Ultradźwiękowa stabilizacja osadu czynnego w pomiarach rozkładu wielkości cząstek przy wykorzystaniu metody dyfrakcji laserowej

Laser diffraction method is one of recently applied method for measurement of active sludge particles size distribution. This method requires mixing of the suspension and then pumping it through the measurement unit. Energy of mixing and process of pumping may destroy flocks of the active sludge and change its properties during the measurement. Thus, stabilization of the active sludge flocks before measurement is required. The purpose of this paper was to determine the possibility of flocks sample stabilization for measurements with application of laser diffraction method. This stabilization should allow comparison of various sludge flocks’ diameters, obtained in different conditions. Resuming our results, we may state that according to practical application, usage of stabilization based on ultrasounds was sufficient. However, in order to obtain the replicable results for various types of the active sludge it is necessary to precise describe the ultrasound energy provided to flocks before the measurement.Jedną z metod ostatnio wykorzystywanych do pomiaru rozkładu wielkości cząstek osadu czynnego jest metoda dyfrakcji laserowej. W metodzie tej konieczne jest mieszanie mierzonej zawiesiny w celu homogenizacji próbki, a następnie przepompowywanie jej przez układ pomiarowy. Energia mieszania i pompowanie mogą rozbijać kłaczki osadu czynnego, przez co zmieniać jego właściwości w czasie pomiaru. Dlatego też niezbędna jest stabilizacja cząstek osadu czynnego przed realizacją pomiaru. Celem niniejszej pracy było określenie możliwości stabilizacji próbki kłaczków osadu czynnego w pomiarach z wykorzystaniem dyfrakcji laserowej. Stabilizacja taka miałaby umożliwić porównywanie ze sobą wielkości (średnic) różnych osadów, uzyskiwanych w różnych warunkach. Podsumowując wyniki, należy stwierdzić, że do celów praktycznych wystarczająca jest stabilizacja przy wykorzystaniu ultradźwięków. Jednakże, aby umożliwić porównywalność wyników uzyskiwanych dla różnych osadów, niezbędne jest dokładne określenie energii ultradźwięków, którymi kłaczki są stablizowane przed pomiarem

The effect of slope incline on the characteristics of particles ejected during the soil splash phenomenon

Slope incline is one of the factors affecting the soil water erosion process. Most of the work to date related to erosion has been on large-scale studies based on rainfall events or laboratory investigations with the use of simulators, where the displaced mass of soil was determined. However, there is a lack of studies providing information about splash erosion on slopes in relation to single-drop impact methodology, that allows for the examination of the basic processes of the phenomenon. Thus, the aim of this study was a quantitative description of the splash phenomenon on a simulated slope affected by a single drop impact, with respect to the influence of slope incline on the number of ejected particles and their characteristics. The investigation was carried out using three types of soil with different textures in moistened conditions (i.e. pressure head corresponding to 1.0 kPa) and three variants of slope incline: 5°, 15°, and 30°. A drop with a diameter of 4.2 mm was allowed to fall freely on soil surface with kinetic energy equal 1.42 mJ. The splash phenomenon was registered by a set of three synchronized high-speed cameras and combined with PTV software (Particle Tracking Velocimetry) to identify and track displaced particles. The methodology used made it possible to observe the course of the phenomenon and determine the following quantities: the number and size of ejected particles, ejection velocity and angle, displacement range, and also the contribution of the kinetic energy of the falling drop transferred to the ejected particles. The measured quantities were specified for the particles ejected in upslope and downslope directions. It was found that: (i) the interaction between different slope inclines and the particle size distribution of the soils influenced the surface conditions, which had a significant effect on the course of the splash phenomenon; (ii) the number of ejected particles decreased with the increasing slope, which was directly related to limited ejection in the upslope direction; (iii) the influence of slope incline was mostly visible in the ejection angle, range of displacement and sizes of ejected particles; (iv) the portion of the falling drop energy transferred to ejected particles decreased with increasing slope. The obtained results could enhance the development of physical models of splash erosion. A more thorough understanding and better recognition of the mechanisms governing this phenomenon at all stages could contribute to the development of more effective methods for protecting soil against erosion