Inactivation Of Three Microorganisms By Ultraviolet Light

Ultraviolet disinfection was a physical method, which could inactivate most microorganisms and had no additional pollutions. Ultraviolet has become a credible, effective and environmental disinfection method after more than 20 years' development. It was used in many fields in foreign countries. In China, due to little knowledge about it, the usage of ultraviolet in wastewater treatment was seldom reported. Recent years, many scholars paid attention to and study on it, and some wastewater treatment factories began to use ultraviolet disinfection.The inactivation of Escherichia coli, Saccharomyces Cerevisiae Hansen and Bacillus sbutilis spores were studied by the low-pressure ultraviolet disinfection equipment; moreover the kinetics of inactivation was obtained. Our results indicated that Escherichia coli could be inactivated effectively by ultraviolet when the initial irradiation processing, the numbers of counting bacteria after exposure to UV and the ratio of inactivation increased with the initial rising. Because of the photoreactivation, Escherichia coli increased fast when the sample was kept in sunny; and the sample kept in dark increased slowly. Many physiological characters of Escherichia coli had been lost after UV exposure. When the depth of water was 5 mm, the turbidity affected the inactivation limitedly. Saccharomyces Cerevisiae Hansen and Bacillus sbutilis spores were also inactivated by ultraviolet. The results indicated that the numbers of counting bacteria after exposure to UV were increased with the initial ri(?)ing as well as the ratios of inactivation. The bacterial strains cultivated 24 hours exhibited less resistance than the samples cultivated 48 hours; they also had the better effect of inactivation.The kinetics of bacterial removal of the three bacteria was analyzed by the model of Chick-Watson, along with the bacteria concentration increasing the relevant parameters of the three bacteria rised accordingly. The theoretical counting data were much different from the actual date when the bacteria concentration was thin. It was suitable to use the model of Abdennaceur when the bacteria concentration decreasing.The relevant parameter of inactivation reduced with the turbidity increasing. The relevant parameters of inactivation of the Saccharomyces Cerevisiae Hansen and Bacillus sbutilis spores cultivated 24 hours were much larger than the samples cultivated 48 hours when the bacteria concentrations were similar, and the microorganisms followed the decreasing order of the relevant parameters: Escherichia coli > Saccharomyces Cerevisiae Hansen > Bacillus sbutilis spores.