High-quality Groundwater Research Articles

Characteristics and genesis of high-quality metasilicate mineral water in Liaocheng City, Shandong Province.

Drinking natural mineral water often contains minerals and trace elements essential for human beings, such as strontium and silicon. As people's quality of life improves, so do their requirements for drinking water. Therefore, it is crucial to identify and develop high-quality groundwater that is rich in metasilicate and other minerals. The aim of this study is to reveal the distribution pattern and causes of high-quality metasilicate-rich groundwater in Liaocheng City through scientific methods, so as to provide a theoretical basis for the rational development and protection of mineral water resources. The results shown that Dong'e County was the main concentration area of high-quality metasilicate mineral water in Liaocheng City. The main reason for its high concentration of metasilicic acid was due to water-rock interaction. There was bedrock fissure water in the underlying water supply rock groups in Dong'e County, and the reaction between the metasilicate minerals in the rock groups and water was the main source of metasilicic acid. In addition, the development of fissures in the area provided a good storage and conductivity system for the enrichment of metasilicic acid in groundwater. Based on the analysis of hydrogeological conditions and the mechanism of formation of enriched areas, the enriched areas were divided into developable areas, protected and restricted development areas, and restricted development areas. The results of the study can lay a theoretical foundation for the systematic and scientific development, utilization, and protection of high-quality metasilicate mineral water in Liaocheng City.

Assessment of spatiotemporal risks for nationwide groundwater nitrate contamination

National assessments of groundwater contamination risks are crucial for sustaining high-quality groundwater supplies. However, traditional methods often treat groundwater contamination risk as a steady-state indicator without considering spatiotemporal variation in risk, both geographically and over time, caused by anthropogenic and climatic factors. In this work, XGBoost, a tree-based algorithm, was applied to comprehensively analyze the drivers of groundwater contamination from nitrate, using data on 13 physical features (as used by the index-based ranking method DRASTIC) and 30 anthropogenic features from 1985 to 2010 in the contiguous United States (CONUS). The results indicate that physical features controlling the transport processes, particularly those affecting contaminant travel time from land surface to groundwater (depth to water table and transmissivity), were the dominant factors for nitrate contamination in groundwater. This was followed by features representing the potential nitrogen loading. Positive correlations between most features and the nitrogen loading time (year) were found, suggesting their growing influence on contamination risk. Based on the drivers identified for nitrate concentrations exceeding 10 mg/L in groundwater and their varying temporal contributions, this study proposes a reformulated index-based method for contamination risk assessment. With this method, an overall accuracy of around 70 % was achieved based on the validation data set. The predicted high-risk areas are mainly intensive irrigation regions, such as the High Plains, northern Midwest, and Central Valley. This new approach contributes to a more accurate and effective assessment of the contamination risks of groundwater on a regional and national scale under temporally varying environmental conditions.

Hydro-chemical characteristics and groundwater quality evaluation in south-western region of Bangladesh: A GIS-based approach and multivariate analyses

The study focuses on the chemistry of groundwater and if it is suitable for drinking and for use in agriculture using water quality indices, GIS mapping, and multivariate analyses in Sharsa Upazila, Jashore district, Bangladesh. In this study, the concentration of NH4+, K+, Ca2+, EC, Turbidity overstep BDWS drinking standards in 69 %, 14 %, 100 %, 40 % (WHO), 73 % of samples respectively. The value of Water Quality Indices (WQI) results inferred that the maximum specimen was held good quality for drinking uses, and the values distributed central eastern part to the south-eastern part were good quality water in the selected studied area. The study area's PH, EC, SAR, Na (%), TH, and NO3− values were mapped using GIS tools to show their spatial distribution. The cluster and correlation matrix analyses are used to validate for Principle Component Analysis (PCA). The five PCA results exhibited that the presence of EC, turbidity, K+, SO42− and NO3− was significant and was caused by both geogenic (rock weathering and cation exchange) and anthropogenic (agrochemicals, animal feedback) factor. According to the hydro-geochemical data, the maximum number of samples is of the Ca–Mg–HCO3–Cl type and is dominated by rocks. The irrigation water indices like MH, KR, SAR, and %Na indicate show high-quality groundwater for irrigation purposes. Most of the samples were satisfactory and compiled with WHO and Bangladeshi criteria for standard drinking water guideline values.

Hydrochemical characterization of groundwater for consumption and agriculture: A case study from Phulpur Upazila, Bangladesh

The aim of this study was to assess the suitability of groundwater for drinking and irrigation in Phulpur Upazila, Bangladesh, based on its hydrochemical attributes. In our research, we examined twenty groundwater specimens from shallow and hand tube wells, adhering to international and national guidelines. The data showed groundwater pH levels from 5.67 to 6.84, signifying slightly acidic to neutral properties. Total dissolved solids ranged from 79 to 298 mg/l, and conductivity varied between 120 and 832 μS/cm. Notably, the primary cations and anions were sequenced as Ca > Mg > Na > K and HCO3 > Cl > SO4 > PO4, respectively. A marked correlation was discerned among the physicochemical parameters, and the predominant groundwater type was magnesium-bicarbonate (Mg-HCO3). The main geochemical activity was identified as silicate weathering, pointing to significant rock-water interactions in the region. The groundwater displayed moderate salinity and low alkalinity, qualifying them as 'excellent to good' and 'normal' in quality metrics, respectively. The soluble sodium percentage was rated as 'excellent'. On multiple assessment scales, the groundwater quality was deemed 'good' for irrigation. In line with established classification systems, most samples were suitable for drinking and irrigation. Hence, the area's groundwater is viable for consumption and agricultural utilization. Cumulatively, our research offers critical insights for sustainable groundwater stewardship in the region, providing a foundation for policymakers to guarantee the sustained provision of high-quality groundwater for diverse applications.

Optimal layout design of groundwater pollution monitoring network using parameter iterative updating strategy-based ant colony optimization algorithm.

The scientific layout design of the groundwater pollution monitoring network (GPMN) can provide high quality groundwater monitoring data, which is essential for the timely detection and remediation of groundwater pollution. The simulation optimization approach was effective in obtaining the optimal design of the GPMN. The ant colony optimization (ACO) algorithm is an effective method for solving optimization models. However, the parameters used in the conventional ACO algorithm are empirically adopted with fixed values, which may affect the global searchability and convergence speed. Therefore, a parameter-iterative updating strategy-based ant colony optimization (PIUSACO) algorithm was proposed to solve this problem. For the GPMN optimal design problem, a simulation-optimization framework using PIUSACO algorithm was applied in a municipal waste landfill in BaiCheng city in China. Moreover, to reduce the computational load of the design process while considering the uncertainty of aquifer parameters and pollution sources, a genetic algorithm-support vector regression (GA-SVR) method was proposed to develop the surrogate model for the numerical model. The results showed that the layout scheme obtained using the PIUSACO algorithm had a significantly higher detection rate than ACO algorithm and random layout schemes, indicating that the designed layout scheme based on the PIUSACO algorithm can detect the groundwater pollution occurrence timely. The comparison of the iteration processes of the PIUSACO and conventional ACO algorithms shows that the global searching ability is improved and the convergence speed is accelerated significantly using the iteration updating strategy of crucial parameters. This study demonstrates the feasibility of the PIUSACO algorithm for the optimal layout design of the GPMN for the timely detection of groundwater pollution.

Hydrochemical Characterization and Water Quality Assessment for Drinking and Irrigation Purposes Using WQI and GIS Techniques in the Upper Omo River Basin, Southern Ethiopia

Groundwater is an important source of drinking water and irrigation in Ethiopia’s present study area of the upper Omo River catchment. The present study area has an increasing demand for high-quality groundwater. Extensive irrigation and urban expansion are ongoing in the study area, seriously compromising groundwater quality. A study was conducted in Ethiopia’s upper Omo River catchment to assess groundwater’s suitability for drinking water and agricultural purposes. In total, 58 water samples were collected for this study. Based on the WHO and Ethiopian standards for assessing water quality, the study’s results have been analyzed and compared. The groundwater’s primary ion and physicochemical properties were plotted using GIS technology. Based on the results of the hydrochemical analysis, three water quality index (WQI) zones were identified: excellent (58.82%), good (35.29%), and poor (5.88%). From the Piper diagram plots, five different types of water were identified as Ca-HCO3, Na-HCO3, mixed Ca-Na-HCO3, NaCl, and CaCl, out of the total of fifty-eight samples collected from the study area. The present study found that in the area, most water samples are suitable for drinking, except for a few parameters above the standards for drinking water set by the World Health Organization and Ethiopian drinking water quality standards. Except for the three samples, EC, SAR, and PI data indicate that most of the area’s water samples are suitable for irrigation. Water quality indices, irrigation water quality methods, and GIS techniques are crucial for assessing water quality based on the study.

Estimating Groundwater Pumping for Irrigation: A Method Comparison.

Effective groundwater management is critical to future environmental, ecological, and social sustainability and requires accurate estimates of groundwater withdrawals. Unfortunately, these estimates are not readily available in most areas due to physical, regulatory, and social challenges. Here, we compare four different approaches for estimating groundwater withdrawals for agricultural irrigation. We apply these methods in a groundwater-irrigated region in the state of Kansas, USA, where high-quality groundwater withdrawal data are available for evaluation. The four methods represent a broad spectrum of approaches: (1) the hydrologically-based Water Table Fluctuation method (WTFM); (2) the demand-based SALUS crop model; (3) estimates based on satellite-derived evapotranspiration (ET) data from OpenET; and (4) a landscape hydrology model which integrates hydrologic- and demand-based approaches. The applicability of each approach varies based on data availability, spatial and temporal resolution, and accuracy of predictions. In general, our results indicate that all approaches reasonably estimate groundwater withdrawals in our region, however, the type and amount of data required for accurate estimates and the computational requirements vary among approaches. For example, WTFM requires accurate groundwater levels, specific yield, and recharge data, whereas the SALUS crop model requires adequate information about crop type, land use, and weather. This variability highlights the difficulty in identifying what data, and how much, are necessary for a reasonable groundwater withdrawal estimate, and suggests that data availability should drive the choice of approach. Overall, our findings will help practitioners evaluate the strengths and weaknesses of different approaches and select the appropriate approach for their application.

Evaluation of groundwater quality using multivariate, parametric and non-parametric statistics, and GWQI in Ibadan, Nigeria

ABSTRACT An attempt was made to assess the properties of groundwater in the Ibadan Metropolitan area, Nigeria by applying multivariate statistical methods on samples collected from various parts of the study area. Out of all the physio-chemical features of groundwater, the quality is a major concern since the long-term progress of groundwater researches in numerous study fields is reliant on the accessibility to high-quality groundwater. Several quantitative methodologies have been successfully used to analyze groundwater hydrochemistry. One other major way to explaining groundwater quality is multivariate statistical analysis, of which hierarchical cluster analysis (HCA) and principal component analysis (PCA) comprise. The Kruskal–Wallis Test, Pearson Correlation, and the Independent Sample Test were employed in assessing water quality. The groundwater quality index was used to examine the suitability of water for ingestion. pH is significantly correlated with Na+ and Ca2+, (0.480 and 0.257), and negatively correlated with Cl− and HCO3 _, (−416 and −0.398). TDS levels correlated with K+ concentration levels (0.228). Na+ significantly correlated with Ca2+ and Mg2+ (0.849 and 0.968). pH, EC, magnesium and chloride, were significantly influenced by the lithology (p < 0.05). Furthermore pH, K+, Na+, Mg2+, Ca2+, HCO3 −, and NO3 −, all differ significantly from the WHO limits (p < 0.05). The water quality index indicates that the water from the different sampling point fall under the good category of the index. Various statistical analysis assists in determining the spatiality of main explanatory variables and in determining the extent to which planning is required.

Assessment of Rainwater Quality Regarding its Use in The Roztocze National Park (Poland)—Case Study

The aim of this study was to determine the quality of rainwater and the possibility of using it for various purposes in the Roztocze National Park (RNP), Poland. This study was carried out in 2021–2022. Samples of rainwater that drained from the roofs of farm buildings in the RNP were tested for their organoleptic, physicochemical and microbiological qualities. The organoleptic tests were run to evaluate the water for a foreign odour and the threshold odour number. The physical and chemical tests included turbidity; colour; pH; conductivity; concentrations of ammonium ions, nitrates, nitrites, manganese, iron and chlorides; and general hardness. The microbiological tests included total microbial counts at 36 °C and 22 °C, coliform bacteria, Escherichia coli, intestinal enterococci and Pseudomonas aeruginosa. The rainwater quality results were compared with the quality parameters of surface water collected from the River Świerszcz, as well as with the Polish drinking water standards. The findings indicated that rainwater collected in the RNP had good organoleptic, physicochemical and microbiological properties, which, in some cases, complied with the standards for potable water. Exceedances of the permissible limits, mainly for ammonium ions and microbiological indicators, were periodically observed in the tested rainwater. This was probably due to contamination of roof surfaces with bird droppings. However, these exceedances did not exclude the use of the rainwater for economic purposes, e.g., flushing toilets, washing vehicles or watering plants, which may significantly reduce the abstraction of high-quality groundwater. The rainwater that is planned to be used as drinking water for the Polish konik horses living in the park will have to be pre-treated via filtration and disinfection processes (e.g., with a UV lamp).

Integrated approach for the investigation of groundwater quality using hydrochemical and geostatistical analyses in Wadi Fatimah, western Saudi Arabia

The Wadi Fatimah area suffers from a lack of freshwater resources, so this study aimed to analyze the groundwater in this region and evaluate its quality for irrigation and drinking purposes. Eleven water quality parameters, including pH, total dissolved solids (TDS), Ca2+, HCO−3, NO−3, F−, Cl−, K+, Mg2+, SO2−4, and Na+, were utilized to evaluate the quality of the water and produce a water quality index (WQI). These parameters were measured at 100 different chosen locations. The spatial distribution map revealed that all parameters are high in the southern part except K+. Using the correlation matrix, a high positive correlation is obtained among TDS, Cl−, Mg2+, and Ca2+ in addition to a high correlation among TDS with Cl− and Na+. From PCA analysis, PCA1, PCA2, and PCA3 represent about 52%, 12%, and 10% of all components along the study area, respectively. PCA1 has low variance than PCA2 and PCA3. The majority of the Southern region’s sites went from having extremely poor to poor water classifications and from poor to unsuitable water. However, the center part possesses exceptionally high-quality groundwater. According to the results from the current study’s water quality index, the presence of nitrate and fluoride in the groundwater samples was primarily responsible for their high WQI values. The statistics showed that a higher percentage of the population had poor drinking water due to direct pollutant release, agricultural effects, and excessive groundwater resource use. The study offers a groundwater quality modeling technique that is both affordable and replicable in other areas.

Development of a new design of deironing granulated filter for joint removal of iron and ammonium nitrogen from underground water

ABSTRACT Providing the population with high-quality drinking water is one of the main state tasks. Rural water supply systems and water supply systems of small settlements in the region require special attention, namely, the development of technologies for individual, small-sized water treatment equipment, as well as equipment for collective use, designed to purify groundwater for drinking purposes. In many areas, there are groundwaters containing excess levels of several pollutants, which makes their purification much more difficult. Elimination of shortcomings in the known methods of water iron removal is possible by reconstructing existing water supply systems from underground sources in small settlements. A rational solution is to search for groundwater treatment technologies that make it possible to provide the population with high-quality drinking water at a lower cost. The result of increasing the concentration of oxygen in water was obtained in the process of modifying the filter by changing the excess air exhaust system, which was made in the form of a perforated pipeline located in the lower half of the granular filter layer connected to the upper branch pipe. At the same time, high-quality groundwater treatment, sufficient simplicity and reliability in operation are ensured, local conditions and the inaccessibility of many objects and settlements in the region are taken into account as much as possible. After the filter was upgraded, the concentration of iron decreased from 4.4 to 0.27 mg/L and ammonium nitrogen from 3.5 to 1.5 mg/L.

Groundwater hydrochemistry and its appropriateness for consumption and irrigation: Geographic and temporal variation: Integrated approach

The goal of the study is to determine the ground water quality for public drinking, irrigation purpose, and other uses along the Coimbatore South region of Tamil Nadu. The water quality samples are collected along the zones of Coimbatore area. Since these areas are still in development phase, attention should be paid the quality of groundwater and its suitability for use in agriculture. This research was conducted for proper management of all these important issues by physicochemical analysis and irrigation suitability assessment. 52 samples are collected from the selected area. Evaluation taken place along the physicochemical parameters and irrigation suitability parameters like pH, EC, TDS, TH, Ca, Na, Mg, K, F, Cl, SO4 & HCO3. SAR, RSC, and Na% were estimated. The plots, such as Piper timber diagrams, Gibb's plots, USSL Classification, and Wilcox diagrams, demonstrate that the sample sites are suitable for irrigation and drinking purposes Several of the regions, including Sadivayal, Semmedu, Alanthurai, and Nashe Grounden, are suitable for irrigation and have high-quality groundwater. Some of the regions, including Kuniyamuthur, Kuruchi, and Kovaipudur, have contaminated groundwater that makes it unsuitable for irrigation.

Review of Colloid (Nano‐ and Micro‐Particle) Transport and Surface Interaction in Groundwater. William P. Johnson and Eddy F. Pazmino. The Groundwater Project. 111 pp. ISBN: 978‐1‐77470‐070‐9. DOI: https://doi.org/10.21083/978‐1‐77470‐070‐9

Review of <i>Colloid (Nano‐ and Micro‐Particle) Transport and Surface Interaction in Groundwater</i>. William P. Johnson and Eddy F. Pazmino. The Groundwater Project. 111 pp. ISBN: 978‐1‐77470‐070‐9. DOI: https://doi.org/10.21083/978‐1‐77470‐070‐9

Groundwater quality assessment of protected aquatic eco-systems in cross-border areas of Serbia and Croatia

Research results define basis for specific monitoring programs of groundwater quality in wetland eco-systems in Serbia and Croatia. The main purpose of the research was to determine the impact of nonpoint diffuse source pollution on the groundwater quality, as well as seasonal variations on the concentration levels of selected physicochemical parameters. Statistical analyses, PCA, HCA, ANOVA and t-test, encompass 18 monitored parameters in groundwater. Statistical data indicated that protected area in Serbia has a significantly higher load of pollution from agricultural activities compared to Wetlands Tompojevci. The highest load in groundwater was detected from total nitrogen, ammonia and nitrogen anions, indicating contamination of groundwater by nitrogen-based fertilizers. The results obtained within the two-year seasonal monitoring program, from 2018 to 2020, are highly essential for achieving a comprehensive database that could be used as platform for highquality groundwater management in selected protected areas with the aim of minimizing environmental pollution.

Environmental rethinking of wastewater drains to manage environmental pollution and alleviate water scarcity.

The conservation of water resources in developed countries has become an increasing concern. In integrated water resource management, water quality indicators are critical. The low groundwater quality quantitates mainly attributed to the absence of protection systems for polluted streams that collect and recycle the untreated wastewater. Egypt has a limited river network; thus, the supply of water resources remains inadequate to satisfy domestic demand. In this regard, high-quality groundwater is one of the main strategies for saving water supplies with water shortage problems. This paper investigates the critical issues of groundwater protection and environmental management of polluted streams, leading to overcoming water demand-about 18 × 103 km of polluted open streams with a discharge of 9.70 billion Cubic Metter (BCM). We have proposed proposals and policies for the safe use of groundwater and reuse of wastewater recycling for agriculture and other purposes. This study was carried out using the numerical model MODFLOW and MT3DMS—(Mass Transport 3-Dimension Multi-Species) to assess the Wastewater Treated Plant's (WWTP) best location and the critical path for using different lining materials of polluted streams to avoid groundwater contamination. The three contaminants are BOD, COD, and TDS. Five scenarios were applied for mitigating the impact of polluted water: (1) abstraction forcing, (2) installing the WWTP at the outlet of the main basin drain with and without a lining of main and sub-basin streams (base case), (3) lining of main and sub-main streams, (4) installing WWTP at the outlet of the sub-basin streams, and (5) lining of the sub-basin and installing WWTP at the outlet of the sub-basin. The results showed that the best location of WWTP in polluted streams is developed at the outlets of sub-basin with the treatment of main basin water and the lining of sub-basins streams. The contamination was reduced by 76.07, 76.38, and 75.67% for BOD, COD, and TDS, respectively, using Cascade Aeration Biofilter or Trickling Filter, Enhancing Solar water Disinfection [(CABFESD)/(CATFESD)] and High-Density Polyethylene lining. This method is highly effective and safe for groundwater and surface water environmental protection. This study could be managing the water poverty for polluted streams and groundwater in the Global South and satisfy the environmental issues to improve water quality and reduce the treatment and health cost in these regions.

Numerical Modeling of Saltwater Intrusion in the Rmel-Oulad Ogbane Coastal Aquifer (Larache, Morocco) in the Climate Change and Sea-Level Rise Context (2040)

Many coastal aquifers have experienced seawater intrusion (SWI) into fresh groundwater aquifers. The principal causes of SWI include over-pumping and events such as climate change (CC) and rising sea levels. In northern Morocco, the Rmel-Oulad Ogbane coastal aquifer (ROOCA) supplies high-quality groundwater for drinking water and agriculture. This favorable situation has led to increased pumping, resulting in environmental challenges such as dropping water table and SWI. Furthermore, the climate has resulted in less recharge, with an estimated annual precipitation of 602 mm and an average temperature of 18.5 °C. The goal of this study is to determine how CC, over-pumping, and sea-level rise (SLR) affect SWI. Computational groundwater and solute transport models are used to simulate the spatial and temporal evolution of hydraulic heads and groundwater solute concentrations. The calibration is based on steady and transient groundwater levels from 1962 to 2040. SWI simulations show that the NW sector of the coastal area would be polluted, with the toe reaching 5.2 km inland with a significant salinity (15–25 g/L). To protect the fresh water in the reservoir from SWI, enhanced groundwater development and management approaches for this aquifer are required, such as artificial recharge from surface water.

მუხრანის არტეზიული აუზის მიწისქვეშა წყლების რესურსები

The Mukhrani artesian basin is a reservoir containing high quality groundwater. Well-known aquifers and galleries are located within the artesian basin, which are one of the main sources of drinking and household water supply for the city of Tbilisi. The article summarizes the hydrogeological conditions of the Mukhrani artesian basin. The hydrogeological parameters of the productive aquifer were determined based on the results of studies carried out at the existing water intakes. A hydrodynamic map of the artesian basin was compiled. The spatial and quantitative distribution of groundwater resources in the basin has been estimated. Established dynamic (natural) resources and static (natural) reserves of groundwater.

Current situation and human health risk assessment of fluoride enrichment in groundwater in the Loess Plateau: A case study of Dali County, Shaanxi Province, China

This study aims to investigate the mechanisms and health risks of fluoride enrichment in groundwater in the Loess Plateau, China. By taking Dali County, Shaanxi Province, China as an example, this study obtains the following results through field investigation and the analyses of water, soil, and crop samples. (1) The groundwater can be divided into two major types, namely the Quaternary pore-fissure water and Karst water. The Karst area and sandy area have high-quality groundwater and serve as the target areas for optional water supply. The groundwater in the study area is slightly alkaline and highly saline. Meanwhile, high-fluoride groundwater is mainly distributed in the loess and river alluvial plains in the depression area of the Guanzhong Basin and the discharge areas of the groundwater, with the highest fluoride concentration exceeding seven times the national standard. (2) Fluoride in groundwater mainly originates from a natural source and human activities. The natural source refers to the fluoride-bearing minerals in rocks and soil, and the fluoride from this source is mainly controlled by natural factors such as climate, geologic setting, pH, specific hydrochemical environment, ion exchange, and mineral saturation. Human activities in modern life can be further divided into industrial and agricultural sources primarily. (3) The health risks of fluoride contamination are very high in the Loess Plateau, especially for children compared to adults. Meanwhile, the risks of fluoride exposure through food intake are higher than those through drinking water intake. The authors suggest selecting target areas to improve water supply and ensure the safety of drinking water in the study area. Besides, it is necessary to plant crops with low fluoride content or cash crops and to conduct groundwater treatment to reduce the fluoride concentration in drinking water. These results will provide a theoretical basis for safe water supply in the faulted basin areas in the Loess Plateau.© 2021 China Geology Editorial Office.

Tracing recharge and groundwater evolution in a glaciated, regional-scale carbonate bedrock aquifer system, southern Ontario, Canada

Where carbonate bedrock aquifers are overlain by glacial sediments, these sediments control the locations and geochemical signatures of recharge to the bedrock groundwater system. In these settings, geochemical and isotopic tracer tools may be rendered ineffective due to geochemical fingerprinting that can develop as groundwater migrates through the sediments and carbonates of the recharge pathway. In this investigation, traditional tracer tools are assessed in an 8000 km2 study area in southern Ontario, Canada, where the Early Silurian carbonate bedrock aquifers are overlain by glacial sediments. These carbonate aquifers contain significant quantities of high-quality groundwater resources and provide the sole drinking water source to many large cities and private residences. The glacial history of the study area is complex, with the advance and retreat of three ice lobes having deposited sediments that vary widely in permeability, mineralogy, and geochemistry. Results show that spatial trends of higher tritium correlate with aerobic redox chemistry in the carbonate groundwater systems underlying areas of thin or permeable sediment cover. Groundwater chemical evolution beyond recharge areas is assessed with general chemistry, redox characteristics and an investigation of water-rock interactions. A comparison of strontium isotope ratios (87Sr/86Sr) in bedrock and groundwater shows that long residence times may be required for the isotopic signature of the carbonate bedrock to imprint on the groundwater, though this does not occur consistently. The isotopic composition of sulphate (δ34SSO4 and δ18OSO4) in groundwater was most informative, showing isotopic evidence of sulphide oxidation in recharge areas, and a Silurian sulphur isotopic signature of the host bedrock in areas of thick and low permeability sediment, downgradient of identified recharge areas. The set of tracer tools deemed most useful in this investigation provides the empirical evidence needed to support a conceptual model of recharge and groundwater evolution and is recommended for use in similar settings elsewhere.

Backwash water treatment by coagulation in the presence of phosphates at underground water iron removal stations

Introduction. The analysis of the present-day condition of water resources has proven the relevance and expediency of developing highly effective backwash water treatment methods to be used at iron removal stations designated for groundwater treatment. In accordance with effective technical regulations, backwash water must be reused. The operation of iron removal stations has proven the inefficiency of backwash water treatment facilities. Water and wastewater treatment companies stop using backwash water treatment facilities and refrain from reusing backwash water. Highly concentrated iron-bearing backwash water is discharged into sewage networks, nearby water bodies or onto the terrain, which means irrational use of high-quality groundwater and environmental pollution with iron compounds.&#x0D; Materials and methods. The results of experimental research efforts and statistical processing of data on the qualitative and quantitative composition of backwash water at iron removal stations are presented. The chemical nature of the components and the principle underlying the formation of the backwash water composition in the process of groundwater deferrization have been studied. It’s been identified that if backwash water supplied by iron removal stations is treated by sodium phosphate reagent Na3PO4 and aluminum sulphate Al2(SO4)3 as a coagulant, precipitation of iron compounds intensifies, as colloidal particles FePO4 are formed. They have very low solubility, and they are effectively removed by coagulation. It has been theoretically proven and experimentally confirmed that anions H2 PO4– and PO4 3– fformed in the process of hydrolysis of sodium phosphate Na3PO4 help to reduce the electrokinetic charge of the colloidal particle of iron hydroxide Fe(OH)3, and high purification efficiency reaching 99.0–99.9 % is attained by attaching iron compounds to the surface of the colloidal particle of aluminum hydroxide Al(OH)3.&#x0D; Conclusions. The co-authors have developed a math-and-stats model simulating the backwash water treatment process that employs coagulation in the presence of phosphates. It describes the dependence between the concentration of residual iron, doses of sodium phosphate Na3PO4, aluminum sulphate Al2(SO4)3 and the settling time. A backwash water treatment technology has been developed. It employs coagulation in the presence of phosphates, and it is designated for use at iron removal stations. This technology comprises a chemical plant for sodium phosphate and aluminum sulphate used as a coagulant, a post-treatment filter, and sludge dewatering facilities. The application of this technology enables to reduce iron concentration to 0.05–0.20 mg/l, to reuse backwash water for drinking and other household purposes, or to have this water reused by iron removal stations, this, preventing pollution of water sources with iron compounds.