Considerations for Combining Ozone and UV Disinfection

One of the principle goals of water treatment is to produce drinking water that is safe from microbial contaminants and disinfection by-products. The promulgation of the Long Term 2 Enhanced Surface Water Treatment Rule places more stringent performance demands on disinfection systems and have, therefore, increased the need for improvements in the design of such systems. The discovery that Cryptosporidium, Giardia, and other waterborne pathogens can effectively be inactivated by UV light has utilities considering adding UV treatment to their existing system to meet the LT2ESWTR requirements. Many of the utilities may already have an ozonation system in place. This paper describes the design considerations for combining ozone and UV disinfection.