Bonnybrook wastewater treatment plant switches to renewable energy

Through a newly introduced expansion, the Bonnybrook treatment plant will now be largely energy self-sufficient. The new upgrades will separate biogas from wastewater so that it can be used to fuel the treatment plant, reducing fossil fuel consumption.

Bonnybrook is the largest of Calgary's three wastewater treatment plants, and it serves the north side of the city. Throughout its history, Bonnybrook has gone through multiple upgrades and expansions to fit Calgary's growing population.

The current expansion is said to increase the plant's capacity by 30 percent, and will include flood prevention measures. An aspect of the upgrades will be to implement a co-generation energy project that will reduce utility costs and greenhouse gas emissions. The upgrade will expand the plant's power generation and heating facility through two new turbines.

The plant will also capture biogas, a byproduct of the wastewater treatment process. Biogas is a free and renewable source that will be used for power generation and heating. Biogas will substantially reduce utility costs, as the plant will not have to rely on fossil fuels for power.

Orin MacIntyre, leader of wastewater treatment engineering with utility delivery at the City of Calgary, spoke more about how the biogas process takes place.

"At Bonnybrook, we separate the organic matter from the wastewater, and we have a separate treatment process where we take that organic matter and break it down into methane through the use of microbes. These microbes are similar to the ones found in your stomach, and they do a lot of the work in your own digestive system," he said.

"The microbes break the organic matter down into methane, which is the biogas. We then put it into a combustion turbine similar to natural gas. On a regular day without biogas, we would be importing electricity from the grid. Now, rather than doing that, we use the biogas to offset our consumption."

This new upgrade is also eco-friendly, as it reduces the greenhouse gas emissions made by the plant.

"The new system will reduce Bonnybrook's greenhouse gas emissions by about 17,500 tCO2e/year by reducing natural gas use and electricity import, minimizing biogas flaring, and improving plant energy efficiencies," he said.

"This is roughly the equivalent of taking 5,600 cars off Calgary's roads."

MacIntyre says that this upgrade can also give back to the city in another way.

"We are capable of giving back electricity to the grid, although we don't really intend to do that a lot. Our current system is sized to maximize all the biogas that we’re creating through our digestion process, and so we’re maximizing all that biogas potential right now," he said.

"Essentially, it means that we’re greening our electricity. Rather than buying off the grid, we are making our own green electricity and reducing our consumption for the plant's functions."

The upgrades and expansion projects were started in 2015, and all projects are slated to be completed by 2030. For more information surrounding the upgrades, visit the City of Calgary website.

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