Water

17 pages, 537 KiB

Open AccessReview

Addressing the Uncertainties in the Environmental Analysis, Modeling, Source and Risk Assessment of Emerging Contaminants

by Wenxing Zhao, Bin Wang and Gang Yu

Water 2025, 17(2), 215; https://doi.org/10.3390/w17020215 - 14 Jan 2025

Abstract

Emerging contaminants (ECs) have become a growing source of worry for environmental researchers and stakeholders in recent decades. Compared with conventional pollutants, ECs can pose environmental risks even at a trace level. The analysis of ECs is typically significantly more challenging than that [...] Read more.

Emerging contaminants (ECs) have become a growing source of worry for environmental researchers and stakeholders in recent decades. Compared with conventional pollutants, ECs can pose environmental risks even at a trace level. The analysis of ECs is typically significantly more challenging than that of conventional pollutants because of their trace amounts and diverse chemical structures. For sound environmental management, it is necessary to perform a comprehensive study of these pollutants. Global concern has increasingly grown over the occurrence, fate, environmental modeling, and risk assessment of such contaminants. Due to the dearth of knowledge in this area, various unc3ertainties inevitably exist in the investigation of ECs. Environmental problems cannot be precisely understood due to the ubiquitous uncertainties in environmental research. Uncertainties and their sources have been reviewed in this study, including spatial and temporal variability, uncertainty in sample collection and analysis, uncertainty in environmental modeling, uncertainty in risk assessment, and uncertainty in source characterization. Some suggestions to reduce uncertainties are summarized. An awareness of uncertainty is necessary for us to have a more accurate understanding and contribute to sound environmental decision-making and management. In addition, more work remains to be performed to reveal the uncertainties in the analysis and risk assessment of ECs. Full article

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

17 pages, 2949 KiB

Open AccessArticle

Impact of Organic and Chemical Fertilizers on Nutrient Co-Migration in Different Types of Ditches of Red Soil Sloping Orchards

by Wenbin Li, Chongjun Tang, Jie Zhang, Jinjin Zhu, Xiaoan Chen and You Hu

Water 2025, 17(2), 214; https://doi.org/10.3390/w17020214 - 14 Jan 2025

Abstract

The planting of fruit trees on sloping land can bring significant benefits to the local economy, but it also causes different degrees of soil and water erosion problems. In this study, we investigated the differences in nutrient migration in slope ditch runoff. In [...] Read more.

The planting of fruit trees on sloping land can bring significant benefits to the local economy, but it also causes different degrees of soil and water erosion problems. In this study, we investigated the differences in nutrient migration in slope ditch runoff. In 39 scouring tests, a grass ditch reduced the loss of carbon (C), nitrogen (N), and phosphorus (P) by intercepting runoff. There was a positive correlation between runoff and the loss rate of N and P. The flow affected the retention time of runoff in the ditch, and then changed the dissolved organic carbon (DOC) loss rate in the runoff. The concentration of N and P did not affect the N and P loss rate, but did affect the total amount of N and P lost and the DOC loss rate in the runoff. The addition of organic fertilizer significantly increased the N loss rate in the runoff, and the change rule of the P and DOC loss rate was similar; thus, co-migration might have occurred. To sum up, the importance of the four factors on the migration and loss of C, N, and P in ditch runoff was as follows: organic fertilizer (100%) > fertilizer concentration (74.8%) > ditch type (12.6%) > initial flow (10%). Full article

(This article belongs to the Special Issue Soil and Water Management: Practices to Mitigate Nutrient Losses in Agricultural Watersheds, 2nd Edition)

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17 pages, 3533 KiB

Open AccessArticle

Ultrafiltration of Car Wash Wastewater: Pilot-Scale Studies

by Wirginia Tomczak, Piotr Woźniak and Marek Gryta

Water 2025, 17(2), 213; https://doi.org/10.3390/w17020213 - 14 Jan 2025

Abstract

Currently, the world faces serious challenges in meeting the growing demand for clean water. The present paper demonstrates the possibility of using the ultrafiltration (UF) process to reuse water from wastewater generated in car washes. Car washes commonly use foaming agents with dyes, [...] Read more.

Currently, the world faces serious challenges in meeting the growing demand for clean water. The present paper demonstrates the possibility of using the ultrafiltration (UF) process to reuse water from wastewater generated in car washes. Car washes commonly use foaming agents with dyes, which, although they are not necessary for washing cars, may hinder water reuse. For this reason, the aim of this work was to investigate the effect of the dyes present in car wash wastewater on the membrane fouling intensity. For this purpose, experimental tests were conducted with the application of a pilot plant with an industrial PCI B1 membrane module. The module was equipped with tubular FP100 (100 kDa) polyvinylidene fluoride (PVDF) membranes. For the feed, two types of cleaning agents and synthetic wastewater were used. The results obtained in the current study demonstrated that the UF membranes allowed the obtainment of the permeate characterized by high quality. In addition, it has been shown that the presence of Indigo carmine dye in the wastewater led to an increase in the fouling intensity. To sum up, it should be pointed out that the findings presented in the current study may be of key importance in the design of pilot installations used for the treatment of car wash wastewater. Full article

(This article belongs to the Special Issue Novel Methods in Wastewater and Stormwater Treatment)

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16 pages, 4492 KiB

Open AccessFeature PaperArticle

Advanced Oxidation Processes and Adsorption Technologies for the Removal of Organic Azo Compounds: UV, H₂O₂, and GAC

by M. Ferre, M. J. Moya-Llamas, E. Dominguez, Nuria Ortuño and D. Prats

Water 2025, 17(2), 212; https://doi.org/10.3390/w17020212 - 14 Jan 2025

Abstract

This research focuses on the removal of emerging contaminants (CEC) present in synthetic aqueous matrices. Azole compounds were selected as CEC of interest due to their persistence and toxicity, particularly the triazole and oxazole groups. These compounds are also trace contaminants listed in [...] Read more.

This research focuses on the removal of emerging contaminants (CEC) present in synthetic aqueous matrices. Azole compounds were selected as CEC of interest due to their persistence and toxicity, particularly the triazole and oxazole groups. These compounds are also trace contaminants listed in the proposed revision of Directive 91/271/EEC on urban wastewater treatment and the 3rd European Union Observation List (Implementing Decision EU 2020/116), highlighting their regulatory importance. The draft Directive includes the implementation of quaternary treatments to achieve the highest possible removal rates of micropollutants. Among the technologies used on a large scale are some advanced oxidation processes (AOP), often combined with adsorption on activated carbon (AC). Laboratory-scale pilot plants have been designed and operated in this research, including UV photolysis and oxidation with H₂O₂ and adsorption with GAC. The results demonstrate that UV photolysis is able to remove all the selected CECs except fluconazole, reaching eliminations higher than 86% at high doses of 31.000 J/m². Treatment by H₂O₂ achieved removals of 4 to 55%, proving to be ineffective in the degradation of persistent compounds when acting as a single technology. Adsorption by AC is improved with longer contact times, reaching removals above 80% for benzotriazole and methyl benzotriazole at short contact times, followed by sulfamethoxazole and tebuconazole. Fluconazole had a mean adsorption capacity at low contact times, while metconazole and penconazole showed low adsorption capacities. Full article

(This article belongs to the Special Issue Physical–Chemical Wastewater Treatment Technologies)

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18 pages, 2765 KiB

Open AccessArticle

Groundwater Recharge Evaluation Using Stable Isotopes and the NETPATH Model in Al-Madinah Al-Munawarah Province, Saudi Arabia

by Milad Masoud, Maged El Osta, Nassir Al-Amri, Burhan Niyazi, Abdulaziz Alqarawy, Riyadh Halawani and Mohamed Rashed

Water 2025, 17(2), 211; https://doi.org/10.3390/w17020211 - 14 Jan 2025

Abstract

In this study, hydrogeochemistry and environmentally stable isotopes were employed to examine the processes involved in recharging aquifer systems and the changes in the groundwater chemistry caused by the interaction between the water and the aquifer matrix. Based on data derived from 113 [...] Read more.

In this study, hydrogeochemistry and environmentally stable isotopes were employed to examine the processes involved in recharging aquifer systems and the changes in the groundwater chemistry caused by the interaction between the water and the aquifer matrix. Based on data derived from 113 groundwater wells, various tools and techniques, including stable environmental isotopes Oxygen-18 and Deuterium (δ¹⁸O and δD) for 33 samples and geochemical modeling with NETPATH, were used to evaluate the recharge mechanism and the evolution of the groundwater, combining GIS with hydrological and hydrochemical methods. The results revealed that groundwater from the Quaternary was the main source for irrigation; the water quality was categorized as relatively fresh to saline, with the total dissolved solids (TDSs) ranging from 261.3 to 8628.56 mg/L, exhibiting an average value of 2311.68 mg/L. The results of the environmental isotope analysis showed that the range of oxygen δ¹⁸O isotopes in the groundwater was from −5.65‰ to +0.39‰, while the range of hydrogen δD isotopes was from −32.60‰ to 4.73‰. Moreover, the δ¹⁸O–δD relationship indicated that the groundwater samples fell around the global meteoric precipitation line, showing a strong relationship, with a coefficient (R²) of approximately 0.82. The NETPATH model revealed that the dissolved chemical species within the groundwater system primarily originated from processes such as mineral weathering and dissolution, ion exchange, and evaporation. Full article

36 pages, 6613 KiB

Open AccessReview

Recent Advances in the Synthesis, Characterization, and Application of Carbon Dots in the Field of Wastewater Treatment: A Comprehensive Review

by Yaxuan Xiao, Zelong Wang, Jingran Fu, Jing Zhang, Qiulai He, Haijun Lu, Qiaohong Zhou and Hongyu Wang

Water 2025, 17(2), 210; https://doi.org/10.3390/w17020210 - 14 Jan 2025

Abstract

Carbon dots (CDs), as a revolutionary nanomaterial, exhibit unique advantages in terms of wastewater treatment, offering new opportunities for the development of water treatment technologies due to their simple synthesis methods, excellent biocompatibility, tunable optical properties, and favorable environmental performance. This review systematically [...] Read more.

Carbon dots (CDs), as a revolutionary nanomaterial, exhibit unique advantages in terms of wastewater treatment, offering new opportunities for the development of water treatment technologies due to their simple synthesis methods, excellent biocompatibility, tunable optical properties, and favorable environmental performance. This review systematically discusses the synthesis methods, structural characteristics, and application progress of carbon dots in wastewater treatment, highlighting several key findings. (1) Excellent adsorption performance: CDs can effectively remove heavy metal ions, dyes, and organic pollutants from water. (2) Outstanding photocatalytic performance: Some carbon-dot-enhanced photocatalytic systems can efficiently remove pollutants under visible light. (3) Exceptional selective detection ability: CDs are capable of highly sensitive detection of heavy metals and organic pollutants in water, with the detection limits reaching the nanomolar level. (4) Enhanced membrane separation performance: The high water flux and excellent selectivity of carbon-dot-modified membranes make them suitable for efficient water treatment and water quality separation. (5) Enhancement of biological treatment: In biological treatment systems, CDs can significantly improve the microbial activity and electron transfer efficiency to enhance the efficiency of biological degradation processes. (6) Sustainable utilization of waste as a raw material and regeneration of CDs are conducive to reducing the cost of preparation of CDs. These findings indicate that CDs have broad application potential in wastewater treatment. Furthermore, this review looks ahead to the future development directions of CDs in wastewater treatment, proposing potential innovations in catalytic performance enhancement, cost control, and practical applications, aiming to provide important references and guidance for future research and industrial application of CDs in wastewater treatment. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Water and Wastewater Treatment)

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24 pages, 7022 KiB

Open AccessArticle

Evaluation of the Sensitivity of the Weather Research and Forecasting Model to Changes in Physical Parameterizations During a Torrential Precipitation Event of the El Niño Costero 2017 in Peru

by Alejandro Sánchez Oliva, Matilde García-Valdecasas Ojeda and Raúl Arasa Agudo

Water 2025, 17(2), 209; https://doi.org/10.3390/w17020209 - 14 Jan 2025

Abstract

This study evaluates the sensitivity of the Weather Research and Forecasting (WRF-ARW) model in its version 4.3.3 during different experiments on a torrential precipitation event associated with the 2017 El Niño Costero in Peru. The results are compared with two reference datasets: precipitation [...] Read more.

This study evaluates the sensitivity of the Weather Research and Forecasting (WRF-ARW) model in its version 4.3.3 during different experiments on a torrential precipitation event associated with the 2017 El Niño Costero in Peru. The results are compared with two reference datasets: precipitation estimations from CHIRPS satellite data and SENAMHI meteorological station values. The event, which had significant economic and social impacts, is simulated using two nested domains with resolutions of 9 km (d01) and 3 km (d02). A total of 22 experiments are conducted, resulting from the combination of two planetary boundary layer (PBL) schemes: Yonsei University (YSU) and Mellor–Yamada–Janjic (MYJ), with five cumulus parameterization schemes: Betts–Miller–Janjic (BMJ), Grell–Devenyi (GD), Grell–Freitas (GF), Kain–Fritsch (KF), and New Tiedtke (NT). Additionally, the effect of turning off cumulus parameterization in the inner domain (d02) or in both (d01 and d02) is explored. The results show that the YSU scheme generally provides better results than the MYJ scheme in detecting the precipitation patterns observed during the event. Furthermore, it is concluded that turning off cumulus parameterization in both domains produces satisfactory results for certain regions when it is combined with the YSU PBL scheme. However, the KF cumulus parameterization is considered the most effective for intense precipitation events in this region, although it tends to overestimate precipitation in high mountain areas. In contrast, for lighter rains, combinations of the YSU PBL scheme with the GD or NT parameterization show a superior performance. It is worth nothing that for all experiments here used, there is a clear underestimation in terms of precipitation, except in high mountain regions, where the model tends to overestimate rainfall. Full article

(This article belongs to the Special Issue Impacts of Climate Change on Extreme Hydro-Climatic Events: Droughts and Floods)

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12 pages, 2718 KiB

Open AccessArticle

Impact of Deep-Rooted Vegetation on Deep Soil Water Recharge in the Gully Region of the Loess Plateau

by Jingjing Jin, Xiaoyun Ding, Fengshi Li, Zichen Jia, Haoyan Wei, Junchao Li and Min Li

Water 2025, 17(2), 208; https://doi.org/10.3390/w17020208 - 14 Jan 2025

Abstract

To investigate the impacts of vegetation change on deep soil water recharge, it is essential to identify the sources of deep soil water and deep drainage. The combination of stable and radioactive water isotopes is an effective method for studying deep vadose zones, [...] Read more.

To investigate the impacts of vegetation change on deep soil water recharge, it is essential to identify the sources of deep soil water and deep drainage. The combination of stable and radioactive water isotopes is an effective method for studying deep vadose zones, though it has been rarely applied in complex gully areas. In this study, we measured δ²H, δ¹⁸O, and ³H in soil water under long-term natural grassland and C. korshinskii on the same slope. Both natural grassland and C. korshinskii plots received deep soil water from rainfall during the rainy season; however, the replenishment thresholds for soil water at depths of 2–10.4 m differed between the two vegetation types, corresponding to rainfall intensities of ≥20 mm and ≥50 mm, respectively. Following the conversion of natural grassland to C. korshinskii vegetation, the rate of soil water storage deficit increased by 46.4 mm yr⁻¹, and deep drainage shifted from 39.6 mm yr⁻¹ to 0 mm yr⁻¹. Deep-rooted vegetation significantly depletes soil water to meet transpiration demands, thus hindering rainfall recharge. These findings have important implications for water and land resource management, especially in areas undergoing significant vegetation changes. Full article

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22 pages, 3519 KiB

Open AccessArticle

Use of Modified Activated Carbon in Groundwater Remediation for Human Consumption

by Cadme-Arévalo María Lorena, Andrade-Yucailla Verónica Cristina, Geijo López Alda, Villamar-Torres Ronald Oswaldo, Campisi Cadme Raisha Lorena, Arreaga Cadme Thais Sarah, Fernández González Javier, Benavente Herrera José, Sesan Abiodun Aransiola and Naga Raju Maddela

Water 2025, 17(2), 207; https://doi.org/10.3390/w17020207 - 14 Jan 2025

Abstract

This study aimed to produce activated carbon from desilicated rice husks using various carbonization and activation methods, including a tube furnace, muffle furnace, and artisanal pyrolysis. The resulting activated carbons were characterized for their adsorptive capacity through the determination of iodine number and [...] Read more.

This study aimed to produce activated carbon from desilicated rice husks using various carbonization and activation methods, including a tube furnace, muffle furnace, and artisanal pyrolysis. The resulting activated carbons were characterized for their adsorptive capacity through the determination of iodine number and methylene blue adsorption; these are key indicators of specific surface area and adsorbent quality. Advanced characterization techniques were employed, such as scanning electron microscopy (SEM), which revealed a highly porous and irregular surface structure, and energy dispersive X-ray spectroscopy (EDS), confirming the effective removal of impurities and optimization of the elemental composition. Atomic force microscopy (AFM) demonstrated favorable surface roughness for adsorption processes. Among the samples, CaDH162-CADH53 exhibited the highest performance, with an iodine number of 1094.8 mg/g and a yield of 93.5%, signifying a high adsorption capacity. The activation treatments with phosphoric acid and calcium carbonate significantly improved the porous structure, further enhancing the material’s adsorptive properties. In conclusion, the activated carbons produced in this study demonstrated optimal physicochemical properties for water purification and contaminant treatment applications. These findings highlight the potential of using agricultural waste, such as rice husk, as a sustainable and scalable alternative for industrial-scale activated carbon production. Full article

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

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23 pages, 4056 KiB

Open AccessArticle

Generalised Additive Model-Based Regional Flood Frequency Analysis: Parameter Regression Technique Using Generalised Extreme Value Distribution

by Laura Rima, Khaled Haddad and Ataur Rahman

Water 2025, 17(2), 206; https://doi.org/10.3390/w17020206 - 14 Jan 2025

Abstract

This study examines the effectiveness of Generalised Additive Models (GAMs) and log-log linear models for estimating the parameters of the generalised extreme value (GEV) distribution, which are then used to estimate flood quantiles in ungauged catchments. This is known as the parameter regression [...] Read more.

This study examines the effectiveness of Generalised Additive Models (GAMs) and log-log linear models for estimating the parameters of the generalised extreme value (GEV) distribution, which are then used to estimate flood quantiles in ungauged catchments. This is known as the parameter regression technique (PRT). Using data from 88 gauged catchments in New South Wales, Australia, flood quantiles were estimated for various annual exceedance probabilities (AEPs) of 50%, 20%, 10%, 5%, 2%, and 1%, corresponding to return periods of 2, 5, 10, 20, 50, and 100 years, denoted by Q₂, Q₅, Q₁₀, Q₂₀, Q₅₀, and Q₁₀₀, respectively. These flood quantiles were then used as dependent variables, while several catchment characteristics served as independent variables in the regression. GAMs were employed to capture non-linearities in flood generation processes. This study evaluates different GAMs and log-log linear models, identifying the best ones based on significant predictors and various statistical metrics using a leave-one-out (LOO) validation approach. The results indicate that GAMs provide more accurate and reliable predictions of flood quantiles compared to the log-log linear models, demonstrating better performance in capturing observed values across different quantiles. The absolute median relative error percentage (REr%) ranges from 33% to 39% for the GAMs and from 36% to 45% for the log-log models. GAMs demonstrate better performance compared to the log-log linear models for quantiles Q₂, Q₅, Q₁₀, Q₂₀, and Q₅₀; however, their performances appear to be similar for Q₁₀₀. Full article

(This article belongs to the Special Issue Urban Flood Frequency Analysis and Risk Assessment)

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26 pages, 18247 KiB

Open AccessArticle

Experimental Assessment of the Turbulent Flow Field Due to Emergent Vegetation at a Sharply Curved Open Channel

by Hamidreza Raeisifar, Ali Rahm Rahimpour, Hossein Afzalimehr, Oral Yagci and Manousos Valyrakis

Water 2025, 17(2), 205; https://doi.org/10.3390/w17020205 - 14 Jan 2025

Abstract

Emergent vegetation in river corridors influences both the flow structure and subsequent fluvial processes. This investigation aimed to analyze the impact of the bending and vegetation components in a sharply curved open channel on the flow field. Experiments were undertaken in a meandering [...] Read more.

Emergent vegetation in river corridors influences both the flow structure and subsequent fluvial processes. This investigation aimed to analyze the impact of the bending and vegetation components in a sharply curved open channel on the flow field. Experiments were undertaken in a meandering flume (0.9 m wide, wavelength of 3.2 m, and a sinuosity of 1.05) with a 90-degree bend at the end of it, with and without vegetation, to achieve this goal. The individual vegetation elements arranged across the 90-degree bend of the flow channel were physically modelled using rigid plastic stems (of 5 mm and 10 mm diameters). Analysis of the findings from the flow velocimetry, taken at five cross-sections oriented at angles of 0°, 30°, 45°, 60°, and 90°, along the 90-degree bend indicates that as the plant density increases, the effect of centrifugal force from the channel’s bend on the cross-sectional flow patterns decreases. At the same time, the restricting influence of vegetation on lateral momentum transfer becomes more pronounced. Specifically, for increasing vegetation density: (a) higher transverse and vertical velocities are observed (increased by 4.35% and 9.68% for 5 mm and 10 mm reed vegetation, respectively, compared to the non-vegetated case); (b) greater turbulence intensity is seen in the transverse flow direction, along with increased turbulent kinetic energy (TKE); and (c) reduced near-bed Reynolds stresses are found. The average transverse flow velocity for the non-vegetated case is 18.19% of the longitudinal flow velocity and the average vertical velocity for the non-vegetated case and 5 mm and 10 mm reed vegetation is 3.24%, 3.6%, and 5.44% of the longitudinal flow velocity, respectively. Full article

(This article belongs to the Special Issue Advances in Hydraulic and Water Resources Research (2nd Edition))

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25 pages, 7427 KiB

Open AccessArticle

Design of Combined Rainwater-Harvesting and Stormwater-Detention System with Passive Release for New Buildings in Taiwan

by Hsin-Yuan Tsai, Chia-Ming Fan and Chao-Hsien Liaw

Water 2025, 17(2), 204; https://doi.org/10.3390/w17020204 - 14 Jan 2025

Abstract

Taiwan experiences abundant rainfall, but faces significant water shortages, making rainwater harvesting (RWH) a potential alternative water source. Additionally, extreme rainfall events strain urban flood control systems, highlighting the need for integrated stormwater management. To address these challenges, Taiwan mandates stormwater detention (SWD) [...] Read more.

Taiwan experiences abundant rainfall, but faces significant water shortages, making rainwater harvesting (RWH) a potential alternative water source. Additionally, extreme rainfall events strain urban flood control systems, highlighting the need for integrated stormwater management. To address these challenges, Taiwan mandates stormwater detention (SWD) in new buildings. However, the current RWH and SWD systems are designed independently, with no combined design guidelines available. This study proposes three combined RWH and SWD systems, series, parallel, and enhanced parallel with a valve using a passive release mechanism. System performance was evaluated through short-term and long-term simulations. Short-term simulations were conducted to ensure the system’s compliance with the domestic flood control design standards. These simulations assessed the peak flow mitigation and lag times for 5-, 10-, and 25-year design storms under four scenarios. Long-term simulations used historical rainfall data to analyze the differences in the combined systems and operational plans for continuous rainfall events. Three performance indicators—volumetric reliability, the stormwater retention ratio, and the stormwater detention ratio—were employed to assess water supply and the stormwater detention performance. The short-term simulation results revealed that the system performance was sensitive to the initial conditions. The series and parallel systems performed well, while the enhanced parallel system outperformed the others under specific initial conditions and valve operations. In contrast, long-term simulations revealed that the series and parallel systems achieved higher stormwater retention and a more stable performance than the enhanced parallel system. Among the three systems, the parallel system offers reduced installation space, lower costs, and easier maintenance, making it the recommended option for Taiwan. This study provides valuable guidance for designing combined RWH and SWD systems. Full article

(This article belongs to the Special Issue Stormwater Management in Sponge Cities)

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19 pages, 5929 KiB

Open AccessArticle

Vertical Profile Characteristics of Dissolved Organic Matter Biochemistry in the Tropical Reservoir Shaped by Hydrodynamic Forces

by Zongyue Liu, Miao Chen, Huiran Liu, Han Wang, Ziyu Ning, Wen Zhang, Yuqin Liu and Min Tang

Water 2025, 17(2), 203; https://doi.org/10.3390/w17020203 - 14 Jan 2025

Abstract

Dissolved organic matter (DOM) exerts a crucial role in biogeochemical processes and ascertaining water quality in reservoirs, where it is vulnerable to the dynamic impacts of surface water inflows. However, understanding how DOM quantity and biochemical features responds to hydrodynamic forces in tropical [...] Read more.

Dissolved organic matter (DOM) exerts a crucial role in biogeochemical processes and ascertaining water quality in reservoirs, where it is vulnerable to the dynamic impacts of surface water inflows. However, understanding how DOM quantity and biochemical features responds to hydrodynamic forces in tropical reservoirs remains limited. To enhance our understanding of the vertical profiles of DOM characteristics under varying hydrodynamic forces (strong, moderate, and weak regions) in the Chitian Reservoir (18°43′–18°42′ N, 109°68′–109°70′ E), in December 2023, we investigated the concentrations and biochemical characteristics of water column DOM samples using multispectral techniques, a parallel factor model, and two-dimensional correlation analysis. Our results indicated that DOM concentrations (4.34 ± 0.36 mg/L) are the highest in the reservoir center, whereas total nitrogen (0.52 ± 0.04 mg/L), total phosphorus (0.02 ± 0.03 mg/L), and nitrate nitrogen (1.01 ± 0.07 mg/L) present their highest values in the inlet region. As hydrodynamic force decreases, microbial activity increases, whereas DOM’s humification degree and molecular weight decline. DOM in the Chitian Reservoir comprises humic-like components, including three terrestrial sources (accounting for 85.38%~87.03%) and one microbial source, with dominant characteristics of allochthonous origin. The relative abundance of microbial components decreased from 14.62% to 12.97% with the increasing hydrodynamic force and increased with depth. DOM functional groups in the strong hydrodynamic force region and the reservoir’s upper layer show high consistency and uniformity. Phenolic O–H is the most reactive functional group concerning changes in water depth across all hydrodynamic areas, followed by polysaccharide C–O, owing to its high photoactivity. In contrast, aromatic C–H demonstrates the weakest reactivity. DOM’s spectral features are closely linked to nutrient form concentrations (N and P). Full article

(This article belongs to the Special Issue Advance in Hydrology and Hydraulics of the River System Research 2025)

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14 pages, 1938 KiB

Open AccessArticle

Continuous Flow Electrocoagulation System for Enhanced Phosphorous Removal in Decentralized Wastewater Treatment Systems

by James Hayden and Bassim Abbassi

Water 2025, 17(2), 202; https://doi.org/10.3390/w17020202 - 14 Jan 2025

Abstract

Decentralized wastewater treatment systems (DWTS) are significant contributors to the eutrophication of surface water bodies due to a lack of treatment mechanisms that target dissolved phosphorus removal. Existing advanced treatment systems are expensive to operate, large in nature, and require frequent maintenance, making [...] Read more.

Decentralized wastewater treatment systems (DWTS) are significant contributors to the eutrophication of surface water bodies due to a lack of treatment mechanisms that target dissolved phosphorus removal. Existing advanced treatment systems are expensive to operate, large in nature, and require frequent maintenance, making them unattractive to DWTS owners. This study aims to investigate the development of a continuous flow treatment system that uses electrocoagulation (EC) to remove dissolved phosphorus from small wastewater streams such as septic tank effluent (STE). Operational parameters, including system hydraulic retention time (HRT), applied current density, and wastewater composition, were optimized to maximize total phosphorus (TP) removal most cost-effectively. Using an HRT of 10 min, an applied current density of 2.0 mA/cm², and an influent concentration of 20 mg/L, the orthophosphate (OP) and TP removal percentages achieved were 99.9 and 88.1%, respectively. Under these conditions, the average effluent Al³⁺ concentration in the treated effluent was measured to be 1.0 mg/L while the total suspended solids concentration was measured to be 51 mg/L. The operation cost was estimated to be 0.056 CAD/m³. The results demonstrate that the EC reactor is effective in removing dissolved phosphorus from wastewater and is therefore a viable option in mitigating the risk of downstream eutrophication caused by inadequately treated STE. Full article

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

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15 pages, 1071 KiB

Open AccessReview

Microplastics as Emerging Contaminants: Challenges in Inland Aquatic Food Web

by Prajna Ritambhara Swain, Pranaya Kumar Parida, Priti Jyoti Majhi, Bijay Kumar Behera and Basanta Kumar Das

Water 2025, 17(2), 201; https://doi.org/10.3390/w17020201 - 13 Jan 2025

Abstract

Microplastic (MP) pollution in inland water bodies, such as rivers, lakes, and reservoirs, is a growing environmental concern, yet research on its ecological impacts in freshwater ecosystems remains limited compared to marine environments. Microplastics, defined as particles smaller than 5 mm, have been [...] Read more.

Microplastic (MP) pollution in inland water bodies, such as rivers, lakes, and reservoirs, is a growing environmental concern, yet research on its ecological impacts in freshwater ecosystems remains limited compared to marine environments. Microplastics, defined as particles smaller than 5 mm, have been detected in freshwater systems globally, and their presence is widespread across diverse aquatic habitats. This review examines the sources, distribution, persistence, and ecological consequences of microplastics in freshwater ecosystems, emphasizing their bioaccumulation in organisms from plankton to fish, and the potential risks to human health through microplastic-contaminated fish consumption. Ingestion of microplastics by aquatic organisms can cause physical harm, such as entanglement, and chemical toxicity, including oxidative stress and the accumulation of harmful substances. The trophic transfer of microplastics through the food web raises concerns about higher-level organisms, including humans. Despite these risks, significant knowledge gaps exist regarding the long-term effects of microplastics on freshwater ecosystems. The review calls for improved monitoring, mitigation strategies, and regulatory frameworks to address this issue. Further research is needed to understand the full extent of microplastic pollution in freshwater environments and its impacts on both biodiversity and human health. Full article

(This article belongs to the Special Issue Impact of Microplastics on Aquatic Ecosystems)

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16 pages, 1330 KiB

Open AccessArticle

Contaminated Characteristics Variation in Different Aquaculture Modes: A Case Study in Northern China

by Jingqing Gao, Yuang Fu, Kexin Lu, Jie Li, Shaofeng Yan, Chi Liu and Yu Shen

Water 2025, 17(2), 200; https://doi.org/10.3390/w17020200 - 13 Jan 2025

Abstract

Various aquaculture modes have been developed to satisfy the growing demands of aquatic products. The contaminated characteristics may distribute along with the aquaculture modes, threatening the ecological environment to varying degrees. Herein, the five most common aquaculture modes (small-scale intensive mode, extensive free-range [...] Read more.

Various aquaculture modes have been developed to satisfy the growing demands of aquatic products. The contaminated characteristics may distribute along with the aquaculture modes, threatening the ecological environment to varying degrees. Herein, the five most common aquaculture modes (small-scale intensive mode, extensive free-range mode, concentrated contiguous mode, funnel-type mode, and recirculating aquaculture system) were selected to study the contaminated characteristics (including nine kinds of water quality parameters and eight kinds of antibiotics) in Henan Province, a province in northern China, and analysed using high-performance liquid chromatography tandem secondary mass spectrometry (HPLC–MS/MS). The funnel-type mode, as a unique mode developed in Henan Province, appears highest in nutrient content, wherein TN and TP concentrations reach 29.28 mg/L and 2.20 mg/L, respectively. The small-scale intensive mode has the highest average antibiotic concentration in five different aquaculture modes, with a concentration of 502 ng/L. Overall, the most abundant antibiotic was quinolones (QNs), followed by sulfonamides (SAs), chloramphenicols (CAs), and tetracyclines (TCs). Pearson correlation analysis showed that ENR had a strong positive correlation with TN, TP, and Zn, indicating the enrofloxacin (ENR) may have existed as the addictive in aquaculture feed. Moreover, the risk quotient (RQ) analysis indicated that ENR posed a medium to high risk, highlighting the importance of antibiotics man-agement in aquaculture. This work provides theoretical guidance for the formulation of aquaculture water pollutant control of different aquaculture modes. Full article

(This article belongs to the Special Issue Advances in Biological Technologies for Wastewater Treatment)

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22 pages, 45346 KiB

Open AccessArticle

Spatial Coupling Relationship Between Water Area and Water Level of Dongting Lake Based on Multiple Temporal Remote Sensing Images Data at Its Several Hydrological Stations

by Qiuhua He, Cunyun Nie, Shuchen Yu, Juan Zou, Luo Qiu and Shupeng Shi

Water 2025, 17(2), 199; https://doi.org/10.3390/w17020199 - 13 Jan 2025

Abstract

It is very well-known that the reliable coupling relationship between water area and water level is very important in analyzing the risks of floods and droughts for big lakes, such as Dongting Lake, especially when remote sensing images are absent and in situ [...] Read more.

It is very well-known that the reliable coupling relationship between water area and water level is very important in analyzing the risks of floods and droughts for big lakes, such as Dongting Lake, especially when remote sensing images are absent and in situ measurements cannot be carried out. To obtain this relationship, two types of mathematical models—polynomial regression (PR) based on the least square algorithm and machine learning regression (MLR) based on the BP (Backpropagation) neural network algorithm—are constructed using the water area data extracted from multiple temporal remote sensing images and water levels recorded at several representative hydrological stations for nearly 30 years. In this study, Dongting Lake is divided into three parts: East Dongting Lake (EDL), South Dongting Lake (SDL), and West Dongting Lake (WDL). This is because water slope exists on its surface, which is formed by several inflow rivers and the high and low terrain. To calculate the total water area of this lake, two ways are put forward by choosing the water levels: from EDL, SDL, and WDL in their turn; or from all three simultaneously. In other words, three univariate and one multivariate regression. For PR, there are perfect coefficients of determination (most nearly 0.95, the smallest being 0.76), which is in line with regression test relative errors (between 0.27% and 6.7%). For MLR, which was initially applied to this problem, the best node number (10 for the first way, 8 for the second way) in the hidden layer of the neural network is adaptively chosen, with coefficients of determination (similar to PR), together with training and testing error performances (between 1% and 10%). These results confirm the validity and reliability of them. The regression and prediction results on the two models are better than the documented way (only focus on the water level of EDL). These results can provide some references for researchers and decision makers in studying similar big Lakes. Full article

23 pages, 1324 KiB

Open AccessArticle

Unveiling the Multi-Dimensional Vulnerabilities of Flood-Affected Communities in Khyber Pakhtunkhwa, Pakistan

by Wahid Ullah, Haijun Dong, Ashfaq Ahmad Shah, Chong Xu and Bader Alhafi Alotaibi

Water 2025, 17(2), 198; https://doi.org/10.3390/w17020198 - 13 Jan 2025

Abstract

Climate-induced migration is increasingly affecting communities, disrupting livelihoods, and intensifying socio-economic inequalities, particularly in disaster-prone regions. Despite the prevalence of recurring flood hazards, there remains limited research on the multi-dimensional impacts of migration particularly in socio-culturally sensitive and resource-constrained settings like Khyber Pakhtunkhwa [...] Read more.

Climate-induced migration is increasingly affecting communities, disrupting livelihoods, and intensifying socio-economic inequalities, particularly in disaster-prone regions. Despite the prevalence of recurring flood hazards, there remains limited research on the multi-dimensional impacts of migration particularly in socio-culturally sensitive and resource-constrained settings like Khyber Pakhtunkhwa (KPK), Pakistan. This study seeks to bridge this gap by exploring the post-migration challenges of flood-affected communities in District Nowshera. Using a qualitative methodology, we conducted in-depth interviews with 25 diverse key informants. The study results revealed profound socioeconomic instability, inadequate access to essential services, and cultural disruptions. Key findings include significant challenges such as inadequate housing, the loss of traditional livelihoods, persistent financial hardships, health issues, and the breakdown of social support networks. Moreover, displaced families face marginalization and language barriers, which hinder integration into host communities, amplifying feelings of isolation and identity loss. Environmental degradation in resettlement areas further intensifies these challenges, prolonging poor living conditions and heightened vulnerability. To address these issues, the study recommends community-based interventions such as developing resilient, culturally appropriate housing, implementing targeted skills training programs to restore livelihoods, promoting climate-smart agricultural practices, and enacting inclusive social policies to promote integration and cohesion to address climate-induced migration in disaster-prone regions. Full article

(This article belongs to the Special Issue Inclusive Disaster Risk Reduction: Gender, Community-Based Approaches, and Local Governance in Mitigating Water-Related Hazards)

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22 pages, 7195 KiB

Open AccessArticle

The Optimization of River Network Water Pollution Control Based on Hydrological Connectivity Measures

by Jiuhe Bu, Chunhui Li, Tian Xu, Tao Wang, Jinrong Da, Xiaoyun Li, Hao Chen, Weixin Song and Mengjia Sun

Water 2025, 17(2), 197; https://doi.org/10.3390/w17020197 - 13 Jan 2025

Abstract

Urbanization, driven by socio-economic development, has significantly impacted river ecosystems, particularly in plain city regions, leading to disruptions in river network structure and function. These changes have exacerbated hydrological fluctuations and ecological degradation. This study focuses on the central urban area of Changzhou [...] Read more.

Urbanization, driven by socio-economic development, has significantly impacted river ecosystems, particularly in plain city regions, leading to disruptions in river network structure and function. These changes have exacerbated hydrological fluctuations and ecological degradation. This study focuses on the central urban area of Changzhou using a MIKE11 model to assess the effects of four hydrological connectivity strategies—water diversion scheduling, river connectivity, river dredging, and sluice connectivity—across 13 different scenarios. The results show that water diversion, river dredging, and sluice connectivity scenarios provide the greatest improvements in water environmental capacity, with maximum increases of 54.76%, 41.97%, and 25.62%, respectively. The spatial distribution of improvements reveals significant regional variation, with some areas, particularly in Tianning and Zhonglou districts, experiencing declines in environmental capacity under sluice diversion and river-connectivity scenarios. In addition, the Lao Zaogang River is identified as crucial for improving the overall water quality in the network. Based on a multi-objective evaluation, combining environmental and economic factors, the study recommends optimizing water diversion scheduling at sluices (Weicun, Zaogang, and Xiaohe) with flow rates between 20–40 m³/s, enhancing connectivity at key river hubs, and focusing management efforts on the Lao Zaogang and Xinmeng rivers to strengthen hydrological and water quality linkages within the network. Full article

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