UV dose distribution characterization using fractal concepts for system performance evaluation

This paper presents a mathematical model for estimating the UV dose distrib ution delivered by continuous-flow UV disinfection processes. The model ado pts fractal concepts and a stochastic method to simulate microorganism (par ticle) trajectories through the irradiation zone of an open-channel UV syst em. The irregularity of particle trajectories attributable to random moveme nts was characterized by fractal dimension. In turn, trajectory-specific do ses were calculated by integrating UV intensity over travel time. Results o f these simulations indicated that radiation intensities along the trajecto ries could be highly variable. Therefore, microorganisms are expected to re ceive a broad range of radiation doses as a result of variations in radiati on intensity along their trajectories and spatial heterogeneity in the radi ation intensity field. This supports previous assertions that the conventio nal averaged-dose approach will result in substantial deviations between pr edicted and actual system performance. Implications of the results in terms of treatment efficiency and system design are discussed. The presented app roach is found to be useful as a tool for rapid estimation of the dose dist ribution delivered by UV processes.