Heating, Cooling System Uses Treated Wastewater

A former factory renovated into an office building in Williamsport, Penn., is using an innovative heating and cooling system that makes use of treated effluent from a nearby wastewater plant.

A former factory renovated into an office building in Williamsport, Penn., is using an innovative heating and cooling system that makes use of treated effluent from a nearby wastewater plant.

When developers were designing the new Water Tower Square, they initially planned to use water from the nearby Susquehanna River as a heat source/sink for their GeoExchange heat pump system, said Keith Eck, President of Centura Development and managing partner of the complex.

“I just happened to be at the Williamsport Sanitary Authority and saw an aerial view of their building, treatment plant, and our building, all in one photo. I knew the plant pumped about 12 to 20 million gallons of effluent into the river every day, so I asked ‘could we use some of it?’”

With the town’s permission, the company built a pump station over the effluent discharge pipe on its way to the river. “We basically borrow up to 1.5 million gallons of effluent a day,” Eck said. “The treated effluent ranges in temperature from 47 to 78 degrees Fahrenheit throughout the year, which is less variable than the river itself. And this option required less permitting and the least installation costs.”

In the system, the effluent circuit is an open loop. Two pumps with variable speed drives send the effluent water through about 1200 feet of 12-inch PVC pipe to a pair of plate-and-frame heat exchangers located just outside the office building. A 16-inch PVC pipe returns the effluent water by gravity to the discharge line.

The water circuit through the heat exchangers on the building side is closed loop, driven by three pumps with variable speed drives. “These pumps allow us to regulate flow requirements as needed – as we add tenants and more heat pumps, and as weather extremes place demands on the system.”

According to Eck, the resulting 550-ton system needs little maintenance. “The only thing that can break down is our pumps. No cooling towers, no auxiliary heating system. The initial cost is somewhat more, but the efficiency and estimated life-cycle costs are phenomenally good.”

The effluent heat source/sink system is a demonstration project partially funded by the Geothermal Heat Pump Consortium and Pennsylvania Power & Light. The two-year study will provide information on system efficiency and energy use.

The Williamsport Sanitary Authority is providing the effluent at no charge for 10 years. After that time, the Authority will have the option to charge for its use. The Authority decided to support the Water Tower Square project to help with economic development in the town. The project was done at no cost to the Authority and had no impact on its discharge permits.

“We estimated it would be 3 years before we could get permits to draw water from the river, by the time the Army Corps of Engineers and River Basin Commission got involved,” Eck said. “We contacted the Pennsylvania Department of Environmental Resources about this project, and they said no permit was needed.”

Flooding, debris and clogged intakes were also concerns with using the river. The high quality Williamsport effluent does not require any treatment, Eck said.

“I just happened to be at the Williamsport Sanitary Authority and saw an aerial view of their building, treatment plant, and our building, all in one photo. I knew the plant pumped about 12 to 20 million gallons of effluent into the river every day, so I asked ‘could we use some of it?’”

Keith Eck is President of Centura Development and managing partner of the complex

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