Full Description

A Calgon 36-in Sentinel ultraviolet (UV) reactor was selected to provide disinfection at the Rossdale WaterTreatment Plant (WTP) in Edmonton, Alberta. Nine Sentinel reactors were designed to fit in theexisting filter gallery, one after each filter. Each reactor has three10 kW Medium Pressure UV lamps. Due to the very restricted space, there was need for thereactors to be mounted in a unique vertical arrangement with limited straight piping upstream ordownstream of the reactors.The reactors were designed to achieve 3-log Cryptosporidium reduction under the Tier 2guidelines of the June 2003 Draft of the U.S. Environmental Protection Agency (USEPA) Ultra Violet Disinfection Guidance Manual(UVDGM) at maximum design flow of the filters, 92% UV transmittance and a 70% End ofLamp Life/Fouling factor. A number of issues such as maintaining steady state conditions, achieving adequate mixing withthe limited head available, piping alterations for discharging the effluent, etc. made on-sitevalidation difficult and expensive. Therefore, reactor performance was validated at the largescaleUV validation facility in Portland, Oregon with a piping configuration simulating that of theWTP. A test protocol was developed in accordance with the UVDGM that allowed interpolationof dose delivery and monitoring as a function of flow, UVT, and lamp output for measuredreduction equivalent doses (RED) ranging from 17 to 69 mJ/cmaup2/sup.Because the unique piping at the Rossdale WTP was anticipated to create an undesirable flowdistribution into the installed reactors, Calgon Carbon Corporation conducted a ComputationalFluid Dynamics (CFD) analysis of the proposed reactors to simulate their performance in all thevarious piping configurations at the plant. The CFD analysis performed with CFX software byANSYS, Inc. studied the influence that the various piping scenarios had on flow dynamics and,thus, reactor performance. Because performance was threatened, possible flow correctionsolutions were also studied. The effects of different flow-correcting baffle arrangements andtheir locations were assessed to maximize dose delivery.Based on the CFD analysis of flow correction, it was determined that two 9" baffles upstream ofthe reactors provided the highest degree of optimization. Further, the reactor treating Filter 5effluent was determined to administer a lower UV dose compared to the other reactors installedat the plant. Therefore, Calgon recommended that Rossdale WTP validate the Filter 5 piping inPortland with a dual 9" baffle plate as the most conservative case. Includes 3 references, tables, figures.

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Edition: Vol. - No. Published: 06/17/2005 Number of Pages: 13File Size: 1 file , 2.2 MB