UV Dose Measurement and Prediction in a Thin Film UV Contactor

Abstract

A novel UV photoreactor based on the principle of a water bell had been shown in earlier studies to be effective in disinfecting liquids of high UV absorptivities. The water bells were produced using a nozzle in which an annular jet was made to impact on a plane disc. Photographs taken of bells produced in this way were overlayed with the outlines of bells as predicted by the hydrodynamic model of Lance and Perry [1] and showed good agreement. The hydrodynamic bell model was coupled with a volumetric emission model in order to determine the UV dose delivered to the bell by a single UV source located centrally inside the bell. The value obtained using this model, and including a correction factor to account for the UV absorption of the quartz thimble shrouding the UV source, was 0.43 mW-s.cm−2at a flowrate of 650 1 hr−1 which compared with a value of 0.31 mW-s.cm−2 obtained using potassium ferrioxalate actinometry and with a value of 0.43 mW-s.cm−2 obtained from a direct measurement of UV intensity using a radiometer. The combined model was used to predict the effect of changing the principal nozzle characteristic-the nozzle gap opening- on bell profile, UV dose and thickness of the water film comprising the bell.