Nov 01, 2006

New UV Treatment Systems Improve Water Quality

The city of Kelowna, located in British Columbia, recently unveiled new ultraviolet (UV) water treatment facilities at its Poplar Point, Eldorado, and Swick Road intakes on Okanagan Lake, which are providing improved drinking water to customers in north, central and south Kelowna.

The $7.1-million project involved retrofitting UV treatment into existing intake pump stations and chlorination facilities while maintaining operation of the facilities to ensure continued water supply to the city. With the addition of UV reactors, the city’s water utility is now providing its customers with a two-stage disinfection system consisting of UV primary disinfection followed by chlorination.

Kelowna’s water utility supplies water to more than 50,000 residents and 1,700 industrial, commercial and institutional properties.

The raw water source is Okanagan Lake, with four intake locations. Previously, water treatment had been limited to chlorine disinfection; however, in recent years, concerns over water quality and protozoa such as Giardia and Cryptosporidium have led the city to seek enhancements to the primary disinfection system at all intake locations.

The city hired Associated Engineering to design the upgrades. The city’s primary reason for selecting the firm was its innovative approach, which involved relocating the UV treatment equipment from the discharge side to the suction side of the high lift pumps. This approach reduced the risks associated with high operating and transient pressures, and reduced any concerns associated with UV lamp breakage.

The largest and most challenging of the three facilities was the Poplar Point site, which is the city’s primary water supply and treatment facility. The Poplar Point site consisted of two high lift pump stations and a chlorination building located on a confined site immediately adjacent to Okanagan Lake.

 

UV system installation

The scope of the project included providing increased intake capacity and increasing the overall facility’s design capacity to 39.6 million gal per day. The challenge for Associated Engineering’s design team was to find a way to integrate the UV treatment facilities into this extremely constrained site, while improving suction side hydraulics to the high lift pumping system and providing an opportunity for the city to add future filtration.

The ultimate solution was developed through some innovative thinking by Associated Engineering’s Sean Bolongaro and the city of Kelowna’s Adrian Weaden. The solution involved transferring existing high lift pumps from the oldest high lift pump station to the newer facility. The footprint of the old station was used to accommodate a new intake connection, low lift pumps and UV equipment. A new interconnection structure was installed to tie the new facilities to the existing intake pipe on the suction side of the high lift pump station.

To address the city’s energy efficiency objectives, the design and contracting strategy included a number of energy-efficient design features, such as using lake water as the building’s heating and cooling energy source.

 

Sinking the new intake

The project was scheduled to allow the components impacting water delivery capacity to be constructed during the low-demand winter months, thereby ensuring that the city could maintain full water supply throughout the construction period.

To address the project’s unique scheduling and operational challenges, the implementation strategy involved a collaborative effort involving the supplier, the installation contractor and the city. The city took on responsibilities for certain construction components as well as programming and controls integration. The supply of the UV equipment was tendered and awarded to Calgon Carbon Corp., and additional responsibilities included in the construction contract were awarded to Graham Engineering and Construction, Inc.

Construction began in January 2005. The transfer of pumping equipment, demolition of the existing pump station, and excavation and construction of the substructure for the new UV disinfection facility was then completed by the end of the winter.

The 1,600-mm-diameter intake was floated and sunk to a depth of 30 meters in May. Construction of the new superstructure and installation of the low lift pumps and UV equipment and associated electrical and mechanical work was completed by the year’s end. The city then completed the programming and controls integration to allow the new facilities to be commissioned in a staged manner at the three sites in early 2006.

When asked about system performance near the end of a several-week hot spell, City Project Manager Robin Barnes said, “Despite having record water demands, the new facilities met all supply and treatment requirements. We have been pleased with the performance of the overall system.”

 

About the author

Bill Harvey, P.E., is project manager, water supply and treatment for Associated Engineering. He can be reached at 250/763-3638 or by e-mail at [email protected].

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