Comparative effectiveness of UV wavelengths for the inactivation of Cryptosporidium parvum oocysts in water

Cryptosporidium parvum oocysts in water were exposed to distinct wavelength bands of collimated beam ultraviolet (UV) radiation across the germicidal UV wavelength range (210-295 nm) that were emitted from a medium pressure ( MP) mercury vapour lamp. The dose of UV radiation transmitted though each n arrow bandpass filter was measured utilising potassium ferrioxalate actinom etry. Oocyst infectivity was determined using a cell culture assay and titr e was expressed as an MPN. The log(10) inactivation for each band of radiat ion was determined for a dose of 2 mJ/cm(2). Doses from all wavelengths bet ween 250-275 nm resulted in approximately 2 logo inactivation of Cryptospor idium parvum oocyst infectivity while doses with wavelengths higher and low er than this range were less effective. Because polychromatic radiation fro m MP UV lamps had about the same germicidal activity between the wavelength s of 250-275 nm for inactivation of oocyst infectivity, there was no unique advantage of MP UV over low pressure (LP) UV except for the simultaneous d elivery of a wide range of germicidal wavelengths.