AWWA WQTC71631

Metro Vancouver (MV) owns and operates the Coquitlam Water Treatment Facility (CWTF), which has a rated capacity of 1,200 ML/day (317 MGD) and treats water from Coquitlam Lake, one of the regions' three water supply sources. This gravity-fed unfiltered supply is currently treated by a process train that includes ozone and chlorine for disinfection and soda ash for corrosion control. Under the Coquitlam UV Disinfection Project, a new ultraviolet (UV) disinfection facility will provide a multi-barrier, sequential ozone-UV-chlorine disinfection strategy. Under this strategy, ozone will provide disinfection for 4-log virus inactivation and oxidation for improved UV transmittance (clarity) of the raw water and disinfection by-product (DBP) precursor reduction, UV will provide disinfection for 3-log Cryptosporidium and Giardia inactivation, and chlorine will provide disinfection to maintain a secondary chlorine residual in the distribution system. In addition, ozone will provide 3-log Giardia inactivation as a back-up disinfection barrier to UV, and chlorine will provide up to 2-log virus inactivation as a back-up disinfection barrier to ozone. This paper presents the results of the basis of design phase of the Coquitlam UV Disinfection Project. It includes a discussion of process design criteria, UV equipment selection, UV facility layout alternatives and results of the Basis of Design Decision Workshop. It also presents a discussion of hydraulic issues associated with the VPL system, including results of a physical model laboratory study undertaken to optimize inlet hydraulics to the individual UV units. Includes 5 references, table, figures.