Huuuuuuuuge New Thermal Hydrolysis System For DC Wastewater Is World’s Hugest

Sign up for daily news updates from CleanTechnica on email. Or follow us on Google News!

The world’s biggest thermal hydrolysis waste-to-energy system has just revved up its engines this week at the Blue Plains wastewater treatment plant on the banks of the Potomac River, making the District of Columbia — that would be the capital of the US — home to the only facility of its kind in all of North America. Oh, the irony! While certain members of Congress continue to deny that climate change is a thing, they will be making a direct contribution to some of the most advanced renewable energy technology on Earth every time they flush the toilet.

wastewater treatment DC

A Huuuuuuge Wastewater Treatment Plant

At a price tag of $470 million, the new thermal hydrolysis system has been 10 years in the making, and it adds a significant new layer of waste reclamation to the busy Blue Plains wastewater treatment plant. That’s no accident — Blue Plains is operated by the utility DC Water, which is well known for its in-house wastewater treatment R&D.

At peak flow, Blue Plains handles 1 billion gallons of wastewater daily from Washington, DC (yes, that includes the Capitol) as well as several neighboring jurisdictions, making it the biggest plant of its kind in the world. By way of comparison, New York City produces about 1.3 billion gallons daily on average, but that’s parceled out among 14 different treatment plants in all five boroughs.

Even without the new system, Blue Plains is already the largest wastewater treatment plant in the world to deploy tertiary treatment, nitrification/denitrification. That’s part of a broader program to keep pollutants out of the Chesapeake Bay watershed (the plant discharges into the Potomac River).

The New Thermal Hydrolysis System

Thermal hydrolysis deploys high heat and pressure to “pressure cook” the biosolids that are left over at the end of the wastewater treatment process. It’s a ramped up version of biogas capture, in which biosolids are put in closed tanks where wastewater-loving microorganisms digest them and produce renewable methane.

The difference is in the efficiency. With the addition of high heat and pressure, the cell walls of organic material in wastewater are weakened, making more energy accessible to the microbes. At Blue Plains, the captured methane is fed to three turbines the size of jet engines, which produce electricity to the tune of a net 10 megawatts.

But wait there’s more. The system also produces “cleaner” leftover biosolids, in the Class A category. DC Water’s biosolids are already Class A and are distributed around the city as a soil enhancer for urban parks, gardens, and green infrastructure. The improved quality makes DC biosolids a good candidate for commercial marketing as a compost.


Along with the three turbines, the nut of the new system consists of 32 thermal hydrolysis vessels and four concrete anaerobic digesters. At 80 feet high, each can hold about 3.8 million gallons of solids.

Here’s DC Mayor Muriel Bowser enthusing over the project:

“This is yet another example of the District leading the nation in the adoption and implementation of sustainable practices. DC Waters Blue Plains facility is converting waste to clean water and a nutrient-rich soil byproduct, producing energy and helping to put the District on the path towards a zero waste future.”

An Oil Company Goes For Renewable Energy

Cambi, the company behind the new thermal hydrolysis system, has an interesting history. It began as Kambi in 1989 as a project of Norway’s Glommen Skogeierforening forestry association, with the aim of developing steam-based processes for the country’s paper and pulp industry.

Norway’s Petrol Holding AS, an oil trading company seeking to diversify, bought Kambi in 1992, changed the name to Cambi, and successfully developed the Cambi Thermal Hydrolysis Process for sludge and organic waste, first used commercially in 1994.

The technology quickly took hold in the UK and Ireland as well as mainland Europe and elsewhere around the world, and Cambi now lays claim to more than 50 of its systems either built or under construction around the world.

Now that the technology has traveled across the pond, you may see more thermal hydrolysis systems popping up in the US as water and wastewater system managers seek to squeeze more juice out of an increasingly valuable resource.

So, apparently there is no law against oil companies investing in renewable energy (take that, ExxonMobil).

As for the aforementioned certain members of Congress, collectively they have earned the distinction of belonging to the only conservative political party in the world that has refused to acknowledge that our climate is changing.

Keep up the good work! Meanwhile, despite the denialism, the world keeps turning and the toilets keep flushing in the Capitol Building.

There is no escape — Blue Plains is far from the only wastewater treatment plant in the US that is churning out renewable biogas, and when some of those deniers recess to their home states, the biogas digesters will be primed and ready.

Follow me on Twitter and Google+.

Photo (cropped) via DC Water.

Have a tip for CleanTechnica? Want to advertise? Want to suggest a guest for our CleanTech Talk podcast? Contact us here.

Latest CleanTechnica TV Video

CleanTechnica uses affiliate links. See our policy here.

Tina Casey

Tina specializes in advanced energy technology, military sustainability, emerging materials, biofuels, ESG and related policy and political matters. Views expressed are her own. Follow her on LinkedIn, Threads, or Bluesky.

Tina Casey has 3246 posts and counting. See all posts by Tina Casey