Application of computational fluid dynamics (CFD) to ozone contactor optimization

Abstract

Many approaches have been used to model the performance and efficiency of ozone contactors based on some assumptions to characterize the backmixing in fluids. Recently, computational fluid dynamics (CFD) technique has been proposed to simulate and optimize ozone contactors by calculating residence time distribution of fluid. To improve the ozone contactor performance of Bijianshan Water Treatment Plant in Shenzhen in South China, CFD was used for simulation and development of new optimization measures. Results showed that the low depth/length ratio of the contactor chambers in the original design resulted in short circuiting and backmixing, with the T10/HRT being only 0.40. Installation of guide plates substantially reduced short circuiting and backmixing with a much higher T10/HRT (0.66), increased by 73% compared with the original design.

Latest Developments in Sustainable Water Management

“…The use of CFD models (openFOAM, Ansys, COMSOL) enables prediction of flow fields and turbulent mixing to the various levels of detail. A large number of studies have shown that CFD is a powerful tool for analysing and optimising particular water treatment processes, such as optimization of ozone contactors for microbial inactivation [60], [61], disinfection performance of UV reactors [62], oxidation processes [63], investigation of electrochemical variables in the operation of a continuous upflow electrocoagulation process in treating textile wastewater [64], simulation of the grit and sand separation effectiveness of a typical hydrodynamic vortex separator (HDVS) system [65], simulation of mixing characteristics of a small circular anaerobic digester tank [66], working performance of closed-loop bioreactor [67][66], verification of compliance of a water reclamation plant disinfection stage with respect to modal time [68], or analysing efficiency of the electrocoagulation (EC) process with stainless-steel electrodes for total nitrogen removal [69].…”

Tracer experiment and RTD analysis of DAF separator with bar-type baffles

“…The standard parameter of Ö10 relates to the degree of short-circuiting. A smaller numerical value of this parameter corresponds to a larger short circuit (Stamou 2002;Li et al 2006). The hydraulic characteristics in the separation chamber of the DAF tank could be represented by two stratified zones (Lundh et al 2000) of top white water zone and bottom clecir water zone as shown in Figure 2 (left).…”

Computational Fluid Dynamics in Drinking-Water Treatment

“…Several studies show that CFD serves as a powerful tool to optimise ozone contactors (Cockx et al, 1999;Huang et al, 2004;Li et al, 2006;Zhang et al, 2007). They showed that the hydraulics and/or microbial inactivation are improved by changing the contactor geometry.…”

“…Due to suboptimal hydraulics, different parts of the water receive a different ozone dose, which results in such a distribution. Several authors used CFD as a tool to optimise ozone contactors (Cockx et al, 2001;Huang et al, 2004;Li et al, 2006;Zhang et al, 2007). Therefore, hydraulic optimisations that increase the lowest ozone doses are very beneficial for the disinfection.…”

“…A disadvantage of the use of ozone is the formation of disinfection by-products, especially the production of bromate in bromide containing water is a point of concern (von Gunten, 2003a). Li et al (2006) used a particle tracking technique to determine the residence time distribution, but no disinfection calculation was made here. By Dutch legislation a maximum bromate concentration of 5 μg/L is allowed (90th percentile), or 10 μg/L if ozone is used as a primary disinfection barrier (VROM, 2001).…”