Multiple Reactor Validation Under the UVDGM
Abstract:Three large WEDECO potable-water disinfection systems were subjected to validation testing closely following the Ultraviolet Disinfection Guidance Manual (draft) (UVDGM, USEPA, 2003). This third-party validation testing was conducted by HydroQual, Inc. at the UV Validation and Research Center of New York, Johnstown NY (UV Center). HydroQual, Inc. wrote the validation test plan, installed and operated the units, conducted all testing and laboratory analyses, and prepared the final reports detailing the Tier 1 validated disinfection performance of the reactors. The purpose of this presentation is to give an overview of the validation and to summarize four significant aspects of the results.
First, a series of technical tests were oriented to validating and characterizing the behavior of each WEDECO disinfection system. Such testing resulted in data relating the intensity (fluence rate) to the lamp-power setting at various UV transmittance levels, and in detailed power measurements at the full range of lamp-power settings. The uncertainty of the intensity sensor was validated by comparison to six reference sensors with very favorable results, and headloss data were acquired over a wide range of flow rates.
Second, biodosimetric flow tests were conducted with MS2 bacteriophage to determine the credited performance of each reactor at UV transmittance levels in the range of 65% to 98%, and at a range of flows up to 15 mgd. Flows were conducted at intensities reduced from that present with new lamps at 100% power to simulate end-of-life conditions. Worst-case hydraulic conditions were simulated with elbows on the inlet and outlet flanges. A family of four curves was generated for each reactor where the credited Reduction Equivalent Dose (RED) is a function of flow rate at each UVT.
Third, each of the 17 Tier 1 assumptions presented in the UVDGM was evaluated. This work presents an analysis of the assumptions related to the dose-response uncertainties from dose calculation and some of the uncertainties associated with the biodosimetric flow tests.
Finally, a subset of flow tests was conducted using the alternative challenge bacteriophage Qâ and the results are compared to those from MS2. This allows a preliminary evaluation of the RED bias of the disinfection system and the RED bias assumptions presented in the UVDGM.
Document Type: Research Article
Publication date: January 1, 2005
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