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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.

Growth and Capacity

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.

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

Project Update

The City of Calgary will be removing the coffer dam in the Bow River that was put in place in 2018 for the installation of the in-bed diffusers for the new Bonnybrook Wastewater Treatment Plant Treated Effluent Outfall. This work will take place from April 6 - 30, 2019 and will be carried out by Whissell Contracting. This timing is outside the Alberta Government's Restricted Period in the Bow River to ensure fish, their eggs and juveniles are protected from harm. 

Increased sedimentation in the river during the removal of the coffer dam may occur. The work is being sequenced to minimize the amount of sedimentation and a turbidity curtain will be placed downstream of the coffer dam 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.

Improvements to the Bonnybrook Wastewater Treatment Plant

The program will upgrade existing facilities and equipment as well as expand treatment capacity. We are also improving resiliency and environmental performance, which will protect the Bow River for future generations.

Planned improvements include:

  • capacity upgrades to existing facilities plus improvements to essential equipment.
  • a new Plant D expansion, including new primary and secondary treatment facilities to further increase capacity.
  • upgrades to plant digesters which break down organic materials and generate biogas.
  • upgrades to ultra violet (UV) disinfection facilities which kill waterborne germs, pathogens and bacteria.
  • new outlet pipe (outfall) from the plant to the river.
  • flood resiliency work to prevent river back-up and overland flow into the plant during high water events.
  • expansion of the co-generation facility which converts bio-gas (generated from the wastewater treatment process) into electricity to power the plant.
  • construction of a new dewatering facility that produces biosolids to The City’s new composting facility. Biosolids will supplement the garden waste received from the Green Cart program.
  • modernize and expand the electrical distribution system, including a new power feed to the plant.
  • upgrades to improve energy efficiency and environmental performance.
  • lifecycle replacement of some existing equipment. 

Project Updates

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 will provide the first increase in treatment capacity and will be complete by the end of 2018. This will take the total capacity of the plant to over 1 million people. The Plant B and C capacity upgrades commenced in 2014 and is expected to be complete by the end of 2018.

The work consists 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 has been installed south of the CN Rail river crossing to isolate the working area and protect the river from the construction activities. This cofferdam will temporarily decrease the width of the river in this location. The cofferdam will remain in place until April 2019 when it will be removed and the river restored to normal conditions.

A buoy line has been installed to allow safer passage for river users. Boaters and rafters are advised to exercise caution and follow the signs provided while passing through the area as the water velocities will be higher than normal.

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 begins, with anticipated completion in summer 2022.
  • Fall 2016 – flood protection berm work begins and is expected to be complete by fall 2018
  • 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 begins, with completion anticipated by 2022, Phase 2 is scheduled for completion by the end of 2024
  • Spring 2018 – upgrade and retrofit of the Ultraviolet Disinfection Facility begins, completion scheduled for September 2021
  • Summer 2018 – construction of new Plant outfall begins
  • End 2018 – completion of the Plant B and C upgrades