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Bonnybrook Wastewater Treatment Plant Expansion Program

Expanding the world’s largest cold-weather BNR plant

  • 135M


  • $500M

    Construction Value

  • Calgary, Alberta

    Calgary, Alberta

Increasing Calgary's wastewater treatment capabilities

The Bonnybrook Wastewater Treatment Plant is one of the largest biological nutrient removal (BNR) plants in Canada and the largest cold-weather BNR plant in the world. Influent temperatures reach a minimum of 10 C with air temperatures as low as -40 C in the winter.

Population growth and increasingly stringent treatment standards have been the primary drivers for numerous plant expansions since it was constructed in 1932. Currently, the plant provides treatment up to an average capacity of 396 ML/d and peak capacity of 1,069 ML/d to serve 946,000 Equivalent Population (EP), but it is nearing its installed capacity.

Upgrade projects for Secondary Plants B and C are complete and operational which provide the capacity needed for the near-term population growth in Calgary. Parallel to these upgrades, Stantec led the design of a full treatment plant expansion (Plant D) which increases the installed capacity by another 325,000 EP (135 ML/d). Peak flow capacity increased to 1,390 ML/d.

The project includes upgrades to primary influent conveyance, primary treatment, primary effluent conveyance, BNR process, secondary clarification, effluent filtration, UV disinfection, plant outfall, chemical and process utility systems, secondary sludge thickening, secondary sludge dewatering, thermal hydrolysis of dewatered waste activated sludge, sludge digestion, and biogas management.

At a Glance


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