Search Results (121)

In recent years, nitrate has emerged as a significant groundwater pollutant due to its potential ecotoxicity. In particular, nitrate contamination of brackish groundwater poses a serious threat to both ecosystems and human health and remains difficult to treat. A promising, sustainable, and environmentally friendly solution when biological treatments are not applicable is the conversion of nitrate to harmless nitrogen (N₂) or ammonia (NH₃) as a nutrient by electrocatalytic nitrate reduction (eNO₃R) using solar photovoltaic energy. This review provides a comprehensive overview of the current advances in eNO₃R for the production of nitrogen and ammonia. The discussion begins with fundamental concepts, including a detailed examination of the mechanisms and pathways involved, supported by Density Functional Theory (DFT) to elucidate specific aspects of ammonium and nitrogen formation during the process. Furthermore, the integration of artificial intelligence (AI) and machine learning (ML) offers promising advancements in enhancing the predictive power of DFT, accelerating the discovery and optimization of novel catalysts. In this review, we also explore various electrode preparation methods and emphasize the importance of in situ characterization techniques to investigate surface phenomena during the reaction process. The review highlights numerous examples of copper-based catalysts and analyses their feasibility and effectiveness in ammonia production. It also explores strategies for the conversion of nitrate to N₂, focusing on nanoscale zerovalent iron as a selective material and the subsequent oxidation of the produced ammonia. Finally, this review addresses the implementation of the eNO₃R process for the treatment of brackish groundwater, discussing various challenges and providing reasonable opinions on how to overcome these obstacles. By synthesizing current research and practical examples, this review highlights the potential of eNO₃R as a viable solution to mitigate nitrate pollution and improve water quality. Full article

Using geochemical and pumping test data from 80 groundwater wells, the chemical, hydrologic, and hydraulic properties of the fractured Eocene carbonate aquifer located west of the Al-Minya district, the Western Desert, Egypt, have been characterized and determined to guarantee sustainable management of groundwater resources under large-scale desert reclamation projects. The hydrochemical data show that groundwater from the fractured Eocene carbonate aquifer has a high concentration of Na⁺ and Cl⁻ and varies in salinity from 2176 to 2912 mg/L (brackish water). Water–rock interaction and ion exchange processes are the most dominant processes controlling groundwater composition. The carbonate aquifer exists under confined to semi-confined conditions, and the depth to groundwater increases eastward. From the potentiometric head data, deep-seated faults are the suggested pathways for gas-rich water ascending from the deep Nubian aquifer system into the overlying shallow carbonate aquifer. This mechanism enhances the dissolution and karstification of carbonate rocks, especially in the vicinity of faulted sites, and is supported by the significant loss of mud circulation during well drilling operations. The average estimated hydraulic parameters, based on the analysis of step-drawdown, long-duration pumping and recovery tests, indicate that the Eocene carbonate aquifer has a wide range of transmissivity (T) that is between 336.39 and 389,309.28 m²/d (average: 18,405.21 m²/d), hydraulic conductivity (K) between 1.31 and 1420.84 m/d (average: 70.29 m/d), and specific capacity (Sc) between 44.4 and 17,376.24 m²/d (average: 45.24 m²/d). On the other hand, the performance characteristics of drilled wells show that well efficiency ranges between 0.47 and 97.08%, and well losses range between 2.92 and 99.53%. In addition to variations in carbonate aquifer thickness and clay/shale content, the existence of strong karstification features, i.e., fissures, fractures or caverns, and solution cavities, in the Eocene carbonate aquifer are responsible for variability in the K and T values. The observed high well losses might be related to turbulent flow within and adjacent to the wells drilled in conductive fracture zones. The current approach can be further used to enhance local aquifer models and improve strategies for identifying the most productive zones in similar aquifer systems. Full article

In coastal plains, saline water intrusion (SWI) and potentially hazardous pollutants are harmful to local human health. The southern Laizhou Bay has become a typical representative of the northern silty coast due to its extensive silt sedimentation and the significant impact of human activities. This research focuses on a portion of the southern Laizhou Bay, using GIS-based spatial analysis, water quality index methods and health risk assessments to evaluate the impact of saltwater intrusion and potential hazardous pollutants. The results show that the groundwater in the study area is significantly impacted by saline water intrusion, leading to major ion concentrations that far exceed World Health Organization (WHO) standards. The groundwater chemical types of brine and brackish water in the study area are mainly Cl-Na, and the main chemical types of fresh water are HCO₃-Ca·Na. The average concentration sequence of the main ions in groundwater is K⁺ > HCO₃⁻ > Cl⁻ > Na⁺ > SO₄²⁻ > Ca²⁺ > Mg²⁺. The average hazard quotient (HQ) sequence in typical pollutants is Cl⁻ > F⁻ > NO₃-N > Se > Mn > NO₂-N > Cu > Pb > Zn > Fe, and the carcinogenic risk (CR) sequence caused by carcinogenic heavy metals is Cd > As > Cr. The noncarcinogenic health risk area is mainly distributed in the northwest of the study area, while the potential carcinogenic risk area is in the central region. The Cl is the greatest noncarcinogenic risk to adults and children. The mean HQ values for adults and children were 95.69 and 146.98, indicating a significant noncarcinogenic risk. The mean CR values for adults and children were 0.00037 and 0.00057, suggesting a relatively low carcinogenic risk. SWI is the main influencing factor on human health; therefore, it is necessary to prevent and control SWI. Moreover, potentially hazardous pollutants are carcinogenic and noncarcinogenic risks and are caused by agriculture, industry and other human activities. The findings of this research offer scientific insights for groundwater pollution control and saline water intrusion management in similar coastal areas. Full article

The objective of this study is to assess the suitability of the AquaCrop model for growing maize using brackish water irrigation in Northwest China. Additionally, this study aims to examine how maize utilizes water in various soil layers when irrigated with varying water qualities. The AquaCrop model was calibrated and verified using experimental data from the years 2022 and 2023 in this research. (1) The findings indicated that the AquaCrop model effectively simulated the canopy cover, biomass, and yield of maize when irrigated with brackish water. The validation year’s R², MAPE, and RMSE values for canopy cover, biomass, and yield of maize were 0.95, 5.36%, and 4.77%, respectively. For biomass, the R², MAPE, and RMSE values were 0.91, 16.61%, and 2.12 t·hm⁻², respectively. For yield, the R², MAPE, and RMSE values were 0.84, 3.62%, and 0.42 t·hm⁻², respectively. (2) Irrigation with water of high mineral content, measured at 1.6 ds/m, as well as with fresh water over the whole reproductive period, resulted in an increased reliance on groundwater for maize cultivation. There was no notable disparity in the usage of various soil layers between the irrigation with alternating freshwater and brackish water. (3) The AquaCrop model simulated the effects of seven different irrigation water quality treatments. It was shown that using water with mineralization levels of 0.5 and 0.8 ds/m resulted in decreased freshwater use without causing a substantial decrease in maize yield and biomass. Full article

A two-stage pilot plant study has been completed that evaluated the performance of a reverse osmosis (RO) membrane process for the treatment of feedwater that consisted of a blend of a nanofiltration (NF) concentrate and brackish groundwater. Membrane performance was assessed by monitoring the process operation, collecting water quality data, and documenting the blended feedwater’s impact on fouling due to microbiological or organic means, plugging, and scaling, or their combination. Fluorescence and biological activity reaction tests were used to identify the types of organics and microorganisms present in the blended feedwater. Additionally, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to analyze suspended matter that collected on the surfaces of cartridge filters used in the pilot’s pretreatment system. SEM and EDS were also used to evaluate solids collected on the surfaces of 0.45 µm silver filter pads after filtering known volumes of NF concentrate and RO feedwater blends. Water quality analyses confirmed that the blended feedwater contained little to no dissolved oxygen, and a significant amount of particulate matter was absent from the blended feedwater as defined by silt density index and turbidity measurements. However, water quality results suggested that the presence of sulfate, sulfide, iron, anaerobic bacteria, and humic acid organics likely contributed to the formation of pyrite observed on some of the membrane surfaces autopsied at the conclusion of pilot operations. It was determined that first-stage membrane productivity was impacted by the location of cartridge filter pretreatment; however, second-stage productivity was maintained with no observed flux decline during the entire pilot operation’s timeline. Study results indicated that the operation of an RO process treating a blend of an NF concentrate and brackish groundwater could maintain a sustainable and productive operation that provided a practical minimum liquid discharge process operation for the NF concentrate, while the dilution of RO feedwater salinity would lower overall production costs. Full article

Climate change significantly impacts agriculture and forage production, requiring the implementation of strategies toward increased water and energy use efficiency. So, this study investigated the yield of forage cactus (Opuntia stricta (Haw.) Haw) under different irrigation depths using brackish groundwater (1.7 dS m⁻¹), whose management was based on reference evapotranspiration (ETo) estimated by the Hargreave–Samani (HS) and Penman–Monteith (PM) equations. The research was conducted in Independência, Ceará, Brazil, under the tropical semi-arid climate. A randomized block design in a 2 × 5 factorial scheme was employed, varying the ET₀ estimation equations (HS and PM) and irrigation levels (0; 20; 40; 70; and 100% of total required irrigation—TRI). Growth, productivity, and water use efficiency variables were evaluated at 6, 12, and 18 months after treatment initiation. The economic analysis focused on added value, farmer income, and social reproduction level. The results showed no isolated effect of the equations or their interaction with irrigation depths on the analyzed variables, suggesting that irrigation management can be effectively performed using the simpler HS equation. Furthermore, there was no statistical difference between the means of 100% and 70% TRI as well as between 70% and 40% TRI for most variables. This indicates satisfactory crop yield under deficit irrigation. Dry matter productivity and farmer income at 12 months resulting from complementary irrigation with depths between 40% and 70% of TRI were significantly higher than under rainfed conditions. The 70% depth resulted in yields equivalent to those at 100% TRI, with the social reproduction level being achieved on 0.65 hectares in the second year. Full article

Water scarcity in Tunisia’s semi-arid regions necessitates advanced brackish water desalination solutions. This study evaluates the long-term performance and fouling characteristics of the largest brackish water reverse osmosis desalination plant in southern Tunisia over a period of 5026 days. The plant employs two-stage spiral-wound membrane elements to treat groundwater with a salinity of 3.2 g L⁻¹. The pre-treatment process includes oxidation, sand filtration, and cartridge filtration, along with polyphosphonate antiscalant dosing. Membrane performance was assessed through the analysis of operational data, standardization of permeate flow (Q_ps) and salt passage (SP_s), and the calculation of water (A), solute (B), and ionic (B_j) permeability coefficients. Over the operational period, there was an increase in operating pressure, pressure drop, and permeate conductivity, accompanied by a gradual increase in SP_s as well as in the solute B and ionic B_j permeability coefficients. The average B increased by 82%, reflecting a decrease in solute rejection over time. Additionally, the ionic permeability coefficients for both SO₄²⁻ and Cl⁻ ions increased, with Cl⁻ showing an 88% increase and SO₄²⁻ showing an 87% increase. The produced water’s salinity increased by 67%, indicating a significant loss of membrane performance. To identify the cause of these problems, membrane characterization was analyzed using visual inspection, X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR). The characterization revealed the complex nature of the foulants, with a predominant presence of calcium sulfate, along with minor quantities of calcite, dolomite, and silica. The extent of CaSO₄ deposition suggests poor antiscaling efficiency, highlighting the critical importance of selecting an effective antiscalant to mitigate membrane fouling. Full article

With a deficit of about 20 BCM in 2022, Egypt faces a severe water shortage due to rapid population growth (109.3 million in 2022). Egypt launched a program to utilize non-conventional water sources, like treated wastewater, agriculture drainage water, and desalination. Egypt is expanding its non-conventional water resources, boosting desalination capacity from 86,000 m³/day in 2015 to 680,000 m³/day in 2022, with plans to reach 1,250,000 m³/day by 2025. Despite the improvements in desalination technologies and cost, its high energy use and environmental impacts are still limiting its use. Egypt’s desalination relies on grid electricity, but renewable energy is crucial for remote areas where no electricity grid exists. Scaling up renewable energy in desalination faces challenges like land availability and high costs. GIS was used for optimal site selection for a brackish groundwater solar desalination plant in the Western North Nile Delta. Factors like solar radiation, groundwater quality, aquifer potentiality, geology, and seawater intrusion were carefully assessed. An evaluation of a sustainable 1000 m³/day solar-powered RO desalination pilot plant’s economic and technical viability is provided, along with its performance assessment. Limitations, challenges, and potential improvements are discussed. The study finds that RO–PV desalination for brackish groundwater is technically mature, with competitive Capex costs (USD 760-USD 850/m³) and low Opex (USD 0.55–USD 0.63/m³). Solar desalination for brackish groundwater with salinity less than 23,000 ppm can reduce energy consumption to 3.6–4.2 kWhr/m³. Water storage and hybrid systems with solar and conventional energy are suggested to enhance efficiency. This implies a growing market for small- to medium-scale RO solar-powered desalination in remote areas in the near future. Full article

Ensuring the sustainability of a product or a system requires a thorough evaluation of its environmental and socioeconomic impacts. In this context, one of the objectives of the EU-PRIMA SmaCuMed project is to evaluate the socioeconomic and environmental impacts of the Smart Cube system. The Smart Cube was developed for the PV-powered desalination of brackish groundwater with membrane capacitive deionization (MCDI) and low-pressure reverse osmosis (LPRO); it additionally uses smart sensors for controlled irrigation in remote agricultural areas in Morocco, as an example for the North African region. Based on the Life Cycle Sustainability Assessment approach, this paper aims to assess the environmental and economic impacts of the Smart Cube, using Life Cycle Costing (LCC) and Life Cycle Assessment (LCA) analyses for environmental evaluation. Various scenarios have been defined for both environmental and economic assessments. Based on 1 m³ of produced desalinated water, the LCC results showed that, when using the desalination technologies directly connected to the grid, the prices are lower than those obtained when it was supplied by the PV system. This is only due to the very low energy prices from the Moroccan grid (EUR 0.10/kWh). The LCC results showed that LPRO is a more cost-effective option for producing desalinated water, with a lower total cost compared to MCDI. However, LCA results indicated that LPRO has a higher environmental impact compared to MCDI. If higher water production capacity is a priority, MCDI connected to PV is the best choice, with lower carbon emission but higher overall water costs. Full article

To elucidate the hydrochemical characteristics, controlling factors, sources and mechanisms of strontium ion enrichment in groundwater in the northwest plain of Shandong Province, China, 88 groundwater samples were collected, including 51 shallow pore groundwater samples, 29 deep pore groundwater samples and 8 karst groundwater samples. The hydrochemical characteristics of the different types of groundwater were quite different. The karst groundwater samples were all fresh water with a single hydrochemical type, either HCO₃-Ca or HCO₃-Ca·Mg. The deep pore groundwater samples were mainly brackish water, and the shallow pore groundwater samples were brackish water–salt water, which has complex hydrochemical types. The hydrochemical characteristics of all the types of groundwater were controlled by mineral dissolution and active positive cation exchange. In shallow pore groundwater, deep pore groundwater and karst groundwater, the dissolution of silicate, evaporite and carbonate minerals dominated the hydrogeochemical process. The strontium in groundwater was derived from the dissolution of minerals with strontium isomorphism. The average contents of strontium in shallow, deep and karst groundwater were 1.59 mg/L, 0.58 mg/L and 0.50 mg/L, respectively. The strontium in shallow pore groundwater was mainly derived from the enrichment of groundwater runoff, and its sources are abundant, with silicic rock being the main source. The deep pore groundwater mainly derived from the evaporative minerals containing strontium, and the karst water mainly derived from carbonate rock dissolution with similar characteristics. Full article

Climate change and human activities lead to freshwater shortage, soil salinization, and food security crises in arable land. To explore the natural and irrigation factors on soil water and salt movement, this study quantitatively analyzed the dynamic characteristics of soil water and salt movement under precipitation, groundwater irrigation, and brackish water irrigation conditions for the next 30 years using Hydrus-1D model-based parameters obtained from the winter wheat–summer maize rotation experiments in the Yellow River Irrigation District. The results showed that precipitation was the key factor of climate change affecting soil water and salt migration, especially in the 0–20 cm soil layer. Under both SSP585 and SSP245 climate scenarios, rainfall in normal and wet years promoted salt leaching up to 1 m below the surface soil. But in dry years, salt washing treatment was required for the tillage layer to prevent salt accumulation. The higher the groundwater level was, the higher the soil water and salt content was in the 0–100 cm soil layer. In this soil layer, a 2 m groundwater level contributed 30% to wheat water needs, while a 3 m groundwater level contributed 18%, and no significant contribution was observed for a 4 m groundwater level. The salinity of the soil profile showed an overall increasing trend with irrigation using 1–3 g/L brackish water for 30 years. However, the salinity in the 0–100 cm soil layer was below the salt tolerance threshold of winter wheat and summer maize with salts accumulated in the 1–2 m soil layer. Considering the salinization of the root zone and crop water needs, it is recommended that the safe groundwater level for brackish water irrigation should be 3 m in the study region. This study provides scientific reference for groundwater–farmland ecosystems to utilize brackish water and treat saline–alkali lands. Full article

This study utilizes geophysical investigations, combining both surface and subsurface methods, assessing quality and mapping aquifers in Haryana’s Mewat district, India. The primary objectives are to delineate the interface between freshwater and saline water, both horizontally and vertically and to perform a quality and sustainability analysis. It has been observed that topsoil, approximately 12 m thick, has resistivity values ranging from 11 to 35 ohm-m, where higher values indicate lower soil saturation. Resistivity exceeding 15 ohm-m correlates with granular zones housing fresh groundwater, while values below 15 ohm-m signal saline to brackish groundwater. Approximately 55% of the region features saline groundwater, mainly in central, western, and southern areas. Freshwater resources within a depth of 30 m cover 26–30% of the area, mainly in the northwest and southwest parts. Beyond 40 m, freshwater availability drops significantly, with depths exceeding 100 m likely encountering hard rock or saline horizons. This study also highlights low freshwater yield challenges due to thin granular zones and variable bedrock depths, some as shallow as 90 m. Additionally, the research examines infiltration rates, ranging from 90 mm/h to 660 mm/h initially and 5 mm/h to 164 mm/h ultimately, with an average rate of 151 mm/h, highlighting sandy soils with some clay limitations. Utilizing available data, a three-dimensional hydrogeological model was constructed, shedding light on groundwater-related issues, such as depletion, waterlogging, water quality, and excess salinity. Groundwater development reached ~80%, categorized as semi-critical. Depletion affects areas with fresh groundwater, and waterlogging is a concern in central and north-eastern regions. In addition to salinity, other water quality issues are higher nitrate, sodium, and chloride concentrations, leading to salt-affected soils in specific blocks like Nuh and Nagina. In summary, this study offers a comprehensive assessment of groundwater resources in Mewat, Haryana, emphasizing sustainable utilization and tailored management of localized challenges. This underscores the importance of integrated water resource management to ensure prudent use while preserving the environment for future generations. Full article

Tropical coastal karst areas represent dynamic, fragile, and biodiverse environments. Central America’s karst regions have been scarcely studied, with most of the research focused on the northern part of the region and on several larger cave systems. The coastal carbonate zones of the Central American region represent a unique karstic landscape, which, so far, has been insufficiently studied. Therefore, in this paper, we aim to describe the (i) landscape geomorphology and (ii) chemical conditions that define Ciénega de El Mangle in Panama as a distinctive karstic site. Carried geomorphological mapping and the characterization of karstic features have resulted in the identification of the different karstic forms and processes that are present within this unique karstic area. Considering that the chosen karstic study area is located in a marine–coastal fringe on the periphery of a lagoon, it is affected by a combination of several factors and processes, including seawater intrusion (through sinkholes), the formation of conchiferous limestone (CaCO₃), and NaCl precipitation related to efflorescence. Due to the seasonally humid tropical climate, the chemical weathering processes are intense, thus forming alkaline soils that are hindering the development of mangrove vegetation. The geomorphology of the area results from intense evaporation combined with an influx of brackish groundwater, due to which a landscape has evolved in the marine–coastal strips, of seasonal tropical climates, that exhibit saline beaches, known as a littoral shott. In total, 24 karstic microdolines have evolved within the shott, of which six represent domical geoforms formed by gradual evaporitic precipitation, while seven other geoforms represent active karstic sinkholes filled with brackish water. These results are key for understanding the past and present climate interactions and conditions that have led to the formation of tropical karst environments. Full article

The objective of our study is to estimate the contamination concentrations in the Permian Basin, US. A total of 481 observation samples were chosen within the following study areas: Andrews, Martin, Midland, Ector, Crane, and Upton Counties. The Dockum, Pecos Valley, Edwards-Trinity Plateau, and Ogallala aquifers were evaluated for inorganic contaminants. Level reports for parameters such as Arsenic (As), Nitrate (NO₃⁻), Fluoride (F), Chloride (Cl), total dissolved solids (TDS), and Uranium (U) were provided by the Texas Water Development Board (TWDB) analyzed with other counties. We demonstrated the average level in each county with different time periods: 1992–2005 and 2006–2019. Our results were compared with the Environmental Protection Agency (EPA) standards and concluded the safety of water consumption in the study areas. We concluded that inorganic pollutants resulted mainly from human impacts such as agriculture, fertilizers, and energy developments. This research offers significant information about inorganic pollutants and brackish aquifers in the Permian Basin, US, contributing to our understanding of how groundwater resources respond to contaminations in dry regions. With freshwater becoming scarcer in arid climates such as the Permian Basin, US, it is important to ensure successful water management in these dry and arid locations. Full article

Coastal areas have made substantial contributions to global economic development but are plagued by challenges such as groundwater salinization. Groundwater serves as the primary source for drinking, industrial, and domestic purposes in these coastal areas. Therefore, understanding the causes and processes of groundwater salinization holds paramount significance for effective groundwater management. The coastal area of Laizhou Bay in northern China serves as a quintessential example of such a scenario. With substantial groundwater extraction and severe groundwater salinization issues, it exacerbates the disparity between water-resource supply and demand. Currently, our understanding of the processes and influencing factors related to groundwater salinization in this region remains limited. In this study, employing hydrochemical and stable chlorine isotope analyses on 35 groundwater and seawater samples, an in-depth investigation into the complex mechanisms underlying groundwater salinization in the Quaternary aquifers of the eastern coastal plain of Laizhou Bay was conducted. The test results of the samples indicate that brine and saline groundwater are primarily of the Na-Cl type, exhibiting a hydrochemical composition similar to that of seawater. Brackish groundwater exhibits a diverse hydrochemical composition. The hydrogen and oxygen isotope characteristics of brackish and fresh groundwater resemble atmospheric precipitation, while brine, seawater, and saline groundwater show hydrogen and oxygen isotope depletion. Compared to seawater, brine exhibits significant δ³⁷Cl depletion. The analysis of the test results reveals that the formation of brine aquifers results from a complex interplay of climate change, tectonic movements, and sea–land evolution, involving lagoon development during seawater regression, salt concentration through evaporation, and subsequent water–rock interactions. The genesis of saline groundwater involves a complex interplay of brine–seawater mixing, significant evaporation, and potential input of fresh groundwater from atmospheric precipitation and river sources. The formation of brackish groundwater is predominantly influenced by atmospheric precipitation, and agricultural activities, with significant variations in NO₃⁻ concentrations attributed to varying intensities of fertilizer application in the northern plain area. These insights contribute to a deeper understanding of the origins of groundwater and can inform the development of policies for groundwater protection in this area. Full article