Quantitative analysis of variations in initial Bacillus pumilus spore densities in aqueous TiO2 suspension and design of a photocatalytic reactor

Spore-forming Bacillus pumilus was used as a model for TiO2-based photocatalysis. Previous results have shown that for different initial spore densities between 10(4) and 10(10) CFU/ml, more inactivation of viable spores in aqueous TiO2 suspension occurred with an increase in spore density. The results were different from published results for different initial concentrations of organic pollutants and non-spore-forming organisms (e.g., E. coli). To determine a plausible explanation for the results obtained for the B. pumilus spores, a quantitative analysis has been performed based on the theory of probability. Since hydroxyl radicals (. OH) have been thought to be the primary species responsible 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. pumilus spore will occur, or that a hydroxyl radical interacting with determined based on this model, these theoretical values will be compared to the experimental values obtained for each initial B. pumilus spore density. Also, a design of a simple photocatalytic reactor system-regardless of the amount of initial spore densities present-will be given to determine parameters which could be used to scale-up to an engineering scale design.