Anionic surfactants are commonly determined with the use of the methylene blue active substances (MBAS) standard method, which is time‐consuming and labor‐intensive. Therefore, new methods for determination of anionic surfactants are needed. In this study, the standard MBAS method for determination of anionic surfactants was modified and adjusted to work in a continuous flow system combined with spectrophotometric measurement. The developed method was found to be satisfactory in terms of sensitivity and precision, with a short time of analysis. The quantification limit for anionic surfactants was at 16 μg L⁻¹, with a relative standard deviation of 1.3 % for a model sample and 3.8 % for a river water sample. The results obtained for environmental samples were comparable to those obtained by using the standard MBAS method; however, the developed continuous flow method is faster, more sensitive and consumes smaller doses of chemical reagents.

The aim of this study was to evaluate the work of a two types of household sewage treatment plant: wetland wastewater treatment plant (ORS type) and treatment plant of SBR type (SBR-K-6 type). Physicochemical analyses of selected pollution indices (BOD₅, COD, total suspension, total phosphorus) and surfactants were carried out and compared with currently applicable values of such indexes according to the Regulation of the Minister of the Environment in Poland on the conditions to be met when discharging sewage into water or soil, and on the substances particularly harmful to the aquatic environment. The removal efficiency of organic compounds, expressed as COD and BOD₅, reached the threshold of 90%, which is required in regulations. In contrast, the effects of removal of biogenic compounds were low – in case of total nitrogen the removal rate reached approx. 40% and the desired admissible concentration of 30 mg N/L was not achieved. The reduction efficiency of total suspended solids reached 57.0 and 59.6% for the ORS and SBR-K-6 type objects, respectively, and therefore the required threshold of minimum 90% was not reached. Anionic surfactants were removed by up to 98 and 88% in the ORS and SBR-K-6 type wastewater treatment plants, respectively. Lower removal efficiency was achieved in case on non-ionic surfactants, which reached 76% for the ORS type object and 56% for the SBR-K-6 type object. This article proven high wastewater treatment efficiency and lower than necessary concentrations in the effluent from domestic wastewater treatment plants may be achieved mainly by proper exploitation of the devices and appropriately selected vegetation.

A method for the determination of cationic surfactants in soil samples was developed and applied to a biodegradation study. Five different cationic surfactants (benzalkonium chloride, 1-dodecyl-3-methylimidazolium bromide, didecyldimethylammonium bromide, trihexyl(tetradecyl)phosphonium bromide and trihexyl(tetradecyl)phosphonium chloride) were selected for the study with the developed method upon extraction from soil samples with methanol. The samples were subjected to analysis as disulphine blue active substances using a visible spectrophotometer. The limits of detection for the proposed method ranged from 2 to 27 μg/g, which enabled the determination of cationic surfactants in soil samples. The results obtained in the biodegradation study were confirmed using liquid chromatography coupled with tandem mass spectrometry.

The article provides an overview of the design and operation of pulse jet engines, alongside a historical perspective on their development. It examines a selection of readily available fuels with diverse physicochemical properties, including methane, methanol, ethanol, gasoline, and LPG. A detailed chemical and energetic analysis of the combustion process for each fuel is conducted to determine key kinematic and thermodynamic parameters critical for the design and optimization of pulse jet engines. Computational methods and numerical tools used for simulating combustion chamber processes are discussed, with a focus on numerical analyses performed in the ANSYS environment. These simulations evaluate the impact of geometric parameters on the specific work of the engine, enabling the identification of optimal design solutions and key areas requiring further research and modifications. The study concludes by exploring potential design changes necessary for adapting pulse jet engines to operate efficiently with multiple fuel types. This includes considerations related to material selection for resistance to high temperatures and aggressive combustion conditions, as well as solutions for effective fuel distribution.