Canadian Company Extracts Heat From Raw Sewage

Canadian Company Extracts Heat From Raw Sewage
The SHARC system can capture about 90 percent of lost energy, which is then transferred to domestic hot water or hot water heating systems.

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International Wastewater Systems of Burnaby, British Columbia, is putting its own twist on the recovery of heat from sewage and wastewater. The company’s SHARC system employs sewage filtration to ensure that heat recovery works equally well for both raw sewage and wastewater. The system is also scaleable, from smaller multi-dwelling buildings to larger installations that can tap the heat from municipal sewer systems. 

A study conducted by the U.S. Department of Energy in 2005 estimated that 350 billion kilowatt-hours of heat energy disappears down the country’s drains each year. With the help of a heat exchanger, the SHARC system can capture about 90 percent of that energy, which is then transferred to domestic hot water or hot water heating systems. 

The SHARC can be installed in new buildings or retrofitted, and can be paired up with either an existing or IWS-supplied geothermal system, which can store excess heat energy until needed. 

“We’ve been offering the system for about four years now and have already gained industry acceptance,” says Lynn Mueller, IWS founder and president. 

System design

For a typical condominium or apartment building, the system is designed around a fiberglass tank capable of holding 2,000 to 3,000 gallons of sewage and wastewater. 

“We bury it under the P1 parking level, where it can still drain by gravity into the sewage system,” Mueller says. “It’s a very predictable flow, with no wild swings in volume or temperature. Water would normally leave the building at temperatures between 70 and 77 degrees F.” 

The SHARC system pumps the warm fluid, while filtering raw sewage to a state where it can pass easily through the heat exchanger. The heat is then transferred to domestic hot water or water used for radiant heat. 

After the heat has been extracted, a solids-handling pump recombines the solids with the cooler wastewater, which drains into the sewer system. 

Mueller points out that the waste and fresh streams of water never come into contact — only energy is transferred though the double-walled heat exchanger. 

The SHARC system can also perform double duty, disposing of excess heat collected by an air conditioning system, for example, by transferring that energy to outgoing sewage. 

Mueller ballparks the cost for a 200-unit residential building system at between $200,000 and $300,000.

“On a project that size, it typically takes between three and five years to break even,” he says. “Larger-scale projects can accelerate the break-even point, because even on a building of 600 to 700 units, capital costs don’t go up.” 

Plan of attack

The company’s sales contract includes remote monitoring via Internet and quarterly service calls where the units are inspected and the heat exchangers backflushed. “We also replace such components as screens and wiper blades annually,” Mueller says. “Although we haven’t seen them fail, they are inexpensive to replace.” 

In 2012, IWS installed a SHARC system in the 60-unit seven35 townhouse complex in North Vancouver. The installation was completed on behalf of Adera Development Corp. and provides the units with domestic hot water. The system helped the project earn Leadership in Energy and Environmental Design Platinum and Built Green Gold ratings and allowed the complex to decrease energy consumption for water heating by 75 percent. 

Adera ordered another SHARC for its Sail project, a 172-unit condominium located in Vancouver. The system generates 220,000 Btus per hour and produces both domestic hot water and radiant floor heating. 

Mueller says the company is working worldwide on installations that include locations in the United States, Australia and the United Kingdom. Hospitals and correctional facilities are prime candidates for the technology because of their intensive hot water use. On a recent large private hospital project where expensive electric hot water heaters were used, he estimates that the break-even point for an $800,000 system was achieved in as little as six months. 

Municipal potential

A recent project in Richmond, British Columbia, demonstrates the potential of the technology for municipal sewer and water systems. The city’s Gateway Theatre is a 50,000-square-foot public theater facility, heated by a boiler employing 29 heat pumps. 

“We installed a SHARC system with a 250 gpm design flow that diverts 1 million Btus from a municipal sewer line into the heat pumps,” Mueller says. 

Richmond’s District Energy Manager Alen Postolka notes that the site was chosen because of its proximity to a sewage lift station and a large volume of sewer flow. 

“It’s a demonstration project which is being carefully monitored,” he says. “Unfortunately, the theater’s boiler had to be replaced after half a season. We’ll need continuous data using the new boiler for more than one year to report on its level of effectiveness.” 

However, Postolka says that the SHARC was recently selected as the preferred technology for a second upcoming project in the city. 

“Richmond has a significant number of pumping stations,” Mueller concludes. “Each of them is an energy opportunity.”


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