Evaluation of new photochemical systems for water disinfection by the integration of particle tracking into kinetic models for microbial inactivation

This work presents the development of a novel methodology for the simulation of photochemical processes for
water disinfection using computational fluid dynamics (CFD). A new approach was implemented to calculate and
visualise the disinfection performance as the microorganisms move along the photoreactor. Hydrodynamics and
microorganism’s statistical trajectories were computed using the discrete phase model, which also provides the
distribution of microbial residence times. The distribution of radiation in the reactor was calculated using the
discrete ordinate method. The local values of incident radiation were integrated over each statistical trajectory
path to get the accumulated dose received for each microbial particle. The coupling in situ of the cumulative
radiation dose with the inactivation kinetics allows monitoring of the disinfection process concurrently with the
particle tracking. This methodology introduces significant advantages over the traditional estimation of the
microorganism inactivation sequentially after calculating the dose histograms estimated from the statistical
trajectories. The developed tool enables evaluating the photoreactor efficiency in each reactor position, a useful
capability for optimising and scaling up complex geometries. It also allows the easy, intuitive visualisation of
microbial inactivation trajectories, improving the understanding of the influence of the reactor features on the
disinfection process. Application of this computational approach to two different photoreactor geometries using a
virus as a representative target microbe is presented.