Artificial groundwater recharge utilizing stormwater is an effective tool to reduce urban flooding and artificially increase groundwater resources. However, porous media clogging due to the solid polydisperse particles carried in stormwater severely restricts the application of recharge technology. In addition, solid particles play a crucial role in aquifer contamination. If particles are easily transport in groundwater flows, they can act as contaminant carriers to facilitate the movement of contaminants. Conversely, if particles cause porous media clogging, they can form barriers that prevent contaminant migration. While the transport and clogging mechanism of particles has been explored by many macroscopic physical experiments, the intrinsic connection between the deposition behavior of particles in pore scale and the macroscopic presentation of clogging phenomenon remains unclear. In this study, laboratory-scale sand column experiments were combined with scanning electron microscopy (SEM) observations to explore the effect of polydisperse particle size on the mechanism of particle transport and clogging. The median particle sizes (d_p50) of the polydisperse particles used in the experiments were 0.66, 4.05, and 11.83 μm, respectively. The interaction energy between particles and porous media grains was calculated using XDLVO theory, indicating that the experiments were conducted under unfavorable condition. The sand column experiments revealed that the influence of large particles on the porous media permeability is limited to shallow layers, and small particles are more likely to transport to deeper layers. Particles with d_p50=0.66 μm were tend to form aggregates, reducing particle recovery rate and promoting clogging. The pore-scale observations illustrated that the vast majority of the particles are preferentially deposited in concave regions of the media grain surface. The larger the particle size, the higher the proportion of deposition in concave regions. Due to the different transport mechanisms of particles in pore space, the ratio of d_p50 to porous media grain size is not the only basis for identifying the type of clogging. The results proved that the particles with d_p50=0.66 μm can form mixed clogging faster than particles with d_p50=4.05 μm. The proposed results provide a reference for the theoretical study of the particle transport and deposition mechanism, the prevention and control of aquifer pollution, as well as the development of more effective artificial groundwater recharge scheme.

How to cite: Niu, S., Shu, L., Zou, Z., Yu, L., Li, Y., Chen, Y., and Wang, Z.: Evaluating polydisperse particles transport and clogging in porous media during artificial groundwater recharge by pore-scale observation and column experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-80, https://doi.org/10.5194/egusphere-egu24-80, 2024.

Geographic Information System (GIS), a computer-based technique is used in groundwater management, especially for the estimation of groundwater vulnerability to contamination. The objective of the present study was to delineate the groundwater contamination zones around the Sewage Farm using Geographic Information System. The study area lies between North Latitude 8° 26ʹ 26ʺ to 8° 29' 29" and East Longitude 76° 54ʹ 51ʺ to 76° 57ʹ 33ʺ. Inverse Distance Weighted Method (IDW) interpolation technique was used for the delineation of groundwater pollution zones in the study area. The sampling locations were mapped with the help of Survey of India toposheet of the scale 1:25000 and a handheld Global Positioning System (GPS). Groundwater pollution (stress) zonation in the study area was done on the basis of the selected water quality parameters of 42 groundwater samples (29 dug wells and 13 tube wells) during pre-monsoon, monsoon and post-monsoon seasons. The highly significant water quality parameters selected for the present study included pH, total dissolved solids (TDS), total hardness (TH), total alkalinity (TA) and total coliforms (TC). TC was given more weightage among the selected parameters. Based on the analysis, the entire study area was classified into three distinct zones, viz., low, moderate and high pollution zones. The results of the present study suggested that the extent of groundwater pollution was relatively lower during monsoon, compared to pre-monsoon and post-monsoon seasons, which might be a reflection of enhanced dilution due to heavy monsoon rainfall occurring in the region. Further, during post-monsoon and pre-monsoon seasons, the areal extent of high pollution zone showed close similarity. From the GIS-based analysis for the delineation of groundwater pollution zones over the area, it was inferred that multiple sources such as Sewage Farm, leachates from soak pits/septic tanks and Parvathy Puthanar, a man-made canal, governed the deterioration of groundwater quality in the study area.

How to cite: Varghese, J. and Divakaran Sarasamma, J.: Delineation of Groundwater Pollution Zones around Sewage Farm in the coastal area of Kerala, South India using Geographic Information System Technique, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2351, https://doi.org/10.5194/egusphere-egu24-2351, 2024.

Microplastics are tiny plastic particles, less than 5 millimetres in size and their access to food chain have a significant hazard to ecosystems and environmental health. Their concern also extends to drinking water and our limited understanding of their occurrence in groundwater aquifers poses a potential research gap. Our preliminary investigation suggests the presence of microplastics in groundwater samples from near vicinity of Ganga Channel and subsequently, 60 groundwater samples were collected for the detailed study from Devprayag (Uttarakhand) to Gangasagar (West Bengal), India. This is the first study that investigates the distribution and quantification of microplastics from the groundwater aquifers influenced by Ganga River water, the largest fresh water source in Northern India. The water samples are filtered through 0.45-micron size nitrocellulose filter membrane and the residue is visually inspected under a stereo microscope. Further, the abundance, type, and size of MPs were determined by micro-Raman spectroscopy following a well-established and quality-controlled analytical route. The findings indicate the presence of microplastics (MPs) in all samples, with Polyethylene (PE), Polypropylene (PP), and Polyvinyl chloride (PVC) identified as common types in each sample. Various shapes of microplastics, such as fibres, fragments, films, and foam, were detected. MPs with size less than 150 µm are significantly abundant, likely owing to their mixing in ground water through the infiltration from surface waters. Contamination of groundwater with microplastics (MPs) poses a significant health risk, especially given its importance as a crucial source for drinking and irrigation. If this problem left untreated or if concentrations of MPs continue to rise, this has the potential to evolve into a man-made disaster.

How to cite: Chaudhary, N. and Maurya, A. S.: Microplastic Contamination in Groundwater Aquifers along the Ganga River Basin: A Comprehensive study from Devprayag to Gangasagar, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1140, https://doi.org/10.5194/egusphere-egu24-1140, 2024.

Ca-citrate complex has been proposed as a substance capable of simultaneously removing both nutrients (i.e., nitrate and phosphate), which may lead to serious environmental issues such as eutrophication. Citrate serves as a carbon source for denitrification process, and calcium precipitates to form phosphate minerals. The purpose of this study was to comprehend the mechanisms involved in the removal of nitrate and phosphate. In this study, column experiments were conducted to simulate the simultaneous removal of nitrate and phosphate. Upon injecting the Ca-citrate complex into the column, both nutrients were eliminated. In the process, bacterial communities in the soil and effluent were investigated to identify removal mechanism for nitrate. The bacterial communities significantly differed between the soil and the effluent. The bacteria in the soil (Bacillus, Enterobacter, and Arthrobacter) were primarily involved in processes of NO₃ or NO₂ reduction, while those in the effluent (Pelosinus, Azospirillum, and Pseudomonas) carried out the complete denitrification process. These results suggested an active denitrification process in the column, resulting in the complete removal of nitrate to N₂ gas. Meanwhile, in order to identify the removal mechanism of phosphate, phosphate minerals for the soil samples after the reactions with Ca-citrate complex were observed using electron probe micro analysis (EPMA). In the raw soil, silicate minerals were abundant, including quartz and plagioclase feldspar group such as anorthite, oligoclase, and orthoclase. Silicon (Si), oxygen (O), and aluminum (Al) were abundantly distributed throughout the scanned area, supporting that the presence of silicate minerals. On the other hand, for the soil after 24 hours of the reaction, phosphate minerals found included hydroxyapatite (Hap), calcium-deficient hydroxyapatite (CDHA), and amorphous calcium phosphate (ACP). The Ca/P molar ratio was a range of 1.61–1.66, supporting that the phosphate was removed by precipitation of Hap. Moreover, CDHA and ACP serve as intermediaries in Hap crystallization, indicating that the experimental environment was in Hap formation phase. After 120 hours, anapaite was observed in the soil, which is a type of Ca-Fe-P-mineral. In this study, the experimental condition was a highly reducing environment, as indicated by the changes of iron concentration. Ultimately, phosphate was precipitated with calcium and iron. The EPMA results indicate that Ca-citrate can remove the phosphate by precipitation of phosphate minerals (e.g., hydroxyapatite, amorphous calcium phosphate, and anapaite). This study concluded that the simultaneous removal mechanisms for nitrate and phosphate involved denitrification and precipitation by the Ca-citrate complex.

How to cite: Kang, J., Lim, S., and Jeen, S.-W.: Reaction Mechanisms of Simultaneous Removal for Nitrate and Phosphate in Groundwater Using Ca-citrate Complex, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5013, https://doi.org/10.5194/egusphere-egu24-5013, 2024.

The use of groundwater as a freshwater source must be increased to mitigate the increasing pressure over water resources, resulting from growing population and climate change. However, many aquifers are commonly polluted by a wide range of anthropogenic substances, especially those aquifer located in urban areas. Therefore, to use groundwater resources safely, it is needed to establish the presence and fate of pollutants that can endanger human health. This is the case of Gadolinium. Integrated in Gadolinium-based contrast agents it is harmless and used for medical purposes, but it can cause serious health issues when released in the environment.

This research arose during a water sampling campaign undertaken in Barcelona where Gadolinium anomalies (i.e., resulting from anthropogenic activities) were detected in surface and underground water bodies which were hydraulically connected. What was striking was that Gadolinium pollution in groundwater bodies was less frequent and at lower concentrations than in surface water bodies. These observations suggested that Gadolinium was attenuated during its transport through the subsurface. To establish the mechanisms controlling the attenuation of Gadolinium, laboratory based batch experiments were carried out and then modelled using PHREEQC. Experimental results suggested that main process affecting the concentration of Gadolinium was sorption which could reduce considerably its presence in groundwater. Our results contribute to understanding the fate of anthropic Gadolinium in aquifers which is of paramount importance to use groundwater safely.

How to cite: Pujades, E., Ekiz, M. Ç., Scheiber, L., Jurado, A., Izquierdo, M., Vázquez-Suñé, E., and Foppen, J. W.: Batch experimental results about the occurrence and fate of Gadolinium in aquifers  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9002, https://doi.org/10.5194/egusphere-egu24-9002, 2024.

Polychlorinated biphenyls (PCBs) are synthetic organic compounds (209 possible isomers) of high physical, chemical and biological stability, and persist for long periods in a contaminated environment: they are undegradable (Hutzinger et al., 1974). They are biotoxically active compounds, and in animals and people cause acute and chronic damage to the skin, liver and lungs. In addition they cause metabolic disorders and disturbances to the action of the endocrine system, and are associated with loss of bodyweight and immuno-sensitivity. They are mutagenic and teratogenic, and are suspected to be carcinogenic (Safe, 1984). In Slovenia was an increase in use of PCBs after 1960. Between 1962 and 1983, a capacitor manufacturer disposed of PCB contaminated oil in the karstic region of Bela Krajina where it contaminated the spring of the Krupa River. The PCB pollution problems in karstic area of Krupa River are related to sinking surficial streams that mix with the regional groundwater supply, thus endangering the quality of the groundwater reservoirs.

The PCB pollution of the Krupa River drew the public’s attention to the chemical burden of Slovenians, and the demand for studies has been rising since. This study presents the application of the passive sampling technique for monitoring PCBs within the Krupa spring. Monitoring programmes for groundwater are largely based on the collection of grab (spot) samples. One of the methods used for such studies can also be passive sampling. Contrary to grab sampling, passive sampling is less sensitive to accidental extreme variations of the organic pollutant concentration in natural waters and it also allows for a large range of contaminants to be detected at once. A passive sampler can cover a long sampling period, integrating the pollutant concentration over time. Passive samples were analyzed by gas chromatography mass spectrometry (GC-MS). For the interpretation of chromatograms, the AMDIS deconvolution was used. The deconvolution was covered by the GC-MS library with retention times for 921 organic contaminants from Agilent USA, as well as by the NIST 2008 library of mass spectra.

The legacy of the PCB pollution of the Krupa River in Bela krajina is still measurable and passive sampling with active carbon fibres was proved to be an appropriate method for monitoring PCB pollutants in groundwater.

How to cite: Koroša, A., Mali, N., and Auersperger, P.: PASSIVE SAMPLING OF POLYCHLORINATED BIPHENYLS (PCB) IN POLLUTED KARST GROUNDWATER; Study case: Krupa, Slovenia , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9139, https://doi.org/10.5194/egusphere-egu24-9139, 2024.

The adsorptive removal of pollutant is a widely applicable process in environmental engineering. The major issue associated with many promising adsorbents is their low hydraulic conductivity, which renders their applicability in column based field level operation despite of their proved efficacy in batch mode in the laboratory. In this context, development of a novel sequential batch type reactor (SBTR) in the field of adsorption has shown its applicability in continuous operation using the benefits of the adsorbent characteristics in batch mode (Indian Patent No: 416891).

In the present study, SBTR was applied on fluoride removal from water by two adsorbents, viz. calcined Ca-Al-(NO₃) layered double hydroxide and Alumina Olivine Composite. Those adsorbents could not be used for column study due to their fine particle size and low hydraulic conductivity, although their adsorption capacity was found high in batch study. In the continuous operation, the assessment of time for filling, batch scale adsorption reaction, separation of adsorbent by settling, collection of treated water and taking out of the adsorbent from reactor is computed from the batch scale preliminary studies. The cycle of fill (4 h), batch adsorption reaction (4 h) and separation, collection etc. (4 h) was considered. Three numbers of the tank are taken in parallel. The adsorption studies in the SBTR were conducted for various adsorbent dose, concentration, time, agitation rate, etc. The reactor can bring down the fluoride from 10 mg/L to below the standard at an agitation rate of 500 rpm and an adsorbent dose of 1.5 and 5 g/L for calcined Ca-Al-(NO₃) LDH and AOC, respectively. SBTR exhibited its promising opportunity in continuous operation universally in field irrespective of the size and characteristics of the adsorbent. The present work brings this type of reactor for the first time in the field of adsorption with significant advancement in water treatment.

Keywords Continuous reactor, Batch Study, Sequencial operation, Water treatment, Adsorbent

How to cite: Ghosal, P. S. and Sahu, S.: Sequential type batch reactor (SBTR): A novel advancement in adsorption system for removal of pollutant from drinking water, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17636, https://doi.org/10.5194/egusphere-egu24-17636, 2024.

How to cite: Gasco Cavero, S., Marazuela, M. Á., Cruz-Pérez, N., Martín Rodríguez, L. F., Laspidou, C., Contreras-Llin, A., Quintana, G., Díaz-Cruz, S., Santamarta, J. C., and García Gil, A.: Comprehensive Study of Emerging Pollutants in El Hierro Island: A Showcase of Good Practices with Zero Pesticide Impact, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20203, https://doi.org/10.5194/egusphere-egu24-20203, 2024.

The increasing demand for water in industry, agriculture, and private households as well as climate change are leading to more dynamic river and groundwater levels. This demands a new and improved monitoring approach to groundwater resources. The BMBF-funded research project iMolch (project number: 02WGW1667D) aims to develop sustainable water management concepts for Germany using innovative monitoring strategies. The general purpose of the investigations is to gain a complex understanding of hydrodynamic and hydrochemical processes in order to enable a more sustainable use of water resources on the basis of the indicator concept. This study investigates the spatial and temporal variation of different substances using as one example the urban bank filtration site in Düsseldorf, Germany. This site is used to draw conclusions on groundwater quality and dynamics as well as redox processes using the transport and retention of organic trace substances.

Hydraulic and hydrochemical measurements were carried out fortnightly over a period of 1,5 years (31/01/2018–08/05/2019) across a study transect on the Rhine riverbanks with 15 measuring points. The analyses focus on changes in the concentrations of organic trace substances over time and the relationship to flow distance, flow duration and climatic conditions. Based on land use and occurrence, various organic compounds, such as fertilisers and pesticides, but also pharmaceuticals and detergents are monitored. The dependence between substance concentrations and Rhine river level decreases with increasing distance to the Rhine. Following the extreme drought in the summer of 2018, during which only low concentrations of trace substances were detected in the entire study area, there was an abrupt increase in substances entering the Rhine. This coincides with a significant Rhine high stand in the winter of 2018/2019. It is noticeable here that an increased concentration of substances discharged from the Rhine can also be detected at measuring points beyond the well gallery, on the land side of the measuring point transect.

In dry periods, such as the summer of 2018, the proportion of bank filtrate in the raw water is significantly lower. In contrast, the Rhine floods the pumping well gallery during high water level periods, such as the winter of 2018/2019. During this time there is no landward flow to the pumping wells. The occurrence of organic trace substances even shows that the flood of the river Rhine pushes the water in the bank filtrate up to the well gallery and far beyond into the hinterland despite ongoing water pumping. These observations are crucial for the subsequent water management during different water levels of the river Rhine. Prediction models will be built up to help as water management tools to improve monitoring systems and for transfer of these results to other sites.

How to cite: Hellwig, A., Woschick, L., Vogt, C., Droste, B., Antunovic, D., Albrecht, A., Rohns, H.-P., and Scheytt, T.: Use of organic trace substances for water management at a bank filtration site at the Rhine, Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17996, https://doi.org/10.5194/egusphere-egu24-17996, 2024.

The removal of fluoride from groundwater is a major challenge in environmental engineering especially while dealing with real-life groundwater from field. The presence of other ions in groundwater impacts significantly which renders the efficacy of many adsorbent which may show significant performance in synthetic water. The present study was conducted with groundwater of fluoride level 8.8 mg/L that mostly representative the moderate to high level fluoride concentration in the area of the western part of the state of West Bengal, India. The adsorbent chosen in the study as Alumina Olivine Composite (AOC) prepared by a wet impregnation method followed by calcination.

The adsorption system with real‒time groundwater was test with variation of dose, reaction time and agitation rate. The isotherm study, the variation of the adsorbent dose was chosen as 0.5 to 6 g/L. The best fitted model was found as Freundlich isotherm (R²=0.907 and K_f =0.527 (mg/g)(L/mg)^1/n, 1/n = 0.641) along with the three parameter isotherm models, such as Hill, Redlich–Peterson, Toth with comparable R². Thus, the adsorption model exhibited a favourable adsorption with significant capacity. The Kinetic study was conducted for 5‒480 min. The adsorption kinetic models are chosen as pseudo‒first-order (PFO), pseudo‒second‒order (PSO) and Elovich’s equation (EL) were used as the reaction‒based kinetic models, whereas, the liquid film diffusion model (LFD), intraparticle diffusion model (IDS and IDL) and double-exponential model (DEM). The Elovich’s equation was found to be the best‒fitted among the reaction based models with R² value of 0.970. The applicability of double-exponential equation significantly described the adsorption diffusion model with a R² value of 0.983, showed that the mechanism of adsorption govern by both intraparticle diffusion and film diffusion. This is further supported by the significant C value of 6.40 from intraparticle diffusion model. The present work established the wide applicability of the present adsorption system in field level water treatment units.

Keywords Isotherm, Kinetics, Batch Study, Water treatment, Fluoride

How to cite: Ghosal, P. and Ghosal, P. S.: Adsorption of fluoride from groundwater by Alumina Olivine Composite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17879, https://doi.org/10.5194/egusphere-egu24-17879, 2024.

The overexploitation of the Korba aquifer (Cap Bon, North Tunisia) has led to the drawing down of its static water level and the degradation of its quality due to the intrusion of saline water from the sea. To address this situation, treated wastewater is used for the artificial recharge of the aquifer through three infiltration basins.
Treated wastewater is known to carry various emerging contaminants and pharmaceuticals as they are often not retained in traditional wastewater treatment plants. To tackle this problem the use of biochars is often recommended to conduct a second stage low-cost decontamination strategy. Indeed, biochar can be produced easily at a low cost, with different agricultural residues. In this study, the impact of biochar derived from Rosemary, Bamboo, St. John's Wort, Olive, Cypress, and Palm Trees on the mobility and retention of emerging contaminants was evaluated.

The first stage of this work was to evaluate the potential retention capacity of the different biochars produced in a low-cost metallic kiln with local biomass residues. Therefore we used Methylene Blue (MB) as a proxy for organic contaminants to establish adsorption isotherms to quantify their respective specific surface area and adsorption capacities.

The adsorption isotherms at 20°C were established to evaluate their respective specific surface areas and were fitted to different adsorption models.
The surface functional groups of biochars were characterized by FTIR spectroscopy.
The analysis of the results showed that the biochar obtained from Rosemary, Bamboo, and St. John's Wort exhibited remarkable elimination and better adsorption capacity with values of 1.6g/L for Rosemary, 0.4g/L for St. John's Wort, and 0.2g/L for Bamboo. An average adsorption capacity was observed with 0.09g/L for Cypress, 0.055g/L for Olive, and low adsorption with a value of 0.03g/L for traditional Olive and Palm Trees.

The second stage was to test the dynamic retention properties of biochar on soil monolith experiments, where the MB elution curves were analyzed with and without the addition of biochar. The presence of biochar in the soil monoliths drastically reduced the retention of MB, demonstrating its efficiency as an adsorbent filter. These results underscore the strong potential of biochar in water treatment to enhance quality by reducing pollution.

How to cite: Hammecker, C., Maalaoui, H., Hmaied, A., and Lachaal, F.: Improvement of contaminant retention with the use of biochar in the groundwater infiltration basin of Korba (Tunisia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11014, https://doi.org/10.5194/egusphere-egu24-11014, 2024.