Walnut Creek, Calif. — On Oct. 7, Brown and Caldwell joined DC Water to unveil its $470 million waste-to-energy project that is producing a net 10 megawatts (MW) of electricity from the wastewater treatment process, providing clean, renewable energy to power about one-third of the Blue Plains plant’s energy needs.
CAMBI thermal hydrolysis vessels in foreground; anaerobic digesters in the background. Photo: DC Water
DC Water CEO and General Manager George S. Hawkins was joined to commission the project by District of Columbia Mayor Muriel Bowser, Congresswoman Eleanor Holmes Norton, EPA Acting Deputy Administrator Stan Meiburg, US Department of Energy Deputy Assistant Secretary Kathleen Hogan and local elected and appointed officials.
The facilities include a dewatering building, 32 sleek, shiny thermal hydrolysis vessels, four concrete 80-foot high anaerobic digesters that hold 3.8 million gallons of solids each and three turbines the size of jet engines.
Brown and Caldwell served as program manager and lead developer and designer for the project, which was only viable through the use of innovative technology never before used in North America. DC Water not only brought the CAMBI thermal hydrolysis process to the continent, in addition Blue Plains is now the largest thermal hydrolysis installation in the world.
Pre-dewatering building (left), Center-thermal hydrolysis (center), and anaerobic digesters (right). Photo: DC Water
Thermal hydrolysis uses high heat and pressure to “pressure cook” the solids left over at the end of the wastewater treatment process. This weakens the solids’ cell walls and the structure between cells to make the energy easily accessible to the organisms in the next stage of the process — anaerobic digestion. The methane these organisms produce is captured and fed to three large turbines. Steam is also produced and directed back into the process.
Finally, the solids at the end of the process are a cleaner Class A biosolids product that DC Water uses as a compost-like material. Biosolids products are currently being used around the District for urban gardens, and green infrastructure projects. DC Water is also working to bring a compost-like product to market.
DC Water CEO and General Manager George S. Hawkins, said “This project embodies a shift from treating used water as waste to leveraging it as a resource. We are proud to be the first to bring this innovation to North America for the benefit of our ratepayers, the industry and the environment.”
“We are extremely proud to have collaborated with DC Water on this ambitious project,” Phil Braswell, Program Manager at Brown and Caldwell said. “From the beginning, we’ve worked as a true partner … helping achieve their vision for a sustainable and world-class program.”
The project received the 2012 Grand Prize in Planning Award from the American Academy of Environmental Engineers & Scientists, the 2012 Global Honour Award in Planning from the International Water Association, as well as one of two WERF Excellence in Innovation Awards, first presented at WEFTEC 2011.
For more information on the project or the ceremony, visit dcwater.com/digesterdedication.