Influence of Oxygen and Carbon Dioxide on Water Purification from Bacteria and Yeast Under Cavitation Conditions

Abstract

Purpose is to study the purification process of water polluted by containing Bacillus cereus bacteria type and Saccharomyces сerevisiae yeast type under cavitation conditions and atmosphere of different gases nature (oxygen and carbon dioxide); to evaluate and to compare the destruction efficiency of bacterial with yeast cells, and to determine the effective gas nature during cavitation treatment of the aqueous system. Methods. The investigated model media were sounded by the action of an ultrasonic generator (UZDN-2T) with a frequency of 22 kHz, with a power of 35 watts. Оxygen and carbon dioxide were gas bubbles as an additional embryos of cavitation. Microorganisms number before and after sonication was determined by counting of the colonies grown on the nutrient medium in a Petri dish and expressed in colony-forming units (CFU). Results. The results of the morphological characteristics of bacteria and yeast, as well as images of cells according to the results of microscopic studies at a corresponding magnification characteristic of a particular microorganisms types are presented. Degrees of microorganisms destruction, expressed in a percentage, were calculated. According to the results of studies, Bacillus cereus bacteria type were more likely to be destroyed, compared with Saccharomyces cerevisiae yeast type at the conditions of simultaneous action of gas and cavitation. The resistance of yeast cells is explained by the result of the specific effect of cavitation on the yeast cell wall and their inter-genetic difference in cell wall structures. Higher efficiency of oxygen in the processes of cavitation treatment of both bacteria and yeast, compared to the action of carbon dioxide is shown experimentally. Conclusions. More active destruction of bacterial cells compared to yeast in the gas/cavitation conditions shown that is explained by the age-related signs of the bacteria. It has been investigated that oxygen under cavitation conditions is described by a larger value of the microorganisms destruction, that is explained by the nature of the gas action at the experimental conditions. It is shown that the efficiency of water purification from microorganisms depends on the nature of the gas bubbled under cavitation conditions.