Integrated UV disinfection model based on particle tracking

A general probabilistic particle-centered model is developed that combines kinetic information (dose-response function) from a well-mixed batch reactor with a dose-distribution function to predict disinfection efficacy in practical ultraviolet (UV) systems. An interpretation in terms of a generalized segregated-flow model also is given. The particular case of disinfection using vertical (perpendicular to the direction of the open-channel flow) UV lamps in a staggered configuration is studied. A dose-distribution function that incorporates the effects of spatial nonuniformities in both hydrodynamics (through a random-walk model) and UV intensity (through a point-source summation model) is estimated. The flow-field information necessary for the random-walk model was obtained from laboratory measurements of the turbulent flow using laser Doppler velocimetry. The dose-response function for microorganisms was obtained from completely mixed batch reactor experiments with a collimated beam. Predictions of disinfection efficacy based on the developed dose-distribution function and the laboratory kinetic data compared well with measurements from a pilot-scale vertical UV system. The results also suggest that the regions near the channel sidewalls where UV intensity is low represent a limiting factor in the process performance of continuous-dow UV disinfection systems.