The article presents an assessment of the potential for using low temperature geothermal water from the C-PIG-1 well (Małopolskie Voivodship, southern Poland) for electricity generation, as the first stage in a geothermal cascade system. The C-PIG-1 well is characterised by a temperature of geothermal water of 82 °C and a maximum flow rate of 51.22 kg/s. Geothermal water is currently only utilised for recreation purposes in swimming pools. In such locations, with the potential to use renewable energy for energetic purposes, the possibility of comprehensive management of the geothermal waters extracted should be considered both in the first stage of the cascade and after recreational use. Thermodynamic calculations were conducted assuming the use of the Organic Rankine Cycle (ORC) or Kalina Cycle. Two variants were analysed—the use of the maximum flow rate of geothermal waters and partial use with an assumption of a priority for recreational/heating purposes. The analysis and calculations indicate that the gross capacity in the most optimistic variant will not exceed 250 kW for the ORC and 440 kW for the Kalina Cycle. As far as the gross electricity generation is concerned, for ORC this will not exceed 1.9 GWh/year and for the Kalina Cycle it will not exceed 3.5 GWh/year.

Accurate and reliable laboratory results are an extremely important and integral part of conducting scientific research. Many factors influence the results obtained, including the type of determination method, accuracy and precision of measurements, and laboratory equipment used for the tests. This paper presents the results of measurements of heavy metal concentration in soil using two methods for adding soil components into solution and different laboratory methods and types of measuring equipment. The first method used was hot digestion of soil samples with a mixture of concentrated HNO₃ and HClO₄, after prior ashing of organic matter (IUNG method). The second method was a two-stage decomposition, where soil samples were hot digested, initially with oxidizing acid (HNO₃) and subsequently with non-oxidizing acid (HF) (two-stage decomposition). The concentrations of selected heavy metals (Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined in solutions obtained by both digestion methods. The solutions obtained from soil decomposition were determined twice using atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP MS) methods in different laboratories using different types of spectrometers. In most cases, the measured concentrations of heavy metals are the highest for the two-stage solution samples and the measurements of their concentrations carried out using ICP. The exceptions are the measurements of Cu and Ni concentrations. In the case of Cu, lack of significant differentiation in concentrations of this metal may result from different forms of occurrence of Cu in soil than in the case of other metals. For Ni, however, a reversal of the trends seen for the other metals is observed and the type of spectrometer used for measurements is important. There may be an interference of the spectrometric spectrum of Ni with the spectra of the other determined metals. However, this is not clear at the present stage of the study. In conclusion, the results of this study indicate that the choice of soil sample preparation and the type of spectrometer used for measurements can, in many cases, determine the value of laboratory results, even if it is in an expected range of standard material. Research of published papers proved that most of them show only results based on one selected course of methodology without comparison with others. The novelty of the paper is the comparison of the measurements of heavy metal concentration in soil using two methods for adding soil components into solution and different laboratory methods and types of measuring equipment. Additionally, the article includes a discussion of the importance of methodology. We believe that the conclusions may help to better understand how sample preparation and measurement methods applied may influence the results obtained.

The paper presents the results of the analysis concerning the verification of the actual hydraulic load and the load of organic pollutants compared to the conditions designed for 4 household wastewater treatment plants. The researches were carried out in the annual period from May 2015 to April 2016. Based on the conducted analysis, it was found that objects act as underloaded hydraulically and the actual inflow of sewage to the analysed objects during the research period ranged from 7.3% to 32.7% in relation to the inflow assumed in the project. Furthermore, in the case of loading the treatment plant with the load of pollutants expressed as PE, it was fund that the actual PE values were lower than assumed in the project. Therefore, it is important that the sizes of the series of household sewage treatment plants were selected depending on the individual conditions of household, i.e. the number of inhabitants or the amount of consumed water.