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Water, Volume 15, Issue 5 (March-1 2023) – 173 articles

Cover Story (view full-size image): The response of coastal systems to global acidification depends strongly on inputs from rivers, since continental water runoff can significantly alter alkalinity and dissolved inorganic carbon (DIC) in seawater. DIC discharge depends mainly on natural processes in river basins, such as biological activities, gas exchange with the atmosphere and rock weathering. However, the effects of anthropogenic and climate disturbances are expected to increasingly alter these processes in the future. The northern Adriatic Sea is a continental shelf that is strongly influenced by river runoff, where climatic and anthropogenic forcings produce more rapid responses than in the oceans. This aim of this study is to quantify this input on a regional scale and to provide a basis for further studies on the evolution of coastal acidification under the influence of rivers. View this paper
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16 pages, 3567 KiB  
Article
Successive-Station Streamflow Prediction and Precipitation Uncertainty Analysis in the Zarrineh River Basin Using a Machine Learning Technique
by Mahdi Nakhaei, Fereydoun Ghazban, Pouria Nakhaei, Mohammad Gheibi, Stanisław Wacławek and Mehdi Ahmadi
Water 2023, 15(5), 999; https://doi.org/10.3390/w15050999 - 6 Mar 2023
Cited by 5 | Viewed by 2184
Abstract
Precise forecasting of streamflow is crucial for the proper supervision of water resources. The purpose of the present investigation is to predict successive-station streamflow using the Gated Recurrent Unit (GRU) model and to quantify the impact of input information (i.e., precipitation) uncertainty on [...] Read more.
Precise forecasting of streamflow is crucial for the proper supervision of water resources. The purpose of the present investigation is to predict successive-station streamflow using the Gated Recurrent Unit (GRU) model and to quantify the impact of input information (i.e., precipitation) uncertainty on the GRU model’s prediction using the Generalized Likelihood Uncertainty Estimation (GLUE) computation. The Zarrineh River basin in Lake Urmia, Iran, was nominated as the case study due to the importance of the location and its significant contribution to the lake inflow. Four stations in the basin were considered to predict successive-station streamflow from upstream to downstream. The GRU model yielded highly accurate streamflow prediction in all stations. The future precipitation data generated under the Representative Concentration Pathway (RCP) scenarios were used to estimate the effect of precipitation input uncertainty on streamflow prediction. The p-factor (inside the uncertainty interval) and r-factor (width of the uncertainty interval) indices were used to evaluate the streamflow prediction uncertainty. GLUE predicted reliable uncertainty ranges for all the stations from 0.47 to 0.57 for the r-factor and 61.6% to 89.3% for the p-factor. Full article
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12 pages, 5405 KiB  
Article
Feasibility of Achieving Efficient Nitrite Accumulation in Moving Bed Biofilm Reactor: The Influencing Factors, Microbial Structures, and Biofilm Characteristics
by Hongyi Li, Zhaoxia Xue, Tongxin Yin, Tingfeng Liu and Zhixin Hu
Water 2023, 15(5), 998; https://doi.org/10.3390/w15050998 - 6 Mar 2023
Cited by 1 | Viewed by 1426
Abstract
Moving bed biofilm reactor (MBBR) is considered as a promising technology for wastewater treatment owing to the high biomass retention and low cost. In this study, the performance of using MBBR for partial denitrification (PD) was investigated. Denitrifying biofilm was successfully formed after [...] Read more.
Moving bed biofilm reactor (MBBR) is considered as a promising technology for wastewater treatment owing to the high biomass retention and low cost. In this study, the performance of using MBBR for partial denitrification (PD) was investigated. Denitrifying biofilm was successfully formed after 40 days with the biomass and nitrite reduction rate of 40.83 mg VSS/g carriers and 51.52 mg N/(gVSS·h), respectively. Morphology analysis by scanning electron microscope (SEM) showed that the biofilm surface was dominant by cocci, filamentous bacteria, and extracellular polymeric substances (EPS). Investigation about the influencing factors of PD found that the optimal COD/NO3-N and pH for efficient nitrite production (nitrate to nitrite ratio: 96.49%) was 3 and 9, respectively. Moreover, Saccharimonadales was proved to be dominant functional microbes in the constructed PD systems with different influent conditions because its relative abundance exhibited good correlation with the nitrite accumulation. By analyzing the biofilm characteristics under different conditions, PD was observed to mainly occur in the range of 300–700 μm inside the biofilm, where most of the dissolved oxygen was consumed. This study confirmed the feasibility and superior performance of PD-MBBR system. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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16 pages, 1537 KiB  
Article
Hard-Bottom Polychaetes Exposed to Multiple Human Pressure along the Mediterranean Coast of Egypt
by Rasha Hamdy, Noha Elebiary, Faiza Abdel Naby, Jacopo Borghese, Mohamed Dorgham, Amira Hamdan and Luigi Musco
Water 2023, 15(5), 997; https://doi.org/10.3390/w15050997 - 6 Mar 2023
Cited by 2 | Viewed by 1940
Abstract
The complex mixture of anthropogenic pressure determines the impact on the marine biota, hampering the ecosystem’s functioning. The coast of Alexandria, Egypt, experiences multiple human pressure, including sewage discharge, engineering activities (urbanization) for armoring purposes, and beach nourishment. Hard-bottom polychaete assemblages are demonstrated [...] Read more.
The complex mixture of anthropogenic pressure determines the impact on the marine biota, hampering the ecosystem’s functioning. The coast of Alexandria, Egypt, experiences multiple human pressure, including sewage discharge, engineering activities (urbanization) for armoring purposes, and beach nourishment. Hard-bottom polychaete assemblages are demonstrated to reflect coastal areas’ environmental status, though their use in monitoring programs is uncommon. The sensitivity of hard-bottom polychaete assemblages in depicting variations in environmental conditions of two sites exposed to the discharge of polluted water and three sites exposed to urbanization was analyzed. The high spatial and temporal variation in species abundance and diversity probably hid differences among the assemblages exposed to the two forms of pressure while highlighting differences among sites exposed to the same impact form. In addition, changes in the algal substrate probably influenced the observed pattern. Temporal variation of salinity and differences in biological oxygen demand (BOD) and the organic matter appeared to indirectly affect polychaete abundance and diversity by favoring tolerant algal taxa such as Ulva sp. Contrary to what was expected, assemblage variation due to site-specific environmental features accounted for more than the variations due to the two forms of human pressure in shaping differences among polychaete assemblages. Full article
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19 pages, 21976 KiB  
Article
Slurry Leakage Channel Detection and Slurry Transport Process Simulation for Overburden Bed Separation Grouting Project: A Case Study from the Wuyang Coal Mine, Northern China
by Tianhao Kou, Shuaixin Wen, Wenping Mu, Nengxiong Xu, Zexin Gao, Zhongxiang Lin, Yankui Hao, Weitao Yan and Honglei Liu
Water 2023, 15(5), 996; https://doi.org/10.3390/w15050996 - 6 Mar 2023
Cited by 1 | Viewed by 1646
Abstract
The 8006 working face at the Wuyang Coal Mine adopts grout injection into bed separation technology for surface subsidence control. Surface grout leakage occurred during the grout injection into the bed separation process of this working face. Grout leakage has adverse effects on [...] Read more.
The 8006 working face at the Wuyang Coal Mine adopts grout injection into bed separation technology for surface subsidence control. Surface grout leakage occurred during the grout injection into the bed separation process of this working face. Grout leakage has adverse effects on the grouting filling effect, grouting cost and the environment. To determine the grout leakage channels and the slurry transport process, and to provide a theoretical basis for slurry leakage prevention and control, this paper first used 3D seismic exploration technology to identify the fault distribution characteristics of the study area, and then used COMSOL Multiphysics to carry out the numerical simulation of the grout transport process. The conclusions are as follows. Fifteen normal faults were identified in the vicinity of the 8006 working face. Among all the faults, the F1, F11, F18, F19 and F27 faults penetrate the surface and are the main channels for the grout to run to the surface. Based on the distribution characteristics of the faults and the spatial location relationship among the bed separation, faults and grout leakage points, the theoretical analysis of the leakage causes of each grout leakage point was carried out, and the main leakage channels of the grout injection into bed separation were proposed to be the bed separation and faults. The results of the numerical simulation of grout transport show that, as the permeability of the bed separation space and fault is much better than that of the surrounding rock, during the grout injection process the grout diffuses through the bed separation and fault in turn, and finally to the surface, where leakage occurs. The simulation results confirm that the main leakage channels for the grout are bed separation and faults. Full article
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20 pages, 5419 KiB  
Article
Historical Drought Events in the Early Years of Qing Dynasty in Shanxi Based on Hydrological Reconstructions
by Yanping Qu, Xuejun Zhang, Jingyu Zeng, Zhe Li and Juan Lv
Water 2023, 15(5), 995; https://doi.org/10.3390/w15050995 - 6 Mar 2023
Cited by 6 | Viewed by 1997
Abstract
Droughts are serious natural disasters that adversely affect water resources, agriculture, the economy, and the environment. Reconstructing historical drought records is necessary to assess the impact of droughts and their evolution and has become a top priority to support and improve sustainable water [...] Read more.
Droughts are serious natural disasters that adversely affect water resources, agriculture, the economy, and the environment. Reconstructing historical drought records is necessary to assess the impact of droughts and their evolution and has become a top priority to support and improve sustainable water management decisions. In this study, we used Shanxi Province as the research area, and meteorological data from the early years of Guangxu in the Qing Dynasty were reconstructed using historical rain and snow records. The Variable Infiltration Capacity (VIC) model is driven by the reconstruction of historical meteorological data. The study area’s monthly runoff and soil water sequence from 1875 to 1879 were simulated, and the hydrology and soil of the ancient historical period were reproduced in the absence of data. The results show the following: (1) The idea of reconstructing hydrological parameters using historical data is feasible and the VIC model can be used to study drought characteristics under specific scenarios. (2) The proportions of areas with runoff depths less than 10 mm throughout Shanxi from 1875 to 1879 were 55%, 48%, 58%, 19%, and 30%. The annual runoff depth in each region from 1875 to 1877 was less than 60 mm. The hydrological drought from 1875 to 1877 was very serious, and the area covered by the drought was relatively large. (3) The annual average soil water content of various regions was stable between 150 and 510 mm from 1875 to 1879. The soil water content had no apparent interannual variation. The area with soil water content less than 180 mm accounted for ratios as high as 31%. This research provides new ideas for ancient drought research and a scientific basis for regional drought prevention, mitigation, and water resources management, and ensures the orderly progress of agricultural production activities. Full article
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25 pages, 52028 KiB  
Article
Two-Dimensional Modelling for Dam Break Analysis and Flood Hazard Mapping: A Case Study of Papadia Dam, Northern Greece
by Christos Mattas, Dimitris Karpouzos, Pantazis Georgiou and Theodoros Tsapanos
Water 2023, 15(5), 994; https://doi.org/10.3390/w15050994 - 6 Mar 2023
Cited by 3 | Viewed by 2753
Abstract
Dams are expensive technical constructions that ensure food production, sustain farmers’ income, and cover a large percentage of urban water supply demands. However, the threat of a dam break flood, which can be extremely dangerous for the local society, should be taken into [...] Read more.
Dams are expensive technical constructions that ensure food production, sustain farmers’ income, and cover a large percentage of urban water supply demands. However, the threat of a dam break flood, which can be extremely dangerous for the local society, should be taken into account, and proactive mitigation measures should be planned. Towards this direction, dam break modelling and flood hazard assessment are essential for developing flood crisis management and evacuation plans. In this study, a hypothetical case of failure of the Papadia dam in the Florina Regional Unit in northern Greece is examined. Two scenarios of failure were considered: overtopping and piping. A two-dimensional numerical model for the two failure scenarios was used to simulate the dam break process and flood wave routing using HEC-RAS software. A sensitivity analysis of the mesh size and breach parameters was performed to better understand their impact on the critical outputs of the simulation model. Flood hazard maps were produced in GIS environment based on water depth and velocity criteria. Furthermore, two classification approaches were adopted to assess the flood hazard using the product of water depth and velocity. The results showed that the extent of the inundated area could affect most of the study area and could cause severe damage to agricultural activities. Full article
(This article belongs to the Special Issue Flood Risk and Response Management)
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14 pages, 2002 KiB  
Article
Simulation of Hydrologic Change of Linggo Co during 1979–2012 Using Hydrologic and Isotopic Mass Balance Model
by Xueying Zhang, Yue He, Lijun Tian, Hanxi Duan and Yifan Cao
Water 2023, 15(5), 1004; https://doi.org/10.3390/w15051004 - 6 Mar 2023
Viewed by 1471
Abstract
The Tibetan Plateau (TP) and surrounding areas contain the largest number of glaciers outside the polar regions. The region affects downstream water supply and food security, thereby directly influencing one-third of the world’s population. The lakes in the central TP expanded rapidly in [...] Read more.
The Tibetan Plateau (TP) and surrounding areas contain the largest number of glaciers outside the polar regions. The region affects downstream water supply and food security, thereby directly influencing one-third of the world’s population. The lakes in the central TP expanded rapidly in recent decades, which has attracted growing attention. Glacier meltwater was considered as a major component in the water balance of TP lakes, although few studies quantified its contribution. Stable isotope analysis is a powerful tool to trace hydrologic circulation, while its interpretation in paleoclimate records has been controversial. To bridge the gap between hydrologic and paleoclimatic studies, we performed a hydrologic and isotopic mass balance model to simulate the lake level change of Linggo Co in the central TP. The model was forced by the meteorological data, calibrated through observed lake level changes, and validated by oxygen isotope compositions (δ18O) of lake water. Our results indicated that glacier meltwater contributed 73.94% of the inflow water to Linggo Co before 1993 but decreased thereafter. Increasing glacier meltwater together with positive water balance (precipitation/evaporation) in the catchment contributed to the rapid expansion of Linggo Co after the mid-1990s. Lake water δ18O in Linggo Co was more sensitive to changes in the precipitation amount and precipitation δ18O than temperature. Our findings could shed light on the usage of δ18O proxy in future paleoclimate research on the TP. Full article
(This article belongs to the Section Hydrogeology)
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15 pages, 7412 KiB  
Article
Refined Calculation of Multi-Objective Ecological Flow in Rivers, North China
by Yufei Jiao, Jia Liu, Chuanzhe Li, Zhenghe Xu and Yingjie Cui
Water 2023, 15(5), 1003; https://doi.org/10.3390/w15051003 - 6 Mar 2023
Cited by 2 | Viewed by 1455
Abstract
The concepts and calculation of basic, suitable, and fine ecological flow are put forward, and an integrated multi-method to calculate the ecological flow in rivers under multi-objectives is explored. Based on this, a refined calculation theory and method of a multi-objective ecological flow [...] Read more.
The concepts and calculation of basic, suitable, and fine ecological flow are put forward, and an integrated multi-method to calculate the ecological flow in rivers under multi-objectives is explored. Based on this, a refined calculation theory and method of a multi-objective ecological flow division based on time and space is proposed. That is, three commonly used methods, namely, the hydrology method, the hydraulics method, and the habitat method, are selected to finely calculate the ecological flow demand at different periods, in different sections, and under different ecological objectives. This approach breaks through the traditional ecological water demand calculation method based on hydrology and develops a river ecological flow calculation method based on water environmental protection objectives. A refined calculation method of ecological flow division based on time and space is developed to ensure that the ecological-hydrological process in rivers and lakes meets the ecological flow demand in different periods, different reaches, and different ecological objectives. Taking eight rivers entering Baiyangdian Lake as an example, the ecological flow demand in different river sections under different ecological objectives at different times is calculated to ensure the ecological flow process. The results show that the range of basic ecological flow demand range is 0.07–3.87 m3/s, the range of suitable ecological flow demand is 0.51~10.74 m3/s, and the range of fine ecological flow demand is 0.71~20.29 m3/s. In terms of spatial distribution, Ping River has the lowest demand for ecological flow, and the Zhulong River has the largest. In terms of the interannual ecological demand, those of the Baigou River, Fu River, Xiaoyi River, and Zhulong River are larger. In the demand process across the year, the demand is the largest from July to September, while the demand is the smallest from March to May. Similarly, most rivers face such problems as a sharp decline in runoff, drying up of the river, and an urgent need to restore ecology in northern China. This study also has insights and reference significance for other regions. Full article
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22 pages, 10868 KiB  
Article
Failure Characteristics of the Water-Resisting Coal Pillar under Stress-Seepage Coupling and Determination of Reasonable Coal Pillar Width
by Quanhui Liu, Yuanbo Xue, Dan Ma and Qiang Li
Water 2023, 15(5), 1002; https://doi.org/10.3390/w15051002 - 6 Mar 2023
Cited by 6 | Viewed by 1690 | Correction
Abstract
Groundwater inrush hazard has always been a great threat to the construction of vertical shafts in coal mines. Generally, the failure of the water-resisting coal pillar under coupled stress-seepage conditions around the vertical shaft is the main reason for the generation of the [...] Read more.
Groundwater inrush hazard has always been a great threat to the construction of vertical shafts in coal mines. Generally, the failure of the water-resisting coal pillar under coupled stress-seepage conditions around the vertical shaft is the main reason for the generation of the water inrush channel. In order to understand the mechanical behaviors of the water-resisting coal pillar, the strength of typical coal affected by the size and water content was investigated, and the stress sensitivity of permeability was investigated by a stress-seepage coupling test. The stress field and deformation of the water-resisting coal pillar were investigated by numerical simulation, the stability of the water-resisting coal pillars with different widths was evaluated, and the reasonable width of the coal pillars under coupled stress-seepage condition was determined. Results show that the water content and coal pillar width have a great influence on the mechanical characteristics of coal samples. Under the conditions of lower water content and larger coal sample width, the coal sample presents higher strength, smaller axial deformation, smaller permeability and porosity, and weak sensitivity to stress. The simulation results show that the boundary of the main roadway at the end of the coal pillar is dominated by tensile stress, and fractures can significantly contribute to the destruction of coal pillars. With the increase in the width of the water-resisting coal pillar, the internal damage variable, maximum tensile stress, porosity, and average water flow velocity of the coal pillar decrease, which reduces the risk of water inrush and improves the safety of the water-resisting coal pillar. An evaluation model of the reasonable width of the water-resisting coal pillar under the stress-seepage coupling was proposed, and the model was verified by the shear slip law and experimental results. This study provides theoretical and experimental guidance for the risk management of groundwater inrush disaster during the construction of vertical shafts in coal mines. Full article
(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)
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14 pages, 4828 KiB  
Article
Abnormal Waves Observation and Analysis of the Mechanism in the Pearl River Estuary, South China
by Hui Shi, Yao Luo, Fenghua Zhou, Chunhua Qiu, Dongxiao Wang and Zhenqiu Zhang
Water 2023, 15(5), 1001; https://doi.org/10.3390/w15051001 - 6 Mar 2023
Viewed by 1649
Abstract
The Pearl River Estuary is a typical estuary region in southern China, and the study of surface wave occurrence and characteristics is of great importance for shipping management, nearshore engineering, and monitoring shoreline changes and other human activities. Long-term and continuous observational data [...] Read more.
The Pearl River Estuary is a typical estuary region in southern China, and the study of surface wave occurrence and characteristics is of great importance for shipping management, nearshore engineering, and monitoring shoreline changes and other human activities. Long-term and continuous observational data are critical for achieving a better understanding of waves. In this study, the wave measurements based on a high-precision wave gauge were analyzed and observation data over approximately two years at a sampling frequency of 2 Hz were obtained. The wave system in the Pearl River Estuary was found to deviate from the assumption of a stationary stochastic process similar to that in the open ocean, due to the effects of abnormal waves caused by human activities. Therefore, traditional distribution functions such as Rayleigh and Weibull were not suitable for accurately fitting the main wave parameters (Hs, Tp, etc.), particularly in the tail. Consequently, abnormal wave signals were extracted from all wave sets, and through the comparison and analysis of the wave spectral features, it was determined that these abnormal waves are caused by the ship wakes. The spectral characterization of these waves was performed to determine the characteristics of different ship wake processes. Ship wakes in the Pearl River Estuary are an important part of the wave system, and their wave height is significantly larger than the normal wave. Based on the spectral characteristics of ship wakes, this study proposed some news characteristics of ship wakes in the main channel of the Pearl River Estuary. Full article
(This article belongs to the Special Issue Hydrodynamics in Coastal Areas)
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15 pages, 3447 KiB  
Article
The Performance of Carbonate-Modified Nonionic Surfactants in Microplastic Flotation
by Daniel Brüggemann, Tahereh Shojamejer, Michelle Tupinamba Lima, Dzenna Zukova, Rahel Marschall and Reinhard Schomäcker
Water 2023, 15(5), 1000; https://doi.org/10.3390/w15051000 - 6 Mar 2023
Cited by 3 | Viewed by 1670
Abstract
For a group of nonionic surfactants with polar head groups synthesized by the copolymerization of ethylene oxide and carbon dioxide, the potential for their application in the foam flotation of microplastic particles was investigated. Their performance was compared to conventional that of nonionic [...] Read more.
For a group of nonionic surfactants with polar head groups synthesized by the copolymerization of ethylene oxide and carbon dioxide, the potential for their application in the foam flotation of microplastic particles was investigated. Their performance was compared to conventional that of nonionic surfactants and correlated with their adsorption behavior at the water–air surface through the maximum-bubble-pressure technique. The carbonate content of the surfactant head groups increased the biodegradability of the surfactants and affected their foaming properties and their performance in the flotation process. Since the inserted carbonate units increased the hydrophilicity of the whole surfactant but decreased the polarity of their headgroups, the number of carbonate units can be considered as an independent tuning parameter for adjusting these surfactants to a particular application. With this feature, the countercurrent trends of the two most important performance indicators, namely the removal rate and enrichment factor, can be resolved. Full article
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25 pages, 5767 KiB  
Article
Numerical Simulation Study on the Influence of Construction Load on the Cutoff Wall in Reservoir Engineering
by Yongshuai Sun, Anping Lei, Ke Yang and Guihe Wang
Water 2023, 15(5), 993; https://doi.org/10.3390/w15050993 - 5 Mar 2023
Cited by 1 | Viewed by 1437
Abstract
Relying on the Beijing-Shijiazhuang Expressway widening project near the impervious wall of a reservoir, this paper uses FLAC3D two-dimensional and three-dimensional numerical simulation methods to establish the whole process model of the impervious wall of the reservoir affected by the construction load of [...] Read more.
Relying on the Beijing-Shijiazhuang Expressway widening project near the impervious wall of a reservoir, this paper uses FLAC3D two-dimensional and three-dimensional numerical simulation methods to establish the whole process model of the impervious wall of the reservoir affected by the construction load of the high-way reconstruction section. The stress and strain state of the cut-off wall in the high-way reconstruction section and the nearby reservoir is simulated in detail, the overall deformation of the cut-off wall in the reservoir is directly reflected, and the interaction and differential deformation between the wall structures are reflected. The safety and stability of the cutoff wall of the reservoir affected by the construction load are evaluated so that various advanced mechanical behaviors of the cutoff wall can be predicted. Research results show that the horizontal displacement value of the wall gradually increases from bottom to top, and the maximum value appears at the top of the wall. The horizontal displacement value of the 1–3 walls is relatively large, with the maximum value of 22.368 mm, and the horizontal displacement value of the 4–10 walls shows little difference. This is on account of the gravity of the backfill, the strata in the whole project area having settled, and the settlement at the bottom of the cut-off wall being 2.542 mm. At the root of the rigid cut-off wall, the compressive stress concentration occurs, with the maximum value between 1.75 MPa and 2.15 MPa. Due to the size of the structure, the maximum tensile stress of 0.237 MPa appears in the local area near the guide wall of the rigid cut-off wall, which will not endanger the rigid cut-off wall because of its small value. The maximum stress in the rigid impervious wall and the plastic impervious wall are 1.90–2.15 MPa and 1.00–1.12 MPa, respectively. Apart from the small tensile stress at the connecting guide wall between the rigid cut-off wall and the plastic concrete cut-off wall, the cut-off wall is under pressure, especially the plastic cut-off wall. Combined with the analysis of the stress state of the wall, it can be determined that the anti-seepage wall (rigid cut-off wall and plastic concrete cut-off wall) is stable and safe during the construction period. Full article
(This article belongs to the Special Issue Application of Artificial Intelligence in Hydraulic Engineering)
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17 pages, 6589 KiB  
Article
Numerical Simulation of Drilling Fluid Flow in Centrifugal Pumps
by Jianxin Hu, Ke Li, Wenfeng Su and Xinyi Zhao
Water 2023, 15(5), 992; https://doi.org/10.3390/w15050992 - 5 Mar 2023
Cited by 4 | Viewed by 2274
Abstract
Centrifugal pumps are widely used in the oil and mining industries. In contrast to water pumps, the centrifugal pumps in the oil and mining industries are used for the transportation of drilling fluid, which is typically non-Newtonian fluid. Drilling fluids are usually modeled [...] Read more.
Centrifugal pumps are widely used in the oil and mining industries. In contrast to water pumps, the centrifugal pumps in the oil and mining industries are used for the transportation of drilling fluid, which is typically non-Newtonian fluid. Drilling fluids are usually modeled as power-law fluids with varying shear viscosity and imposed shear rates. In this paper, a numerical simulation of power-law fluid flow in a centrifugal pump was simulated, varying only in the flow-rate magnitude, using water flow as a comparison. The simulation results show that the pump used for drilling fluid presents a lower head and efficiency but a higher shaft power than that used for water. The flow patterns of both the water pump and the drilling fluid pump were investigated in terms of pressure fluctuation, turbulent kinetic energy, and radial force on the impeller. In contrast to the literature, this paper also analyzes the pressure pulsations in the individual blades of the impeller, as well as those in the volute path. In the case of drilling fluid, it was found that the viscous effect made the flow at the end of the blades highly irregular, and this could be attributed to the pressure generated by them. At the same time, the fluid flow at the small cross-section of the volute was more sensitive to the rotation of the impeller. In addition, the effects of the shear collision exerted on the outlet fluid of the impeller and the fluid in the volute, as well as the dynamic and static interferences, made the non-Newtonian power-law fluid consume more mechanical energy than the water. The results of this paper can be used as a reference for improving the design of centrifugal pumps using non-Newtonian fluids as media. Full article
(This article belongs to the Topic Computational Fluid Dynamics (CFD) and Its Applications)
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18 pages, 4480 KiB  
Article
Analysis of Water-Lifting Aerator Performance Based on the Volume of Fluid Method
by Zhiying Chang and Tinglin Huang
Water 2023, 15(5), 991; https://doi.org/10.3390/w15050991 - 5 Mar 2023
Cited by 1 | Viewed by 1711
Abstract
Water quality deterioration is a major problem faced by reservoirs globally, owing to the inflow of pollution from industrial and municipal activities. Water-lifting aeration is an in situ water quality improvement technology that mixes and oxygenates deep water bodies in reservoirs to improve [...] Read more.
Water quality deterioration is a major problem faced by reservoirs globally, owing to the inflow of pollution from industrial and municipal activities. Water-lifting aeration is an in situ water quality improvement technology that mixes and oxygenates deep water bodies in reservoirs to improve pollution control efficiency and water quality. While previous studies have mainly focused on the mixing process in the reservoir outside the water-lifting aerator (WLA), knowledge of the internal flow remains limited. In this study, a two-phase flow within a WLA system was numerically studied using the volume of fluid (VOF) method to comprehensively analyze the internal two-phase flow characteristics and the influence on the water-lifting and oxygenation performance of the system. The statistical analysis results showed that increasing the aeration chamber volume enhanced the bottom oxygenation performance by 27% because of the prolonged time of the deflector plate outlet outflow. Additionally, increasing the air release rate enhanced the water-lifting performance by 47%, which was induced by the shortened air piston release period. This study demonstrates the internal flow mechanism of the WLA and provides technical support for parameter optimization design, which has significant scientific research and engineering application value. Full article
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16 pages, 3218 KiB  
Article
Impact of a Sand Filtration Pretreatment Step on High-Loaded Greywater Treatment by an Electrocoagulation Technique
by Khalid Bani-Melhem, Abeer Al Bsoul, Zakaria Al-Qodah, Nada Al-Ananzeh, Muhammad Rasool Al-Kilani, Mohammad Al-Shannag and Walid Bani-Salameh
Water 2023, 15(5), 990; https://doi.org/10.3390/w15050990 - 5 Mar 2023
Cited by 6 | Viewed by 2105
Abstract
Greywater (GW) treatment by the electrocoagulation (EC) technique alone might not meet the required standards in terms of pollutant removal, specifically when GW contains high loads of pollutants. In this preliminary study, a sand filtration (SF) unit was integrated with the EC technique [...] Read more.
Greywater (GW) treatment by the electrocoagulation (EC) technique alone might not meet the required standards in terms of pollutant removal, specifically when GW contains high loads of pollutants. In this preliminary study, a sand filtration (SF) unit was integrated with the EC technique as a pretreatment step to enhance the EC process for treating high-loaded GW. Three different voltage gradients were investigated (5 V/cm, 10 V/cm, and 15 V/cm) in the EC unit. The results demonstrated that the pretreatment SF step can contribute significantly to reducing pollutant concentrations in the greywater to be treated by EC. In terms of physical impurities, the results showed that the SF pretreatment step reduced the turbidity and the color of the treated GW by 28.4%, and 9.4%, respectively. The COD concentration was reduced by 25.5% by the SF step, which allowed a reduction of EC steady state time in the EC unit from 45 min to 30 min at an applied voltage of 15 V/cm. In addition, a high COD removal rate of 87.8% from high-load greywater was achieved with an energy consumption of only 4.11 kWh/m3 in comparison with 6.21 kWh/m3 without the SF step, which is equivalent to a 34% saving in energy consumption. Full article
(This article belongs to the Special Issue Water and Wastewater Treatment: Latest Advances and Prospects)
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14 pages, 3275 KiB  
Article
Optimizing Low Impact Development for Stormwater Runoff Treatment: A Case Study in Yixing, China
by Qian Cao, Jiashun Cao and Runze Xu
Water 2023, 15(5), 989; https://doi.org/10.3390/w15050989 - 4 Mar 2023
Cited by 6 | Viewed by 2443
Abstract
Low-impact development (LID) practices have been recognized as a promising strategy to control urban stormwater runoff and non-point source pollution in urban ecosystems. However, many experimental and modeling efforts are required to tailor an effective LID practice based on the hydraulic and environmental [...] Read more.
Low-impact development (LID) practices have been recognized as a promising strategy to control urban stormwater runoff and non-point source pollution in urban ecosystems. However, many experimental and modeling efforts are required to tailor an effective LID practice based on the hydraulic and environmental characteristics of a given region. In this study, the InfoWorks ICM was applied to simulate the runoff properties and determine the optimal LID design in a residential site at Yixing, China, based on four practical rainfall events. Additionally, the software was redeveloped using Ruby object-oriented programming to improve its efficiency in uncertainty analysis using the Generalized Likelihood Uncertainty Estimation method. The simulated runoff was in good agreement with the observed discharge (Nash–Sutcliffe model efficiency coefficients >0.86). The results of the response surface method indicated that when the sunken green belt, permeable pavement, and green roof covered 8.6%, 15%, and 10%, respectively, of the 11.3 ha study area, the designed system showed the best performance with relatively low cost. This study would provide new insights into designing urban rainfall-runoff pollution control systems. Full article
(This article belongs to the Special Issue Urban Runoff Control and Sponge City Construction II)
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18 pages, 7067 KiB  
Article
Estimation of Precipitation Fraction in the Soil Water of the Hillslope Vineyard Using Stable Isotopes of Water
by Zoran Kovač, Vedran Krevh, Lana Filipović, Jasmina Defterdarović, Borna-Ivan Balaž and Vilim Filipović
Water 2023, 15(5), 988; https://doi.org/10.3390/w15050988 - 4 Mar 2023
Viewed by 1742
Abstract
This paper presents research related to the estimation of the precipitation fraction in the soil water of a sloped vineyard at the SUPREHILL Critical Zone Observatory (CZO) in Zagreb, Croatia. Numerous investigations have shown that exploration of hillslope soils can be very challenging [...] Read more.
This paper presents research related to the estimation of the precipitation fraction in the soil water of a sloped vineyard at the SUPREHILL Critical Zone Observatory (CZO) in Zagreb, Croatia. Numerous investigations have shown that exploration of hillslope soils can be very challenging due to the existence of heterogeneity and different soil properties, as well as due to anthropogenically induced processes, which can affect precipitation infiltration and soil water flow. Within this research, physicochemical soil properties, soil water content (SWC), and isotopic composition of soil water and precipitation (δ2H and δ18O) have been examined. The isotopic signature of soil water was monitored in 24 points, at 4 depths, throughout the hillslope vineyard. Soil water isotopic composition from all monitoring points coincided with the Local Meteoric Water Line (LMWL), with almost no variability at 100 cm depth, which was consistent with the smallest variation of SWC at 80 cm depth and indicated that most of water mixing takes place in the shallower part of the hillslope. Results suggested the existence of heterogeneity, uneven erosion processes in the footslope of the observed vineyard, and different infiltration patterns. Fractions of precipitation varied significantly depending on the depth and position in the vineyard, from approximately 1% up to 98%, where more precipitation fraction has been determined in the surface and subsurface runoff. Additionally, statistical analysis and a more detailed evaluation of precipitation fractions at the 40 cm depth, where wick lysimeters are installed, have shown that Corg content is related to the silt fraction, while the first results indicate that the infiltration patterns were dependent on the common influence of all observed physicochemical properties. Full article
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17 pages, 6992 KiB  
Article
Aquavoltaics Feasibility Assessment: Synergies of Solar PV Power Generation and Aquaculture Production
by Moslem Imani, Hoda Fakour, Shang-Lien Lo, Mei-Hua Yuan, Chih-Kuei Chen, Shariat Mobasser and Isara Muangthai
Water 2023, 15(5), 987; https://doi.org/10.3390/w15050987 - 4 Mar 2023
Cited by 4 | Viewed by 3724
Abstract
The negative effects of climate change have burdened humanity with the necessity of decarbonization by moving to clean and renewable sources of energy generation. While energy demand varies across the sectors, fisheries, including fishing and aquaculture, are among the most energy intensive processes [...] Read more.
The negative effects of climate change have burdened humanity with the necessity of decarbonization by moving to clean and renewable sources of energy generation. While energy demand varies across the sectors, fisheries, including fishing and aquaculture, are among the most energy intensive processes in the food production industry. The synergistic opportunities for co-located aquaculture and renewable energy can thus provide a multifunctional use of space and resources, creating opportunities to meet the identified energy demands of a variety of aquaculture operations. This study has investigated a sustainable energy model for a small-scale shrimp farm in western Taiwan with synergies for the dual use of the water area for solar photovoltaic electricity generation and aquaculture. Based on the simulation results and SWOT analysis, recommendations have been made for the design and operation of a solar-powered aeration system for shrimp farms. The average monthly energy production of 32 MWh is attainable at the estimated canopy space on a carport by installing 896 solar modules on the proposed site, fully covering the power demand of the shrimp farm. These findings have significance for encouraging effective practices in deploying solar techniques in aquaculture and making them replicable in global settings. Full article
(This article belongs to the Special Issue Sustainable Development of Water, Energy, and Environment Systems)
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23 pages, 3957 KiB  
Review
Advances in Assessing the Reliability of Water Distribution Networks: A Bibliometric Analysis and Scoping Review
by Swati Sirsant, Mohamed A. Hamouda and Mostafa F. Shaaban
Water 2023, 15(5), 986; https://doi.org/10.3390/w15050986 - 4 Mar 2023
Cited by 2 | Viewed by 2273
Abstract
The reliability of Water Distribution Networks (WDNs) is a critical topic that has been explored by many researchers over the last few decades. Nevertheless, this research domain has gained momentum in the last decade. WDN reliability was addressed in the literature using different [...] Read more.
The reliability of Water Distribution Networks (WDNs) is a critical topic that has been explored by many researchers over the last few decades. Nevertheless, this research domain has gained momentum in the last decade. WDN reliability was addressed in the literature using different approaches and techniques. This study presents a bibliometric analysis and scoping review of the progress and gaps in research on WDN reliability. The analysis was performed on a total of 347 articles from 2000 to 2022, which were retrieved from the SCOPUS database. The bibliometric analysis identified trends and gaps by focusing on articles output, citation network of articles, co-authorship and collaboration analysis, co-citation, and clustering analysis. In addition, coupling keywords analysis with thematic maps analysis helped identify basic, niche, emerging, and declining research themes in the field of WDN reliability. Three major research themes were found: WDN optimization, reliability assessment, and consideration of GHG emissions and energy-cost for WDN expansion. Reliability surrogate measures (RSMs) were found to be one of the most widely researched topics in this field. Performance assessment of various RSMs, as well as the consideration of energy and cost for WDN design and expansion stood out as the emerging trends for future research in the field of WDN reliability. Full article
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16 pages, 5065 KiB  
Article
Modelling Plume Development with Annual Pulses of Contaminants Released from an Airport Runway to a Layered Aquifer, Evaluation of an In Situ Monitoring System
by Helen K. French, Mona C. Hansen, Kamilla G. Moe and Julie Stene
Water 2023, 15(5), 985; https://doi.org/10.3390/w15050985 - 4 Mar 2023
Cited by 3 | Viewed by 1616
Abstract
In cold climates, the use of de-icing chemicals in the winter can lead to groundwater contamination, especially when used in large quantities, such as at airports. Oslo Airport, Gardermoen, is situated on Norway’s largest rain-fed aquifer. Potassium formate is used to remove ice [...] Read more.
In cold climates, the use of de-icing chemicals in the winter can lead to groundwater contamination, especially when used in large quantities, such as at airports. Oslo Airport, Gardermoen, is situated on Norway’s largest rain-fed aquifer. Potassium formate is used to remove ice from runways and propylene glycol from airplanes; the organic parts are degradable. Most of the wells to monitor the spread of de-icing chemicals in the underlying aquifer have well screens near the groundwater level, while the runways and the source of de-icing chemicals are near the groundwater divides, where vertical flow is expected. The objective of this study is to demonstrate the importance of layers and time-varying recharge on the spreading of contaminant plumes in an aquifer near a groundwater divide. This is done with numerical modelling. The model results show increased vertical transport of the added tracer in the presence of horizontal layers, both continuous and discontinuous, in the aquifer. With certain distributions of hydraulic conductivity, Ks, we demonstrate that deeper monitoring wells are required. With the scenarios modelled here, time-varying recharge has a weaker effect on plume distribution. Measured concentrations of potassium and total organic carbon show the cyclic effect of seasonally varying recharge of contaminants, and an asymptotic accumulation of concentration over time, that is consistent with the model runs. In conclusion, groundwater monitoring systems near a groundwater divide should include multi-level samplers to ensure control of the vertical plume movement. Full article
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16 pages, 3645 KiB  
Article
The Copula Application for Analysis of the Flood Threat at the River Confluences in the Danube River Basin in Slovakia
by Veronika Bačová Mitková, Dana Halmová, Pavla Pekárová and Pavol Miklánek
Water 2023, 15(5), 984; https://doi.org/10.3390/w15050984 - 4 Mar 2023
Cited by 5 | Viewed by 1872
Abstract
In hydrological practice, individual elements of the hydrological cycle are most often estimated and evaluated separately. Uncertainty in the size estimation of extrema discharges and their return period can affect the statistical assessment of the significance of floods. One example is the simultaneous [...] Read more.
In hydrological practice, individual elements of the hydrological cycle are most often estimated and evaluated separately. Uncertainty in the size estimation of extrema discharges and their return period can affect the statistical assessment of the significance of floods. One example is the simultaneous occurrence and joining of extremes at the confluence of rivers. The paper dealt with the statistical evaluation of the occurrence of two independent variables and their joint probabilities of occurrence. Bivariate joint analysis is a statistical approach for the assessment of flood threats at the confluence of rivers. In our study, the annual maximum discharges monitored on four selected Slovak rivers and their tributaries represent the analyzed variables. The Archimedean class of copula functions was used as a set of mathematical tools for the determination and evaluation of the joint probability of annual maximal discharges at river confluences. The results of such analysis can contribute to a more reliable assessment of flood threats, especially in cases where extreme discharges occur simultaneously, increasing the risk of devastating effects. Finally, the designed discharges of the different return periods calculated by using the univariate approach and the bivariate approach for the gauging station below the confluence of the rivers was evaluated and compared. Full article
(This article belongs to the Special Issue Advance in Flood Risk Management and Assessment Research)
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15 pages, 10203 KiB  
Article
Large-Eddy Simulation of Compound Channels with Staged Floodplains: Flow Interactions and Turbulent Structures
by Prateek Kumar Singh, Xiaonan Tang and Hamidreza Rahimi
Water 2023, 15(5), 983; https://doi.org/10.3390/w15050983 - 3 Mar 2023
Viewed by 1769
Abstract
Numerous sources of overtopping and flood events suggest different cross-sectional land characteristics of the river and urban river water systems. Multiple stages of floodplains in compound channels are viable in urban areas to facilitate bank slope stability and a higher discharge capacity for [...] Read more.
Numerous sources of overtopping and flood events suggest different cross-sectional land characteristics of the river and urban river water systems. Multiple stages of floodplains in compound channels are viable in urban areas to facilitate bank slope stability and a higher discharge capacity for different flow rates. The complexity of the contiguous floodplains’ compound channel flows manifold with the interactive geometry and roughness of the surrounding floodplains. In the present study, a large-eddy simulation study is undertaken to investigate the turbulent structure of open channels with multiple-stage floodplains. The validation uses experimental data collected at individual contiguous multiple-stage floodplains for three depth ratios from shallow to deep flow regimes. The wall-modelled large eddy simulations were validated with the depth-averaged velocity, primary velocity and secondary currents. Furthermore, the impact of the multiple-stage floodplains on the instantaneous flow fields and large-scale vortical structures is predicted herein. It was found that vortical structures affect the distribution of the momentum exchange over multiple-stage floodplains. Full article
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19 pages, 11048 KiB  
Article
Comparative Study on the Decontamination Efficacy of Peelable Coatings for Heavy Metals Removal
by Gabriela Toader, Daniela Pulpea, Aurel Diacon, Edina Rusen, Raluca Elena Ginghina, Traian Rotariu, Alice Ionela Podaru, Andreea Elena Moldovan, Maria Gavrilescu, Ana-Mihaela Gavrila and Bogdan Trica
Water 2023, 15(5), 982; https://doi.org/10.3390/w15050982 - 3 Mar 2023
Cited by 3 | Viewed by 2444
Abstract
This study presents the formulation and application of strippable coatings for the entrapment and removal of heavy metals (HMs) and radio nuclides (RNs). The “green” formulations involve the use of a water-based solution consisting of a synthetic biodegradable polymer, polyvinyl alcohol (PVA), together [...] Read more.
This study presents the formulation and application of strippable coatings for the entrapment and removal of heavy metals (HMs) and radio nuclides (RNs). The “green” formulations involve the use of a water-based solution consisting of a synthetic biodegradable polymer, polyvinyl alcohol (PVA), together with a natural polymer (sodium alginate) as the polymer matrix and bentonite as the reinforcing agent with cation exchange capacity. Four chelating agents comprising two classical chelating agents (ethylenediaminetetraacetic acid (EDTA), diethylenetriamine-pentaacetic acid (DPTA)) and two “green” chelating agents (iminodisuccinic acid (IDS), 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC)) were used to evaluate the capacity to remove Cu, Sb, Zn, Sr, Pb, Co, and Hg from the contaminated surfaces. This decontamination method leads to the formation of a solid waste, thus eliminating the need for wastewater treatment. Atomic absorption spectroscopy (AAS), inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and ultraviolet-visible (UV–Vis) spectroscopy were used to comparatively evaluate the decontamination efficacy. EDX elemental mapping confirmed the entrapment of the contaminants inside the polymeric matrix. Full article
(This article belongs to the Special Issue Ecological Risk Assessment of Heavy Metal Pollution)
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20 pages, 6006 KiB  
Article
Analysis of the Effect of Pore Water Pressure on a Small Radius Curve Section of a Fine Sand Layer under Cyclic Metro
by Xiaorui Wang, Xu Liu, Yunhong Lin and Fei Tan
Water 2023, 15(5), 981; https://doi.org/10.3390/w15050981 - 3 Mar 2023
Viewed by 1803
Abstract
Small curved metro shield tunnels located in fine sand layers are sensitive to the response of horizontal and vertical cyclic loads from train operations, especially for centrifugal horizontal loads. The majority of Zhengzhou’s strata are dominated by this geological composition. Therefore, the dynamic [...] Read more.
Small curved metro shield tunnels located in fine sand layers are sensitive to the response of horizontal and vertical cyclic loads from train operations, especially for centrifugal horizontal loads. The majority of Zhengzhou’s strata are dominated by this geological composition. Therefore, the dynamic response of the fine sand layer under the train vibration load will lead to the settlement of the sand layer, which brings great hidden danger to the train operation. Long-term pore water monitoring was carried out in this paper, and the use of MIDAS-GTS (Multi-candidate Iterative Design with Adaptive Selection) finite element calculation platform to establish the metro ballast-lining-soil coupling dynamic model for mutual verification. The variation patterns of pore water pressure and super pore water pressure during train operation and the vibration response pattern of the soil layer around the tunnel were investigated. The results suggest that: (1) The pore and excess pore water pressures generated at the start of vibration are not easily dissipated and transferred, making them larger in the early stages of train operation. In contrast, the fine-grained powdered sandy soil has a small amount of clay particles, giving strength and cohesion to the soil layer. Vibrating hole pressure and excess pore water pressure stabilize with the train at a later stage; (2) The low probability of liquefaction in the silt layer surrounding the tunnel; (3) Under vibrating loads, areas of significant soil settlement are concentrated on the soil surface, on the upper side of the tunnel in the silty sand layer and at the bottom 3 m of the tunnel, however, its low variation in settlement has a low impact on the tunnel. Full article
(This article belongs to the Section Soil and Water)
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21 pages, 2819 KiB  
Article
Performance, Modeling, and Cost Analysis of Chemical Coagulation-Assisted Solar Powered Electrocoagulation Treatment System for Pharmaceutical Wastewater
by Tharaa M. Al-Zghoul, Zakaria Al-Qodah and Ahmad Al-Jamrah
Water 2023, 15(5), 980; https://doi.org/10.3390/w15050980 - 3 Mar 2023
Cited by 11 | Viewed by 2407
Abstract
The combination of the chemical coagulation-assisted electrocoagulation (CC-EC) process with a solar photovoltaic energy source has attracted increasing attention for the efficient removal of chemical oxygen demand (COD) from pharmaceutical wastewater. In this paper, the CC-EC process has been utilized as an alternative [...] Read more.
The combination of the chemical coagulation-assisted electrocoagulation (CC-EC) process with a solar photovoltaic energy source has attracted increasing attention for the efficient removal of chemical oxygen demand (COD) from pharmaceutical wastewater. In this paper, the CC-EC process has been utilized as an alternative to conventional chemical processes for the treatment of pharmaceutical wastewater. The effects of the various operating parameters, such as coagulant dosage, coagulant type, number of electrodes, the distance between electrodes, electrode configuration, operating time, and current density, on COD removal efficiency were investigated. The results indicated that the optimum conditions were achieved at 500 mg/L of alum dosage, 3.105 mA/cm2 of current density, six electrodes with a distance of 4 cm between electrodes, and the MP-S electrode configuration, where the operating cost of conventional energy was 0.283 $/m3. Indeed, by using the CC process alone, the COD removal efficiency was 26% and 61.5% at the optimal dosages of 750 mg/L of NaOH and 500 mg/L of alum, respectively. In the CC-EC treatment, the removal efficiencies of COD were 88.7, 92.9, 94.4, and 89.4% using six electrodes, 2 cm of distance between electrodes, MP-S electrode configuration, and 20 min with 1.553 mA/cm2 of current density, respectively. The removal efficiencies of COD achieved through CC, EC, and CC-EC processes were 61.5, 85.4, and 94.4%, respectively. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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13 pages, 2304 KiB  
Article
A Method for Calibrating the Transient Storage Model from the Early and Late-Time Behavior of Breakthrough Curves
by Eleonora Dallan, Andrea Bottacin-Busolin, Mattia Zaramella and Andrea Marion
Water 2023, 15(5), 979; https://doi.org/10.3390/w15050979 - 3 Mar 2023
Viewed by 1461
Abstract
Solute transport in rivers is controlled by mixing processes that occur over a wide spectrum of spatial and temporal scales. Deviations from the classic advection–dispersion model observed in tracer test studies are known to be generated by the temporary trapping of solutes in [...] Read more.
Solute transport in rivers is controlled by mixing processes that occur over a wide spectrum of spatial and temporal scales. Deviations from the classic advection–dispersion model observed in tracer test studies are known to be generated by the temporary trapping of solutes in storage zones where velocities and mixing rates are relatively small. In this work, the relation between the early and late-time behavior of solute breakthrough curves (BTCs) and the key parameters of the Transient Storage Model (TSM) is analyzed using non-asymptotic approximations of the model equations. Two main slopes are identified corresponding to the rising and decreasing limbs of the BTCs which are linked by specific relationships to transport and storage parameters. The validity of the proposed approximations is demonstrated with both synthetic and experimental data. Consistent with the TSM assumptions, the range of validity of the proposed approximations represents the limit of separability between surface dispersion and transient storage and can be expressed as a function of a nondimensional parameter. The results of this work can help environmental scientists identify solute transport and transient storage parameters and support the design of enhanced field tracer experiments. Full article
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13 pages, 2383 KiB  
Article
Spatial Distribution of Pine Pollen Grains Concentrations as a Source of Biologically Active Substances in Surface Waters of the Southern Baltic Sea
by Magdalena Maria Pawlik and Dariusz Ficek
Water 2023, 15(5), 978; https://doi.org/10.3390/w15050978 - 3 Mar 2023
Cited by 4 | Viewed by 1995
Abstract
Pine pollen is a very important component of the marine environment: it is a valuable source of both carbon and macro- and microelements, and it is also a major food resource for many marine organisms. Its characteristic optical properties distinguish it from other [...] Read more.
Pine pollen is a very important component of the marine environment: it is a valuable source of both carbon and macro- and microelements, and it is also a major food resource for many marine organisms. Its characteristic optical properties distinguish it from other suspended particulate matter (SPM), but it can also distort measurements of the latter. Hence, it affects a range of sea water properties as well as a number of key biogeochemical processes taking place in the marine environment. Pollen concentrations were determined with satisfactory accuracy in samples of sea water taken from selected stations in the southern Baltic Sea in May 2018. This paper aims to highlight the spatial differentiation of pollen levels in southern Baltic surface waters and to show that pollen in May is a significant, hitherto overlooked, source of a great many substances essential for the ecosystem’s functioning. Our measurements indicated that pollen was present over the entire area of the southern Baltic studied. Spatially, its concentrations in surface waters differed very widely. Very high levels were recorded both very close to the shore and a long way from it. Any analysis of the influence on the ecosystem of the various substances that pollen brings to the water must take into account the ratio of the concentration of pollen to that of other SPM in the ecosystem. This study showed that even a small concentration of SPM in the central Baltic means that pollen grains can periodically supply substances key to the ecosystem’s functioning. In many areas, pine pollen can make up as much as ca. 50% of the SPM in the 1.25–250 µm size range. Full article
(This article belongs to the Section Oceans and Coastal Zones)
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25 pages, 3478 KiB  
Article
Response Surface Modelling of Methylene Blue Adsorption onto Seaweed, Coconut Shell and Oak Wood Hydrochars
by Eric Danso-Boateng, Melissa Fitzsimmons, Andrew B. Ross and Ted Mariner
Water 2023, 15(5), 977; https://doi.org/10.3390/w15050977 - 3 Mar 2023
Cited by 5 | Viewed by 2300
Abstract
Adsorption of methylene blue (MB) dye from an aqueous solution onto hydrochars produced from brown seaweed (Fucus Serratus) (FS-HC), coconut shell (CS-HC), and oak wood (Oak-HC) at different temperatures (200–250 °C) was investigated in a batch system. Response surface modelling (RSM) [...] Read more.
Adsorption of methylene blue (MB) dye from an aqueous solution onto hydrochars produced from brown seaweed (Fucus Serratus) (FS-HC), coconut shell (CS-HC), and oak wood (Oak-HC) at different temperatures (200–250 °C) was investigated in a batch system. Response surface modelling (RSM) was used to investigate the effect of initial MB concentration (50–300 mg/L), contact time (0–240 min), and solution pH (2–12) on the adsorption process. RSM was also used to model and optimise these parameters for efficient adsorption. Kinetic and isotherms studies were carried out to study the adsorption mechanism onto the hydrochars. It was found that the best adsorbent from the RSM model was FS-HC200, and the optimal conditions for greater MB dye uptake were lower initial MB concentration (50 mg/L), pH 6 and contact time of 84 min; removing >99% of MB. Langmuir and Redlich–Peterson isotherm models fitted the adsorption of MB onto hydrochars prepared at 200 and 250 °C. Freundlich and Redlich–Peterson isotherms were suitable for hydrochars produced at 220 °C. FS-HCs have the highest maximum adsorption capacity of MB of about (8.60–28.57) mg/g calculated from the Langmuir isotherm. The adsorption process for all the hydrochars followed a pseudo-second-order model (R2 = 0.96–1.00), and film diffusion and intraparticle diffusion were the rate-determining steps. Therefore, this work identifies cheap adsorbents from biowaste that are effective for the removal of cationic pollutants from wastewater. Full article
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17 pages, 3090 KiB  
Article
Chironomid-Based Modern Summer Temperature Data Set and Inference Model for the Northwest European Part of Russia
by Larisa Nazarova, Liudmila Syrykh, Ivan Grekov, Tatiana Sapelko, Andrey B. Krasheninnikov and Nadia Solovieva
Water 2023, 15(5), 976; https://doi.org/10.3390/w15050976 - 3 Mar 2023
Cited by 1 | Viewed by 1835
Abstract
Northwestern Russia remains the only region in Northern Eurasia where no regional chironomid-based inference model for quantitative palaeoclimatic reconstructions has been developed. Using palaeolimnological methods, we investigated the subfossil chironomid remains in surface sediments from a data set of 98 lakes from nine [...] Read more.
Northwestern Russia remains the only region in Northern Eurasia where no regional chironomid-based inference model for quantitative palaeoclimatic reconstructions has been developed. Using palaeolimnological methods, we investigated the subfossil chironomid remains in surface sediments from a data set of 98 lakes from nine subregions of the European part of Northern Russia. We identified 143 chironomid taxa in the investigated lakes. Multivariate statistical analyses of chironomid and environmental data demonstrated that the mean July air temperature (T July), distance from the tree line, water depth, pH, and altitude explain the most significant variance in chironomid distribution. T July appeared to be the most important environmental variable. We established a chironomid-based inference model for reconstructing T July from subfossil data. The resulting West Russian two-component WA-PLS model includes 96 lakes (two lakes were excluded as outliers), 143 chironomid taxa, r2 = 0.84 (r2 boot = 0.60), RMSEP boot = 1.34 °C, and can be recommended for application in palaeoclimatic studies in the East of Northern Eurasia. Full article
(This article belongs to the Section Water and Climate Change)
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25 pages, 1568 KiB  
Review
Impact of Antibiotic Pollution on the Bacterial Population within Surface Water with Special Focus on Mountain Rivers
by Klaudia Kulik, Anna Lenart-Boroń and Kinga Wyrzykowska
Water 2023, 15(5), 975; https://doi.org/10.3390/w15050975 - 3 Mar 2023
Cited by 23 | Viewed by 9856
Abstract
Environmental aquatic pollution with antibiotics is a global challenge that affects even pristine mountain environments. Monitoring the concentration of antibiotics in water is critical to water resource management. In this review, we present the sources and degradation routes of antibiotics polluting surface waters, [...] Read more.
Environmental aquatic pollution with antibiotics is a global challenge that affects even pristine mountain environments. Monitoring the concentration of antibiotics in water is critical to water resource management. In this review, we present the sources and degradation routes of antibiotics polluting surface waters, with particular focus on mountain environments and pristine areas. This pollution is strongly related to anthropopressure resulting from intensive tourism. An important aspect of the threat to the environment is water containing antibiotics at sub-inhibitory concentrations, which affects bacterial populations. Antibiotics are ecological factors driving microbial evolution by changing the bacterial community composition, inhibiting or promoting their ecological functions, and enriching and maintaining drug resistance. We paid attention to the stability of antibiotics and their half-lives in water related to biotic and abiotic degradation, which results from the structures of molecules and environmental conditions. Wastewater treatment combined with advanced treatment techniques significantly increase the efficiency of antibiotic removal from wastewater. Modern methods of wastewater treatment are crucial in reducing the supply of antibiotics to aquatic environments and enhancing the possibility of economic and safe reuse of wastewater for technical purposes. We provide a perspective on current research investigating antibiotic emergence in mountain areas and identify knowledge gaps in this field. Full article
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