In drinking water treatment plants, oxidation contactors are baffled reactors in which water and an oxidant, either ozone or chlorine, are in contact for a period of time to eliminate viruses and bacteria. To quantify the disinfection efficiency of working contactors, a residence time distribution (RTD) is measured. To quantify the efficiency of proposed contactor designs or operating conditions, CFD is used. Both single phase (water only) and multiphase (water and ozone) systems can be studied in this manner. For example, oxidation contactors at several drinking water treatment plants in France (Annet Sur Marne, Nice, and Neuilly Sur Seine) have been simulated to diagnose the disinfection efficiency. The FLUENT results were used to suggest changes in the contactor geometry to bring about performance improvements during the rehabilitation phase of the process.

Velocity field and path lines inside an oxidation contactor provide useful information such as the localization of dead zones, recirculation loops, and short cut
Courtesy of Veolia Environnement