Full Description

Making an active approach to upcoming requirements of the Long Term 2 Enhanced Surface Water Treatment Rule, the Greater Cincinnati (Ohio) Water Works (GCWW) investigated ultraviolet (UV) disinfection as an additional treatment process for the Richard Miller Treatment Plant (RMTP). Currently, the facility treats Ohio River water with conventional treatment followed by granular activated carbon filters. RMTP has only a single inactivation barrier, chlorination, which has been shown to be ineffective for inactivation of Cryptosporidium. Given the inherent susceptibility of surface water sources to microbial contamination, GCWW believed a multibarrier approach would be effective. Results showed that UV alone or UV followed by chlorine effectively controlled all microorganisms tested. There were no apparent signs of synergistic effects between sequentially applied UV light doses and free chlorine. In addition, no evidence of increased disinfection byproduct formation or regrowth was observed at a UV dose typically used for disinfection. From both cost and benefit perspectives, UV represents an attractive technology for primary disinfection of drinking water. The treatment scenario evaluated in this article could be adapted by other water suppliers to address both site specificity and costs associated with safe-guarding supplies through multibarrier treatment.