Investigating Multibarrier inactivation for Cincinnati.

The Greater Cincinnati (Ohio) Water Works strives to continually improve the effectiveness of its water treatment processes. Questions regarding the vulnerability of the Ohio River watershed to microbial contamination and concerns about compliance with the Long Term 2 Enhanced Surface Water Treatment Rule led the utility to initiate an in-depth study of ultraviolet (UV) disinfection. The study was designed to determine how exposing treated Ohio River water to UV affected (1) the inactivation of Cryptosporidium parvum, bacteria, and viruses, (2)the susceptibility of these microorganisms to free chlorine after partial inactivation with UV, (3) the formation of oxidation and chlorinated disinfection by-products (DBPs), and (4) microbial regrowth (measured by assimilated organic carbon) following UV disinfection. Results indicated that UV alone or UV followed by free chlorine effectively controlled all microorganisms tested. Additionally, no evidence of increased DBP formation or regrowth was observed at UV doses typically used for disinfection. [ABSTRACT FROM AUTHOR]