Demonstrating 4–log adenovirus inactivation in a medium–pressure UV disinfection reactor

Previous bench‐scale results demonstrated that polychromatic medium‐pressure (MP) ultraviolet (UV) disinfection could achieve 4‐log adenovirus inactivation at equivalent UV doses well below those required under the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). These findings were confirmed and extended to a full‐scale UV disinfection reactor using a live adenovirus challenge. The MP UV disinfection system was able to measure > 4‐log adenovirus disinfection at an MS2 coliphage reduction equivalent dose (RED) of < 100 mJ/cm2. The highest observed adenovirus‐based RED achieved, referenced to a low‐pressure (LP) UV dose‐response, was 233 mJ/cm2; the validated RED, including relevant validation factors, was equivalent to that required by the LT2ESWTR for 4‐log virus inactivation credit. These results proved that required virus disinfection doses can be validated and that MP UV is capable of meeting the 4‐log virus disinfection standard in the LT2ESWTR at a measurable and achievable UV dose substantially lower than that of LP UV technology.