MODELING OF THE FLOW PATTERN IN OZONATION CHAMBERS CONTACTOR BY RESIDENCE TIME DISTRIBUTION STUDIES AND BY COMPUTATIONAL FLUID DYNAMICS APPROACH

摘要

The hydrodynamics of water flow in drinking water ozonation tanks is of extreme importance for the efficiency of the disinfection process. Since several decades bubble diffuser contact chambers are widely used because of their high yields of transfer, easy scale-up and low hydraulic loss. The main subject of this particular study is the problem of optimizing the design and operation of these units. In a first stage, the hydraulic behaviour of several pilot and full scale systems has been studied using the classical approach, based on tracer tests and Residence Time Distribution curve modeling. To gain a better understanding of the performance of ozone contact chambers a Computational Fluid Dynamics Model has been developed, in a second stage, based on the solution of Navier-Stokes equations associated to k-ε model of turbulence. Different conditions of flow regime and various geometries have been studied in order to determine the optimum design of the contactor and improve its efficiency of disinfection. The results of numerical simulations have been compared to experimental data and showed that the model predictions were accurate. However, they concern only the continuous phase flow at present. The actual CFD model does not provide reasonable data relative to the two-phase flow because of the limits in its assumptions.