Assessment of indigenous surrogate microorganisms for UV disinfection dose verification

This study aimed to isolate waterborne heterotrophic organisms indigenous to water treatment processes with suitable ultraviolet (UV) dose–response profiles for estimation of the UV doses delivered by operational UV disinfection systems. The UV dose–response profiles of two isolated organisms, Flavobacterium succinicans and Sphingopyxis chilensis , were determined. S . chilensis has a UV dose–response with potential for use as an indigenous surrogate for Cryptosporidium inactivation, up to 2.2‐logs in the dose range 2–7 mJ/cm 2 of monochromatic UV light at 253.7 nm. F . succinicans was more sensitive and tailing was observed above 4 mJ/cm 2 making it unsuitable for UV dose verification above this dose. As a single species in the water samples used in this study, S . chilensis is unlikely to be present in sufficient numbers for routine use as an indigenous surrogate. However, the Sphingomonadaceae family to which it belongs is abundant in various drinking water sources and warrants further investigation.