Author(s): Athanasios Angeloudis; Thorsten Stoesser; Dongjin Kim; Roger Alexander Falconer
Keywords: Contact Tanks; Acoustic Doppler Velocimetry; Tracer Experimentation; RANS; Disinfection Performance
Abstract: With the aim of optimising contact tank design through numerical model simulations, results are presented herein of an experimental and computational fluid dynamics (CFD) study in a scaled laboratory model. Three-dimensional numerical simulations of flow and transport characteristics were conducted using a Reynolds Averaged Navier-Stokes equation approach. Experimental results were obtained through Acoustic Doppler Velocimetry measurements and a series of conservative tracer experiments. Focus is given on turbulent structures and undesirable flow patterns that lead to a reduced disinfection efficiency, through phenomena such as short circuiting and recirculation zones. The laboratory data analysis indicates extensive three-dimensionality as a result of the current inlet geometry with a confirmed negative impact on the disinfection performance of the contact tank model, as demonstrated by Residence Time Distribution curves. Disinfection performance is evaluated through hydraulic efficiency indicators commonly used in the industry to monitor field-scale disinfection facilities. Correlations between CFD and experimental data confirm the adequate reproduction of hydrodynamic conditions and reinforce the predictive capabilities of numerical models as tools to simulate field scale tanks or optimize existing designs.