Wastewater Heat Recovery
& Flow Energy Management

Heat Recovery

Resource recovery, part of our wastewater management strategy, could also take the form of heat recovery. This heat could be used at the plant site or in a community or institutional heating system.

Where does the heat come from?

Our sanitary sewer pipes run warm with wastewater. This heat energy, as well as the energy of wastewater flow itself as it travels from source to treatment plant, is currently an untapped energy resource. Heat taken from wastewater lines could help heat residential and institutional boilers and save fuel. Potential customers for this heat energy could include local hospitals, the University of Victoria or the Provincial Government. Future building developments could also utilize this energy, by planning for district heating which could incorporate wastewater heat. Heat could also be used in the wastewater treatment plant itself, helping to lower operating costs.

Where is the CRD's heat demand?

Heat Recovery

Demand for heat is largest near district heating systems (boilers systems), where the temperature of wastewater would be sufficient to heat buildings to a comfortable level for most of the year. Boiler systems make the most sense when utilizing wastewater heat because their large scale can more effectively use the heat. When analyzing heat demand, land use, floor area ratios and energy demand for buildings were used to create a map of potential heating opportunities.

Where will energy recovery take place?

Heat recovery works best when situated in a location where there is sufficient heat in the wastewater system to supply energy and where there are a number of consumers who can benefit from the heat. These areas tend to have:

  • High density (commercial or residential development)
  • Institutional structures (such as hospitals or universities)
  • Redevelopment potential
  • Presence of hot water boilers (not steam)

Based on these characteristics, 38 energy recovery areas were selected. Details on the areas can be found in the full version of Discussion Paper 036-1. Once selected, these areas were analyzed for greatest potential. Areas were ranked based on a number of criteria, including:

  • Supply of source heat
  • Amount of heat demand
  • Boiler availability
  • Demand development timing
  • Number of parties involved
  • Treatment and energy recovery potential
  • Reuse production
  • Suitability of reuse demand
  • Combined environmental considerations

Some of the 38 areas have great potential for resource recovery, while others may not be as successful.

Next Steps

The next step will be to determine how to create viable distributed treatment plant facilities that can take advantage and provide opportunity for the most promising of these 38 areas. This will involve creating a number of distributed treatment plant scenarios and evaluating them for greatest success. Success will be measured based on the CRD's triple bottom line methodology, which takes into account financial, social and environmental factors, as well as potential revenue from resource recovery.

Flow Energy

Ocean

Once wastewater leaves a home or business, it can often take a great deal of energy to convey it to a treatment plant. Flow energy management looks at alternatives that aim to reduce the pumping energy required to convey wastewater to a plant. Recent technologies, such as turbines or pump turbines, also can harness the flow of wastewater itself, turning flow energy into a power source.

Wastewater Flow Management

Flow energy savings can be achieved through:

  • Locating wastewater treatment facilities at low elevations to minimize or avoid pumping
  • Maintaining high water levels in pump station wet wells to minimize the height wastewater is lifted
  • Installing low flow plumbing devices to reduce the amount of wastewater that passes through sewer pipes
Pressure Energy Recovery Technology

Pressure energy uses a mechanical device such as a turbine or pump as turbine to capture energy contained in flowing water. Pumps and turbines are installed inside wastewater pipes; these technologies are in use in large hydro projects but are not currently being marketed for use with raw wastewater.

Flow Energy Recovery Potential

The topography of the CRD Core Area is favourable for flow energy recovery—40% is estimated to be recoverable using in-pipe turbines.

The regional potential for energy recovery was calculated based on the scenario of a large wastewater plant in the Macaulay/McLoughlin area and smaller distributed facilities in the West Shore and Saanich East areas. Using dry weather flow rates, energy recovery would amount to approximately 305 MWh today and 540 MWh in 2065. This could provide enough energy to power approximately 30 and 50 households.

© Image courtesy of Cheyenne Glasgow