ANALYSIS OF PROCESS PERFORMANCE IN POLYCHROMATIC UV DISINFECTION SYSTEMS

Ultraviolet disinfection systems based on polychromatic radiation sources have emerged as an important process alternative. A substantial database of empirical information exists to suggest that these systems are effective for control of waterborne microorganisms; however, several fundamental information gaps exist regarding the wavelength-dependent behavior of these systems, including the radiation intensity field and the dose-response behavior of waterborne microorganisms. The aim of this research was to apply numerical and experimental methods to illustrate wavelength-dependent behavior in UV radiation intensity fields and microbial dose-response behavior. The line-source integration method was used to represent intensity fields at several characteristic wavelengths for UV systems based on the measured output power spectra of medium-pressure lamps and measured optical characteristics of the transmitting media. These simulations illustrated spatial variations in intensity and the effects of lamp output power and absorbance characteristics. Wavelength-dependent dose-response behavior was estimated using a tunable UV laser system. The laser-based system provides monochromatic, coherent radiation to a well-mixed, shallow vessel such that a single radiation dose is delivered to an entire microbial suspension. Microbial suspensions were exposed to a range of UV doses for specific wavelengths in the wavelength range of 240-350 nm.