Synergies of UV Disinfection and Ozone in Water Treatment

Two case studies outlining the benefits of using ozone and UV are presented in this paper. They demonstrate the cost effectiveness and robustness that can be observed when the synergies of these two treatment alternatives are utilized. In the first study, ozone and UV disinfection were used at the Weber Basin Water Conservancy District’s Water Treatment Plant No. 3. The ozone system was designed to improve pretreatment, control taste and odor (T&O) compounds, and provide an additional Giardia barrier, while UV was used to provide 2-log of Cryptosporidium inactivation. The capital cost savings obtained by using this option, as opposed to using ozone alone, were nearly 50%. In the second study, the effectiveness of ozone and UV were assessed on the challenging water of Lake Okeechobee. With the goal of meeting all US Primary and Secondary Drinking Water Standards, the data analysis indicated that a combination of ozone and UV disinfection would result in the most cost-effective option. The use of ozone to reduce color and decrease UV transmittance (UVT) resulted in substantial cost savings by decreasing the ozone dose over what would be required to achieve Cryptosporidium disinfection and allowing for the elimination of an ozone contactor. Furthermore, the increase in UVT that was observed resulted in a smaller UV system, thereby reducing the cost of the overall system even further.