QUANTITATIVE-ANALYSIS OF VARIATIONS IN INITIAL BACILLUS-PUMILUS SPOREDENSITIES IN AQUEOUS TIO2 SUSPENSION AND DESIGN OF A PHOTOCATALYTIC REACTOR

Spore-forming Bacillus pumilus was used as a model for TiO2-based phot ocatalysis. Previous results have shown that for different initial spo re densities between 10(4) and 10(10) CFU/ml, more inactivation of via ble spores in aqueous TiO2 suspension occurred with an increase in spo re density. The results were different from published results for diff erent initial concentrations of organic pollutants and non-spore-formi ng organisms (e.g., E. coli). To determine a plausible explanation for the results obtained for the B. pumilus spores, a quantitative analys is has been performed based on the theory of probability. Since hydrox yl radicals (. OH) have been thought to be the primary species respons ible for degrading/inactivating contaminants in water, a probabilistic approach will be used to determine quantitatively the likelihood that an interaction, or a collision, between a hydroxyl radical and a B. p umilus spore will occur, or that a hydroxyl radical interacting with d etermined based on this model, these theoretical values will be compar ed to the experimental values obtained for each initial B. pumilus spo re density. Also, a design of a simple photocatalytic reactor system-r egardless of the amount of initial spore densities present-will be giv en to determine parameters which could be used to scale-up to an engin eering scale design.