Innovative Use of Existing Infrastructure for new Ultraviolet Disinfection provides sustainable and economical solution for City of Medicine Hat

UV reactor piping

The City of Medicine Hat, Alberta has recently undertaken an expansion of their Water Treatment Plant to increase firm production capacity, treated water quality, and pathogen reduction through disinfection. Associated Engineering provided predesign, design, and contract administration services for the Plant 5 expansion and Ultraviolet addition.

Originally constructed in 1911, the Medicine Hat Water Treatment Plant has undergone several expansions over the years. Associated Engineering assisted the City with their last Water Treatment Plant Expansion in 1994/1995 with the addition of Plant 4 and, most recent- ly, with the Plant 5 expansion and the addition of UV disinfection as part of this expansion. The Plant 5 expansion will accommodate future growth in the city, up to a population of 75,000 and the UV disinfection system will ensure the city meets new environmental standards for water quality.

Although chlorine gas has been used as the primary disinfectant in potable water plants for over one hundred years, new Alberta Environment Standards and Guidelines for Municipal Waterworks introduced in January 2006 require higher levels of pathogen inacti- vation than could be reasonably obtained using chlorine. To provide the increased pathogen reduction, the city decided to integrate a UV disinfection system at the Medicine Hat Water Treatment Plant. The UV system was commissioned in the fall of 2007 with the final com- missioning of the entire upgrade in the summer of 2008. Project Manager Bill Chisholm states, “The addition of UV to the existing process allowed the City to achieve 5.5 log inactivation of Giardia and Cryptosporidium pathogens (a minimum of 3.0 log removal is required in accordance with the new standards).”

The UV disinfection system includes conversion of the existing secondary clearwell to a dry chamber to house the new UV disinfection sys- tem. Integration of the UV equipment into the existing secondary clearwell below Plant 4 provided a more sustainable, economical, and viable solution than other alternatives, and achieved economic and space savings by re-using existing infra- structure. Equipment installation, however, was more difficult in the secondary clearwell. 1500 millimetre pipe spools with multiple tee branch- es had to be manoeuvred through two existing standard-sized doors and lowered through an opening cut through the floor which required precision measurements and rigging methods to accomplish. The clearwell had a manganese dioxide residue coating the existing walls after twelve years of operation which had to be removed before the surfaces were sealed.

With the addition of the Plant 5 upgrade, a duplicate of the Plant 4 clarifier and filters, the primary process is made up of pre-treatment chemical addition, five solids contact clarifiers, twenty dual-media filters, disinfection, clearwell contact time, three UV trains, and high lift pumping. Prior to decommissioning the secondary clearwell, the new Plant 5 clearwell needed to be constructed and commissioned to maintain adequate on site storage and disinfection time during higher plant flows. The implementation plan included short notice evacuation plans to deal with high demand events that would require the secondary clearwell to be temporarily put back into service. The plant shutdowns were limited by plant operations to a 24 hour productive work window followed by a 24 hour period to replenish water supplies in the City reservoirs.

Members of the AE team include Bill Chisholm, Gord Roberts, Doug Olson, Risto Protic, Corinne Arkell, Marvin Akister, Louis de Lange, and Scott Witzke.

Pitt River Bridge construction is proceeding on schedule

Photo left: (L to R): Executive Assistant, Karen Kinakin; Burnaby Receptionist, Ginny Gerry; and Project Administrator, Marie Chandler inspect bridge construction	Directors (L to R) Rod Karius, Doug Olson, Herb Kuehne, Elizabeth Dowdeswell, Allan Scott, and John Fussell tour the Pitt River site.

Construction of the $200 million Pitt River Bridge in Pitt Meadows in the Lower Mainland area of BC is well underway. The project has provided opportunities for our staff to see construction of a world- class, cable-stayed bridge first hand. John Fussell, Vice President, Transportation has led tours for our Bridge Discipline Group, Young Professionals, Board of Directors, and administrative staff. The project is on schedule for completion in November 2009. For more information on the project see AE Today 2008, issue 3.