New Validation Methods Account for RED Bias with Wastewater UV Reactors

The reduction equivalent dose (RED) measured during biodosimetric UV validation depends on the test microbe's UV dose-response kinetics as well as the reactor's UV dose distribution. Because of these effects, the RED delivered to the test microbe will differ from the RED delivered to a target pathogen or indicator microbe if the dose-response of the test microbe differs from that of the pathogen or indicator. The difference is referred to as the RED bias. Recently, two approaches have been developed and demonstrated with drinking water UV reactors for analyzing validation data that accounts for the RED bias. This paper reports on the application of these methods with a wastewater UV reactor. The first approach incorporates a term for the UV sensitivity of the microbe into the equation used to fit the validation data. The second approach incorporates a lognormal prediction of the UV reactor's dose distribution into the dose-monitoring algorithm and predicts log inactivation using the microbe's UV dose-response curve. Both approaches calibrated using validation data measured using MS2 and T1 phage provided accurate predictions of the log inactivation of QB phage, fecal coliform, and total coliform.