Evaluating Piping Layout Impacts on UV Dose Delivery

摘要

The Ultraviolet Disinfection Guidance Manual (UVDGM) provides technical information and guidance on design and operation of UV systems for receiving disinfection credit under the Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). An important topic in the UVDGM relates to inlet and outlet piping configurations installed in the full-scale UV facility and how they relate to the piping configuration used during validation testing and associated impacts on UV dose delivery. Several design approaches are cited in the UVDGM to ensure that "the inlet and outlet piping to the UV reactor in the UV facility results in a UV dose delivery that is equal to or greater than the UV dose delivered when the reactor was validated." The purpose of this paper is to present an alternative method for meeting the UVDGM dose delivery objective, while allowing for flexibility in the design of UV piping systems to meet project-specific design constraints. The proposed method involves use of physical or computational fluid dynamics (CFD) modeling to evaluate and optimize inlet hydraulics to the UV reactor until acceptable velocity profiles are achieved, and then verification of actual performance by taking measurements of inlet velocity profiles during validation and start-up of the full-scale UV facility. Conservative "acceptance" criteria for comparing these results are proposed to ensure improved UV dose delivery at full-scale. This method was applied to the design of a new UV disinfection facility for the Coquitlam Water Treatment Facility-an unfiltered gravity- fed water system owned and operated by Metro Vancouver in British Columbia, Canada.