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DC waste treatment facility will be largest of its kind in the world

The digester tanks being built

The D.C. Water and Sewer Authority's new digester system is well on its way to delivering a much greener waste management system to the D.C.-metro area and will be the largest of its kind in the world. With construction of the new digester systems, the first of its kind in North America, along with two other green initiatives taking place at Blue Plains, D.C. Water has used up almost all of its headquarters' remaining land.

Two of the new CAMBI-brand digester systems being built on-site are at full height with another two almost at full height, says Pamela Mooring, communications manager at DC Water The digesters use a process called thermal hydrolysis and anaerobic digestion to break down solids left over after the water and sewage has been treated. The process, in essence, heats the solids to a very high temperature and pressure cooks them to produce methane gas, which is used to produce electricity and class A biosolids—human waste that's clean enough to be used as fertilizer.

With about 13 MW of electricity being produced, three of those megawatts will be used to run the new digesters and the other 10 MW will be left over for other units at the Blue Plains treatment plant. The electricity savings is estimated at $10 million a year for the treatment plant.  And the manure produced from these digesters will be refined and healthy enough to sell for agricultural needs at a prime price.

Spain, Denmark and the U.K. are just some countries in Europe already using the CAMBI thermal hydrolysis digesters, but Blue Plains is the largest facility of its kind in the world—processing an average 370 million gallons of wastewater per day.  Mooring says the facility will be the first of its kind in North America and house the largest CAMBI thermal hydrolysis digesters in the world.

"DC Water is the largest consumer of electricity in the District, and the digesters should cut our consumption by a third," said General Manager George S. Hawkins in a 2011 ground-breaking statement. "That’s enough to power 8,000 homes. We’re also saving $10 million in trucking costs and reducing our carbon emissions by cutting the amount of solids at the end of the process in half."

The design idea for the new digesters were initially egg-shaped, but after researching costs, space and time needed to build the egg-shaped facilities, D.C. Water went with a more conventional build.

The $400 million project will be done by late 2014.

Read more articles by Lisa Spinelli.

Lisa Spinelli is Elevation DC's development editor as well as a freelance journalist, copy editor and mother of two. After receiving her Master of Science in print journalism from Columbia University in 2004, Lisa worked across the country and in Italy as a journalist, editor and Web editor. Her website LisaSpinelli.com has links to a smattering of her published clips.
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