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Bonnybrook Wastewater Treatment Plant Upgrades and Expansion

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.

Photo Gallery - Unclassified

  • The proposed filtration treatment facility will improve the filtered effluent quality
  • The thermal hydrolysis process building will heat and pressurize solids to reduce the amount of solids generated by the plant. This plant is the first of its kind in Canada, and the second in North America

About the Project

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.

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.

Project Update - August 2019

The City of Calgary will be working along the west side of the Bow River bank to build the Bonnybrook emergency outfall channel, which is an integral part of the flood protection plan for the Bonnybrook WWTP. This work will take place from July 15, 2019 to September 16, 2019 and will be carried out by KLS Earthworks & Environmental. This timing is outside the Alberta Government's Restricted Activity Period in the Bow River to ensure fish, their eggs and juveniles are protected from harm.

Increased sedimentation in the river during the construction of the emergency outfall channel may occur. The work is being sequenced to minimize the amount of sedimentation and a turbidity curtain will be placed downstream of the work site to further reduce sedimentation in the river. If the levels of turbidity in the river begin to exceed guideline levels, all work will be slowed or stopped entirely until the sediment subsides.

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.

Plant B and C capacity upgrades

Plant B and C capacity upgrades

The upgrades at Plants B and C are now complete.

The work consisted of:

  • 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.

Plant D expansion

The Plant D expansion is the largest component of the Bonnybrook Expansion Program and 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.
Plant D expansion  

Outfall Construction and Flood Resiliency  

Outfall Construction and Flood Resiliency

This new outfall is being upgraded to accommodate increased flows from the plant due to the expansion. It will be located just south of the Calf Robe Bridge and CN Rail river crossing. The outfall is also being extended a further 900m downstream system to provide further flood resiliency and includes an improved diffusion system in the river to enhance environmental performance.

To allow the installation of the new effluent diffusers in the river bed, a cofferdam was installed south of the CN Rail river crossing to isolate the working area and protect the river from the construction activities. This cofferdam was removed in April 2019 and the river was restored to normal conditions. Additional in river work is also required to build the emergency outfall channel that will help mitigate the risk of flooding at the Bonnybrook WWTP.

In addition to the new outfall, we are constructing a new flood protection berm on the east side of the plant site. This will help prevent overland flooding of the site. The berm work also includes a new section of river pathway.

Dewatering facility

This facility removes water from anaerobically digested biosolids from the Plant, and is taken to The City's new composting facility.

This facility was built in collaboration with Waste & Recycling Services to ensure approximately 10,000 dry tonnes of biosolids will be processed annually. The facility was commissioned on schedule and began delivering biosolids to the composting facility in October 2017.

Dewatering facility  

Co-generation facility expansion  

Co-generation facility expansion

One of the key improvements to the plant, is the expansion of the existing power generating and heating (co-generation) facility. The existing facility uses bio-gas, which is a by-product of the wastewater treatment process, and turns it into electricity to power the plant and steam to heat it.

Benefits of this expansion:

  • a highly efficient and flexible system that will enable the plant to approach energy self-sufficiency.
  • significant step forward in the use of bio-gas to efficiently generate steam and electricity for the plant.
  • use all current and future amounts of bio-gas produced by the plant to generate steam and electricity
  • anticipated to produce enough electricity to meet most of the electrical demands of the plant, and during low demand periods may export electricity to Alberta’s power grid.
  • a significant reduction in the emission of greenhouse gas from operation of the plant.

Electrical upgrades

These upgrades are required to enhance capacity and increase reliability of the Plant. This includes:

  • Upgrades to the plant’s electrical systems.
  • a new power feed from the grid to enhance reliability and capacity.
  • a new power management system to monitor and optimize the use of power on site.
  • equipment to allow export of power from the plant.

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

Program timeline

Construction commenced in 2014 and continues to 2024. Below is a summary of some of the key milestones for the program.

  • 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
  • Spring 2018 – 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
  • December 2018 – completion of the Plant B and C upgrades
  • Summer 2019 – began construction of primary treatment expansion (2021 completion), new biogas storage facility (2020 completion), and cogeneration facility expansion (2021 completion)