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Innovative Approaches for Validation of Ultraviolet Disinfection Reactors for Drinking Water Systems
Citation:
Wright, H., M. Heath, T. Brooks, AND Jeff Adams. Innovative Approaches for Validation of Ultraviolet Disinfection Reactors for Drinking Water Systems. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-20/094, 2020.
Impact/Purpose:
Public water systems (PWSs) implement 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. This documentation presents new approaches and procedures for monitoring and validation that leverage these advances. The contents of this document meet the requirements of the LT2ESWTR and conform to the underlying principles of the UVDGM. These additional approaches and recommendations are presented for consideration when applying UV disinfection for the inactivation of Cryptosporidium, Giardia, and viruses. The beneficiaries for this document include UV system manufacturers, validators, consultants, utilities, and regulators. Detailed information is presented on designing test plans, conducting evaluations, and reporting of results associated with four new UV calculated dose monitoring approaches. These methods and procedures may provide utilities with more cost-effective and robust implementation of UV disinfection. In addition, checklists and validation report outlines are presented to aid Regulators in approving systems. This document also provides recommendations on general procedures and reference documentation that support approaches currently being used but not documented in the UVDGM for validating and operating a UV system.
Description:
Public water systems (PWSs) implement 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. This documentation presents new approaches and procedures for monitoring and validation that leverage these advances. The contents of this document meet the requirements of the LT2ESWTR and conform to the underlying principles of the UVDGM. These additional approaches and recommendations are presented for consideration when applying UV disinfection for the inactivation of Cryptosporidium, Giardia, and viruses. The beneficiaries for this document include UV system manufacturers, validators, consultants, utilities, and regulators. Detailed information is presented on designing test plans, conducting evaluations, and reporting of results associated with four new UV calculated dose monitoring approaches. These methods and procedures may provide utilities with more cost-effective and robust implementation of UV disinfection. In addition, checklists and validation report outlines are presented to aid Regulators in approving systems. This document also provides recommendations on general procedures and reference documentation that support approaches currently being used but not documented in the UVDGM for validating and operating a UV system. Detailed approaches and procedures include: Microbial methods and dose-response QA/QC bounds for commonly used microbial surrogates in UV reactor validation; including MS2, T1UV and T7 phage, which are currently used with a majority of validations conducted per the UVDGM, as well as B. Pumilus spores, currently used to validate UV reactors for high dose applications; Approaches for the development of calculated UV dose monitoring algorithms with improved accuracy that eliminate the need for RED bias factors; Approaches for the development of UV dose monitoring algorithms that do not require an online UV transmittance monitor for simplified UV system operations; For UV reactors equipped with medium pressure UV lamps, implementation of “low wavelength” UV sensors and approaches for the development of UV dose monitoring algorithms that account for the disinfection associated with wavelengths below 240 nm; Criteria for the development of a robust validation test matrix, monitoring algorithm goodness of fit and QA/QC requirements, and standardized approaches for defining the validated range of UV reactors; Target UV doses for 4.5, 5.0, 5.5 and 6.0 log inactivation of Cryptosporidium, Giardia and virus for UV applications requiring higher levels of disinfection than the maximum 4.0 log presented in the UVDGM; General validation and data analysis procedures that are commonly implemented in UV reactor validation but are not explicitly documented in the UVDGM; Modifications to the operating recommendations of the UVDGM to improve the accuracy of UV dose-monitoring with the water treatment application.