News Feature | December 21, 2015

DC Water Gets Charged Up On Human Excrement

Sara Jerome

By Sara Jerome,

The wastewater servicer in the nation’s capital has harnessed human excrement to generate 13 megawatts of electricity.

“The stench of clogged toilets fills the air at the U.S. capital's wastewater treatment facility. And for good reason — it's one of the world's largest projects to transform human waste into electricity,” Agence France-Presse (AFP) recently reported.

“DC Water's Blue Plains plant treats 370 million gallons (1,400 million liters) of dirty water from more than two million households on a daily basis, purging it with micro-organisms that first ingest carbon and then transform nitrates into nitrogen gas,” the report said.

As the treated water flows back into nearby waterways, the noteworthy part of the process occurs: Some of the excrement is used to generate 10 megawatts of electricity. The utility implemented this new step in the process this year.

The electricity generated is considerable, and it is used to power the plant. In theory, it is enough to supply around 8,000 households with power, the report said.

The project makes D.C. Water “the first utility in North America to use a Norwegian thermal hydrolysis system to convert the sludge left over from treated sewage into electricity,” The Washington Post reported.

The hydrolysis technique “allows the plant to extract organic material and convert it to methane. When burned, the methane generate power that is used to help run the plant,” AFP reported, citing engineer Chris Peot, director of resource recovery at DC Water.

Peot provided details on how this works, per the AFP report:

The methane is produced through the decomposition of organic waste by bacteria in huge vats that stand 80 feet (25 meters) tall, with each capable of "digesting" 3.8 million gallons of solid matter. The biogas is then used to operate three turbines, each the size of a jet engine, to produce 13 megawatts of electricity, three of which are immediately used for the hydrolysis. The 10 remaining megawatts are used by the water treatment plant — the biggest energy consumer in Washington — reducing its carbon footprint by a third and cutting operating costs by millions of dollars a year.

Experts in the field say DC Water is “an innovator among U.S. water utilities, especially with its work toward emissions reduction and energy independence," E&E Publishing reported.

For similar stories, visit Water Online’s Sludge And Biosolids Processing Solutions Center.