Turning waste into a renewable resource

As in many cities, the water utility is the single largest consumer of energy in the District of Columbia. But DC Water now consumes far less power, saving money and reducing emissions, thanks to its first-in-the-nation deployment of new technology and its collaboration with the local electric utility.

The Walter F. Bailey Bioenergy Facility at DC Water’s Blue Plains Wastewater Treatment Plant is the world’s largest thermal hydrolysis and anaerobic digestion project, and the first wastewater treatment plant in North America to generate on-site electricity using biogas. The facility, which began operating in 2015, also uses a combined heat and power plant to efficiently treat wastewater and generate clean energy.

In giving it an award last year, the U.S. Water Alliance praised the project as “a commitment to full-scale sustainability and innovation.”

DC Water treats wastewater and provides drinking water for more than 2 million people in Washington, D.C., and four surrounding counties spread across 725 square miles.

The idea for the project came about in 2011, when DC Water needed to upgrade its biosolids handling system. The utility was adding lime to wastewater to destroy bacteria before pumping the treated wastewater into the river. But Christopher Peot, director of resource recovery for DC Water, wanted a more sustainable solution.

DC Water’s award-winning wastewater and resource recovery team discovered a less expensive and more effective technology already being used widely in Europe. This led to a $470 million collaboration with Pepco Energy Services to operate the Bailey Bioenergy Facility.

At the project’s launch, DC Water CEO and General Manager George Hawkins said it “embodies a shift from treating used water as waste to leveraging it as a resource.” Pepco Energy Services CEO and President John Huffman called the project “a major step forward.”

The process starts with removing the solids from the wastewater in process tanks and then using heat and pressure — thermal hydrolysis — to eliminate pathogens that cause disease. The solids are then put into digesters, which are 80-foot high vessels where more bacteria microbes break down biodegradable material in the absence of oxygen. Anaerobic digestion produces two things: biosolids that can be used as a compost-like material for farms and gardens, and methane that can be burned for electricity. The methane is sent through turbines, producing heat that is converted to steam and used for the thermal hydrolysis process and electricity — 10 Megawatts (MW) or enough to power a third of the treatment plant.

The project has “the rare combination of being both financially and environmentally sustainable,” Peot said. The Bailey Bioenergy Facility is saving DC Water $10 million a year in energy costs and has reduced Blue Plains’ carbon emissions by 50,000 tons each year, he said.

The solution, which can be implemented elsewhere, takes what is literally a waste product and turns it into a renewable resource that can be relied on for electricity. DC Water is sharing its expertise by helping to form a consulting service, Blue Drop, which assists other utilities in making their operations more sustainable and efficient.

While DC Water uses its anaerobic digesters to generate biogas, Peot said other sustainable options are available, such as producing compressed natural gas (CNG), an alternative to gasoline. If the pipeline infrastructure already exists, utilities can clean the biogas and sell it, or use it to power other equipment on-site, such as transport trucks.