Chapter 4: Modelling Photochemical Processes for Water Disinfection

Photochemical processes cover a wide range of technologies for drinking-water and wastewater disinfection, including UV-C, UV/H₂O₂, photo-Fenton, heterogeneous photocatalysis, solar disinfection, etc. They share the absorption of photons as the activation step triggering the global process. However, significant differences appear depending on the specific technology, including the required wavelength, light sources, reactor design and optimal operational conditions. This chapter focuses on the modelling strategies for the simulation and design of photochemical processes for water treatment, with particular emphasis on the use of sunlight and LED light sources. The necessity of a mechanistic description of the kinetics of the process and its explicit coupling with radiation transport in the system is shown as the best approach for the rigorous design of photochemical reactors. Application of computational fluid-dynamics techniques is also described as a way for the optimal simulation of these multiphysics processes.