How city wastewater could be used in the future LeBreton Flats development

Dream LeBreton's proposal for a 1.1-hectare parcel of land on LeBreton Flats includes two residential towers of 30 and 35 storeys. (National Capital Commission)

An Ottawa city committee is looking at a proposed plan to use municipal wastewater to help heat and cool apartment buildings at the future LeBreton Flats development without the use of fossil fuels.

A report prepared for the Environment and Climate Change Committee delves into the possibility of using a "wastewater energy transfer" or WET system to extract heat generated by wastewater and convert it to energy to aid in its goal of building a net-zero carbon development.

A similar technology is in use at the Zibi site, using heat generated by the Kruger plant in Gatineau and water from the Ottawa River to provide heating and cooling.

In this case, the proposed plan is to divert some of the city's wastewater to a separate area where heat energy is recovered before it is sent back into the sewer system. City staff say 545 million liters of wastewater are treated each day at the Robert O. Pickard Environmental Centre, before it is returned to the Ottawa River.

"Water, and sewage which is comprised mostly of water, has a relative high heat capacity. This means that a lot of thermal heat can be extracted per degree of temperature change in the wastewater and it can provide a more consistent source temperature and higher heat capacity than ambient air provides for an air source heat pump," the report states.

Staff say fossil fuel use in buildings is the city's largest source of greenhouse gas emissions and this plan could help reduce that footprint.

Council's involvement comes down to the relative newness of the technology. WET systems were not envisioned in the city's sewage bylaws, so the report is recommending committee and council authorize the general manager of infrastructure and water services, or a designate, to review and consider the approval of a connection to the city’s wastewater infrastructure to supply wastewater to a proposed WET system for the Dream LeBreton development.

According to the report, there are only a small number of similar projects in Canada. Vancouver's False Creek Neighbourhood Energy Utility is the only one currently in operation. One is under construction at Toronto Western Hospital, one is under construction in Halifax, and one is planned for a development in Mississauga.

The city has already entered into a memorandum of agreement with Theia Partners and Envari Holding to pursue the proposed plan, dubbed a pilot project because it would be Ottawa's first WET system, but council approval is needed before these groups will move on to a design phase. Theia is also involved in the Zibi development.

The plan would also require that the proponents of the WET system pay the city an energy transfer fee, based on how many litres of wastewater is used. City staff aren't expecting a great deal of revenue, however, estimating the fee would bring in between $15,000 and $42,000 per year.

If approved by the environment committee, the plan would go before council in April.

The WET system would be incorporated into the Dream LeBreton project, which includes more than 600 rental units in two high-rise towers, set to be completed by 2025. Construction is expected to start this year. According to the Canada Green Building Council, the Dream LeBreton project will be the country’s largest residential zero-carbon development.

Other developments, including an NHL arena for the Ottawa Senators and the city of Ottawa's new central library branch, are also part of the redevelopment of LeBreton Flats.