AWWA JAW56398

Using and selecting microbial surrogates to validate ultraviolet (UV) reactor performance can be a challenging prospect. Water suppliers must recognize both the importance of the relative UV dose-response of the surrogate and target organism and the limitations inherent in using surrogates. This study set out to improve the industry's understanding of how MS2 coliphage can be used as a bioassay surrogate for the waterborne pathogen Cryptosporidium parvum. Side-by-side MS2 and Cryptosporidium bioassays were performed to directly link MS2 and Cryptosporidium inactivation. Although MS2 proved to be a reasonable test organism to validate UV reactor performance, it provided a very conservative estimate of the inactivation that can be achieved with organisms that are very sensitive to UV, such as Cryptosporidium. A more-sensitive test organism would allow much higher levels of inactivation to be validated. Water utilities should carefully consider how conservative their test pathogens must be to meet health protection goals in the most cost-effective manner. Includes 9 references, tables, figures.