Water

15 pages, 1615 KiB

Open AccessArticle

Influence of Physiographic Region on Pathogen Concentrations Between Stream Types

by E. A. Bradley, B. Graeme Lockaby, Todd Steury and Steven Madere

Water 2024, 16(22), 3218; https://doi.org/10.3390/w16223218 (registering DOI) - 8 Nov 2024

Predicting public health risk associated with exposure to and recreational use of surface waters is often challenging due to substantial variability in concentrations of pathogenic bacteria, even among seemingly similar streams. In this study, we document significant differences in the surface water concentrations [...] Read more.

Predicting public health risk associated with exposure to and recreational use of surface waters is often challenging due to substantial variability in concentrations of pathogenic bacteria, even among seemingly similar streams. In this study, we document significant differences in the surface water concentrations of the common bacteria indicators Escherichia coli and fecal coliform between two major stream types—blackwater and redwater streams (p < 0.001). We propose and present evidence that these findings result from natural biogeochemical variation between physiographic regions (p < 0.001). These findings suggest that physiographic stream type may influence the degree of exposure to waterborne pathogens and risk of waterborne disease. Future research is needed to assess whether the inclusion of stream type in risk assessments can improve public health modeling and mapping. Full article

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

15 pages, 5853 KiB

Open AccessArticle

Spatiotemporal Evolution Mine Groundwater’s Hydrogeochemical Characteristics Under Influence of Mining and Grouting in Gubei Coal Mine, China

by Guanhong Xiao and Haifeng Lu

Water 2024, 16(22), 3217; https://doi.org/10.3390/w16223217 (registering DOI) - 8 Nov 2024

Abstract

Geological conditions or human activities will affect the hydrochemical characteristics and formation mechanism of mine groundwater to varying degrees. The northern part of the Beiyi mining area of Gubei Coal Mine is taken as the research area in this study. Based on the [...] Read more.

Geological conditions or human activities will affect the hydrochemical characteristics and formation mechanism of mine groundwater to varying degrees. The northern part of the Beiyi mining area of Gubei Coal Mine is taken as the research area in this study. Based on the data of 52 groups of limestone water (Taihui water) samples in the primary environment, in the mining stage and after grouting, the spatial and temporal variation trend of the chemical characteristics of Taihui water was studied by means of constant index mathematical statistics, a Piper diagram, total ionic salinity, correlation analysis, the ion ratio method and the saturation index. The purpose of this study is to analyze the influence of special geological structures, mining activities and grouting treatment on the formation process of the chemical characteristics of Taihui water, and to provide a basis for the identification of water inrush sources and the resource utilization of deep mine water in this area. The results show that in the three stages, the order of cation concentration is Na⁺ + K⁺ > Ca²⁺ > Mg²⁺, and the order of anion concentration is changed from Cl⁻ > SO₄²⁻ > HCO₃⁻ to Cl⁻ > HCO₃⁻ > SO₄²⁻. The hydrochemical type is the most abundant in the mining stage, and tends to be unified after grouting. The dissolution of carbonate minerals, gypsum, rock salt and silicate minerals; cation exchange; pyrite oxidation; and the mixing of grouting precipitation liquid mainly occur in the limestone water. These effects are enhanced or weakened due to the influence of pumping and drainage and grouting precipitation liquid. The results of this study may be beneficial to the sustainable utilization of deep groundwater resources in other similar mines, and promote the establishment of data management and identification mechanisms of water inrush sources in deep coal seams. Full article

(This article belongs to the Section Hydrogeology)

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30 pages, 881 KiB

Open AccessReview

Managed Aquifer Recharge for Sustainable Groundwater Management: New Developments, Challenges, and Future Prospects

by Muhammad Sufyan, Grazia Martelli, Pietro Teatini, Claudia Cherubini and Daniele Goi

Water 2024, 16(22), 3216; https://doi.org/10.3390/w16223216 (registering DOI) - 8 Nov 2024

Abstract

The combined effect of climate change and increased water demand has put significant strain on groundwater resources globally. Managed aquifer recharge (MAR) has become an effective approach for addressing groundwater depletion problems and sustainable management of groundwater resources. This review article provides an [...] Read more.

The combined effect of climate change and increased water demand has put significant strain on groundwater resources globally. Managed aquifer recharge (MAR) has become an effective approach for addressing groundwater depletion problems and sustainable management of groundwater resources. This review article provides an extensive insight into the existing knowledge of MAR, including the main objectives and applications, implementation techniques (surface spreading, sub-surface, and induced recharge) being practiced over the years, risks and challenges associated with the MAR, and the developments in the field of MAR. This review also explores the potential of MAR in the Friuli Venezia Giulia (FVG) region, north-eastern Italy. An average increase in temperature and a decrease in precipitation and piezometric levels in the region suggest the development of a proper MAR plan to manage water resources in the decades to come. Additionally, a comparative analysis of studies published over the last 20 years, focusing on the quantitative and qualitative aspects of water resource management, is conducted to analyze the research trends in the field of MAR. The reviewed literature reveals a notable research trend towards the quantitative aspect compared to the qualitative one. This review also identifies a notable disparity in qualitative studies during the analysis of water quality parameters considered in different MAR studies. Based on this review, a prospective viewpoint to address the challenges and expand the scope of the field is presented. This calls for an optimized strategy that considers both water quality and quantity issues, along with incorporating environmental and socio-economic aspects within the framework of MAR. Full article

(This article belongs to the Section Hydrogeology)

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Graphical abstract

22 pages, 5228 KiB

Open AccessArticle

Hydrogeochemical Characteristics and Formation Mechanisms of High-Arsenic Groundwater in the North China Plain: Insights from Hydrogeochemical Analysis and Unsupervised Machine Learning

by Xiaofang Wu, Weijiang Liu, Yi Liu, Ganghui Zhu and Qiaochu Han

Water 2024, 16(22), 3215; https://doi.org/10.3390/w16223215 (registering DOI) - 8 Nov 2024

Abstract

Hydrochemical data were utilized in this study to elucidate the hydrogeochemical characteristics and genesis of high-arsenic groundwater in the North China Plain, employing both traditional hydrogeochemical analysis and unsupervised machine learning techniques. The findings indicate that the predominant hydrochemical types of groundwater in [...] Read more.

Hydrochemical data were utilized in this study to elucidate the hydrogeochemical characteristics and genesis of high-arsenic groundwater in the North China Plain, employing both traditional hydrogeochemical analysis and unsupervised machine learning techniques. The findings indicate that the predominant hydrochemical types of groundwater in the study area are HCO₃-Ca·Na and SO₄·Cl-Na·Ca. The primary mechanism influencing groundwater chemistry has been identified as rock weathering. The unsupervised machine learning framework incorporates various methods, such as principal component analysis (PCA), non-negative matrix factorization (NMF), machine learning models (gradient boosting trees and random forests), and cluster analysis to explore the characteristics and genesis of groundwater hydrochemical types within the study area. This study demonstrated that the formation mechanism of high-arsenic groundwater results from multiple interacting factors. Full article

(This article belongs to the Special Issue Water Resources, Environment, and Ecosystems: Application of New Technology)

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19 pages, 2186 KiB

Open AccessArticle

Impact of Flooding on Lands with Emerging Contaminants on the Quality of Receiving Water Bodies

by Samir A. Haddad, Mohieyeddin M. Abd El-Azeim, Ahmad M. Menesi, Esam Ismail, Mariacrocetta Sambito, Mohamed S. Ahmed, Ahmed S. A. Sayed, Ibraheem A. H. Yousif and Nesrin S. Abdelkarim

Water 2024, 16(22), 3214; https://doi.org/10.3390/w16223214 (registering DOI) - 8 Nov 2024

Abstract

Among crucial factors that control flooding events are extreme climate, urban growth, and mismanagement. Islands in the Nile River have experienced successive cycles of flooding and drying due to recent rainy years in the Nile Basin countries. This paper focuses on the impact [...] Read more.

Among crucial factors that control flooding events are extreme climate, urban growth, and mismanagement. Islands in the Nile River have experienced successive cycles of flooding and drying due to recent rainy years in the Nile Basin countries. This paper focuses on the impact of floods on the amounts of ammonium-N released, total concentrations of heavy metals, enzyme activities, and microbial biomass (C and N) in flood soils of 11 Nile River islands. Field moist soils and their airdried counterparts were collected from the outskirts of the island and incubated for 15 days at 30 °C to be analyzed. Results reflected that the amounts of released NH₄-N were higher in airdried than in wet soils. The average hydrolysis rates of the studied six enzyme substrates were correlated significantly with organic C, organic N, microbial bio-mass C and N in the field moist soils. The highest correlation coefficients (r) were with rates of hydrolysis of substrates of asparaginase, amidase, and β-glycosaminidase. A significant intercorrelation between rates of hydrolysis of the six studied enzyme substrates and r values which range from 0.81 to 0.98. At 10 mmol kg⁻¹ soil, Co⁺², Cd⁺², Pb⁺², Cu⁺², Cr⁺³, and Ni⁺² inhibited the release of NH₄-N. Arginine hydrolysis was inhibited by the six heavy metals at 5 mmol kg⁻¹ soil; the most effective inhibitors were Pb⁺², Ni⁺², and Cr⁺³. Due to the complex soil enzymatic and organic nitrogen hydrolase activities that occur during floods, fertile fields on the Nile River islands should not be fertilized before the summer flood seasons, which will prevent contamination of the Nile River water and loss of its island soil fertility. Full article

(This article belongs to the Special Issue Managing Water Resources Sustainably)

12 pages, 2707 KiB

Open AccessArticle

A New Type of Pre-Aeration Stepped Spillway

by Yu Zhou, Fangyong Xin, Ke Xu, Jiakai Mei, Siwei Jia, Haodong Qiu and Yuanyuan Wang

Water 2024, 16(22), 3213; https://doi.org/10.3390/w16223213 (registering DOI) - 8 Nov 2024

Abstract

Aiming to increase energy dissipation and prevent the cavitation potential of a traditional stepped spillway (TSS) at large unit discharges, a kind of pre-aeration stepped spillway, called a hydraulic-jump-stepped spillway (HJSS), is introduced in this paper. Unlike a TSS, a basin added upstream [...] Read more.

Aiming to increase energy dissipation and prevent the cavitation potential of a traditional stepped spillway (TSS) at large unit discharges, a kind of pre-aeration stepped spillway, called a hydraulic-jump-stepped spillway (HJSS), is introduced in this paper. Unlike a TSS, a basin added upstream of the stepped chute in the HJSS plays a vital role in the hydraulic performance owing to the formation of a hydraulic jump in the basin. This paper presents experimental research on the hydraulic performance of the HJSS in comparison to a TSS with the same chute slope (θ = 39.3°) for a wide range of unit discharges, including the flow pattern, energy dissipation, pre-aeration effect, and maximum splash height. The results showed that the HJSS corresponded to a large energy dissipation rate, the air was effectively entrained at the inlet of the stepped chute, and there was an observation of splash formation in the foregoing and downstream steps. Under large unit discharges, the HJSS maintained an energy dissipation rate exceeding 80%. Additionally, at the inlet, the air concentrations reached 4.5% on the bottom and 11.2% on the sidewall. The findings of this research could be used as a general guideline for stepped spillway design with large unit discharges. Full article

(This article belongs to the Special Issue Hydraulic Engineering and Numerical Simulation of Two-Phase Flows)

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27 pages, 8073 KiB

Open AccessArticle

Predicting COD and TN in A2O+AO Process Considering Influent and Reactor Variability: A Dynamic Ensemble Model Approach

by Yingjie Guo, Ji-Yeon Kim, Jeonghyun Park, Jung-Min Lee, Sung-Gwan Park, Eui-Jong Lee, Sangyoup Lee, Moon-Hyun Hwang, Guili Zheng, Xianghao Ren and Kyu-Jung Chae

Water 2024, 16(22), 3212; https://doi.org/10.3390/w16223212 (registering DOI) - 8 Nov 2024

Abstract

The prediction of the chemical oxygen demand (COD) and total nitrogen (TN) in integrated anaerobic–anoxic–oxic (A2O) and anoxic–oxic (AO) processes (i.e., A2O+AO process) was achieved using a dynamic ensemble model that reflects the dynamics of wastewater treatment plants (WWTPs). This model effectively captures [...] Read more.

The prediction of the chemical oxygen demand (COD) and total nitrogen (TN) in integrated anaerobic–anoxic–oxic (A2O) and anoxic–oxic (AO) processes (i.e., A2O+AO process) was achieved using a dynamic ensemble model that reflects the dynamics of wastewater treatment plants (WWTPs). This model effectively captures the variability in the influent characteristics and fluctuations within each reactor of the A2O+AO process. By employing a time-lag approach based on the hydraulic retention time (HRT), artificial intelligence (AI) selects suitable input (i.e., pH, temperature, total dissolved solid (TDS), NH₃-N, and NO₃-N) and output (COD and TN) data pairs for training, minimizing the error between predicted and observed values. Data collected over two years from the actual A2O+AO process were utilized. The ensemble model adopted machine learning-based XGBoost for COD and TN predictions. The dynamic ensemble model outperformed the static ensemble model, with the mean absolute percentage error (MAPE) for the COD ranging from 9.5% to 15.2%, compared to the static ensemble model’s range of 11.4% to 16.9%. For the TN, the dynamic model’s errors ranged from 9.4% to 15.5%, while the static model showed lower errors in specific reactors, particularly in the anoxic and oxic stages due to their stable characteristics. These results indicate that the dynamic ensemble model is suitable for predicting water quality in WWTPs, especially as variability may increase due to external environmental factors in the future. Full article

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

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17 pages, 9449 KiB

Open AccessArticle

Long-Term Changes in the Thermal and Ice Regime of the Biebrza River (Northeastern Poland) in the Era of Global Warming

by Mariusz Ptak, Salim Heddam, Soufiane Haddout, Mariusz Sojka and Teerachai Amnuaylojaroen

Water 2024, 16(22), 3211; https://doi.org/10.3390/w16223211 - 8 Nov 2024

Abstract

In the context of ongoing environmental changes, particularly against the backdrop of global warming, significant attention is being given to areas of exceptional natural value that, in many aspects, retain a pristine character. One such area is the Biebrza River in northeastern Poland, [...] Read more.

In the context of ongoing environmental changes, particularly against the backdrop of global warming, significant attention is being given to areas of exceptional natural value that, in many aspects, retain a pristine character. One such area is the Biebrza River in northeastern Poland, which, together with the wetlands in its basin, forms one of the most valuable ecosystems of its kind in Europe. This study analyses the changes in the thermal and ice regime for two hydrological stations, Sztabin and Burzyn, in the period from 1959 to 2023. It was found that the average annual water temperature in this period for the Biebrza River increased by 0.28 °C/decade, and in the case of ice phenomena, statistically significant changes for both stations showed a decline, with an acceleration of the ice cover disappearance by an average of 3 days/decade. These recorded changes should be considered unfavourable, as they will affect the transformation of both the biotic and abiotic characteristics of the river itself, as well as the natural elements associated with it. Full article

(This article belongs to the Special Issue Bridging the Gaps: Hydrological Research for Sustainable River Management)

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20 pages, 10019 KiB

Open AccessArticle

Computational Fluid Dynamics–Discrete Element Method Numerical Investigation of Binary Particle Mixing in Gas–Solid Fluidized Bed with Different Drag Models

by Chen Han, Xiaoling Fu, Xiaolu Guo, Wei Lu, Shaoqing Zhang, Hui Wang and Yang Yang

Water 2024, 16(22), 3210; https://doi.org/10.3390/w16223210 (registering DOI) - 8 Nov 2024

Abstract

The fluidized bed is a critical reactor in the energy and chemical industries, where the mixing and agglomeration behaviors of binary particles significantly influence both the efficiency of reaction processes and the uniformity of final products. However, the selection of appropriate drag force [...] Read more.

The fluidized bed is a critical reactor in the energy and chemical industries, where the mixing and agglomeration behaviors of binary particles significantly influence both the efficiency of reaction processes and the uniformity of final products. However, the selection of appropriate drag force models remains a subject of debate due to the variability in particle properties and operating conditions. In this study, we investigated the fluidization behavior of binary mixtures composed of two different sizes of Geldart-D particles within a fluidized bed, evaluating nine distinct drag force models, including Wen and Yu; Schiller and Naumann; Ergun; Gidaspow, Bezburuah, and Ding; Huilin and Gidaspow; De Felice; Syamlal and O’Brien; and Hill, Koch, and Ladd. We focused on four key parameters: particle mixing degree, migration characteristics, temperature variation, and mean pressure drop. Simulation results revealed that the choice of drag model markedly affected mixing behavior, migration dynamics, and temperature distribution. Notably, the Ergun; Gidaspow, Bezburuah, and Ding; and Hill, Koch, and Ladd models exhibited superior particle mixing uniformity. While the drag model had a relatively minor impact on particle temperature changes, its selection became critical in simulations requiring high-temperature precision. Regarding pressure drop, the Huilin and Gidaspow and Gidaspow, Bezburuah, and Ding models demonstrated smaller and more stable pressure drop fluctuations. These findings offer valuable theoretical insights into gas–solid two-phase flow under binary particle mixing and provide practical guidance for the design and operation of fluidized bed reactors. Full article

(This article belongs to the Special Issue Design and Optimization of Fluid Machinery, 2nd Edition)

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13 pages, 5510 KiB

Open AccessArticle

Determination and Optimization of Aerobic and Anaerobic Decomposition of Paper Sludge

by Dagmar Samešová, Juraj Poništ, Adam Pochyba, Tatiana Hýrošová, Marián Schwarz and Darina Veverková

Water 2024, 16(22), 3209; https://doi.org/10.3390/w16223209 - 8 Nov 2024

Abstract

The processing of paper sludge is currently an important environmental topic due to its high global production. The aim of this study is to monitor the biodegradation of paper sludge when the initial conditions change. Biodegradability tests 301F and OECD 311 were used [...] Read more.

The processing of paper sludge is currently an important environmental topic due to its high global production. The aim of this study is to monitor the biodegradation of paper sludge when the initial conditions change. Biodegradability tests 301F and OECD 311 were used to determine biodegradation. The data obtained from the tests were subsequently obtained for the simulation in MATLAB R2023b. The highest aerobic decomposition was approximately 80% after 28 days at an initial concentration of paper sludge leachate of 76 g/L. By simulating 3D modelling, we can predict that with a retention time of 1 day with degradation under aerobic conditions at the level of 70%, the ideal initial concentration of organic substances will be 157.55 g/L. Based on this model, it is possible to estimate that with a biogas production of 554 m³/t_VS and a decomposition time of 20 days, it is necessary to set a concentration of approximately 128 g/L. Based on biodegradability tests, paper sludge was evaluated as suitable for aerobic or anaerobic biological decomposition. Full article

(This article belongs to the Special Issue Water Treatment Technology for Emerging Contaminants)

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23 pages, 3117 KiB

Open AccessArticle

Assessing Flood Risks in Coastal Plain Cities of Zhejiang Province, Southeastern China

by Saihua Huang, Weidong Xuan, He Qiu, Jiandong Ye, Xiaofei Chen, Hui Nie and Hao Chen

Water 2024, 16(22), 3208; https://doi.org/10.3390/w16223208 - 8 Nov 2024

Abstract

Constructing a precise and effective evaluation index system is crucial to flood disaster prevention and management in coastal areas. This study takes Lucheng District, Wenzhou City, Zhejiang Province, southeastern China, as a case study and constructs an evaluation index system comprising three criterion [...] Read more.

Constructing a precise and effective evaluation index system is crucial to flood disaster prevention and management in coastal areas. This study takes Lucheng District, Wenzhou City, Zhejiang Province, southeastern China, as a case study and constructs an evaluation index system comprising three criterion levels: disaster-causing factors, disaster-gestation environments, and disaster-bearing bodies. The weights of each evaluation index are determined by combining the Analytic Hierarchy Process (AHP) and the entropy method. The fuzzy matter-element model is utilized to assess the flood disaster risk in Lucheng District quantitatively. By calculating the correlation degree of each evaluation index, the comprehensive index of flood disaster risk for each street area is obtained, and the flood disaster risk of each street area is classified according to the risk level classification criteria. Furthermore, the distribution of flood disaster risks in Lucheng District under different daily precipitation conditions is analyzed. The results indicate that: (1) the study area falls into the medium-risk category, with relatively low flood risks; (2) varying precipitation conditions will affect the flood resilience of each street in Lucheng District, Wenzhou City. The flood disaster evaluation index system and calculation framework constructed in this study provide significant guidance for flood risk assessment in coastal plain cities. Full article

(This article belongs to the Special Issue Reservoir Control Operation and Water Resources Management, 2nd Edition)

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22 pages, 8993 KiB

Open AccessArticle

Variation in Annual Ring and Wood Anatomy of Six Tree Mangrove Species in the Nicoya Gulf of Costa Rica

by Róger Moya, Carolina Tenorio, Danilo Torres-Gómez and Miguel Cifuentes-Jara

Water 2024, 16(22), 3207; https://doi.org/10.3390/w16223207 - 8 Nov 2024

Abstract

There is limited information regarding the adaptation of anatomical features and growth ring formation to ecological site conditions in Costa Rican mangrove trees. We used the methods and principles of ecological anatomy to explore the relationship between wood properties (e.g., ring formation, anatomical [...] Read more.

There is limited information regarding the adaptation of anatomical features and growth ring formation to ecological site conditions in Costa Rican mangrove trees. We used the methods and principles of ecological anatomy to explore the relationship between wood properties (e.g., ring formation, anatomical characteristics) and ecological factors for six mangrove tree species growing in three sites in the Gulf of Nicoya in Costa Rica. We found that variations of ecological conditions affected the growth ring formation of Avicennia bicolor, Avicennia germinans, Pelliciera rhizophorae and two species of Rhizophora but not Laguncularia racemosa. Site conditions affected the anatomical features of the mangrove tree species. Ray dimensions (height and width) were the factors most affected, which were followed by the frequency, diameter, and length of vessels. The fiber dimensions, green density, specific gravity, and carbon content were also affected by the site conditions. The plasticity in ray (increasing of ray dimension) and vessel elements (multiple vessels) facilitate efficient hydraulic conductivity amidst negative growth conditions and physiological restrictions for mangrove trees. We hypothesize that soil salinity, freshwater inputs and intertidal flooding influence these changes. Laguncularia racemosa presented the most changes in anatomical features across the different sites, followed by Pelliciera rhizophorae, with identical changes between Avicennia and Rhizophora spp. Finally, site salinity and wave energy affected the highest number of anatomical changes in mangrove tree species, including 38 changes in the wood structures in site 1. Full article

(This article belongs to the Special Issue Coastal Ecology and Fisheries Management)

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26 pages, 3333 KiB

Open AccessReview

Electrocoagulation as a Remedial Approach for Phosphorus Removal from Onsite Wastewater: A Review

by Arif Reza, Shannon Haller and Xinwei Mao

Water 2024, 16(22), 3206; https://doi.org/10.3390/w16223206 - 8 Nov 2024

Abstract

Onsite wastewater treatment systems (OWTSs), although essential for managing domestic sewage in areas without centralized sewerage treatment plants, often release phosphorus (P) into the environment due to inadequate treatment. This unregulated P discharge exacerbates water quality degradation and jeopardizes aquatic habitats and human [...] Read more.

Onsite wastewater treatment systems (OWTSs), although essential for managing domestic sewage in areas without centralized sewerage treatment plants, often release phosphorus (P) into the environment due to inadequate treatment. This unregulated P discharge exacerbates water quality degradation and jeopardizes aquatic habitats and human health. Among different treatment technologies, electrocoagulation (EC) demonstrates considerable potential for addressing this challenge by efficiently removing P from OWTSs and thus protecting water resources and ecological integrity. Through electrochemical reactions, EC destabilizes and aggregates P-bearing particles, facilitating their removal through precipitation. Compared to conventional treatment approaches, i.e., chemical and biological methods, EC offers several advantages, including high efficiency, minimal chemical usage, and adaptability to varying wastewater compositions. This review underscores the urgent need for mitigating P discharge from OWTSs and the efficacy of EC as a sustainable solution for P removal, offering insights into its mechanisms, reactor design considerations, important operational factors, performance, and potential applications in OWTSs as well as providing future research directions. Full article

(This article belongs to the Special Issue Application of Electrochemical Technology for Water and Wastewater Treatment)

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21 pages, 12616 KiB

Open AccessArticle

Numerical Simulations Using iRIC Nays2DH for Sediment Transport Behaviors in Dam Breach Tests

by Zheng-Yi Feng, Zhi-You Chen and Su-Chin Chen

Water 2024, 16(22), 3205; https://doi.org/10.3390/w16223205 - 8 Nov 2024

Abstract

After the breach of a landslide dam, the sediment in the breach opening will be carried downstream by the breach flood. The river channel will also be eroded by the flood, resulting in bed load transport. Three large-scale dam breach tests were conducted [...] Read more.

After the breach of a landslide dam, the sediment in the breach opening will be carried downstream by the breach flood. The river channel will also be eroded by the flood, resulting in bed load transport. Three large-scale dam breach tests were conducted to investigate the sediment transport behavior after a dam breach. The topography data of the creek channel were measured before and after the dam breach tests to understand the sediment transport behavior. The sediment transport simulations of the dam breach tests were conducted using the iRIC Nays2DH software. The simulations focused on three types of test setups: the single dam, single dam with a spur dike, and double dam models. The terrain (DEM) for the numerical model input was designated based on the LiDAR results, and a flow hydrograph during the dam breach tests was applied. The accuracy of the simulations was assessed using the “coverage index” and “mean absolute percentage error”. A numerical parametrical study was performed to find the major parameters that influenced the simulations. The results showed that the dynamic behavior of water flow and sediment during the dam breach processes were effectively captured by the iRIC Nays2DH simulation, but with limitations. The average flow velocity of the flood in the single dam case was the fastest among the three types of dam breaches. Due to the contraction of the creek channel caused by the spur dike, severe erosion occurred locally, and the flow rate increased in the narrowed section. Water impoundment between the two dams after the first dam breach and the consequent breach of the second dam were also well-simulated for the double dam breach. The findings and simulations in this study help explain dam breaches better and can guide researchers working on sediment transport during dam-breach floods. Full article

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

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15 pages, 2431 KiB

Open AccessArticle

Study on Operation Effect of Two-Stage MSL System for Rural Decentralized Sewage Treatment

by Qingtao Hu, Anhong Bao, Zenan Niu, Wanqi Zhao and Hanzhen Fang

Water 2024, 16(22), 3204; https://doi.org/10.3390/w16223204 - 8 Nov 2024

Abstract

To improve the removal efficiency of rural domestic sewage, a two-stage multi-soil-layer sewage treatment system with an “aeration section + non-aeration section” was designed, and its treatment performance was observed under different influent loads and aeration intensities. The experiment ran for a total [...] Read more.

To improve the removal efficiency of rural domestic sewage, a two-stage multi-soil-layer sewage treatment system with an “aeration section + non-aeration section” was designed, and its treatment performance was observed under different influent loads and aeration intensities. The experiment ran for a total of 150 days, and the results showed that the two-stage multi-soil-layer (MSL) system could effectively reduce the effluent concentration of sewage to meet discharge standards. Under the operating conditions of an influent hydraulic load of 1000 L·m⁻²·d⁻¹ and an air–water ratio of 4:1, the final effluent average concentrations of COD, NH₃-N, TN, and TP were 106.5 mg·L⁻¹, 7.4 mg·L⁻¹, 13.9 mg·L⁻¹, 0.12 mg·L⁻¹, and 18.6 mg·L⁻¹, respectively, with average removal rates of 85.3%, 82%, 72.5%, 96%, and 85%. A longer hydraulic retention time and ideal anoxic conditions were ensured by designing a certain effluent height in the system. Adding aeration to the system allowed for a synchronous nitrification–denitrification reaction under reasonable influent loads, ultimately enabling the effluent to meet discharge standards. Full article

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

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16 pages, 3130 KiB

Open AccessArticle

Mathematical Approach for Directly Solving Air–Water Interfaces in Water Emptying Processes

by Dalia M. Bonilla-Correa, Oscar E. Coronado-Hernández, Alfonso Arrieta-Pastrana, Vicente S. Fuertes-Miquel, Modesto Pérez-Sánchez and Helena M. Ramos

Water 2024, 16(22), 3203; https://doi.org/10.3390/w16223203 - 8 Nov 2024

Abstract

Emptying processes are operations frequently required in hydraulic installations by water utilities. These processes can result in drops to sub-atmospheric pressure pulses, which may lead to pipeline collapse depending on soil characteristics and the stiffness of a pipe class. One-dimensional mathematical models and [...] Read more.

Emptying processes are operations frequently required in hydraulic installations by water utilities. These processes can result in drops to sub-atmospheric pressure pulses, which may lead to pipeline collapse depending on soil characteristics and the stiffness of a pipe class. One-dimensional mathematical models and 3D computational fluid dynamics (CFD) simulations have been employed to analyse the behaviour of the air–water interface during these events. The numerical resolution of these models is challenging, as 1D models necessitate solving a system of algebraic differential equations. At the same time, 3D CFD simulations can take months to complete depending on the characteristics of the pipeline. This presents a mathematical approach for directly solving air–water interactions in emptying processes involving entrapped air, providing a predictive tool for water utilities. The proposed mathematical approach enables water utilities to predict emptying operations in water pipelines without needing 2D/3D CFD simulations or the resolution of a differential algebraic equations system (1D model). A practical application is demonstrated in a case study of a 350 m long pipe with an internal diameter of 350 mm, investigating the influence of air pocket size, friction factor, polytropic coefficient, pipe diameter, resistance coefficient, and pipe slope. The mathematical approach is validated using an experimental facility that is 7.36 m long, comparing it with 1D mathematical models and 3D CFD simulations. The results confirm that the derived mathematical expression effectively predicts emptying operations in single water installations. Full article

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

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14 pages, 4775 KiB

Open AccessArticle

Metagenomic Analysis of Microbial Diversity in the Moroccan Coastal Water of the Gibraltar Strait

by Manal Chrairi, Said Barrijal, Antonio Castellano-Hinojosa, Youssra Boumait, Chahrazade El Hamouti, Afaf Lamzouri, Hassan Ghazal and Rajaa Chahboune

Water 2024, 16(22), 3202; https://doi.org/10.3390/w16223202 - 8 Nov 2024

Abstract

Coastal waters are known for higher productivity and organic matter levels, which support a high diversity and abundance of microorganisms compared to some aquatic environments. The characterization of marine microbiomes can provide valuable information for evaluating the sustainability of coastal waters that are [...] Read more.

Coastal waters are known for higher productivity and organic matter levels, which support a high diversity and abundance of microorganisms compared to some aquatic environments. The characterization of marine microbiomes can provide valuable information for evaluating the sustainability of coastal waters that are increasingly subjected to environmental and human impacts. Our study is the first metagenomic study realized on Moroccan Mediterranean coastal seawater. We analyzed and described the Gibraltar Detroit marine microbiome taxonomic and functional profiling using MG-RAST software. Shotgun sequencing revealed a predominance of bacterial taxa, particularly the Proteobacteria (57.29%) and Bacteroidetes (27.06%) phyla, alongside notable populations of eukaryotes, viruses, and archaea. Alphaproteobacteria and Gammaproteobacteria emerged as the dominant bacterial classes, while Flavobacteria represented a significant portion of Bacteroidetes. Functional profiling of the microbial community highlighted a wide array of metabolic pathways, emphasizing genes related to carbohydrate metabolism, amino acid synthesis, and protein processing. The marine microbiome exhibited essential biogeochemical activities, particularly in nitrogen, sulfur, and carbon cycles, with notable pathways including denitrification, thiosulfate oxidation, and carbon fixation. This functional diversity underlines the microbiome’s role in sustaining ecosystem health through nutrient cycling and organic matter degradation. Our findings offer a crucial baseline for understanding microbial community structure and resilience in Mediterranean coastal ecosystems, with implications for assessing future environmental and anthropogenic impacts on these microbial dynamics. Full article

(This article belongs to the Special Issue Aquatic Environment and Ecosystems)

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24 pages, 15049 KiB

Open AccessArticle

Distribution and Co-Enrichment Factors of Arsenic and Fluoride in the Groundwater of the Plain Area of the Aksu River Basin, Xinjiang, PR China

by Yuanyuan Ji, Yinzhu Zhou, Xiaoyu Zhao, Jinlong Zhou, Ying Sun and Mi Lei

Water 2024, 16(22), 3201; https://doi.org/10.3390/w16223201 - 8 Nov 2024

Abstract

The Aksu River Basin is located in the western region of the middle part of the southern foothills of the Tianshan Mountains and the northwestern edge of the Tarim Basin in Xinjiang, China. High-arsenic (As)/high-fluoride (F) groundwater is widely distributed in this area [...] Read more.

The Aksu River Basin is located in the western region of the middle part of the southern foothills of the Tianshan Mountains and the northwestern edge of the Tarim Basin in Xinjiang, China. High-arsenic (As)/high-fluoride (F) groundwater is widely distributed in this area and is harmful to the life of local residents and to agricultural production. It is of great importance to understand the distribution and causes of As-F co-enrichment in the groundwater in this area. Based on the test results of 138 groundwater samples in the plain area of the Aksu River Basin, the hydrochemical characteristics of groundwater and the spatial distribution of As-F co-enrichment groundwater were analyzed under the following conditions: a single-structure phreatic aquifer (SSPA), a phreatic aquifer in a confined groundwater area (PACGA), a shallow confined aquifer (SCA), and a deep confined aquifer (DCA), all in a recharge area, transition area, and an evaporation area. The hydrogeochemical processes affecting the source, migration, and enrichment of As-F in the groundwater were revealed. The results showed that the chemical types of groundwater in the study area were mainly HCO₃·SO₄-Ca·Mg and SO₄·Cl-Na·Mg. Horizontally, high-As-F groundwater was mainly distributed in the transition area and evaporation area in the middle and lower reaches of the Aksu River Basin. The area is close to the edge of the desert, where the groundwater runoff is sluggish and in an alkaline-reducing groundwater environment. Vertically, high-As groundwater was mainly distributed in the PACGA at a depth of 10–20 m and in the SCA at a depth of 80–100 m. High-F groundwater was mainly concentrated in the PACGA at a depth of 10–30 m and in the SCA at a depth of 80–100 m, and As-F co-enrichment groundwater was mainly concentrated in the PACGA at a depth of 10–20 m and in the SCA at a depth of 80–100 m. The hydrochemical characteristics of the groundwater in the Aksu River Basin were closely related to geological conditions, hydrogeological conditions, and the hydrochemical environment of the groundwater. As-F co-enriched groundwater was mainly affected by the combination of a small topographic gradient, a shallow groundwater burial depth, a weak reducing alkaline groundwater environment, strong evaporation and concentration, the weathering and dissolution of evaporated salt rock, and the alternating adsorption of cations. Full article

(This article belongs to the Special Issue Soil and Groundwater Quality and Resources Assessment)

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24 pages, 10807 KiB

Open AccessArticle

Pollution and Ecological Risk Assessment of Potentially Toxic Elements in Sediments Along the Fluvial-to-Marine Transition Zone of the Don River

by Elizaveta Konstantinova, Tatiana Minkina, Dina Nevidomskaya, Tatiana Bauer, Inna Zamulina, Elizaveta Latsynnik, Tamara Dudnikova, Rajendra Kumar Yadav, Marina Burachevskaya and Saglara Mandzhieva

Water 2024, 16(22), 3200; https://doi.org/10.3390/w16223200 - 7 Nov 2024

Abstract

The quality of sediments in the mixing zone of river freshwater and marine saline water as an important geochemical barrier for potentially toxic elements (PTEs) remains poorly understood. This study aims to analyze the current pollution with PTEs and associated ecological risks in [...] Read more.

The quality of sediments in the mixing zone of river freshwater and marine saline water as an important geochemical barrier for potentially toxic elements (PTEs) remains poorly understood. This study aims to analyze the current pollution with PTEs and associated ecological risks in sediments of the Don River delta and the surrounding area of the Taganrog Bay of the Sea of Azov (Russia). The PTE content was determined in fifty-four collected samples using the WDXRF and assessed using geochemical and ecotoxicological indicators. The source of Cr, Mn, Ni and Pb is mainly river runoff, and Cu, Zn and Cd are from a variety of anthropogenic sources. As shown by the assessment of the geoaccumulation index (Igeo), single pollution index (PI) and contamination factor (CF), these elements are the priority pollutants. According to these estimates, high and very high contamination of sediments in the estuarine zone of the Don River with Cd and Pb was detected in 72–94% and 2–57% of samples, respectively. However, environmental risks are determined almost exclusively by the level of Cd. Total contamination as assessed by the Nemerow pollution index (NPI), modified degree of contamination (mC_d) and metal pollution index (MPI) is of concern in 83–98% of the samples studied. The most heavily polluted sediments are in the vicinity of residential areas of the Taganrog Bay. Despite the lower average pollution levels of deltaic sediments, freshwater biota are exposed to higher potential toxic risks of adverse effects by PTE, particularly from Ni and Pb. Thus, the complex hydrological regime and uneven anthropogenic impact predetermine the geochemical state of the sediments of the estuarine zone of the Don River. Full article

(This article belongs to the Topic Analysis and Separations of Trace Elements in the Environment)

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