC), nitrates, microbial contamination, and heavy metal ions. The findings highlight the growing utility of spectroscopy as a reliable tool in water quality assessment (e.g., COD detection with R2 = 0.86 and nitrate detection with R2 = 0.95 compared to traditional methods) and underpin the need for continued research into scalable, sensor-integrated solutions tailored for use in livestock farming environments. Full article
(This article belongs to the Section Water Quality and Contamination)
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29 pages, 37535 KB  
Article
Evolution of the Hydrological Regime at the Outlet of West Dongting Lake Since 1955
by Shuai Yuan, Changbo Jiang, Yuan Ma and Shanshan Li
Water 2025, 17(16), 2487; https://doi.org/10.3390/w17162487 - 21 Aug 2025
Viewed by 477
Abstract
To quantitatively evaluate the hydrological regime dynamics in West Dongting Lake over the past seven decades, this study utilizes daily average water level series (1955–2024) from key control stations (Nanzui and Xiaohezui) to analyze variations in water level and discharge through change-point detection [...] Read more.
To quantitatively evaluate the hydrological regime dynamics in West Dongting Lake over the past seven decades, this study utilizes daily average water level series (1955–2024) from key control stations (Nanzui and Xiaohezui) to analyze variations in water level and discharge through change-point detection methods, adopting the water level difference between Xiaohezui and Nanzui as a pivotal indicator of hydrological changes; the IHA–RVA framework is then applied to comprehensively assess the degree of alteration in hydrological indicators before and after identifying change points, demonstrating the following: (1) declining trends in water level/discharge at both stations—primarily attributable to reduced inflows from the Songzi and Hudu Rivers—underwent abrupt shifts in 1983 and 2003, while the water level difference displayed an increasing trend with a change point in 1991; (2) the overall degree of hydrologic alteration (DHA) was moderate, with enhanced variability during T2 (2003–2024) relative to T1 (1983–2003), notably for discharge at Nanzui and water level at Xiaohezui; (3) reduced discharge in the Songzi and Hudu Rivers primarily drives the decreased outflow from West Dongting Lake. In the Li and Yuan basins during period T1, anthropogenic factors dominated runoff alterations. During T2, anthropogenic contributions accounted for 76.27% and 48.67% of runoff changes, respectively, resulting in reduced runoff volumes under equivalent precipitation inputs. (4) Under fixed water level differences, a significant positive correlation exists between discharges at Xiaohezui and Nanzui stations. Greater discharge flows downstream through the flow channel adjacent to NZ at West Dongting Lake’s outlet. Collectively, these findings establish a technical foundation for assessing the impact of hydrological regimes and aquatic ecological security in Dongting Lake, thereby advancing sustainable water resource utilization across the basin. Full article
(This article belongs to the Special Issue Global Water Risks Across Shared River Corridors in Transboundary Basins)
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18 pages, 56966 KB  
Article
Changes in Water-Industry Load on River Water Resources in the Volga–Kama and Angara–Yenisei Reservoir Catchments Under Contemporary Global Warming
by Aleksandr G. Georgiadi, Elena A. Barabanova, Irina P. Milyukova, Pavel Y. Groisman and Alexej N. Narykov
Water 2025, 17(16), 2486; https://doi.org/10.3390/w17162486 - 21 Aug 2025
Viewed by 460
Abstract
Changes in river runoff resources, volumes of water intake from surface water sources, and discharge of wastewater into them under contemporary global warming in the basins of the Volga–Kama and Angara–Yenisei reservoirs were analyzed by comparison with the base period, characterized by colder [...] Read more.
Changes in river runoff resources, volumes of water intake from surface water sources, and discharge of wastewater into them under contemporary global warming in the basins of the Volga–Kama and Angara–Yenisei reservoirs were analyzed by comparison with the base period, characterized by colder climatic conditions and the largest volumes of water intake and wastewater discharge. The water stress index (WSI) and the index of reciprocal dilution of polluted wastewater (RDI) were examined to reveal features of the change in the water-industry load on river runoff resources in reservoir basins during the period of contemporary global warming (compared to the previous base period) as a result of climate change combined with changes in the volumes of water intake and discharge of polluted wastewater. Both indices were calculated relative to the annual free flow for years of average river flow and the flow of low-water years. The dilution factor was estimated relative to the annual total flow. 1. The basins of the Volga–Kama reservoirs are characterized by a higher level of water-industry load, which is especially noticeable in the significantly lower RDI. 2. When calculating the dilution factor relative to the annual total flow, the level of water-industry load turns out to be much lower both in the base period and in the period of contemporary global warming. 3. At the same time, under global warming conditions, the dilution level of polluted wastewater in the basins of all reservoirs exceeds the minimum required level. Full article
(This article belongs to the Special Issue Reservoir Control Operation and Water Resources Management, 2nd Edition)
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22 pages, 856 KB  
Article
Farmers’ Safe Behavior of Using Wastewater for Irrigation: The Case of Northeast Iran
by Sasan Esfandiari Bahraseman, Ali Firozzare, Arash Durandish, Hiva Khalili Mararndi, Christine Fürst, Rando Värnik, Iulia Ajtai and Hossein Azadi
Water 2025, 17(16), 2485; https://doi.org/10.3390/w17162485 - 21 Aug 2025
Viewed by 514
Abstract
In countries facing physical water shortages, the safe use of treated wastewater can increase agricultural yields. However, farmers’ willingness to reuse water in agriculture is very low. Therefore, the purpose of this study is to determine the factors that influence 217,215 Iranian farmers [...] Read more.
In countries facing physical water shortages, the safe use of treated wastewater can increase agricultural yields. However, farmers’ willingness to reuse water in agriculture is very low. Therefore, the purpose of this study is to determine the factors that influence 217,215 Iranian farmers who use treated wastewater to adopt safe irrigation practices. This study, which developed the Theory of Planned Behavior (TPB) by including risk perception (RP) and knowledge factors, is a groundbreaking endeavor in the field of the safe use of treated wastewater at the farm level in Iran and around the world. The final model analysis was conducted based on structural equation modeling (SEM). The findings reveal that attitudes, perceived behavioral control (PBC), RP, and knowledge significantly influence farmers’ behaviors regarding safe wastewater use, while subjective norms did not impact intentions. The subjective norm in this study includes the perceived social pressure by farmers (through family, friends, the farming community, and local authorities) to perform or not perform safe behavior in using treated wastewater for irrigation. Notably, PBC was the most important component in the original TPB model, because intention has a beneficial impact on behavior. In the extended model, knowledge and risk perception emerged as critical elements. Therefore, intervention policies should prioritize enhancing farmers’ knowledge, risk perception, and perceived behavioral control to promote safe treated wastewater usage. This study offers valuable insights for developing countries in agricultural practices. Full article
(This article belongs to the Section Water, Agriculture and Aquaculture)
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28 pages, 5969 KB  
Article
Geospatial Analysis of Chloride Hot Spots and Groundwater Vulnerability in Southern Ontario, Canada
by Ceilidh Mackie, Rachel Lackey and Jana Levison
Water 2025, 17(16), 2484; https://doi.org/10.3390/w17162484 - 21 Aug 2025
Viewed by 464
Abstract
Elevated chloride (Cl−) concentrations in surface water and groundwater are an increasing concern in cold region urban environments, largely due to long-term road salt application. This study investigates the Cl− distribution across southern Ontario, Canada, using geospatial methods to identify [...] Read more.
Elevated chloride (Cl−) concentrations in surface water and groundwater are an increasing concern in cold region urban environments, largely due to long-term road salt application. This study investigates the Cl− distribution across southern Ontario, Canada, using geospatial methods to identify contamination hot spots and assess groundwater vulnerability at both regional and watershed scales. Chloride data from 2001 to 2010 and 2011 to 2020 were compiled from public sources and interpolated using inverse distance weighting. A regional-scale vulnerability index was developed using slope (SL), surficial geology (SG), and land use (LU) (SL-SG-LU), and compared it to a more detailed DRASTIC-LU index within the Credit River watershed. Results show that Cl− hot spots are concentrated in urbanized areas, including the Greater Toronto Area and Golden Horseshoe, with some rural zones also exhibiting elevated concentrations. Vulnerability mapping corresponded well with the observed Cl− patterns and highlighted areas at risk for groundwater discharge to surface waters. While the DRASTIC-LU method offered finer resolution, the simplified SL-SG-LU index effectively captured broad vulnerability trends and is suitable for data-limited regions. This work provides a transferable framework for identifying Cl− risk areas and supports long-term monitoring and management strategies in cold climate watersheds. Full article
(This article belongs to the Special Issue Advances in Hydrogeological Investigations: Field Monitoring, GIS, AI, Remote Sensing, Geophysical Techniques, and Hydrochemical Analysis)
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20 pages, 1368 KB  
Article
Assessment of the Surface Water Quality of Ibrahim River (Lebanon): A Spatio-Temporal Analysis
by Sandra Chidiac, Paula El Najjar, Amine Kassouf, Naïm Ouaini, Youssef El Rayess and Desiree El Azzi
Water 2025, 17(16), 2483; https://doi.org/10.3390/w17162483 - 21 Aug 2025
Viewed by 412
Abstract
Monitoring surface water quality offers a clear understanding of its parameters over time and space. The Ibrahim River, one of the main rivers in Lebanon, was monitored over one hydrological year, from March 2021 to April 2022. Samples were collected from seven stations [...] Read more.
Monitoring surface water quality offers a clear understanding of its parameters over time and space. The Ibrahim River, one of the main rivers in Lebanon, was monitored over one hydrological year, from March 2021 to April 2022. Samples were collected from seven stations in the watershed, once every two weeks. A total of 504 samples were then analyzed for pH, conductivity, turbidity, total dissolved solids, dissolved oxygen, biochemical oxygen demand, dissolved nitrate, dissolved potassium, dissolved chloride, total alkalinity, fecal coliforms, and total coliforms. Principal Component Analysis (PCA) was able to highlight two principal components (PCs), representing spatial and temporal variations, identifying areas of pollution and the influence of flow on water quality. The adapted Water Quality Index (WQI) confirmed the PCA trend with an overall average for the entire watershed of 83.70 ± 4.97, indicating a “good” water quality. Full article
(This article belongs to the Section Water Quality and Contamination)
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20 pages, 3960 KB  
Article
Laboratory-Scale Biochar-Aerated Constructed Wetlands for Low C/N Wastewater: Standardization and Legal Cooperation from a Watershed Restoration Perspective
by Mengbing Li, Sili Tan, Jiajun Huang, Qianhui Chen and Guanlong Yu
Water 2025, 17(16), 2482; https://doi.org/10.3390/w17162482 - 21 Aug 2025
Viewed by 516
Abstract
To address the problems of eutrophication exacerbation in water bodies caused by low carbon-to-nitrogen ratio (C/N) wastewater and the limited nitrogen removal efficiency of conventional constructed wetlands, this study proposes the use of biochar (Corncob biochar YBC, Walnut shell biochar HBC, and [...] Read more.
To address the problems of eutrophication exacerbation in water bodies caused by low carbon-to-nitrogen ratio (C/N) wastewater and the limited nitrogen removal efficiency of conventional constructed wetlands, this study proposes the use of biochar (Corncob biochar YBC, Walnut shell biochar HBC, and Manure biochar FBC) coupled with intermittent aeration technology to enhance nitrogen removal in constructed wetlands. Through the construction of vertical flow wetland systems, hydraulic retention time (HRT = 1–3 d) and influent C/N ratios (1, 3, 5) were regulated, before being combined with material characterization (FTIR/XPS) and microbial analysis (16S rRNA) to reveal the synergistic nitrogen removal mechanisms. HBC achieved efficient NH4+-N adsorption (32.44 mg/L, Langmuir R2 = 0.990) through its high porosity (containing Si-O bonds) and acidic functional groups. Under optimal operating conditions (HRT = 3 d, C/N = 5), the CW-HBC system achieved removal efficiencies of 97.8%, 98.8%, and 79.6% for NH4+-N, TN, and COD, respectively. The addition of biochar shifted the dominant bacterial phylum toward Actinobacteriota (29.79%), with its slow-release carbon source (TOC = 18.5 mg/g) alleviating carbon limitation. Mechanistically, HBC synergistically optimized nitrogen removal pathways through “adsorption-biofilm (bacterial enrichment)-microzone oxygen regulation (pore oxygen gradient).” Based on technical validation, a dual-track institutionalization pathway of “standards-legislation” is proposed: incorporating biochar physicochemical parameters and aeration strategies into multi-level water environment technical standards; converting common mechanisms (such as Si-O adsorption) into legal requirements through legislative amendments; and innovating legislative techniques to balance precision and universality. This study provides an efficient technical solution for low C/N wastewater treatment while constructing an innovative framework for the synergy between technical specifications and legislation, supporting the improvement of watershed ecological restoration systems. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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26 pages, 2389 KB  
Article
Application of a Heuristic Model (PSO—Particle Swarm Optimization) for Optimizing Surface Water Allocation in the Machángara River Basin, Ecuador
by Jaime Veintimilla-Reyes, Berenice Guerrero, Daniel Maldonado-Segarra and Raúl Ortíz-Gaona
Water 2025, 17(16), 2481; https://doi.org/10.3390/w17162481 - 21 Aug 2025
Viewed by 561
Abstract
Efficient surface water allocation in reservoir-equipped basins is essential for balancing competing demands within the Water–Energy–Food (WEF) nexus. This study investigated the applicability of Particle Swarm Optimization (PSO) for optimizing water distribution in the Machángara River Basin, Ecuador; a complex, constraint-rich hydrological system. [...] Read more.
Efficient surface water allocation in reservoir-equipped basins is essential for balancing competing demands within the Water–Energy–Food (WEF) nexus. This study investigated the applicability of Particle Swarm Optimization (PSO) for optimizing water distribution in the Machángara River Basin, Ecuador; a complex, constraint-rich hydrological system. Implemented via the Pymoo package in Python, the PSO model was evaluated across calibration, validation, and execution phases, and benchmarked against exact methods, including Linear Programming (LP) and Mixed Integer Linear Programming (MILP). The results revealed that standard PSO struggled to satisfy equality constraints and yielded suboptimal solutions, with elevated penalty costs. Despite incorporating MILP-inspired encoding and repair functions, the algorithm failed to identify feasible solutions that met operational requirements. The execution phase, which includes reservoir construction decisions, resulted in a total penalty exceeding EUR 164.95 billion, with no improvement observed from adding reservoirs. Comparative analysis confirmed that LP and MILP outperformed PSO in constraint compliance and penalty minimization. Nonetheless, the study contributes a reproducible implementation framework and a comprehensive benchmarking strategy, including synthetic test functions, performance metrics, and diagnostic visualizations. These tools can facilitate systematic evaluation of PSO’s behavior in high-dimensional, nonlinear environments and provide a foundation for future hybrid or adaptive heuristic models. The findings underscore the limitations of standard PSO in hydrological optimization but also highlight its potential when enhanced through hybridization. Future research should explore PSO variants that integrate exact solvers, adaptive control mechanisms, or cooperative search strategies to improve feasibility and convergence. This work advances the methodological understanding of metaheuristics in environmental resource management and supports the development of robust optimization tools under the WEF-nexus paradigm. Full article
(This article belongs to the Section Water Resources Management, Policy and Governance)
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18 pages, 9431 KB  
Article
Modeling Hydraulic Transient Process in Long-Distance Water Transfer Systems Using a MUSCL-Type FVM Approach
by Yifei Li and Jijian Lian
Water 2025, 17(16), 2480; https://doi.org/10.3390/w17162480 - 20 Aug 2025
Viewed by 429
Abstract
To gain deeper insights into the influence of pipe parameters on water hammer properties and achieve the accurate simulation of the hydraulic transient process in pipeline systems, the Finite Volume Method (FVM) is adopted. The solution scheme, incorporating a second-order MUSCL-type reconstruction, is [...] Read more.
To gain deeper insights into the influence of pipe parameters on water hammer properties and achieve the accurate simulation of the hydraulic transient process in pipeline systems, the Finite Volume Method (FVM) is adopted. The solution scheme, incorporating a second-order MUSCL-type reconstruction, is derived, and the numerical solution process is detailed. For enhanced accuracy, the unsteady friction term is included in the numerical solution of the governing water hammer equations. The method is validated through a comparison with experimental data and the verification of mesh and Courant number independence, confirming both its efficiency and accuracy. The calculation error of the peak water head is less than 5%. Finally, an engineering case is studied to investigate valve arrangement and operation. Optimization yields the optimal valve position and operating parameters. This analysis provides valuable reference for pipeline system design. Full article
(This article belongs to the Section Hydraulics and Hydrodynamics)
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27 pages, 6596 KB  
Article
A Practical Model Framework for Describing the Flow of Nitrogen and Phosphorus in a Cascade Reservoir Watershed
by Han Ding, Long Han, Zeli Li, Tong Han, Wei Jiang, Gelin Kang and Qiulian Wang
Water 2025, 17(16), 2479; https://doi.org/10.3390/w17162479 - 20 Aug 2025
Viewed by 381
Abstract
The construction of cascade reservoir systems (CRSs) is increasing globally, providing reliable energy and water resources for human social development, while also having significant impacts on the watershed water environment, particularly in terms of nitrogen and phosphorus distribution in the rivers and lakes [...] Read more.
The construction of cascade reservoir systems (CRSs) is increasing globally, providing reliable energy and water resources for human social development, while also having significant impacts on the watershed water environment, particularly in terms of nitrogen and phosphorus distribution in the rivers and lakes of these areas. Watershed management authorities urgently need model tools that can comprehensively analyze the sources of nitrogen and phosphorus in CRSs and the nitrogen and phosphorus cycling in lakes and reservoirs. Therefore, this study establishes a model framework that includes a watershed nutrient load model and a hierarchical reservoir nutrient cycling model, validating and analyzing this framework in the Water Diversion Basin from the Luanhe River to Tianjin (WDBLT) in North China, which yields nitrogen and phosphorus substance flows over different time scales. The conclusions show that banning cage culture and curbing point sources improved reservoir water quality, and the internal TP flux serves as a key environmental indicator. This model framework is scientifically sound, easy to operate, and does not require high data demands, demonstrating high practical value for similar water environmental management in CRS. Full article
(This article belongs to the Section Hydraulics and Hydrodynamics)
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25 pages, 3791 KB  
Review
A Review of Modification of Carbon-Based Materials Based on Defect Engineering in Capacitive Deionization
by Yubo Zhao, Rupeng Liu, Jinfeng Fang, Feiyong Chen and Silu Huo
Water 2025, 17(16), 2478; https://doi.org/10.3390/w17162478 - 20 Aug 2025
Viewed by 422
Abstract
Capacitive deionization (CDI) is a novel water treatment technology based on the principle of double-electric-layer adsorption, which stores ions in the solution on the surface of electrodes by applying a low potential difference to achieve desalination. CDI has the advantages of low operating [...] Read more.
Capacitive deionization (CDI) is a novel water treatment technology based on the principle of double-electric-layer adsorption, which stores ions in the solution on the surface of electrodes by applying a low potential difference to achieve desalination. CDI has the advantages of low operating voltage (<1.2 V), small equipment footprint, low energy consumption, low cost and environmental friendliness. The performance of CDI is heavily dependent on the electrode materials. Carbon-based materials are widely used in CDI systems because of the large specific surface areas, lower price, and remarkable stability. To improve the CDI performance, extensive research efforts have been made for the modification of carbon-based materials. Defects in carbon-based materials play an important role in electrochemical processes and the introduction of defects is an important method to modify carbon-based materials. However, there is a lack of systematic summary of modification of carbon-based materials through introducing defects in CDI system. Therefore, this study makes the first attempt to review the modification of carbon-based materials of CDI based on defect engineering. The mechanism of enhancing CDI performance of carbon-based materials with the induction of different defects is analyzed and the future research prospects are proposed. Full article
(This article belongs to the Special Issue Application of Electrochemical Technology for Water and Wastewater Treatment)
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19 pages, 3672 KB  
Article
Analysis of Fishery Resource Distribution and Seasonal Variations in the East China Sea: Utilizing Trawl Surveys, Environmental DNA, and Scientific Echo Sounders
by Sara Lee, Jung Kwan Lee, Guenchang Park, Wooseok Oh and Kyounghoon Lee
Water 2025, 17(16), 2477; https://doi.org/10.3390/w17162477 - 20 Aug 2025
Viewed by 427
Abstract
Assessing fishery resources is crucial for sustainable marine ecosystem management and the operation of fisheries. This study integrates trawl surveys, environmental DNA (eDNA) analysis, and scientific echo sounder techniques to analyze the fishery resource distribution of and seasonal variations in the East China [...] Read more.
Assessing fishery resources is crucial for sustainable marine ecosystem management and the operation of fisheries. This study integrates trawl surveys, environmental DNA (eDNA) analysis, and scientific echo sounder techniques to analyze the fishery resource distribution of and seasonal variations in the East China Sea. Surveys were conducted in April, July, August, and November 2022, utilizing bottom trawl sampling, eDNA metabarcoding, and acoustic data collection. The results revealed temporal differences in species composition, with crustaceans dominating in terms of abundance and fish species in biomass. The integration of eDNA analysis provided broader species detection, including cryptic and pelagic species, while acoustic techniques enabled large-scale resource assessment. However, discrepancies between methods highlighted the need for methodological refinement. Dominant species exhibited seasonal variation, with Portunus trituberculatus prevailing in spring (April), Trachurus japonicus and Scomber japonicus in summer (July–August), and Pampus argenteus in late autumn (November). A comparative analysis revealed that eDNA is sensitive to pelagic and cryptic species, trawl surveys effectively detect demersal fish, and acoustics allow for broad-scale biomass estimation, highlighting the complementary value of method integration. Full article
(This article belongs to the Section Oceans and Coastal Zones)
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22 pages, 4209 KB  
Article
Applied Hydrogeological Assessment and GIS-Based Modeling of Transboundary Aquifers in the Shu River Basin
by Sultan Tazhiyev, Yermek Murtazin, Valentina Rakhimova, Issa Rakhmetov, Dinara Adenova, Kalamkas Koshpanova, Yevgeniy Sotnikov, Makhabbat Abdizhalel, Aigerim Akylbayeva and Darkhan Yerezhep
Water 2025, 17(16), 2476; https://doi.org/10.3390/w17162476 - 20 Aug 2025
Viewed by 442
Abstract
Groundwater is a strategically important source of drinking water supply in the arid and rural regions of Kazakhstan. The objective of this study is to assess the quality of groundwater at 11 water intakes located in the Kordai, Shu, and Merke Districts of [...] Read more.
Groundwater is a strategically important source of drinking water supply in the arid and rural regions of Kazakhstan. The objective of this study is to assess the quality of groundwater at 11 water intakes located in the Kordai, Shu, and Merke Districts of the Shu transboundary basin in the Zhambyl Region. A comprehensive assessment of physicochemical parameters was performed, including concentrations of nitrates, sulfates, chlorides, iron, manganese, and other constituents, with subsequent comparison against regulatory limits defined by Order No. 26 of the Ministry of Health of the Republic of Kazakhstan (dated 20 February 2023), GOST standards, and ST RK ISO standards. The findings revealed that a number of water intakes exceeded the maximum allowable concentrations for specific indicators, especially in areas subject to significant anthropogenic pressure. The most vulnerable sources were identified near settlements characterized by intensive agricultural practices and inadequate wastewater treatment systems. Spatial comparison of the results enabled the identification of potentially contaminated areas as well as aquifer zones suitable for drinking water supply. The study emphasizes the importance of regular groundwater monitoring and spatial analysis techniques (GIS) to enhance the reliability and comprehensiveness of water quality assessments. The data obtained in this study can serve as a basis for informed decision-making in the area of water resource protection and contribute to the achievement of United Nations Sustainable Development Goal 6 (SDG 6)—to ensure availability and sustainable management of water and sanitation for all. Full article
(This article belongs to the Special Issue Assessment of Groundwater Quality and Pollution Remediation)
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28 pages, 3117 KB  
Article
Water Vulnerability in Dhaka, Narayanganj, and Gazipur Districts of Bangladesh: The Role of Textile Dye Production
by Kamille Hüttel Rasmussen, Martiwi Diah Setiawati and Kamol Gomes
Water 2025, 17(16), 2475; https://doi.org/10.3390/w17162475 - 20 Aug 2025
Viewed by 752
Abstract
Water and chemical use in textile dye production are exacerbating water pollution and extraction across Dhaka, Narayanganj, and Gazipur in Bangladesh, where these industries are concentrated. However, the ability to cope with water-related challenges is influenced by multiple factors. This study applies descriptive [...] Read more.
Water and chemical use in textile dye production are exacerbating water pollution and extraction across Dhaka, Narayanganj, and Gazipur in Bangladesh, where these industries are concentrated. However, the ability to cope with water-related challenges is influenced by multiple factors. This study applies descriptive spatial analysis to map textile dye clusters, river pollution, and water insecurity. As vulnerability is multidimensional and fluctuates across subdistricts, this study develops a Water Vulnerability Index (WVI) consisting of 25 indicators across demographics, socioeconomics, gender, health, WASH, and climate dimensions. The index is based on Multidimensional Vulnerability Assessment (MDVA) and constructed through multicriteria analysis (MCA). The study highlights that the Shitalakhya, Turag-Tongi Khal, Buriganga, and Balu Rivers are highly polluted, with average biochemical oxygen demand (BOD), chemical oxygen demand (COD), and dissolved oxygen (DO) levels exceeding safe limits. Central Dhaka is identified as being extremely water insecure, characterized by significant inequalities in water insecurity across subdistricts. The WVI finds that Gazipur Sadar and Kaliakair subdistricts, housing several textile dye factories, face the highest water vulnerability of the 57 subdistricts. This study furthers the case that Dhaka, Narayanganj, and Gazipur host numerous textile hubs, confront serious water challenges, such as river pollution and water insecurity, and are marked by significant spatial disparities in vulnerability. By exploring anthropogenic pollution alongside multidimensional water vulnerability, this study can inform targeted policy responses, such as stricter regulatory limits, more frequent monitoring and enforcement, and tailored support in high-vulnerability areas. Full article
(This article belongs to the Special Issue Advancing Knowledge of the Impacts of Contaminants in Aquatic Environments)
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15 pages, 5895 KB  
Article
Optimal Control of Iron Release in Drinking Water Distribution Systems Fed with Desalinated Water
by Yongjia Feng, Hui Zhang, Peixin Jia, Mingzhou Fan, Tao Wan, Yimeng Ji and Jingyu Zhu
Water 2025, 17(16), 2474; https://doi.org/10.3390/w17162474 - 20 Aug 2025
Viewed by 446
Abstract
When desalinated water enters the existing drinking water distribution systems (DWDSs), the balance between water and scale will be destroyed, resulting in the release of iron and water quality problems, causing “yellow water”. This study investigated the inhibitory effects of pH, alkalinity, and [...] Read more.
When desalinated water enters the existing drinking water distribution systems (DWDSs), the balance between water and scale will be destroyed, resulting in the release of iron and water quality problems, causing “yellow water”. This study investigated the inhibitory effects of pH, alkalinity, and phosphate on iron release and the optimal control condition using pipe section reactors with a response surface. For steel pipe, the optimal condition for iron release control was pH = 8.5, alkalinity = 250 mg/L CaCO3, and phosphate = 0.1 mg/L. For cast iron pipe, the optimal condition was pH = 8.0, alkalinity = 250 mg/L CaCO3, and phosphate = 0.1 mg/L. This study can provide theoretical support for subsequent water supply safety and lay a foundation for the water supply safety of the municipal pipe network. Full article
(This article belongs to the Special Issue Monitoring and Assessment of Water Quality in Drinking Water Distribution Systems)
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22 pages, 2865 KB  
Article
A Three-Dimensional Evaluation Method for the Metabolic Interaction System of Industrial CO2 and Water Pollution
by Yueqing Yang, Liangliang Wu, Xingjie Lin, Xiaosong Yang, Xuegang Gong, Yu Miao, Mengyu Zhai, Yong Niu, Mingke Luo, Xia Jiang and Jia Wang
Water 2025, 17(16), 2473; https://doi.org/10.3390/w17162473 - 20 Aug 2025
Viewed by 435
Abstract
The inherent complexity of modern supply chains obscures significant hidden CO2 and Water Pollution Equivalent (WPE) emissions, presenting mounting challenges for integrated environmental governance. While prior research has largely treated carbon and water pollution metabolic systems in isolation, this study addresses the [...] Read more.
The inherent complexity of modern supply chains obscures significant hidden CO2 and Water Pollution Equivalent (WPE) emissions, presenting mounting challenges for integrated environmental governance. While prior research has largely treated carbon and water pollution metabolic systems in isolation, this study addresses the critical gap in understanding their bidirectional interactions under socioeconomic dynamics. We develop a novel Three-Dimensional Evaluation Method for the Metabolic Interaction System of Industrial CO2 and Water Pollution (TDE-ISCW). This framework integrates Environmental Input–Output Analysis and Ecological Network Analysis to: (1) identify key industrial sectors and utility relationships within individual CO2 and WPE systems; (2) quantify the mutual disturbance responses between the CO2 and WPE metabolic systems through changes in sectoral emissions/output, inter-sectoral relationships, and sector–system linkages; and (3) propose optimized industrial restructuring strategies for synergistic pollution and carbon reduction. Applied to the highly industrialized Yangtze River Economic Belt, key findings reveal: (i) substantial upstream dependency, exemplified by Advanced Equipment Manufacturing’s 95.7% indirect CO2 emissions; (ii) distinct key sectors for CO2 (e.g., MOO, FTO, MNM) and WPE (e.g., MPM, OTH, FTO) reduction based on competitive relationships; and (iii) complex trade-offs, where emission reductions in one system (e.g., CO2 via FTO restructuring) can trigger heterogeneous responses in the other (e.g., altered WPE influence or downstream CO2/economic shifts). The TDE-ISCW framework provides actionable insights for designing coordinated, adaptive emission reduction policies that account for cascading cross-system effects, ultimately supporting regional industrial upgrading and resource efficiency goals. Future research should incorporate temporal dynamics and full industrial–metabolic cycles. Full article
(This article belongs to the Section Water-Energy Nexus)
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16 pages, 1942 KB  
Article
Ultrasonic Inactivation of Escherichia coli with Multi-Walled Carbon Nanotubes: Effects of Solution Chemistry
by Dong Chen and Elisa I. Chen
Water 2025, 17(16), 2472; https://doi.org/10.3390/w17162472 - 20 Aug 2025
Viewed by 454
Abstract
Disinfection by ultrasound and carbon nanotubes (CNTs) provides attractive alternatives to conventional methods for water and wastewater treatment. This study explored the inactivation of Escherichia coli (E. coli) by 5 mg/L pristine short and long multi-walled CNTs (MWCNTs) and 20 kHz [...] Read more.
Disinfection by ultrasound and carbon nanotubes (CNTs) provides attractive alternatives to conventional methods for water and wastewater treatment. This study explored the inactivation of Escherichia coli (E. coli) by 5 mg/L pristine short and long multi-walled CNTs (MWCNTs) and 20 kHz ultrasound individually or in combinations in DI water, Suwannee River natural organic matter (SRNOM), and sodium dodecyl sulfate (SDS) solution, respectively. The results indicated that the dispersity of MWCNTs was the single most important factor determining the inactivation rate of E. coli. The dispersity of short MWCNTs in solutions increased in the order of DI water <10 mgC/L SRNOM < 2 mM SDS. Correspondingly, the greatest log inactivation of E. coli was achieved in SDS when short MWCNTs were used alone (0.67 ± 0.12) and combined with ultrasound (1.80 ± 0.02) for 10 min. Short MWCNTs alone had a slightly greater inactivation (0.29 ± 0.07) in SRNOM solution than in DI water (0.18 ± 0.05). However, long MWCNTs had a slightly higher inactivation in DI water (0.24 ± 0.03) than short ones (0.18 ± 0.05), because of better dispersity in DI. The observed synergistic inactivation when ultrasound and short MWCNTs were used together in 2 mM SDS shows that ultrasound energized the MWCNTs more effectively when they were well dispersed, although SDS and MWCNTs can occupy the reaction sites at the cavitational bubble–water interfacial regions and scavenge •OH radicals. The results suggest that sonophysical effects are more important to inactivate E. coli than sonochemical effects. Ultrasound inactivates E. coli and/or energizes MWCNTs through the mechanisms of acoustic streaming, microstreaming, microstreamers, transient cavitation collapse-generated shock waves and microjets (transitional forms), and localized hot temperatures. The results of this study indicate that the cytotoxicity of CNTs includes impinging bacterial cells and/or direct contact with the bacteria. Full article
(This article belongs to the Special Issue Membrane Processes and Advanced Oxidation Processes for Wastewater Treatment)
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21 pages, 5044 KB  
Article
Numerical Study of Downstream Sediment Scouring of the Slotted Roller Bucket System
by Payam Heidarian, Seyed Ali Akbar Salehi Neyshabouri, Alireza Khoshkonesh, Rouzbeh Nazari, Saeid Okhravi and Silvia Di Francesco
Water 2025, 17(16), 2471; https://doi.org/10.3390/w17162471 - 20 Aug 2025
Viewed by 454
Abstract
Slotted roller buckets are energy dissipator structures designed to reduce the destructive power of high-velocity water flows in spillways, protecting downstream environments. This study aimed to estimate the critical role of slotted roller bucket design in downstream scour mitigation and hydraulic energy dissipation. [...] Read more.
Slotted roller buckets are energy dissipator structures designed to reduce the destructive power of high-velocity water flows in spillways, protecting downstream environments. This study aimed to estimate the critical role of slotted roller bucket design in downstream scour mitigation and hydraulic energy dissipation. The three-dimensional Navier–Stokes (N-St) equations were solved to simulate the jet flow over the roller bucket using CFD software. The free surface volume tracking using the volume of fluid (VOF) and non-equilibrium sediment transport equations was coupled with N-St to model the local scour downstream of the roller bucket system. Subsequently, the impact of bucket tooth lip angles, tailwater depth, and bucket radius on downstream scour were examined in a numerical 3D framework. The results showed that the 45- to 55-degree lip angle configuration significantly reduced the maximum scour depth by approximately 36%. Furthermore, the study quantified the effects of tailwater depth and bucket radius on scour dimensions and flow patterns. The optimal tailwater depth reduced scour depth by approximately 20% compared with the worst case, while variations in bucket radius led to more than a 50% difference in scour depth. We identified specific ranges for these parameters that further minimized erosion potential. The research also underscored the influence of transverse mixing on surging depth, revealing a crucial mechanism for energy dissipation. These findings contributed to a deeper understanding of the complex interplay between design parameters and scour. It offered practical insights for optimizing and operating hydraulic structures sustainably and understanding the scouring processes downstream of the dams. Full article
(This article belongs to the Section Water Erosion and Sediment Transport)
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25 pages, 1969 KB  
Article
Coastal Wetland Management and Restoration: Importance of Abiotic Factors and Vegetation for Healthy Fish Communities in the Laurentian Great Lakes
by Daniel J. Moore and Nicholas E. Mandrak
Water 2025, 17(16), 2470; https://doi.org/10.3390/w17162470 - 20 Aug 2025
Viewed by 494
Abstract
Coastal wetlands in the Laurentian Great Lakes of North America are under increasing stress due to numerous threats. Restoration and management of the remaining wetlands are necessary to ensure that ecosystem functions, critical for fisheries, persist. This study used long-term monitoring datasets for [...] Read more.
Coastal wetlands in the Laurentian Great Lakes of North America are under increasing stress due to numerous threats. Restoration and management of the remaining wetlands are necessary to ensure that ecosystem functions, critical for fisheries, persist. This study used long-term monitoring datasets for one of the Laurentian Great Lakes, Lake Ontario, including 138 sampling events from 31 different wetlands, to examine the relationship between fish community health and select abiotic and vegetation habitat variables. Eight of 13 habitat variables were found to have significant relationships with fish community health, including total, submerged, and emergent vegetation; submerged aquatic vegetation IBI; water depth; turbidity; conductivity; and water-quality index. Ranges for each significant variable were summarized for each fish community health group to provide guidance when diagnosing impairment or setting restoration goals. An ordination of the fish and environmental data revealed high amounts of variation at sites with poor fish community health relative to excellent health, suggesting a multimetric approach provides valuable insight into community variability. The results from this study provide additional information and alternative methods for assessment of current conditions, target setting, and restoration success assessment for coastal wetland managers. Full article
(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)
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18 pages, 3629 KB  
Article
Nutrient Distribution Characteristics and Eutrophication Evaluation of Coastal Water near the Yellow River Estuary, China
by Jing Xiao, Xiang Chen, Li Zhou, Haibo Zhang, Xiaoshuai Hang and Yudong Chen
Water 2025, 17(16), 2469; https://doi.org/10.3390/w17162469 - 20 Aug 2025
Viewed by 508
Abstract
Coastal ecosystems have faced escalating environmental degradation in recent years, with eutrophication and nutrient imbalances emerging as critical concerns, particularly in estuarine regions. Understanding the spatiotemporal dynamics of key nutrients, including dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and silicate (SiO3 [...] Read more.
Coastal ecosystems have faced escalating environmental degradation in recent years, with eutrophication and nutrient imbalances emerging as critical concerns, particularly in estuarine regions. Understanding the spatiotemporal dynamics of key nutrients, including dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and silicate (SiO3-Si), is essential for effective coastal management. This study examines the spatial and seasonal variations in these nutrients across 36 sampling sites in the Yellow River estuary from 2016 to 2018. Results indicate that DIN was the primary contributor to water quality degradation, with more than 27% of sampling sites exceeding the Class II seawater quality standard in 2018. Nutrient concentrations were notably elevated near the estuary. The eutrophication index (EI) revealed predominantly mild-to-moderate eutrophication levels throughout the study area. The study area exhibited a widespread phosphorus (P) limitation, with 44.4–94.4% of coastal waters experiencing P-restricted eutrophication. The N/P ratio significantly exceeded the Redfield ratio (16), indicating a pronounced nutrient imbalance. Furthermore, SiO3-Si concentrations displayed a declining trend, highlighting the need for balanced nutrient management alongside eutrophication mitigation. Full article
(This article belongs to the Special Issue Water Quality Studies: Assessing the Presence of Nutrients and Pollutants)
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17 pages, 1472 KB  
Article
Bioremediation of Bacteria in Constructed Wetlands: Role of Endophytic and Rhizosphere Fungi
by Richwell Alufasi, Walter Chingwaru, Cuthbert J. Zvidzai, Nancy Musili, Ereck Chakauya, Phiyani Lebea, Marvelous Goredema, Rudo Zhou, Alexandros I. Stefanakis and Wilson Parawira
Water 2025, 17(16), 2468; https://doi.org/10.3390/w17162468 - 20 Aug 2025
Viewed by 677
Abstract
Constructed wetlands are increasingly recognised for their potential in wastewater treatment, particularly in the removal of pathogenic microorganisms. However, the mechanisms of removal are not fully understood. This study investigated the role of endophytic and rhizosphere fungi and associated secondary metabolites in the [...] Read more.
Constructed wetlands are increasingly recognised for their potential in wastewater treatment, particularly in the removal of pathogenic microorganisms. However, the mechanisms of removal are not fully understood. This study investigated the role of endophytic and rhizosphere fungi and associated secondary metabolites in the removal of pathogenic bacteria from wastewater. Endophytic and rhizosphere fungi were isolated from roots of wetland macrophytes (T. latifolia, C. papyrus and P. mauritianus) and screened for their antimicrobial effects on E. coli, Shigella spp., Salmonella spp. and Vibrio spp. Secondary metabolites were extracted from fungal isolates (broth cultures) and tested for their antibacterial activity as a possible mechanism of pathogen removal. Antimicrobial activity of the fungi and their metabolites, measured as zones of inhibition, was analysed using ANOVA at a 5% significance level. Active secondary metabolites were identified using GC-MS techniques. Four fungal isolates (three endophytic, one rhizospheric) from the genus Candida exhibited antimicrobial activity against E. coli, Salmonella spp., Shigella spp. and Vibrio spp. in vitro. There were significant differences in inhibition zones (p < 0.0001) between the different species of fungi. Fungus RTGRS did not show any antibacterial activity on Vibrio spp. and Shigella spp. but showed the highest zones of inhibition of 21.17 ± 0.75 against Salmonella spp. This study demonstrated that the selected wetland macrophytes harbour both endophytic and rhizosphere fungi that can produce bioactive compounds that have antimicrobial properties, inhibiting the growth of pathogenic bacteria E. coli, Salmonella spp., Shigella spp. and Vibrio spp., contributing to pathogen removal in CWs. The findings have implications for the design and operation of CWs, as it is important to select macrophytes that harbour fungi with antimicrobial properties. More research is needed on the use of these fungi in wastewater treatment in full-scale CWs. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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