Modelling the Kinetic of UV Water Disinfection

Ultraviolet disinfection is an attractive tool for treating water and eliminating pathogens with safe and available technology especially in developing countries where waterborne diseases cause the death of thousands of people every year. Even though UV is an easy tool to perform disinfection, concerns over the potential of microorganism reactivation constitute an issue for its development. In order to avoid this phenomenon, estimating the right dose of UV irradiance, the number of viable microorganisms and the sufficient contact time are important parameters to consider when performing UV disinfection. For this purpose, it’s current to use mathematical modelling. This work aimed to study the modelling of the kinetic of water disinfection by UV irradiation. Two kinetic models (Chick-Watson and Hom) were tested as to ability to scale disinfection of Gram negative Escherichia coli and Gram positive Lactobacillus Helveticus by different ultraviolet (UV) light inactivation process: UV alone, UV and TiO2 as a photocatalyst and finally UV and ZnO as a photocatalyst. The two tested models (Chick-Watson and Hom) fitted the kinetic of disinfection of E. coli. However, it must be noticed that, the simple agreement between experimental data and model predictions does not necessarily prove that either of the models is mechanistically correct. For the disinfection of L. Helveticus, neither of the two models fitted the experimental plots. The divergence existing between experimental and modelling results proves only that the empirical models can’t be generalized to all deactivated microorganisms.