Sequential inactivation of bacillus subtilis spores with ultraviolet radiation and iodine

Bacillus subtilis spores were used as an indicator organism to characterize the effects of UV radiation and iodine, alone and in combination, as disinfectants for water. Spore exposures to UV radiation were conducted in shallow, well-mixed batch reactors under collimated beams. Three (essentially) monochromatic collimated UV sources were used in these experiments, with characteristic emission wavelengths of 222, 254, and 282 nm. Iodine exposures were conducted in well-mixed batch reactors. Synergism was demonstrated when UV (at certain doses) and iodine were used as sequential disinfectants; synergism was attributed to UV-induced damage that enhanced the susceptibility of spores to iodine.