Sensitivity of microorganisms to different wavelengths of UV light: implications on modeling of medium pressure UV systems

The responses of three species of coliform bacteria (Citrobacter diversus, Citrobacter freundii and Klebsiella pneumoniae) and the bacteriophage (virus) φX-174 to three wavelengths of UV light (254, 280 and 301 nm) were measured. The values of germicidal efficiency at 280 nm determined for each of the microorganisms were not significantly different. At 301 nm, the values of germicidal efficiency were significantly different, but all values were too small (<0.06) to warrant consideration in the modeling of the germicidal intensity delivered by a medium pressure UV system. The data from this study provide some evidence that the values of germicidal efficiency determined for one species of bacteria or virus may be used to represent the relative responses of all bacteria and viruses to medium pressure UV irradiation.