AWWA ACE61654

A Calgon 36-in Sentinel® ultraviolet (UV) reactor was selected to provide disinfection at the Rossdale Water Treatment Plant (WTP) in Edmonton, Alberta. Nine Sentinel® reactors were designed to fit in the existing filter gallery, one after each filter. Each reactor has three 10 kW Medium Pressure UV lamps. Due to the very restricted space, there was need for the reactors to be mounted in a unique vertical arrangement with limited straight piping upstream or downstream of the reactors. The reactors were designed to achieve 3-log Cryptosporidium reduction under the Tier 2 guidelines 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 of Lamp Life/Fouling factor. A number of issues such as maintaining steady state conditions, achieving adequate mixing with the limited head available, piping alterations for discharging the effluent, etc. made on-site validation difficult and expensive. Therefore, reactor performance was validated at the largescale UV validation facility in Portland, Oregon with a piping configuration simulating that of the WTP. A test protocol was developed in accordance with the UVDGM that allowed interpolation of dose delivery and monitoring as a function of flow, UVT, and lamp output for measured reduction equivalent doses (RED) ranging from 17 to 69 mJ/cm2. Because the unique piping at the Rossdale WTP was anticipated to create an undesirable flow distribution into the installed reactors, Calgon Carbon Corporation conducted a Computational Fluid Dynamics (CFD) analysis of the proposed reactors to simulate their performance in all the various piping configurations at the plant. The CFD analysis performed with CFX software by ANSYS, Inc. studied the influence that the various piping scenarios had on flow dynamics and, thus, reactor performance. Because performance was threatened, possible flow correction solutions were also studied. The effects of different flow-correcting baffle arrangements and their locations were assessed to maximize dose delivery. Based on the CFD analysis of flow correction, it was determined that two 9" baffles upstream of the reactors provided the highest degree of optimization. Further, the reactor treating Filter 5 effluent was determined to administer a lower UV dose compared to the other reactors installed at the plant. Therefore, Calgon recommended that Rossdale WTP validate the Filter 5 piping in Portland with a dual 9" baffle plate as the most conservative case. Includes 3 references, tables, figures.