Comparison of sterilization efficiency of pulsed and continuous UV light using tunable frequency UV system

Abstract Whether or not pulsed UV light was more bactericidal than continuous UV was still debated. The aim of this work was to compare the disinfection efficiency of continuous and pulsed UV light at different frequencies. A tunable frequency UV system was designed to allow indicator bacteria to be exposed to continuous or pulsed UV light with a same low pressure mercury lamp, which can emit UV light with a wavelength of 253.7 nm, and the pulse frequency was adjustable. The germicidal ability against Escherichia coli and Salmonella spp. of pulsed UV light at frequencies 0 (represented continuous irradiation), 2, 4, 6, 8, 10 Hz was compared. The results showed that pulse frequency is a factor influencing the ultimate inactivation ability of pulsed UV light and at specific frequencies pulsed UV light was more bactericidal than continuous UV. Industrial relevance Pulsed UV light for microbial inactivation has been applied for more than 30 years. As a very important factor, pulse frequency has been ignored for a long time. We have demonstrated that at some specific frequencies, pulsed UV light was more bactericidal than continuous UV using low pressure mercury lamp. And if further studies could come to the similar results in inert-gas flash lamps and/or medium-pressure UV lamps and figure out the optimal pulse frequency, it might improve the sterilization efficiency of the existing pulsed UV system.