(156e) Scalability Analysis of An Open Channel UV Wastewater Disinfection Reactor Using CFD Simulation

The scalability of an open channel ultra-violet (UV) wastewater disinfection reactor is numerically investigated using a computational fluid dynamics (CFD) model. The CFD model consists of volume of fluid (VOF) method for capturing water-air interface, Lagrangian particle tracking for calculating microbial particle trajectory and the discrete ordinate (DO) model for resolving the UV intensity field in the reactor. The realizable k-ϵ turbulence model was adopted to simulate the turbulent flow, and the enhanced wall treatment was used to resolve the turbulence near the walls.  Different scaling down procedures were tested to establish similarity of the hydrodynamics and the radiation field between the scale model and the full size reactor. To ensure similarity of the hydrodynamics, Froude number and the Reynolds number were taken into consideration. Scaling methodology for the UV radiation field was formulated to ensure the same reduction equivalent dose (RED) values can be achieved from the full size and scaled down reactors. A parametric study was performed in terms of the flow rate in the reactor and water UV transmittance to characterize the range of scalability. Initially, the model was validated using experimental data on free-surface profile.  The CFD model predicts that the open channel reactor is scalable, thus allowing one to predict the large scale behavior from the small scale laboratory test.