Effect of Three-Dimensional Mixing Conditions on Water Treatment Reaction Processes.

Athanasios Angeloudis, Thorsten Stoesser, Carlo Gualtieri, Roger Falconer

Tuesday 30 june 2015

16:15 - 16:30h at Europe 1 & 2 (level 0)

Themes: (T) Water engineering, (ST) Computational methods

Parallel session: 7E. Engineering - Computational

The performance of water disinfection facilities traditionally relies on Hydraulic Efficiency Indicators (HEIs), extracted from experimentally derived Residence Time Distribution (RTD) curves. This approach has often been undertaken numerically through computational fluid dynamics (CFD) models, which once calibrated to accurately predict RTDs, enable the assessment of disinfection facilities prior to their construction. A significant drawback of the conventional efficiency methodology prescribed for disinfection tanks is associated with the respective indicators, as they are predominantly linked to the internal flow characteristics developed in the reactor rather than the disinfection chemistry which should be optimized. Two methods are considered to evaluate the influence of hydraulic efficiency on kinetics, one through Segregated Flow Analysis (SFA) of experimental RTD curves, and another through CFD modelling. The numerical models were refined to simulate the processes of chlorine decay, pathogen inactivation and the by-product formation in a disinfection contact tank (CT). The main objective of this study is to examine the effect of three-dimensional mixing on reaction processes which can be modeled through finite-rate kinetic models. Comparisons are made between reactive tracer simulation results produced by the 3D CFD model against the conservative tracer experiment SFA findings. In turn, CFD results confirm that three-dimensional mixing affects reaction processes, which however is not apparent through the SFA approach.