EVALUATION OF PHOTOCATALYTIC STERILIZATION RATES OF ESCHERICHIA-COLI-CELLS IN TITANIUM-DIOXIDE SLURRY IRRADIATED WITH VARIOUS LIGHT-SOURCES

Photocatalytic sterilization of Escherichia coli cells with TiO2 parti cles is examined using a rectangular bubble-column reactor irradiated with three kinds of artificial light sources. The three types of used lamps were a black light fluorescent (BL-F) lamp, a blue actinic fluor escent (BB-F) lamp and a daylight fluorescent (DL-F) lamp. Under the c onditions of TiO2 concentration of 1 x 10(-2) kg/m(3) and initial cell concentration of 1 x 10(11) cells/m(3), average light intensities in the reactor were varied in the range of 0 to 22 W/m(2), 0 to 14 W/m(2) and 0 to 1.1 W/m(2) with the BL-F, BA-F and DL-F lamps, respectively, The apparent sterilization rate constants of E. coli cells for these lamps are determined on the basis of a series-event model, and are com pared with those obtained in experiments with a high pressure mercury lamp. Irrespective of the examined lamps, the rate constants can be co rrelated with the light quantities absorbed by TiO2 slurry, which are evaluated by taking into account both the dependency of absorbance of TiO2 slurry on light wavelengths and the spectral distributions of lig ht rays from the respective lamps. From the results obtained in experi ments using the artificial light sources, the sterilization rate const ants of E. coli under the sunlight can be predicted, The experimental data are in good agreement with the predicted results in the reactor i lluminated with sunlight at average light intensities of 14 and 23 W/m (2).