When identifying the conditions required for the sustainable and long-term exploitation of geothermal resources it is very important to assess the dynamics of processes linked to the formation, migration and deposition of particles in geothermal systems. Such particles often cause clogging and damage to the boreholes and source reservoirs. Solid particles: products of corrosion processes, secondary precipitation from geothermal water or particles from the rock formations holding the source reservoir, may settle in the surface installations and lead to clogging of the injection wells. The paper proposes a mathematical model for changes in the absorbance index and the water injection pressure required over time. This was determined from the operating conditions for a model system consisting of a doublet of geothermal wells (extraction and injection well) and using the water occurring in Liassic sandstone structures in the Polish Lowland. Calculations were based on real data and conditions found in the Skierniewice GT-2 source reservoir intake. The main product of secondary mineral precipitation is calcium carbonate in the form of aragonite and calcite. It has been demonstrated that clogging of the active zone causes a particularly high surge in injection pressure during the fi rst 24 hours of pumping. In subsequent hours, pressure increases are close to linear and gradually grow to a level of ~2.2 MPa after 120 hours. The absorbance index decreases at a particularly fast rate during the fi rst six hours (Figure 4). Over the period of time analysed, its value decreases from over 42 to approximately 18 m3/h/MPa after 120 hours from initiation of the injection. These estimated results have been confi rmed in practice by real-life investigation of an injection well. The absorbance index recorded during the hydrodynamic tests decreased to approximately 20 m3/h/MPa after 120 hours.

There is often a need to improve the taste of mineral water by reducing the sulphate ion content. It was found that for such an effect, nanofiltration (NF) process can be used. In the case, the proposed formula was assumed obtaining a mineral water with reduction of H2S and SO42- content through the following processes: stripping - UF/MF or rapid fi ltration - nanofiltration - mixing with raw water or filtration through calcium bed. The paper shows the results of the tests, with use of mineral waters and nanofiltration. Commercial nanofiltration membranes NF-270 Dow Filmtec and NF-DK GE Infrastructure Water&Process Technologies were applied. NF was carried out for mixed water from both water intakes (1 and 2), recovery of 50%, at transmembrane pressure of 0.8-1.2 MPa in the dead-end fi ltration mode. In addition, the permeate obtained in NF was filtered through a column fi lled with 1.0-3.0 mm limestone rock, in order to improve the composition of mineral water. The tested mineral water is the sulphate-chloride-sodium-calcium-magnesium in nature and contains 991 mg/L of SO42- and 2398 mg/L of TDS, while the permeate after NF showed the chloride - sodium hydrogeochemical type (TDS: 780-1470 mg/L, sulfate 10-202.7 mg/L, calcium 23-39.7 mg/L, magnesium 11-28 mg/L). As a result of water treatment in the NF process, high reduction of SO42- ions was obtained (79-98.7%), while the TDS was reduced in 51-64%. Because the process of NF allows for relatively high reduction of bivalent ions, a significant reduction in calcium ion content (84-88%) and magnesium (84-89%) has been also obtained. Monovalent ions were reduced to a lesser extent, i.e. sodium in 46% and bicarbonates in 39-64.1%. Despite obtaining the positive effect of the sulphate ions content reduction, the NF process significantly changed the mineralogy composition of water. The permeate filtration (DK-NF membrane) on the CaCO3 deposit led to a correction of the hydrogeochemical type of water from chloridesodium to chloride-bicarbonate-sodium. The concentration of calcium ions was increased by 60.5% and was 28.2 mg/L, and bicarbonate ions by 7.78% (increased to 195 mg/L). Based on a morphological assessment of the deposits in the SEM image and their chemical composition, the presence of gypsum crystals was detected on the surface of the NF-270 membrane. The deposits formed on the NF-DK membrane were of a completely different character as aggregations of iron and aluminium oxides/hydroxides were found. Such significant mineralogical differences between the secondary deposits crystallising on the surface of the membranes point to the impact of several factors, including membrane characteristics, concentration polarisation, mass transport mechanisms, etc.

M embrane-based water desalination processes and hybrid technologies are often considered as a technologically and economically viable alternative for desalination of geothermal waters. This has been confirmed by the results of pilot studies concerning the UF-RO desalination of geothermal waters extracted from various geological structures in Poland. The assessment of the feasibility of implementing the water desalination process analysed on an industrial scale is largely dependent on the method and possibility of disposing or utilising the concentrate. The analyses conducted in this respect have demonstrated that it is possible to use the solution obtained as a balneological product owing to its elevated metasilicic acid, fluorides and iodides ions content. Due to environmental considerations, injecting the concentrate back into the formation is the preferable solution. The energy efficiency and economic analysis conducted demonstrated that the cost effectiveness of implementing the UF-RO process in a geothermal system on an industrial scale largely depends on the factors related to its operation, including without limitation the amount of geothermal water extracted, water salinity, the absorption parameters of the wells used to inject water back into the formation, the scale of problems related to the disposal of cooled water, local demand for drinking and household water, etc. The decrease in the pressure required to inject water into the formation as well as the reduction in the stream of the water injected are among the key cost-effectiveness factors. Ensuring favourable desalinated water sale terms (price/quantity) is also a very important consideration owing to the electrical power required to conduct the UF-RO process.

Thermal waters have been recognized as a source of health and energy since ancient times, and today there is still interest in balneotherapy as a method of treating various diseases, rehabilitation and prevention. In Poland, as many as 12 spa towns use healing thermal waters in their activities. They include: Busko-Zdrój, Ciechocinek, Jelenia Góra-Cieplice, Gołdap, Inowrocław, Iwonicz-Zdrój, Konstancin-Jeziorna, Lądek-Zdrój, Rabka-Zdrój, Uniejów, Ustka and Ustroń. Healing thermal waters are not only used there for medical treatments, because they also supply the brine graduation towers, are the base for the production of cosmetics and are also used in drinking treatments. Uniejów spa is a part of the cascade system, so the healing waters of higher temperature are also used for heating apartments. Depending on the mineral composition of the waters, they can be used in the treatment of, among others: diseases of the musculoskeletal system, rheumatology, osteoporosis, skin diseases, diseases of the upper and lower respiratory tract, cardiological diseases, diseases of the digestive system, hypertension, obesity, diabetes. All treatments are non-invasive, because the vast majority of them are carried out in the form of bathing, irrigation, inhalation or drinking treatments. The paper also shows the most promising towns in terms of the development of balneotherapy, including Stargard, Pyrzyce, Toruń, Konin and Grudziądz. Balneotherapy in Poland is currently at a difficult time, which is related to the inability to function of many facilities due to the COVID-19 pandemic. However, there is a possibility that when the pandemic and its effects are eliminated, balneotherapy and spa treatment will experience a renaissance.

Geothermal waters are a source of clean energy. They should be used in a rational manner especially in energyand economic terms.

Key factors that determine the conditions in which geothermal waters are used, the amount of energy obtainedand the manner in which cooled water is utilised include water salinity. Elevated salinity levels and the presence oftoxic microelements may often lead to difficulties related to the utilisation of spent waters. Only a few Polishgeothermal facilities operate in a closed system, where the water is injected back into the formation after havingbeen used. Open (with water dumped into surface waterways or sewerage systems) or mixed (only part of the wateris re-injected into the formation via absorption wells while the rest is dumped into rivers) arrangements are morefrequently used. In certain circumstances, the use of desalinated geothermal water may constitute an alternativeenabling local needs for fresh water to be met (e.g. drinking water).

The assessment of the feasibility of implementing the water desalination process on an industrial scale islargely dependent on the method and possibility of disposing of, or utilising, the concentrate. Due to environmentalconsiderations, injecting the concentrate back into the formation is the preferable solution. The energy efficiency and economic analysis conducted demonstrated that the cost effectiveness of implementing the desalinationprocess in a geothermal system on an industrial scale largely depends on the factors related to its operation,including without limitation the amount of geothermal water extracted, water salinity, the absorption parameters ofthe wells used to inject water back into the formation, the scale of problems related to the disposal of cooled water,local demand for drinking and household water, etc. The decrease in the pressure required to inject water into theformation as well as the reduction in the stream of the water injected are among the key cost-effectiveness factors.Ensuring favourable desalinated water sale terms (price/quantity) is also a very important consideration owing tothe electrical power required to conduct the desalination process

The issue of air pollution, resulting to a large extent from the use of fossil fuels for energy purposes, is one of the most serious environmental threats in several Polish cities, but also outside of them. The amount of pollutants emitted into the atmosphere translates into the living conditions of the inhabitants. The utilization of geothermal energy, which is a renewable and ecological source of energy, brings noticeable improvement in the quality of atmospheric air, as evidenced by significant ecological effects achieved by working geothermal district heating plants. The paper presents results of comprehensive considerations focused on assessing the effects of utilization of geothermal water and energy in Poland. Issues related to the implementation of exploration works aimed at acquiring geothermal water resources, as well as environmental aspects of the use of geothermal waters and energy were discussed. The undertaken considerations have been directed at assessing whether the use of such a kind of renewable energy resources could have an impact on improving the living conditions of the local community.

The paper presents the scope of the international curriculum developed under the MOOC4ALL project financed by the Erasmus Plus Strategic Partnerships Program for the MOOC platform https://platform.mooc4all.eu/. The project partners were research units and non-profit organizations from Germany, Poland, Romania and Hungary. Developed under the project, the curricula covers topics in the “green area” such as renewable energy sources, waste management and sustainable development. Research conducted in the consortium countries has demonstrated the need to create online courses in these subject areas to respond to market demand and achieve the goals of the 2030 Agenda for Sustainable Development. Green education is essential for safeguarding a sustainable world, maintaining it and preserving it for future generations. Currently, in times of climate crisis, increasing public awareness through non-formal education is of key importance. In the field of education, MOOCs have attracted a lot of attention as tools for open distance learning in the last decade. They make it possible to use the potential of new technologies in the didactic process and enable a reduction in the differences between developing and developed countries thanks to new interactive digital learning channels, which transpired to be particularly important during the Covid- 19 pandemic. The online courses developed as part of the project are available to participants free of charge in five languages – English, German, Polish, Romanian and Hungarian.

The aim of the presented work was an attempt to verify the geothermal conditions in the Polish Lowlands (Lower Jurassic and Lower Cretaceous reservoir) based on new geological information. The paper presents geothermal conditions in the Polish Lowlands according to the state of recognition at the end of 2022 in order to update the hydrogeothermal conditions in selected regions. Based on the scientific and research works published so far as well as numerous geothermal investments, and geological information from twenty-three new exploratory drilling events performed in the years 2000–2022 (nineteen of which were performed/documented after 2006), the authors undertook to update forecasts of the top surface of Lower Jurassic and Lower Cretaceous formations, the total thickness of these formations and the potential discharge of wells. The analysis was performed using the QGIS Desktop 3.24.1 software, a cross-platform and free open-source geoinformation software application (GIS ) that enables the viewing, editing and analyzing of spatial data and the creation of maps. The correction covered the course of the isolines on all six analyzed maps. The presented analysis made it possible to make a spot correction of the forecasted course of the isoline in relation to the maps published earlier in the Atlas of geothermal resources in the Polish Lowlands. Mesozoic formations developed in 2006, edited by Wojciech Górecki. Information obtained from newly drilled geothermal boreholes enabled the local correction of the forecasted values of individual parameters while maintaining the general trend.