E. coli Inactivation Kinetics Modeling in a Taylor-Couette UV Disinfection Reactor

Abstract

A simple model was developed to predict the survival behavior of E. coli subjected to UV disinfection in a Taylor-Couette reactor. The model includes the CFD evaluation of the counterrotating toroidal vortices developed within the annular space of two coaxial cylinders. The UV lamp was located within the diameter of the internal rotating cylinder. The residence time of the bacteria near the UV lamp is, therefore, a function of both the size of the vortex and its angular velocity. The effect of angular velocity on the formation of counterrotating toroidal vortices and their impact on the kinetics of UV microbial inactivation was experimentally evaluated. The kinetics of microbial inactivation follow an apparent first-order kinetic equation between 300 and 2000 revolutions per minute. Therefore, in this range of angular velocities, a set of k values (indirectly taking into account the hydrodynamic pattern and UV irradiance) was obtained for a given concentration of bacteria. Then, the set of k values was correlated with the range of angular velocities applied using the polynomial equation. A k value can be obtained for an unknown angular velocity through the polynomial equation. Therefore, a simulation curve of microbial inactivation can be obtained from the first-order kinetic equation. The efficiency of bacteria removal improves depending on the angular velocity applied. A good agreement is observed between the simulation of the survival behavior of the microorganisms subjected to UV disinfection with the experimental data.