Water

21 pages, 2619 KiB

Open AccessArticle

Evaluating Agro-Based Waste Materials for Cyanotoxin Sorption for Future Incorporation in Nature-Based Solution Units (NBSUs)

by Guna Bavithra, Joana Azevedo, Alexandre Campos, C. Marisa R. Almeida and Pedro N. Carvalho

Water 2025, 17(2), 285; https://doi.org/10.3390/w17020285 - 20 Jan 2025

Viewed by 391

Abstract

Toxic cyanobacterial blooms are a growing environmental problem, persisting in freshwater bodies globally, and potentially hazardous to populations that rely on surface freshwater supplies. Nature-based solution units (NBSUs) are effective and sustainable approaches for water treatment, with sorption being an important process. The [...] Read more.

Toxic cyanobacterial blooms are a growing environmental problem, persisting in freshwater bodies globally, and potentially hazardous to populations that rely on surface freshwater supplies. Nature-based solution units (NBSUs) are effective and sustainable approaches for water treatment, with sorption being an important process. The purpose of this study was to evaluate unmodified agro-based waste materials (rice husks, olive pulp pomace pellets (OP), cork granules) and the benchmark NBSU substrates (biochar, light expanded clay aggregate (LECA), and sand) for their microcystin-LR (MC-LR) and cylindrospermopsin (CYN) sorption potential. The kinetics and sorption mechanism of the two best sorbent materials were studied for future incorporation into NBSUs. Pre-screening of the sorbents showed highest sorption with biochar (>86% MC-LR and >98% CYN) and LECA (78% MC-LR and 80% CYN) and lower sorption with rice husk (<10%), cork (<10%), and sand (<26%). Leaching from OP made them unsuitable for further use. The sorption of both the cyanotoxins onto biochar was rapid (8 h), whereas onto LECA it was steadier (requiring 48 h for equilibrium). The pseudo-second-order kinetic model fit the sorption of both cyanotoxins onto biochar and LECA (R²: 0.94–0.99), suggesting that the sorption rate is limited by chemisorption. The sorption of MC-LR and CYN to biochar and LECA fit the Freundlich and D–R models better, suggesting multilayer sorption, high heterogeneity, and porosity in the sorbents (which was also confirmed by SEM/EDS). The sorption capacity was observed to be higher for biochar (K_f: MC-LR = 0.05, CYN = 0.16) than LECA (K_f: MC-LR = 0.02, CYN = 0.01). Full article

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

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15 pages, 3002 KiB

Open AccessArticle

Coadsorption of Tetracycline and Copper(II) by KOH-Modified biomass and biochar Derived from Corn Straw in aqueous Solution

by Yiping Guo, Qianqian Zhang, Weijie Feng, Shihang Ni and Guoting Li

Water 2025, 17(2), 284; https://doi.org/10.3390/w17020284 - 20 Jan 2025

Viewed by 443

Abstract

The coexistence of antibiotics and heavy metals in water environments always results in greater toxicity compared to the single pollution. Consequently, the development of efficient and economical technologies for the removal of antibiotics and heavy metals is essential. This study prepared KOH-modified biomass [...] Read more.

The coexistence of antibiotics and heavy metals in water environments always results in greater toxicity compared to the single pollution. Consequently, the development of efficient and economical technologies for the removal of antibiotics and heavy metals is essential. This study prepared KOH-modified biomass (KCS) and KOH-modified biochar (KCSB) for the coadsorption of tetracycline (TC) and Cu(II) in an aqueous solution. The removal performance and mechanism of TC and Cu(II) are to be explored through single-system and binary-system studies, adsorption isotherms, and kinetic models. The results indicate a synergistic effect between TC and Cu(II); the maximum adsorption capacity of KCS for TC and Cu(II) is 107.97 mg/g and 58.44 mg/g, respectively. Meanwhile, KCSB exhibits a maximum adsorption capacity of 109.32 mg/g for TC and 116.61 mg/g for Cu(II). The synergistic removal mechanism of TC and Cu(II) involved pore filling, hydrogen bonding, surface complexation, π–π interaction, ion exchange, and precipitation. Among them, KCS and KCSB have stronger π–π interactions with TC than ion exchange with Cu(II), while KCSB has stronger surface complexation and ion exchange with Cu(II) than KCS. This study provides a more cost-effective biomass adsorbent material for simultaneous removal of TC and Cu(II). Full article

(This article belongs to the Special Issue Green and Low Carbon Development of Water Treatment Technology, 2nd Edition)

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21 pages, 13227 KiB

Open AccessArticle

Dynamic Characteristics and Environmental Driving Factors of Phytoplankton Communities in Plateau Rivers: The Case of the Lhasa River

by Su-Xing Fu, Qiu-Fu Huang, Jun-Ting Li, He Gao, Fei Liu, Yu-Ting Duan, He-Jiao Li, Yin-Hua Zhou, Rong-Rong Liao, Luo Lei, Jian Su, Chao-Wei Zhou and Hai-Ping Liu

Water 2025, 17(2), 283; https://doi.org/10.3390/w17020283 - 20 Jan 2025

Viewed by 456

Abstract

The dynamic changes in plateau river ecosystems and the driving mechanisms of environmental factors have garnered significant attention. Phytoplankton, a core component of aquatic ecosystems, can directly reflect changes in the aquatic environment. This study focuses on the phytoplankton in the Lhasa River [...] Read more.

The dynamic changes in plateau river ecosystems and the driving mechanisms of environmental factors have garnered significant attention. Phytoplankton, a core component of aquatic ecosystems, can directly reflect changes in the aquatic environment. This study focuses on the phytoplankton in the Lhasa River Basin, including the riverbed from the source to the river mouth, five largest tributaries, and two adjacent wetlands. We analyzed the spatial and temporal variation characteristics of phytoplankton and explored the environmental driving mechanisms based on four field surveys conducted between September 2019 and March 2021. Results showed that a total of 127 species of phytoplankton from six algal phyla were identified, including Cyanobacteria. Among these, Bacillariophyta was the dominant group, accounting for 41.7% of the identified species. Spatially, phytoplankton diversity showed a decreasing trend from upstream to downstream while temporally peaking in spring and autumn. Redundancy analysis revealed that upstream phytoplankton were driven by total hardness and altitude, midstream by pH and potassium ions, and downstream by nitrate and ammonium nitrogen. Classification and regression tree analysis showed total hardness, magnesium ions, and nitrite were key factors influencing phytoplankton abundance, diversity, and evenness. This study highlights the ecological dynamics and driving mechanisms of phytoplankton communities in the Lhasa River, demonstrating their high sensitivity to environmental factors. These findings could help to establish phytoplankton as critical indicators of aquatic ecosystem health and provide scientific guidance for the conservation and management of the plateau river ecosystems. Full article

(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)

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12 pages, 2781 KiB

Open AccessArticle

Quantile-Based Approach for Improving the Identification of Preferential Groundwater Networks

by Massimiliano Schiavo

Water 2025, 17(2), 282; https://doi.org/10.3390/w17020282 - 20 Jan 2025

Viewed by 366

Abstract

Identifying preferential paths for groundwater flow is one of the basics for understanding aquifer systems. Shallow free-surface aquifers often have flow directions (locally) similar to those of their surface counterparts, especially if surface and groundwater bodies are directly connected. This work proposes a [...] Read more.

Identifying preferential paths for groundwater flow is one of the basics for understanding aquifer systems. Shallow free-surface aquifers often have flow directions (locally) similar to those of their surface counterparts, especially if surface and groundwater bodies are directly connected. This work proposes a novel and simple framework to improve the identification of Preferential Groundwater Networks in free-surface aquifers. This is possible by proposing a quantile mapping procedure borrowed from stochastic hydrology, usually employed to adjust rainfall simulations (for example, achieved via climate models) upon available gauge-based data. This well-known procedure is applied to redistribute simulations of the aquifer bottom elevation for a real case study in Lombardy, Northern Italy. The result is a spatial redistribution of the elevation quantiles that leads to aquifer bottom surfaces carved with Preferential Groundwater Networks that are spatially consistent with the surface river network. This way, groundwater flow directions are redistributed to mimic their surface counterparts, but aquifer bottom elevations and slopes are far gentler as they were previously simulated from borehole data information. Furthermore, the errors in the spatial reframing of borehole data and the discrepancy of variogram structures before and after the redistribution procedure are not dramatically dissimilar. Full article

(This article belongs to the Section Hydrogeology)

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18 pages, 3397 KiB

Open AccessArticle

Dialdehyde Cellulose Fabric Membranes Enable Chemical Adsorption of Amino-Containing Dyes for Wastewater Treatment

by Zhaoju Zhang, Hongyang Ma and Benjamin S. Hsiao

Water 2025, 17(2), 281; https://doi.org/10.3390/w17020281 - 20 Jan 2025

Viewed by 506

Abstract

Dialdehyde cellulose fabric (DACF) membranes with varying degrees of oxidation were fabricated using periodate oxidation and were employed for the chemical adsorption of amino-groups containing dyes from wastewater. The aldehyde group contents of DACF membranes were adjusted by altering oxidation time, which was [...] Read more.

Dialdehyde cellulose fabric (DACF) membranes with varying degrees of oxidation were fabricated using periodate oxidation and were employed for the chemical adsorption of amino-groups containing dyes from wastewater. The aldehyde group contents of DACF membranes were adjusted by altering oxidation time, which was confirmed by titration experiments. The chemical structure and morphology of DACF membranes were characterized using ATR-FTIR, TGA, SCA, SEM, XPS, and XRD measurements. The optimized DACF membrane, which was treated for an oxidation time of 24 h and has an aldehyde content of 2.97 mmol/g, was used for the chemical adsorption of amino-containing dye molecules. This process relies on the Schiff base reaction between the amino groups of the target dye molecule and the aldehyde groups of the membrane. Two typical cationic dyes, fuchsin basic and chrysoidine, containing aromatic amino groups, were chosen to determine the adsorption capacity of the DACF membrane. The adsorption kinetics, isotherms, and thermal dynamics of the DACF membrane were investigated comprehensively, while both pseudo-first- and pseudo-second-order kinetics models fit well, indicating the complicated chemical/diffusion adsorption process, where the hydrophobic properties of the DACF membrane retarded the adsorption rate. The maximum adsorption capacities of the DACF membrane against fuchsin basic and chrysoidine were 108.69 and 46.29 mg/g, respectively, as determined by Langmuir isotherm simulations. Various competing ions such as Na⁺, Ca²⁺, Cl⁻, and SO₄²⁻ at high concentrations of 10,000 ppm were used to challenge the adsorption capability of the DACF membrane, with negligible effects observed. A new adsorption mechanism based on chemical/diffusion interaction was proposed. Bovine serum albumin (BSA), fuchsin basic, and chrysoidine were mixed to simulate the multicomponent wastewater containing dissolved organic nitrogen (DON) and demonstrated the adsorption process; the direct adsorption capacity of the DACF membrane was up to 63.0%. This work offers a new method for the highly efficient removal of organic pollutants by a chemical reaction approach. Full article

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20 pages, 943 KiB

Open AccessArticle

Sustainability of Water, Sanitation, and Hygiene (WASH) in Post-Emergency Contexts: A Conceptual Framework

by Hala Al-Hamawi, Philip A. Davies, Mohammad Mayouf and Anastasia Nikologianni

Water 2025, 17(2), 280; https://doi.org/10.3390/w17020280 - 20 Jan 2025

Viewed by 540

Abstract

In refugee camps, Water, Sanitation, and Hygiene (WASH) services are essential for health and well-being, yet they face sustainability challenges in post-emergency contexts. Despite considerable research on WASH services in urban and rural areas, a gap exists in addressing sustainability within refugee camps. [...] Read more.

In refugee camps, Water, Sanitation, and Hygiene (WASH) services are essential for health and well-being, yet they face sustainability challenges in post-emergency contexts. Despite considerable research on WASH services in urban and rural areas, a gap exists in addressing sustainability within refugee camps. This study fills that gap by proposing a framework for evaluating WASH system sustainability in such settings. Through a convergent mixed methods research design, sustainability dimensions, metrics, and indicators were first identified via a literature review. These were then validated through expert interviews. The study applies a five-dimensional FIETS (financial, institutional, environmental, technical, and social) framework to assess WASH sustainability. Findings reveal that financial sustainability is the most critical dimension, followed by institutional, technical, social, and environmental factors. The research also identifies key challenges such as limited funding, political barriers, and limited water resource availability. It underscores the importance of coordinated efforts among stakeholders to overcome these obstacles and achieve long-term sustainability. This framework provides a structured approach for practitioners and policymakers to assess and improve WASH services in refugee camps, contributing to broader discourse on sustainable development and water resource management. Full article

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37 pages, 11182 KiB

Open AccessArticle

Conventional and Emerging Desalination Technologies: Review and Comparative Study from a Sustainability Perspective

by Jamel Orfi, Raed Sherif and Musaad AlFaleh

Water 2025, 17(2), 279; https://doi.org/10.3390/w17020279 - 20 Jan 2025

Viewed by 876

Abstract

This work develops a comprehensive review of the main conventional and emerging desalination processes. It presents the state of knowledge of the most known and investigated techniques, highlights their advantages and drawbacks, and draws appropriate conclusions on their respective performances from various angles [...] Read more.

This work develops a comprehensive review of the main conventional and emerging desalination processes. It presents the state of knowledge of the most known and investigated techniques, highlights their advantages and drawbacks, and draws appropriate conclusions on their respective performances from various angles including their energy consumption and efficiency, environmental impacts, reliability, and flexibility in operations. This review reveals the recent large dominance and deployment of the reverse osmosis technology in the Gulf countries, mainly in Saudi Arabia; the importance of hybridization; and the slow penetration of promising processes including membrane distillation and forward osmosis into the industrial desalination market. In addition, this work aims to develop some comparison exercises between these processes using specific criteria. A cross approach allowing an easier comparison between various desalination processes could help identify the advantages and drawbacks of each technology and select the appropriate process. Therefore, various criteria allowing a clear picture to be drawn of the performance and capabilities of the main conventional and emerging desalination processes have been proposed in the frame of sustainable development. As an illustration of this general approach from sustainability prospects and considering specific weights for each proposed criterion for the case of Saudi Arabia, a comparison exercise reveals that the superiority of reverse osmosis (RO) is confirmed. Multiple effect distillation (MED) and membrane distillation (MD) processes are potentially competitive to RO while multi-stage flash (MSF) comes last due to several drawbacks. Full article

(This article belongs to the Topic Sustainable Technologies for Water Purification)

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27 pages, 4196 KiB

Open AccessArticle

Evaluating the Effectiveness of an Interactive Tool for Water Governance in Transboundary Basins: A Participation-Based Approach and Visualization of Water Security from a Vulnerability Perspective

by Yesica Rodríguez-Blásquez, Gustavo Ayala Ticona, Tania Fernanda Santos Santos, Sebastián Aedo-Quililongo, David Zamora, Doreen Brown Salazar, Laura Forni and Miguel Alvarenga

Water 2025, 17(2), 278; https://doi.org/10.3390/w17020278 - 20 Jan 2025

Viewed by 556

Abstract

In this study, we analyzed the effectiveness of a data visualization tool (dashboard) designed to provide insights to decision-makers about the vulnerability of water resources in the tri-national Upper Lempa River Basin (CARL) in the face of future climate and land use uncertainties. [...] Read more.

In this study, we analyzed the effectiveness of a data visualization tool (dashboard) designed to provide insights to decision-makers about the vulnerability of water resources in the tri-national Upper Lempa River Basin (CARL) in the face of future climate and land use uncertainties. The effectiveness of the dashboard was assessed using three methods: (1) a user survey for evaluating dashboard clarity, completeness, and ease of use using seven parameters proposed by Stephen Few. The result of the survey overwhelmingly indicated a positive experience when interacting with the dashboard; (2) pre- and post-use tests were used to assess knowledge acquisition. The users’ correct answers increased by an average of 35%, and incorrect answers decreased by an average of 25% for questions assessing an understanding of water demands, the effects of climate change on the basin’s water security, land use trends, and the sub-basins with the highest vulnerability in the region; and, significantly, (3) user reports on insights drawn from their interaction with the dashboard. Users drew insights on the extent to which different regions will likely experience increased vulnerability regarding water resources and on strategies that could reduce this vulnerability. The key issues that need to be addressed to ensure that the dashboard fosters greater transparency and public participation in governance and is used by decision-makers to improve the management of water resources in this watershed are the following: (1) the incorporation of user feedback and the inclusion of adaptation strategies and their impacts on the dashboard; (2) the commitment and training of a local institution to host and maintain the dashboard and to make it available to the public; (3) the engagement of decision-makers from the three countries regarding the use of the dashboard to understand future uncertainties and the potential impact of adaptation strategies on performance metrics. Full article

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

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20 pages, 2023 KiB

Open AccessArticle

Enhancing Reservoir Design by Integrating Resilience into the Modified Sequent Peak Algorithm (MSPA 2024)

by Issa Saket Oskoui, Maria Manuela Portela and Carina Almeida

Water 2025, 17(2), 277; https://doi.org/10.3390/w17020277 - 20 Jan 2025

Viewed by 474

Abstract

This study introduces the modified sequent peak algorithm (MSPA 2024), an advanced reservoir design framework that incorporates resilience as a key performance metric alongside traditional measures like reliability and vulnerability. By integrating resilience thresholds, MSPA 2024 addresses the complexities of water resource management [...] Read more.

This study introduces the modified sequent peak algorithm (MSPA 2024), an advanced reservoir design framework that incorporates resilience as a key performance metric alongside traditional measures like reliability and vulnerability. By integrating resilience thresholds, MSPA 2024 addresses the complexities of water resource management under diverse hydrological conditions and demand scenarios. Comparative analyses reveal that MSPA 2024 surpasses traditional approaches, such as behavior analysis (BA) and earlier MSPA versions, particularly in maintaining higher resilience and sustainability at lower reliability levels. Although it requires greater storage capacity and experiences higher evaporation losses, MSPA 2024 proves effective in ensuring resilience under challenging conditions, making it especially suitable for long-term water management in drought-prone regions. The key findings highlight its performance across varied demand scenarios, emphasizing the importance of tailoring MSPA 2024 applications to specific hydrological contexts. While achieving 100% resilience is optimal, this study demonstrates the practicality of lower resilience thresholds (e.g., 75% and 50%), showcasing MSPA 2024’s adaptability to diverse operational needs. These results underscore MSPA 2024’s potential to enhance resilient and sustainable water systems, offering a vital tool for addressing increased water scarcity driven by climate change. Full article

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17 pages, 7346 KiB

Open AccessArticle

Comprehensive Hydrochemical Analysis, Controlling Mechanisms, and Water Quality Assessment of Surface and Groundwater in a Typical Intensive Agricultural Area, Northern China

by Zongjun Gao, Tingting Huang, Jinkai Chen, Hong Tian, Menghan Tan, Yiru Niu and Kexin Lou

Water 2025, 17(2), 276; https://doi.org/10.3390/w17020276 - 19 Jan 2025

Viewed by 695

Abstract

Groundwater is a significant source of water, and evaluating its hydrochemical attributes, quality, and associated health risks holds paramount importance in guaranteeing safe water access for the population and fostering sustainable socio-economic progress. Situated within a semi-arid region, the Dianbu area (DBA) features [...] Read more.

Groundwater is a significant source of water, and evaluating its hydrochemical attributes, quality, and associated health risks holds paramount importance in guaranteeing safe water access for the population and fostering sustainable socio-economic progress. Situated within a semi-arid region, the Dianbu area (DBA) features numerous greenhouses interspersed amongst open farmlands. An examination revealed a discernible decline in the overall water chemistry environment in this area. This study extensively examined the fundamental water chemistry characteristics of groundwater and surface water samples through a statistical analysis, Piper’s trilinear diagram, ion ratios, and other analytical methods. The assessment of irrigation water quality was conducted using the entropy weight water quality index (EWQI), sodium adsorption ratio (SAR), percentage of soluble sodium (Na%), among other relevant indicators. The findings demonstrate multiple key aspects: 1. Water cations are chiefly composed of Ca²⁺ and Na⁺, while groundwater anions are notably NO₃⁻ and SO₄²⁻ dominant, defining the water type as NO₃-SO₄-Ca. Conversely, surface water primarily displays HCO₃⁻ and SO₄²⁻ anions, aligning it with an HCO₃-SO₄-Ca water type. 2. The extensive agricultural activities in the region, coupled with the excessive utilization of pesticides, chemical fertilizers, as well as the discharge of domestic sewage, contribute to heightened NO₃⁻ concentrations in groundwater. 3. The water quality assessments indicate that approximately 53% of agricultural water quality meets irrigation standards based on EWQI, with SAR results suggesting around 65.52% suitability for irrigation and Na% findings indicating approximately 55.88% viability for this purpose. Proper water selection tailored to specific conditions is advised to mitigate potential soil salinization risks associated with long-term irrational irrigation practices. Full article

(This article belongs to the Topic Human Impact on Groundwater Environment, 2nd Edition)

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13 pages, 5625 KiB

Open AccessArticle

Establishment of Axenic Cultures for Two Marine Microalgae and the Effects of Antibiotics on Their Growth

by Jin Huang, Shuang Liang, Huiru Liu, Yongren Li, Xiaoyu Wang, Yongjun Guo and Jian Liang

Water 2025, 17(2), 275; https://doi.org/10.3390/w17020275 - 19 Jan 2025

Viewed by 618

Abstract

Chaetoceros muelleri and Isochrysis zhanjiangensis, known for their rapid reproduction, small size, and rich nutritional content, are commonly used as feed microalgae in aquaculture. This study aimed to sterilize these microalgal species and assess the effects of antibiotics on their algal cell [...] Read more.

Chaetoceros muelleri and Isochrysis zhanjiangensis, known for their rapid reproduction, small size, and rich nutritional content, are commonly used as feed microalgae in aquaculture. This study aimed to sterilize these microalgal species and assess the effects of antibiotics on their algal cell density. Phycospheric bacteria were isolated and identified using the spread plate method and 16S rDNA sequencing, and antibiotic susceptibility tests were conducted using four antibiotics: ampicillin, streptomycin, kanamycin, and gentamicin sulfate. A sterile system was established for C. muelleri using ampicillin, streptomycin, and gentamicin, and for I. zhanjiangensis using kanamycin, ampicillin, and streptomycin. Based on the results, antibiotics with sterilization effects were selected and added to the algal cultures. Their effects on cell density were evaluated during a six-day co-culture. Ampicillin and streptomycin effectively inhibited bacteria associated with C. muelleri, initially increasing algal cell density but later causing a decline. For I. zhanjiangensis, kanamycin and ampicillin were effective, with kanamycin significantly promoting growth throughout the cycle, achieving a 36.92% higher cell density on day six (p < 0.05). Full article

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

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17 pages, 10073 KiB

Open AccessArticle

Impact of Extreme Weather Events on the Surface Energy Balance of the Low-Elevation Svalbard Glacier Aldegondabreen

by Uliana V. Prokhorova, Anton V. Terekhov, Vasiliy E. Demidov, Kseniia V. Romashova, Kirill V. Barskov, Dmitry G. Chechin, Igor I. Vasilevich, Mikhail V. Tretiakov, Boris V. Ivanov, Irina A. Repina and Sergey R. Verkulich

Water 2025, 17(2), 274; https://doi.org/10.3390/w17020274 - 19 Jan 2025

Viewed by 468

Abstract

The summer of 2022 was notable for the Svalbard archipelago due to the occurrence of several longstanding heatwaves, making it one of the warmest summers on the regional record. This study used an energy balance model forced with in situ weather observations to [...] Read more.

The summer of 2022 was notable for the Svalbard archipelago due to the occurrence of several longstanding heatwaves, making it one of the warmest summers on the regional record. This study used an energy balance model forced with in situ weather observations to investigate the influence of extreme weather events on the surface energy balance of the low-elevation Aldegondabreen glacier (5.2 km²), located near Barentsburg town, with a focus on the turbulent heat exchange. The annual mass balance for 2022 (−2.13 m w.e.) was one of the most negative on record for Aldegondabreen since 2002/2003 when glaciological monitoring was first initiated. We identified four heatwaves that lasted from 9 to 19 days, the most prominent of which were observed in May and in September–October, which resulted in an anomalously prolonged melt season. In addition, several shorter, 1- to 3-day extreme melt events were identified, representing up to 75 mm w.e. day⁻¹ of glacier-averaged melt. These events were well correlated (r = 0.87, p < 0.01), with discharge from a stream originating from the glacier terminus, and all cases were associated with significant increases in mean daily wind speeds (up to 10.3 m s⁻¹). Full article

(This article belongs to the Section Water and Climate Change)

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18 pages, 3987 KiB

Open AccessArticle

The Response Patterns of Non-Native Rotifer Species Kellicottia bostoniensis (Rousselet, 1908) to Environmental Factors and Its Relationship with Potential Competitors and Predators

by Geun-Hyeok Hong, Yerim Choi, Dae-Hee Lee, Jeong-Hui Kim, Kwang-Hyeon Chang and Hye-Ji Oh

Water 2025, 17(2), 273; https://doi.org/10.3390/w17020273 - 19 Jan 2025

Viewed by 551

Abstract

Kellicottia bostoniensis is a rotifer species originating from North America, with numerous reports documenting its spread to Europe and South America. Meanwhile, in Asia, the occurrence of this non-native species has been scarcely documented, but its presence was recently reported in Korea in [...] Read more.

Kellicottia bostoniensis is a rotifer species originating from North America, with numerous reports documenting its spread to Europe and South America. Meanwhile, in Asia, the occurrence of this non-native species has been scarcely documented, but its presence was recently reported in Korea in 2020. In Korea, the close geographic proximity of artificial reservoirs within a small area is expected to make the region vulnerable to the spread of K. bostoniensis. Therefore, it is deemed necessary to study the spatio-temporal distribution of K. bostoniensis, which appears to have extensively proliferated across the region, and its relationship with environmental factors. We analyzed the response of K. bostoniensis occurrence to environmental factors and aimed to compare its response patterns with those of potential competitor and predator groups, which were classified based on a functional group approach. This study, conducted on 12 small lakes located under similar climatic conditions, revealed that the response of K. bostoniensis to variables representing the trophic state of the lakes differed from those of the potential competitor and predator groups. The study sites, encompassing a wide range of trophic states from oligotrophic to hypereutrophic, across various lakes and survey periods, were well-suited for examining these relationships. Furthermore, when TSI was calculated to compare the abundance of K. bostoniensis and potential competitors across trophic conditions, the abundance of potential competitors was proportional to TSI. In contrast, K. bostoniensis exhibited higher abundances in mesotrophic and lower eutrophic environments, which distinguished it from its competitors. Our results indicate that the impact of introduced K. bostoniensis on native communities is minimal, while the resistance of native communities through the biological filter based on biological interactions is ineffective against this non-native rotifer species. This provides key evidence for explaining the widespread distribution of K. bostoniensis across continents. Full article

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14 pages, 1027 KiB

Open AccessArticle

Membrane Foulant Removal by Ozone-Biocarrier Pretreatment Technology for Industrial Wastewater Reclamation

by Ting-Ting Chang, Sheng-Yi Chiu, Chun-Chi Lee, Yuan-Liang Tai, Guan-You Lin, Chun-Hsi Lai and Po-Yu Chen

Water 2025, 17(2), 272; https://doi.org/10.3390/w17020272 - 19 Jan 2025

Viewed by 377

Abstract

During wastewater reclamation, organic matter is considered the dominant foulant that shortens the lifetime of ultrafiltration (UF) membranes during operation. Additionally, the mineralization efficiency of organic matter in secondary effluent is typically low due to nonbiodegradable carbon sources. Herein, a combination of ozone [...] Read more.

During wastewater reclamation, organic matter is considered the dominant foulant that shortens the lifetime of ultrafiltration (UF) membranes during operation. Additionally, the mineralization efficiency of organic matter in secondary effluent is typically low due to nonbiodegradable carbon sources. Herein, a combination of ozone and a porous biocarrier reactor was applied as a novel pretreatment system to enhance organic matter removal in the effluent in a lab-scale evaluation and pilot test. The results indicated that 70% of the biopolymer was removed, and the chemical oxygen demand (COD) removal efficiency was 1.8 times higher in this combined process than in the process with a porous biocarrier alone. The UF flux increased by 16% after the combined ozonation and porous biocarrier pretreatment process compared with the process with no pretreatment. Interestingly, the genus Flavobacterium (15.59%), containing biopolymer-degrading bacteria, was observed only in the combined ozone plus porous biocarrier process. Moreover, the results show that biopolymers can be removed through the combined ozone and porous biocarrier process due to partial ozone degradation, confirming that this combined process is one of the better pretreatment procedures for organic matter removal and improves the flux of UF during the wastewater reclamation process. Full article

(This article belongs to the Topic Advanced Oxidation Processes for Wastewater Purification)

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15 pages, 7435 KiB

Open AccessArticle

Trends in Flow Intermittency, Variability, and Seasonality for Taiwan Rivers

by Hsin-Yu Chen, Xi Fang and Hsin-Fu Yeh

Water 2025, 17(2), 271; https://doi.org/10.3390/w17020271 - 18 Jan 2025

Viewed by 554

Abstract

In Taiwan, rivers have steep slopes and short lengths, making it difficult to retain water in the rivers. Therefore, understanding the flow characteristics is essential. This study analyzes data from 65 flow stations with over 30 years of records to characterize the annual [...] Read more.

In Taiwan, rivers have steep slopes and short lengths, making it difficult to retain water in the rivers. Therefore, understanding the flow characteristics is essential. This study analyzes data from 65 flow stations with over 30 years of records to characterize the annual mean number of low-flow days, flow variability, and the seasonality of low-flow occurrences. The analysis uses indices such as the intermittency ratio, Richards–Baker flashiness index, and six-month seasonality of the dry period (SD6) and evaluates trends in these indices using the Mann–Kendall test. The results show that nearly 70% of the stations have an intermittency ratio of less than 0.1, although the number of low-flow days has significantly increased over time. Stations in the southwestern watersheds exhibit higher flow variability; however, the trends in flow variability are not statistically significant. Low-flow events predominantly occur during the dry season, with 68% of the stations experiencing them between January and March. The findings on flow characteristics and their long-term trends provide references for river management and water resource planning in the future. Full article

(This article belongs to the Special Issue Impacts of Climate Change on Water Resources: Assessment and Modeling, 2nd Edition)

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14 pages, 1607 KiB

Open AccessArticle

Impact of Polyethylene Terephthalate Microplastics on Aerobic Granular Sludge Structure and EPS Composition in Wastewater Treatment

by Piotr Jachimowicz and Agnieszka Cydzik-Kwiatkowska

Water 2025, 17(2), 270; https://doi.org/10.3390/w17020270 - 18 Jan 2025

Viewed by 532

Abstract

Aerobic granular sludge (AGS) is a promising technology for wastewater treatment. Granules have a compact microbial structure and a high potential for pollutant removal. Despite its advantages, the impact of microplastics (MPs) on AGS remains poorly understood, posing a potential risk to the [...] Read more.

Aerobic granular sludge (AGS) is a promising technology for wastewater treatment. Granules have a compact microbial structure and a high potential for pollutant removal. Despite its advantages, the impact of microplastics (MPs) on AGS remains poorly understood, posing a potential risk to the stability and efficiency of biological wastewater treatment processes. This study investigates the effects of polyethylene terephthalate (PET) MPs on AGS structure and extracellular polymeric substance (EPS) composition, providing new insights into the interaction between MPs and AGS. Four granular sequencing batch reactors (GSBRs) were operated with varying concentrations of PET MPs in the influent wastewater (0, 1, 10, 50 mg/L). Key findings include MP-induced changes in granule size distribution, with an increase in smaller granules (<90 µm) observed in reactors exposed to PET MPs. EPS concentrations (51–77 mg/L) exhibited significant differences among reactors, with notable shifts in protein (PN) and polysaccharide (PS) fractions. A higher PET MP dose resulted in an increased PN/PS ratio (from 1.96 to 5.40) and elevated hydrophobicity of AGS. These changes suggest that MPs can alter AGS structure and EPS composition, potentially affecting granule stability and treatment performance. This study provides novel evidence on the disruptive effects of MPs in wastewater treatment systems, emphasizing the need to address MP pollution in the context of biological treatment processes. The results contribute to a deeper understanding of the interactions between MP and AGS and form the basis for strategies to mitigate their adverse effects. Full article

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

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37 pages, 17853 KiB

Open AccessArticle

COAST-PRO_SIM: A Model for Predicting Shoreline Evolution and Assessing the Impacts of Coastal Defence Structures

by Pietro Scala, Giorgio Manno, Loredana Claudia Cozar and Giuseppe Ciraolo

Water 2025, 17(2), 269; https://doi.org/10.3390/w17020269 - 18 Jan 2025

Viewed by 820

Abstract

Coastal zones, at the interface between land and sea, face increasing challenges from erosion, sea-level rise, and anthropogenic interventions, necessitating innovative tools for effective management and protection. This study introduces COAST-PRO_SIM, a novel numerical model specifically designed to predict shoreline evolution [...] Read more.

Coastal zones, at the interface between land and sea, face increasing challenges from erosion, sea-level rise, and anthropogenic interventions, necessitating innovative tools for effective management and protection. This study introduces COAST-PRO_SIM, a novel numerical model specifically designed to predict shoreline evolution and assess the impacts of coastal defence structures on coastal morphology. Unlike existing models that often face a trade-off between computational efficiency and physical accuracy, COAST-PRO_SIM balances these demands by integrating two-dimensional wave propagation routines with advanced shoreline evolution equations. The model evaluates the effects of interventions such as breakwaters and groynes, enabling simulations of shoreline dynamics with reduced computational effort. By using high-resolution input data, COAST-PRO_SIM captures the interplay between hydrodynamics, sediment transport, and structural impacts. Tested on real-world case studies along the coasts of San Leone, Porto Empedocle, and Villafranca Tirrena, the model demonstrates its adaptability to diverse coastal environments. The results highlight its potential as a reliable tool for sustainable coastal management, allowing stakeholders to anticipate long-term changes in coastal morphology and design targeted mitigation strategies. Full article

(This article belongs to the Special Issue Coast Sediment Dynamics: Historical Development, Current Situation and Perspectives)

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19 pages, 2362 KiB

Open AccessArticle

Respiratory and Enteric Bacterial Pathogens in Municipal Wastewater: A Potential Risk of Infection to Workers

by Evida Poopedi, Tanusha Singh and Annancietar Gomba

Water 2025, 17(2), 268; https://doi.org/10.3390/w17020268 - 18 Jan 2025

Viewed by 480

Abstract

Investigating human pathogens in wastewater is crucial for identifying and predicting potential occupational health risks faced by wastewater treatment plant (WWTP) workers. This study aimed to determine the occurrence and levels of Legionella pneumophila, Mycobacterium spp., Arcobacter butzleri, and Aeromonas hydrophila [...] Read more.

Investigating human pathogens in wastewater is crucial for identifying and predicting potential occupational health risks faced by wastewater treatment plant (WWTP) workers. This study aimed to determine the occurrence and levels of Legionella pneumophila, Mycobacterium spp., Arcobacter butzleri, and Aeromonas hydrophila in untreated municipal wastewater. Grab influent, activated sludge, and secondary settling tank (SST) effluent samples were collected bi-weekly over 6 months from 5 WWTPs in Tshwane, South Africa. Mycobacterium spp., A. butzleri, and A. hydrophila were detected using quantitative PCR (qPCR), while Legionella was detected using both a culture method and qPCR. The four pathogens were identified in most samples at varying levels. Legionella pneumophila had a positivity rate of 92%, ranging from 2 to 5.4 log₁₀ MPN/100 mL. Detection rates of Legionella spp., L. pneumophila, and L. pneumophila serogroup 1 were 97%, 75%, and 69%, respectively, with up to 5.3 log₁₀ gene copies (GC)/mL. Importantly, this study demonstrates molecular typing of L. pneumophila serogroup 1 in wastewater, a topic that has been rarely documented. Mycobacterium spp. were detected in all samples at varying levels (log₁₀ GC/mL) in influent (2.8–7.6), activated sludge (4.8–8.9), and SST effluent (3.8–8.9) samples. Arcobacter butzleri and A. hydrophila were detected in 96% and 82% of the samples, respectively, with GC levels in influent, activated sludge, and SST effluent ranging from 0.8 to 6.6, 1.5 to 6.5, and 0.7 to 6.6 log₁₀ GC/mL for A. butzleri, and similar levels for A. hydrophila. These findings underscore the presence of respiratory and enteric pathogens at various treatment points, suggesting potential occupational exposure for WWTP workers. This emphasises the need for microbiological risk assessments (RAs) or reviewing existing RAs and implementing necessary control measures to protect WWTP workers. Full article

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

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22 pages, 4555 KiB

Open AccessArticle

Adaptive Simplified Calculation of Algal Bloom Risk Index for Reservoir-Type Drinking Water Sources Based on Improved TOPSIS and Identification of Risk Areas

by Shuyi Ji, Jihong Xia, Yue Wang, Jiayi Zu, Kejun Xu, Zewen Liu, Qihua Wang and Guofu Lin

Water 2025, 17(2), 267; https://doi.org/10.3390/w17020267 - 18 Jan 2025

Viewed by 385

Abstract

As a result of global climate change and human production activities, algal blooms are occurring in aquatic environments. The problem of eutrophication in water bodies is becoming increasingly severe, affecting the safety of drinking water sources. In this study, an algal bloom risk [...] Read more.

As a result of global climate change and human production activities, algal blooms are occurring in aquatic environments. The problem of eutrophication in water bodies is becoming increasingly severe, affecting the safety of drinking water sources. In this study, an algal bloom risk index model combining the Improved Fuzzy Analytic Hierarchy Process (IFAHP), Entropy Weight Method (EWM), and Game Theory (GT) was proposed for the Shanxi Reservoir based on the TOPSIS method. After the seasonal and spatial variability in algal bloom risk from 2022 to 2023 was analyzed, an adaptive simplification of the algal bloom risk index calculation was proposed to optimize the model. To enhance its practical applicability, this study proposed an adaptive simplification of the algal bloom risk index calculation based on an improved TOPSIS approach. The error indexes R² for the four seasons and the annual analysis were 0.9884, 0.9968, 0.9906, 0.9946, and 0.9972, respectively. Additionally, the RMSE, MAE, and MRE values were all below 0.035, indicating the method’s high accuracy. Using the adaptively simplified risk index, a risk grading and a spatial delineation of risk areas in Shanxi Reservoir were conducted. A comparison with traditional risk classification methods showed that the error in the risk levels did not exceed one grade, demonstrating the effectiveness of the proposed calculation model and risk grading approach. This study provides valuable guidance for the prevention and control of algal blooms in reservoir-type drinking water sources, contributing to the protection of drinking water sources and public health. Full article

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23 pages, 6353 KiB

Open AccessArticle

Phosphorus Retention in Treatment Wetlands? A Field Experiment Approach: Part 1, Hydrology

by Mohamed Z. Moustafa and Wasantha A. M. Lal

Water 2025, 17(2), 266; https://doi.org/10.3390/w17020266 - 18 Jan 2025

Viewed by 382

Abstract

Stormwater Treatment Areas (STAs) are large wetlands constructed to reduce phosphorus (P) from agricultural and urban runoff into the Everglades Protection area. Wetland vegetation in these STAs reduce P in surface water, affects flow resistance, and causes delays of water deliveries. Vegetation resistance [...] Read more.

Stormwater Treatment Areas (STAs) are large wetlands constructed to reduce phosphorus (P) from agricultural and urban runoff into the Everglades Protection area. Wetland vegetation in these STAs reduce P in surface water, affects flow resistance, and causes delays of water deliveries. Vegetation resistance is commonly determined by the flow regime and vegetation porosity. Field experiments were conducted to seek alternative ways to estimate vegetation resistance in STAs. We generated small sinusoidal discharge perturbations superimposed on near-steady state flow conditions and measured in situ water levels inside the wetland. The elapsed time for the generated waves to reach various locations and wave amplitude attenuations inside the wetland were used to calculate porosity/transmissivity (K), a single parameter representing vegetation resistance. The vegetation index combined with calculated K distribution indicated that transmissivity is a straightforward way to represent vegetation resistance. High K values indicate sparse vegetation density or open water (low vegetation index), resulting in low vegetation resistance. Low K values indicate high vegetation density (high vegetation index), resulting in high vegetation resistance independent of vegetation and flow type. This manuscript describes a field experiment and discusses the relationship between K and the vegetation index (representing vegetation density). Part II will present the consequences of water movement on P retention in these systems. Full article

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15 pages, 526 KiB

Open AccessArticle

The Impact of the River Chief System on Corporate ESG Performance: Evidence from China

by Lan Mu, Chuanzhen Zhang and Haoying Liu

Water 2025, 17(2), 265; https://doi.org/10.3390/w17020265 - 18 Jan 2025

Viewed by 450

Abstract

This paper takes the implementation of the River Chief System (RCS) as a case study representing government-led environmental governance policies. Based on the sample of 11,654 observations of Chinese A-share-listed companies spanning the years 2009 to 2021, it empirically examines the effect of [...] Read more.

This paper takes the implementation of the River Chief System (RCS) as a case study representing government-led environmental governance policies. Based on the sample of 11,654 observations of Chinese A-share-listed companies spanning the years 2009 to 2021, it empirically examines the effect of the RCS on corporate Environmental, Social, and Governance (ESG) performance and the macro- and micro-mechanisms utilizing a staggered Difference-in-Differences (DID) model, controlling for companies’ financial and organizational structure characteristic variables, cities’ economic characteristic variables, and firm-year two-way fixed effects. The results indicate that the implementation of the RCS significantly enhances corporate ESG performance, a conclusion supported by various robustness checks such as the parallel trend test and placebo test. Further investigation reveals that implementing the RCS, at the micro level, boosts corporate green technology innovation, increases environmental protection investment, and, at the macro level, heightens public environmental attention, thus improving corporate ESG performance. Heterogeneity analysis finds that the RCS has a more pronounced impact on enhancing ESG performance for enterprises in central and western regions of China, state-owned enterprises, enterprises with political connections, and enterprises in mature and declining stages. These research findings of this paper provide valuable insights for local governments seeking to enhance the RCS, enrich environmental governance frameworks, and facilitate corporate green transformation. Full article

(This article belongs to the Special Issue Economic Approaches to Sustainable Water Management: Policy, Innovation, and Global Challenges)

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22 pages, 3426 KiB

Open AccessArticle

When Are Models Useful? Revisiting the Quantification of Reality Checks

by Demetris Koutsoyiannis

Water 2025, 17(2), 264; https://doi.org/10.3390/w17020264 - 18 Jan 2025

Viewed by 429

Abstract

The Nash–Sutcliffe efficiency remains the best metric for measuring the appropriateness of a model and reflects a culture developed in hydrology to test models against reality before using them. This metric is not without problems, and alternative metrics have been proposed subsequently. Here, [...] Read more.

The Nash–Sutcliffe efficiency remains the best metric for measuring the appropriateness of a model and reflects a culture developed in hydrology to test models against reality before using them. This metric is not without problems, and alternative metrics have been proposed subsequently. Here, the concept of knowable moments is exploited to provide robust metrics that assess not only the second-order properties of the process of interest but also high-order moments which provide information for the entire distribution function of the process of interest. This information may be useful in hydrological tasks, as most hydrological processes are non-Gaussian. The proposed concepts are illustrated, also in relationship to existing ones, using a large-scale comparison of climatic model outputs for precipitation with reality for the last 84 years on hemispheric and continental scales. Full article

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20 pages, 10795 KiB

Open AccessArticle

Study on Damage Rupture and Crack Evolution Law of Coal Samples Under the Influence of Water Immersion Pressure

by Jianhua Shangguan, Haotian Guo, Shenggen Cao and Jialong Sun

Water 2025, 17(2), 263; https://doi.org/10.3390/w17020263 - 18 Jan 2025

Viewed by 364

Abstract

Underground reservoir technology in coal mines enables the effective storage and utilization of water resources disturbed by mining activities. Owing to the effects of mining operations and water extraction/injection activities, the water head in underground reservoirs fluctuates dynamically. The total bearing capacity of [...] Read more.

Underground reservoir technology in coal mines enables the effective storage and utilization of water resources disturbed by mining activities. Owing to the effects of mining operations and water extraction/injection activities, the water head in underground reservoirs fluctuates dynamically. The total bearing capacity of a coal pillar dam is significantly reduced due to the combined effects of overlying rock stress, dynamic and static water pressures, and mining-induced stresses, which are critical for ensuring the safe operation of underground reservoirs. Based on the correlation between different water head heights and the corresponding water pressures on the coal pillar dam, a custom-made coal rock pressure water immersion test device was used to saturate the coal samples under various water pressure conditions. The mechanical deformation and failure characteristics of the samples and fracture propagation patterns under different water pressure conditions were studied using uniaxial compression, acoustic emission (AE), and three-dimensional X-ray microimaging. The results indicated that, compared with the dry state, the peak strain of the water-immersed coal samples increased to varying degrees with increasing water pressure. Additionally, the average porosity and the number of pores with diameters in the range of 0 to 150 μm significantly increased in water-immersed coal samples. Under the combined influence of water immersion pressure and uniaxial stress, loading the water-saturated coal samples to the fracture damage threshold significantly intensified deformation, failure, and fracture propagation within the samples, and the failure mode changed from tension to a composite tensile–shear failure. Full article

(This article belongs to the Special Issue Mine Water Safety and Environment, 2nd Edition)

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19 pages, 10970 KiB

Open AccessArticle

Variations in Sedimentation Rate and Corresponding Adjustments of Longitudinal Gradient in the Cascade Reservoirs of the Lower Jinsha River

by Suiji Wang

Water 2025, 17(2), 262; https://doi.org/10.3390/w17020262 - 18 Jan 2025

Viewed by 324

Abstract

The Xiangjiaba and Xiluodu reservoirs, as important components of the large cascade reservoirs in the lower Jinsha River, and the interactive changes in sediment trapping amounts, the differences in sedimentation dynamics, and the potential mutual influence mechanisms among them are scientific issues worthy [...] Read more.

The Xiangjiaba and Xiluodu reservoirs, as important components of the large cascade reservoirs in the lower Jinsha River, and the interactive changes in sediment trapping amounts, the differences in sedimentation dynamics, and the potential mutual influence mechanisms among them are scientific issues worthy of attention. Based on the multiple observed data of thalweg elevation before and after the completion of the dam construction, this study calculated the average sedimentation rates of all 20 km segments of the above-mentioned reservoirs in different periods. Meanwhile, the local mean gradients between adjacent segments and the regional mean gradients from the segments to the dam in the corresponding periods were calculated. The results show that the maximum and average sedimentation rates of the Xiangjiaba Reservoir, which was built earliest and is located downstream, were as high as 19.62 m yr⁻¹ and 8.88 m yr⁻¹, respectively, in the first half year after the dam closure. After the completion of the Xiluodu Reservoir, an adjacent cascade reservoir upstream, the average sedimentation rate of the Xiangjiaba Reservoir in the following seven years dropped to 0.67 m yr⁻¹. The maximum and average sedimentation rates of the Xiluodu Reservoir were 9.07 m yr⁻¹ and 4.15 m yr⁻¹, respectively, within one year after the dam closure, and its average sedimentation rate in the following six years was 2.51 m yr⁻¹. The spatial variations of sedimentation rates in these two reservoirs follow different changing patterns. There is an obvious correlation between the change in mean gradient and the change in sedimentation rate. The sequence of dam construction, the relative positions of the reservoirs, the differences in sediment trapping amounts, and operation modes are the key factors controlling the changes in sedimentation rate and gradient in the reservoir area. This study reveals the interactive changes in sedimentation rates among cascade reservoirs and the response mechanism of river channel morphology, and has a guiding role for the formulation of effective measures for the sustainable utilization of cascade reservoirs. Full article

(This article belongs to the Special Issue Regional Geomorphological Characteristics and Sedimentary Processes)

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19 pages, 17922 KiB

Open AccessArticle

Effects of Drying Operation on the Mn²⁺ Removal Activity of MnO_x: Performance and Mechanism

by Ruifeng Zhang, Lina Yang, Jing Yang, Qiuyan Niu and Binrong Zhu

Water 2025, 17(2), 261; https://doi.org/10.3390/w17020261 - 17 Jan 2025

Viewed by 372

Abstract

Mn²⁺ is a prevalent contaminant in groundwater. In this study, manganese oxides (MnO_x) were prepared via a redox method to remove Mn²⁺ from water. The effects of the drying operation in the preparation process, including heat drying at 20–120 [...] Read more.

Mn²⁺ is a prevalent contaminant in groundwater. In this study, manganese oxides (MnO_x) were prepared via a redox method to remove Mn²⁺ from water. The effects of the drying operation in the preparation process, including heat drying at 20–120 °C with different times and freeze drying methods, on the structural properties, manganese removal performance and mechanisms were investigated. The results indicate that the drying conditions can significantly affect the removal performance and stability of MnO_x. The MnO_x dried at 50 °C for 12 h exhibited the best Mn²⁺ removal efficiency and stability, with an adsorption capacity of 125.7 mg/g and removal efficacy of 95.1% after six reuse cycles. The removal pathway experiments revealed that the sample dried at 50 °C for 12 h had superior catalytic oxidation abilities for Mn²⁺, while other samples removed Mn²⁺ by primarily relying on the adsorption process. The investigation of the structure revealed that excessive heat drying led to the shrinkage of the oxide particles, a reduction in the surface voids, and a decrease in the hydroxyl groups. Conversely, insufficient drying time or temperatures resulted in high water content in MnO_x, which occupied the surface active sites. The XPS analysis indicated that the catalytic oxidation of Mn²⁺ primarily relied on Mn(III) and adsorbed oxygen on the surface of MnO_x. With freeze drying or inadequate heat drying, a large amount of Mn(II) remained on the oxide surface, and the over-drying operation resulted in excessive conversion from Mn(II) to Mn(IV), reducing the catalytic activity and resulting in low removal stability. Full article

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33 pages, 3232 KiB

Open AccessReview

Efficiency of Microalgae Employment in Nutrient Removal (Nitrogen and Phosphorous) from Municipal Wastewater

by Marcel Daniel Popa, Ira-Adeline Simionov, Stefan Mihai Petrea, Puiu-Lucian Georgescu, George Adrian Ifrim and Catalina Iticescu

Water 2025, 17(2), 260; https://doi.org/10.3390/w17020260 - 17 Jan 2025

Viewed by 410

Abstract

Growing population, industrialisation, and demand for resources put pressure on the delicate balance of the planet’s ecosystems. From alternative sources of energy, healthier foods, cleaner water, and an overall more sustainable economy, the integration of microalgae in various industries, that otherwise are based [...] Read more.

Growing population, industrialisation, and demand for resources put pressure on the delicate balance of the planet’s ecosystems. From alternative sources of energy, healthier foods, cleaner water, and an overall more sustainable economy, the integration of microalgae in various industries, that otherwise are based on practices that hurt the environment, could be a successful solution. To reach that goal, further research is required on the complex relationship between microalgae and growth parameters (temperature, light intensity and spectrum, nutrient distribution, inhibiting factors, and so on). The scientific community successfully used microalgae to produce healthier foods, pigments, biofuel, animal fodder, methods for sequestering heavy metals, toxic compounds from water, and much more. In this review article, we approach the use of microalgae in municipal wastewater treatment, mainly for using nitrogen and phosphorous present in water as nutrients. Data were collected from articles published in the last 7 years (2018–2024). The results show that microalgae are very efficient at using N and P compounds from wastewater, as well as carbon, converting them in high-value substances (proteins, lipids, carbohydrates, etc.) with further applications in multiple industries. Full article

(This article belongs to the Special Issue Water Treatment Technology for Emerging Contaminants, 2nd Edition)

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26 pages, 14152 KiB

Open AccessArticle

Evaluation of Water Inrush Risk in the Fault Zone of the Coal Seam Floor in Madaotou Coal Mine, Shanxi Province, China

by Shuai Yu, Hanghang Ding, Moyuan Yang and Menglin Zhang

Water 2025, 17(2), 259; https://doi.org/10.3390/w17020259 - 17 Jan 2025

Viewed by 375

Abstract

As coal seams are mined at greater depths, the threat of high water pressure from the confined aquifer in the floor that mining operations face has become increasingly prominent. Taking the Madaotou mine field in the Datong Coalfield as the research object, in [...] Read more.

As coal seams are mined at greater depths, the threat of high water pressure from the confined aquifer in the floor that mining operations face has become increasingly prominent. Taking the Madaotou mine field in the Datong Coalfield as the research object, in the context of mining under pressure, for the main coal seams in the mining area, first of all, an improved evaluation method for the vulnerability of floor water inrush is adopted for hazard prediction. Secondly, numerical simulation is used to conduct a simulation analysis on the fault zones in high-risk areas. By using the fuzzy C-means clustering method (FCCM) to improve the classification method for the normalized indicators in the original variable-weight vulnerability evaluation, the risk zoning for water inrush from the coal seam floor is determined. Then, through the numerical simulation method, a simulation analysis is carried out on high-risk areas to simulate the disturbance changes of different mining methods on the fault zones so as to put forward reasonable mining methods. The results show that the classification of the variable-weight intervals of water inrush from the coal seam floor is more suitable to be classified by using fuzzy clustering, thus improving the prediction accuracy. Based on the time effect of the delayed water inrush of faults, different mining methods determine the duration of the disturbance on the fault zones. Therefore, by reducing the disturbance time on the fault zones, the risk of karst water inrush from the floor of the fault zones can be reduced. Through prediction evaluation and simulation analysis, the evaluation of the risk of water inrush in coal mines has been greatly improved, which is of great significance for ensuring the safe and efficient mining of mines. Full article

(This article belongs to the Special Issue Engineering Hydrogeology Research Related to Mining Activities)

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24 pages, 12445 KiB

Open AccessArticle

Prediction of Flood Processes Based on General Unit Hydrograph

by Nuo Xu, Yingjun Sun, Yizhi Sun, Zhilin Sun and Fang Geng

Water 2025, 17(2), 258; https://doi.org/10.3390/w17020258 - 17 Jan 2025

Viewed by 617

Abstract

The general unit hydrograph (GUH), recently established by Guo, represents the most advanced hydrograph model today, but how to implement it with hydrologic data is another story. In this work, an effective initial value-based method for estimating the parameters in the GUH model [...] Read more.

The general unit hydrograph (GUH), recently established by Guo, represents the most advanced hydrograph model today, but how to implement it with hydrologic data is another story. In this work, an effective initial value-based method for estimating the parameters in the GUH model is proposed and applied to the analysis of flood processes. In contrast to the flood-rainfall united fitting method, which heavily depends on the flood records and has a broad range of parameter variations, which makes it practically intractable, the initial value-based method enables the calculation of model parameters directly from the measured rainstorm data and greatly enriches the discharge dataset so that more accurate prediction of flood processes becomes achievable. From the data collected from several watersheds, we find that smaller-shape parameters usually indicate a multi-peak flood process, and the rainfall patterns have a significant impact on flood peaks. These results provide a reliable approach for the prediction of floods in streams with scarce discharge data. Additionally, it is observed that the peak time lags have a notable increase from the southwest to the northeast of Zhejiang. Full article

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18 pages, 5348 KiB

Open AccessArticle

Analysis of Recharge Efficiency Under Barrier Effects Incurred by Adjacent Underground Structures

by Kelang Yang, Changjie Xu, Chaofeng Zeng, Long Zhu, Xiuli Xue and Lei Han

Water 2025, 17(2), 257; https://doi.org/10.3390/w17020257 - 17 Jan 2025

Viewed by 397

Abstract

Foundation pit dewatering will impact the surrounding underground environment. To mitigate the adverse effects on adjacent underground structures, groundwater recharge is commonly utilized to control groundwater drawdown outside the pit. However, under a barrier effect of underground structures, the recharge effect may be [...] Read more.

Foundation pit dewatering will impact the surrounding underground environment. To mitigate the adverse effects on adjacent underground structures, groundwater recharge is commonly utilized to control groundwater drawdown outside the pit. However, under a barrier effect of underground structures, the recharge effect may be different from that without the barrier effect. Meanwhile, the results of recharging different aquifers may also be different under the barrier effect. Therefore, based on an actual foundation pit project, this paper establishes a three-dimensional finite element model to investigate the impact of recharge on the surrounding environment under the barrier effect. To be specific, the recharge simulations were conducted in aquifers at different depths, and the effects on groundwater, enclosure wall deflection, and ground settlement under each recharge condition were compared and discussed. Furthermore, the optimal recharge scheme under the barrier effect was proposed. The results show the following: (1) When recharge is conducted in an aquifer that is completely cut off by underground structures, both groundwater levels rise and enclosure deflection induced by recharge are dramatic; therefore, caution should be taken when recharging under this condition to avoid an excessive response of recharge on the surrounding environment. (2) When recharge is conducted in an aquifer that is not cut off, most of the recharged water flows far away from the foundation pit, resulting in a low recharge efficiency. (3) When recharge is conducted in an aquifer with a direct hydraulic connection between the inside and outside of the foundation pit, it can significantly raise the groundwater levels of each aquifer, and effectively control the ground settlement without obviously increasing the deflection of the enclosure; engineers could benefit from this recharge scheme to achieve a better recharge effect under the barrier effect. Full article

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15 pages, 7018 KiB

Open AccessArticle

Impact of Mining Area Steep Slope Conditions on the Soil and Water Conservation Benefits of Ecological Restoration

by Xiaofeng Zhao, Haibo Li, Peng Li, Yajun Chen, Qian Dai, Peng Shi, Xin Li, Yonglong Qu and Jianye Ma

Water 2025, 17(2), 256; https://doi.org/10.3390/w17020256 - 17 Jan 2025

Viewed by 349

Abstract

Steep slopes, characterized by their high gradient and limited soil and water resources, pose significant challenges to plant colonization. Consequently, the ecological restoration of steep slopes is one of the major challenges in the field of mine site rehabilitation. This study evaluated the [...] Read more.

Steep slopes, characterized by their high gradient and limited soil and water resources, pose significant challenges to plant colonization. Consequently, the ecological restoration of steep slopes is one of the major challenges in the field of mine site rehabilitation. This study evaluated the impact of slope conditions on the restoration effectiveness during the early stages of ecological restoration. Two ecological restoration slopes with different slope conditions, excavated slope and filled slope, were selected, and restored by hanging net and soil spraying measures. The unrepaired slope was used as the control. The results showed that ecological restoration has a significant effect for soil and water conservation; runoff and sediment were reduced by 61.38% and 99.28%, respectively, and infiltration increased by 104.26%, compared to untreated slopes. Furthermore, ecological restoration could effectively reduce runoff erosion dynamics and soil erodibility, and alter the runoff–sediment relationship on slopes, thereby substantially influencing the yield processes of runoff and sediment of the slopes. Notably, the reduction effect of ecological restoration measures on runoff and sediment was more significant on excavated slopes than on filled slopes. The runoff and sediment yield of excavated slopes were 19.06% and 53.77% lower than that of filled slopes, respectively. From a soil and water conservation perspective, the ecological restoration measures of hanging net and soil spraying were more suitable for application to steep excavated rock slopes. However, further research is needed to evaluate its applicability to filled slopes. Full article

(This article belongs to the Special Issue Soil Erosion and Soil and Water Conservation)

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