UV intensity measurement and modelling and disinfection performance prediction for irradiation of solid surfaces with UV light

UV intensities on the surfaces of solid cylinders were measured in a disinfection chamber by means of a UV bioassay. The bioassay employed spores of the bacterium Bacillus subtilis (ATCC 6633) which had been deposited onto coupons of filter paper. These experimental measurements were then compared to surface intensity predictions obtained using an extense source with spherical emission (ESSE) model. Good agreement was obtained between both sets of data, with the predicted values lying between 75% and 95% of the experimental ones. The model was also applied to the prediction of UV intensities on the surfaces of an object of slab geometry travelling through a conceptualized disinfection facility having the configuration of a tunnel in which UV sources were arranged on the walls of the tunnel. By assuming that the object was uniformly contaminated with spores of B. subtilis, estimates of the extent of disinfection achieved as the object travelled along the tunnel were made using previously published inactivation data for the spores. The versatility of the ESSE model was demonstrated by presenting three dimensional surface intensity plots of the various slab surfaces for both horizontal and vertical arrangements of UV sources in the tunnel. The model described here could prove useful in optimizing the arrangement and numbers of UV sources in surface disinfection facilities.