Polychromatic UV Fluence Measurement Using Chemical Actinometry, Biodosimetry, and Mathematical Techniques

With the growing acceptance of ultraviolet (UV) irradiation for disinfection of water and wastewater, the use of medium pressure Hg-based UV lamps and nonmercury, pulsed UV lamps emitting polychromatic light, are being considered in place of low-pressure, monochromatic UV lamps. However, traditional methods of fluence measurement developed for monochromatic light sources are not appropriate for polychromatic light sources. New approaches for estimation of effective germicidal fluence for polychromatic UV sources were investigated integrating chemical actinometry (uridine and iodide/iodate) with mathematical modeling. Actinometric fluence measurements as well as radiometry were referenced against microbial biodosimetry. Combining traditional chemical actinometry with mathematical analysis improved the accuracy of incident and germicidal polychromatic UV fluence measurement. Uridine actinometer germicidal fluence measurement, with or without mathematical correction, was just outside of the 95% confidence interval of that measured by biodosimetry. Similarly, an iodide/iodate actinometer was observed to accurately measure incident fluence, and coupled with mathematical corrections, it measured germicidal fluence within the 95% confidence interval of that measured by biodosimetry. These methods have potential to develop into flexible, convenient ways to measure germicidally effective UV fluence from any type of UV lamp.