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Development of UV Testing Protocol and Recommendations
Citation:
Adams, Jeff. Development of UV Testing Protocol and Recommendations. To be Presented at ASDWA Annual Conference, Norfolk, VA, October 16 - 19, 2017.
Impact/Purpose:
Public water systems (PWSs) have implemented ultraviolet (UV) disinfection for the inactivation of regulated pathogens in accordance with the requirements of the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) and the Ground Water Rule (GWR), and the guidance provided by the Ultraviolet Disinfection Guidance Manual (UVDGM). Since the UVDGM was published in 2006, there has been considerable advancement in the understanding and application of UV technologies, particularly in the area of UV dose monitoring and validation. The purpose of this document is to present new protocols for UV implementation that leverage these advances and may help to reduce UV disinfection costs and improve ease of implementation and operation at PWSs. This document also provides for clarifications and updates to the UVDGM based on the advances achieved in the UV industry since its publication. The audience for this document includes UV system manufacturers, validators, consultants, utilities and regulators. UV system manufacturers and validators are provided detailed information for defining, validating, and implementing four new calculated dose monitoring algorithms. These approaches may provide utilities with more cost-effective and simpler UV implementation. Regulators are provided details on the new approaches, including checklists and validation report outlines that can be used as the basis for approving systems. Regulators are also provided clarifications on the UVDGM that support approaches currently being used but not documented in the UVDGM.
Description:
The goal of this effort is to develop and present new protocols for UV validation testing and analysis that leverage advances and may help to improve implementation and operation at PWSs. This document also provides for updated clarifications to the UVDGM based on evolving practice in the UV industry since its publication. The new protocols from this effort should not be construed as a replacement to the 2006 UVDGM but rather additional approaches for consideration. This effort focuses on calculated dose approaches. The approach predicts microbe log inactivation as a function of UVT and a combined variable defined as (S/S0)/(Q DL) where DL is the UV dose per log inactivation of the microbe whose log inactivation is being predicted. In theory, the equation can be calibrated using validation conducted with MS2 phage alone and can be used to directly predict the log inactivation of the regulated pathogens, Cryptosporidium, Giardia, and viruses. In practice, we recommend calibrating the equation using validation data sets collected using MS2 and T1UV phage as challenge microorganisms. The validation report should provide an analysis which shows that the equation calibrated using MS2 phage predicts T1UV log inactivation and vice versa. This analysis will provide confidence that the calculated dose approach using the combined variable can directly predict the log inactivation of the targeted or regulated pathogen effectively.