A systematic simulation of disinfection for the flow-through UV reactors with staggered ring baffles under the Eulerian framework

Abstract

An integrated UV disinfection model is presented to simulate the disinfection in the flow through UV reactors. The concentration of microorganisms, the mean residence time, and the mean dose are solved under the Eulerian framework. An unbaffled reactor and three baffled reactors with staggered baffles are simulated. The accuracy of the computation is validated against Sozzi's measurement and simulation in the unbaffled reactor. The staggered baffles improve the flow field and enhance the mixing. The mean residence time is significantly changed by baffles. The cumulative frequency distributions of the mean residence time in the outlet plane may become narrow and wide depending on the size of baffles. The radiation intensity is nearly the same for all reactors. The mean dose is significantly affected by the baffles. The area-averaged mean doses at the outlet are nearly the same for all reactors whereas the range of the mean dose in the outlet plane is narrowed by baffles. Better disinfection levels are obtained in the baffled reactors than the unbaffled reactor, which is determined by the narrower distribution of the mean dose in the outlet plane. The increasing flow rate decreases the disinfection level for all reactors. The reduction equivalent dose is proportional to the minimum mean dose Dmin in the outlet plane and the slope decreases as the inactivation constant increases, meaning a decreasing effect of Dmin on the reduction equivalent dose. Dmin in the outlet plane can be used to characterize the disinfection capability of the flow-through UV reactors.