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Study of sterilization effect of diaphragm discharge in liquids
Holíková, Lenka ; Slámová, Jitka (referee) ; Kozáková, Zdenka (advisor)
The main objective of this thesis is to study the sterilizing effect of diaphragm discharge in liquids. Sterilization is a process, which can eliminate all forms of life. Generally, sterilization is divided into physical and chemical methods. Plasma sterilization is ranked among physical methods although the action of chemical processes participates in the decontamination as well. Effects of UV radiation, free radicals and temperature are utilized in these methods. Fungi spores of Aspergillus niger F8189 and bacteria spores of Bacillus subtilis are selected as model organisms. Aspergillus niger microorganism is suitable for its resistance to changes in pH and it is viable in a wide range of pH values. Bacillus subtilis is chosen because of a good heat resistance. Diaphragm discharge is one of the possible types of electrical discharges in generated liquids. It is a low-temperature plasma, which is generated using a high DC voltage. In the created plasma streamers various physical and chemical processes rise. The chemical processes are mainly the generation of active species and particles that initiate subsequent chemical reactions and attack mould spores and bacteria in liquids. The physical processes include shock waves, strong electric field and ultraviolet radiation. Experiments were conducted in a reactor with separate cathode and anode space. In the dielectric barrier PET diaphragm with a pin-hole (initial diameter of 0.4 mm) was attached. Enlargement of the hole was observed as a result of degradation of material at the edge of holes due to the discharge. Degradation of spores was observed, depending on the time and on the input power. Other parameters measured were pH, conductivity and temperature. Experiments did not show any difference of discharge activity in the cathode and anode area. The main factor in the removal of spores Aspergillus niger was probably the temperature because no demonstrable effect of sterilization by the diaphragm discharge operation had been observed when heat resistant Bacillus subtilis was used. Also, it was made an attempt, which has been studied only the temperature effect of the fungi spores of Aspergillus niger. The samples were placed in a thermoregulator, where it was simulated the same temperature increase as at the discharge. The experiment had a similar course as an attempt at the discharge.
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Study of sterilization effect of diaphragm discharge in liquids
Holíková, Lenka ; Slámová, Jitka (referee) ; Kozáková, Zdenka (advisor)
The main objective of this thesis is to study the sterilizing effect of diaphragm discharge in liquids. Sterilization is a process, which can eliminate all forms of life. Generally, sterilization is divided into physical and chemical methods. Plasma sterilization is ranked among physical methods although the action of chemical processes participates in the decontamination as well. Effects of UV radiation, free radicals and temperature are utilized in these methods. Fungi spores of Aspergillus niger F8189 and bacteria spores of Bacillus subtilis are selected as model organisms. Aspergillus niger microorganism is suitable for its resistance to changes in pH and it is viable in a wide range of pH values. Bacillus subtilis is chosen because of a good heat resistance. Diaphragm discharge is one of the possible types of electrical discharges in generated liquids. It is a low-temperature plasma, which is generated using a high DC voltage. In the created plasma streamers various physical and chemical processes rise. The chemical processes are mainly the generation of active species and particles that initiate subsequent chemical reactions and attack mould spores and bacteria in liquids. The physical processes include shock waves, strong electric field and ultraviolet radiation. Experiments were conducted in a reactor with separate cathode and anode space. In the dielectric barrier PET diaphragm with a pin-hole (initial diameter of 0.4 mm) was attached. Enlargement of the hole was observed as a result of degradation of material at the edge of holes due to the discharge. Degradation of spores was observed, depending on the time and on the input power. Other parameters measured were pH, conductivity and temperature. Experiments did not show any difference of discharge activity in the cathode and anode area. The main factor in the removal of spores Aspergillus niger was probably the temperature because no demonstrable effect of sterilization by the diaphragm discharge operation had been observed when heat resistant Bacillus subtilis was used. Also, it was made an attempt, which has been studied only the temperature effect of the fungi spores of Aspergillus niger. The samples were placed in a thermoregulator, where it was simulated the same temperature increase as at the discharge. The experiment had a similar course as an attempt at the discharge.
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