The stench of clogged toilets fills the air at the US capital’s wastewater treatment facility.
The stench of clogged toilets fills the air at the US capital’s wastewater treatment facility. And for good reason — it’s one of the world’s largest projects to transform human waste into electricity.
“They make green energy,” said engineer Chris Peot of Washington’s toilet-goers during a tour of the sprawling space in the southeast of the city. DC Water’s Blue Plains plant treats 370 million gallons (1,400 million litres) 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.
Once that’s done, the water is clean enough to flow into the nearby Potomac River or Chesapeake Bay without disrupting the fragile ecosystems. As for the excrement, it is either recycled as compost or, in a new step implemented six months ago, used to produce 10 megawatts of electricity.
The “poop power” generated is theoretically enough to supply some 8,000 households, although in practice the energy is ploughed straight back into powering the plant. To do so, plant workers collect the solid matter that slips to the bottom of the treatment pools and subject it to a Norwegian hydrolysis technique that is being used in North America for the first time.
According to Peot, DC Water’s director of resource recovery, the process 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. “This project embodies a shift from treating used water as waste to leveraging it as a resource,” said DC Water’s chief executive, George Hawkins, as he inaugurated the new $470 million facility on October 5, financed by water bills.
The methane is produced through the decomposition of organic waste by bacteria in huge vats that stand 80 feet tall, with each capable of “digesting” 3.8 million gallons of solid matter.
