Integrated Optimization Of Ozone Contactor

Ozonation has become widely used in drinking water treatment due to ozone's strong disinfection capability on Cryptosporidium parvum oocysts and Giardia lamblia oocysts, which have strong resistance to chlorine. However, ozonation of bromide-containing water produces bromate, a human carcinogen regulated in China. Ozone contactor design is of crucial importance since disinfection efficiencies are greatly determined by the CT value, and poor contactor design may lead to low hydraulic efficiency and unevenly distributed ozone concentration.Firstly ozone bubble column was taken as the research object,a numerical model was developed based on computational fluid dynamics (CFD) technique which integrated ozone gas-to-liquid phase transfer, diffusion and decay. Bubble column experiments were conducted and results showed that the model could predict the concentration distribution with acceptable accuracy.Secondly the model was applied to optimize contactor configurations based on CT value. Results showed that both guide plates (GP) and horizontal baffles (HB) could improve the CT value, which agreed with the results based on mere hydraulic efficacy, namely T10/HRT. HB improved the CT value by 36.1%, much higher than the 9.4% of GP. However, the combination of GP and HB only achieved 27.9% improvement. The height of HB from the bottom of the tank influenced the effect of HB on CT value. 2.5m was more effective than 2.0m and 3.0m.Finally, a new ozone contactor was developed based on all simulation work. Simulation result showed that the hydraulic efficiency was greatly improved and a plug flow was approximately achieved with T10/HRT being 0.83.