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Bonnybrook Wastewater Treatment Plant Upgrades and Expansion

Calgary is a big city on a small river, and we continue to grow. This has meant increased amounts of wastewater created and a larger demand on our current wastewater treatment plants.

Bonnybrook Expansion Program

We are investing over $1 Billion in a program of extensive upgrades and expansions to the Bonnybrook Wastewater Treatment Plant, to protect the environment and accommodate our city’s future growth.

This program will:

  • expand the capacity of the plant to treat wastewater, from 950,000 to 1.37 million people and,
  • accommodate population growth until the mid-2030s, and,
  • increase energy efficiency and resiliency.

Aerial view of Bonnybrook Expansion Program

The Bonnybrook Expansion Program covers a large area and it is essential the plant continues to operate and treat wastewater while being upgraded.

Project Update – May 2021

The City of Calgary continues to work along the west side of The Bow River nearing completion of the new Bonnybrook outfall and emergency bypass channel. This infrastructure is an integral part of the flood protection plan for BWWTP.

Heavy construction, including the installation of underground utilities, will continue through to the fall of 2021, with some remaining landscaping work extending into 2022.

Of course, any construction required in and around the Bow River is being timed to adhere to the Alberta Government’s Restricted Activity Period, to ensure fish, their eggs and juveniles are protected from harm, including monitoring and controls to limit the introduction of sediment to the river.

Plant B and C capacity upgrades are now completed.

Plant D expansion

The Plant D expansion is the largest component of the Bonnybrook Expansion Program which will increase the total treatment capacity to approximately 1.4 million citizens. 

Plant D includes a number of key projects, including:

  • installation of three additional secondary treatment bioreactors and six additional secondary clarifiers to provide additional secondary treatment capacity.
  • installation of two new primary clarifiers for additional primary treatment capacity.
  • retrofits and upgrades to the existing solids handling digesters.
  • retrofits and upgrades to the existing ultraviolet (UV) disinfection facility.
  • installation of a new thermal hydrolysis facility for solids handing and the generation of bio-gas for the co-generation facility.
  • installation of new bio-gas handling and storage facilities.
  • construction of a new outfall to the river.

Here are specific details regarding the above key projects: 

2021 Outfall Construction

Aerial view of CN Rail Bridge and Outfall Control Structure looking south

The new outfall was commissioned and put into service in March 2021. 

It has been upgraded to accommodate increased flows from the plant due to the expansion. It is located just south of the Calf Robe Bridge and the CN Rail river crossing. 

The outfall was extended a further 900m downstream system to provide further flood resiliency and includes an improved diffusion system in the river to enhance environmental performance. The old plant outfall just north of the Calf Robe Bridge is no longer in use and has been decommissioned.  The old outlets by the Calf Robe Bridge have been concreted over. Landscaping and finishing work will continue through to the Fall of 2021 in the area adjacent to the Calf Robe Bridge extending south to the new outfall control structure south of the CN Rail Bridge.

Installation of three additional secondary treatment bioreactors and six additional secondary clarifiers

Phase one of these upgrades, consisting of the construction of two secondary treatment bioreactors and four additional clarifiers is scheduled to be complete in September of 2021. The addition of these systems will increase Bonnybrook’s treatment capacity to 1.4 million people, while contributing to the treatment of wastewater. 

Installation of two new primary clarifiers

New Primary Clarifier 16 (under construction - pictured November 2020) Retrofitted solids handling digesters in the background.

Construction of the two new primary clarifiers, which are used for additional primary treatment capacity, entered service in February 2021. 

The addition of two new clarifiers helps increase Bonnybrook’s treatment capacity to approximately 1.4 million EP and contributes to the treatment of wastewater itself.  Landscaping and finishing work will continue through to the Fall of 2021.

Retrofits and upgrades to the existing solids handling digesters

Upgrades and retrofits to Phase 1 of these upgrades is substantially complete.  All of Phase 1 was in-service as of May 2021.  Construction of Phase 2 started in February 2021 and is scheduled for completion in June 2023.

Retrofits and upgrades to the existing ultraviolet (UV) disinfection facility

Retrofitted UV Disinfection Facility in operation April 2021

These retrofits and upgrades will allow the UV Building to continue to disinfect treated effluent from Bonnybrook and is sized to accommodate  growth in north Calgary over the next 25 years. This key project is complete. 

Installation of new bio-gas handling and storage facilities

New Low Pressure Gas Holder in operation January 2021

The installation of new bio-gas handling and storage facilities is complete and the facilities are in service. 

These new storage facilities will assist and increase the capacity of the biogas system for the Cogeneration Facility at Bonnybrook.

Brief History

The Bonnybrook Wastewater Treatment Plant is the largest of Calgary's three wastewater treatment plants.

Originally built in the 1930s, Bonnybrook has undergone significant modifications and upgrades over time to increase its treatment capacity to meet the needs of a growing city. Bonnybrook serves the communities north of Glenmore Trail in the city, as well as Cochrane, Airdrie and the Elbow Valley.

Related Documents

Program timeline

Construction commenced in 2014 and continues to 2024.

Here are some of the key milestones achieved to date:

  • Summer 2016 – Plant D Digester upgrades began, with anticipated completion in summer 2022.
  • Fall 2016 – flood protection berm work began and is expected to be complete by fall 2021
  • Fall 2017 – completion of the Dewatering facility
  • Fall 2018 – complete Phase One of the electrical upgrades
  • Spring 2018
    • construction of Phase 1 of the Plant D Expansion Secondary Treatment process began, with completion anticipated by 2021. Phase 2 is scheduled for completion by the end of 2024
    • upgrade and retrofit of the Ultraviolet Disinfection Facility began, completion scheduled for September 2021
  • Summer 2018 – construction of new Plant outfall began, with completion anticipated in fall 2020
  • Winter 2018 – completion of the Plant B and C upgrades
    • 6 new secondary clarifiers.
    • replacement of mechanical equipment in existing clarifiers.
    • replacement of sludge pumps and pipework.
    • upgrades to the existing Dissolved Air Flocculation (DAF) facility. 
  • Summer 2019 – began construction of primary treatment expansion (2021 completion), new biogas storage facility (2020 completion), and cogeneration facility expansion (2021 completion)
  • Winter 2020 – The City of Calgary continues to work along the west side of the Bow River bank, building a new Bonnybrook outfall and emergency bypass channel.

Additional updates

A number of other projects that support the expansion program and the general reliability and efficiency of the plant:

  • modernization and expansion of the air blower facilities on site. The use of air is a vital component of the treatment process and improves energy efficiency and reliability.
  • replacement of old boilers in heating plant with high capacity, energy efficient ones.
  • a new fats, oils and grease facility that increases our capacity to receive these waste products and the efficiency of treatment.
  • a new treated effluent water facility. This facility takes treated wastewater and circulates it around the plant to support the treatment process. It also pumps treated wastewater to the ENMAX Shepard Energy Centre for use as cooling water.


Please call or submit a 311 Service Request. For media inquiries please call 403-828-2954