How D.C.’s Sewage Will Soon Generate Electricity

CREDIT: PoShutterstock

Potomac River, Washington D.C.

When the D.C. Water and Sewer Authority was first planning to build its Blue Plains wastewater treatment facility back in the 1930s, it seemed logical to choose a site that would minimize the cost of pumping water uphill. That’s why the facility, which today serves over 2 million people in D.C., Maryland, and Virginia and treats around 370 million gallons of wastewater a day, is located at the lowest point in all of the District of Columbia.

But the 150-acre facility, on the banks of the Potomac River, is now confronting the downside of what was once a strategic siting decision — the entire facility is extremely vulnerable to the flooding predicted by future sea level rise.

So while the existence of human-caused climate change is alternatively debated, scoffed at and ignored elsewhere in the nation’s capital, the D.C. Water Authority is investing millions into projects to protect a city’s water from sea level rise, storm surge, and the type of destruction brought by Superstorm Sandy.

D.C. Water isn’t alone. Across the country there are a handful of water and sewer utilities that are going above and beyond meeting basic requirements, choosing instead to invest in infrastructure and research to become more efficient, more self-sufficient, and more resilient to climate change.

Construction has already begun in D.C. on a 17.2 foot-high sea wall designed to protect the plant from a 500-year storm surge that could otherwise flood D.C. with raw sewage. The sea wall will cost an estimated $13.2 million and is expected to be completed in 2021.

D.C. Water is also investing $450 million on an on-site digester that will transform its daily 120 tons of treated solid waste into enough natural gas to keep the plant running even if extreme weather knocks out power to the area.

Biosolids once sent to surrounding farms for use as fertilizers, will now stay on site and be processed by 4 anaerobic digesters. An anaerobic digester is essentially just an airtight tank filled with a special mix of bacteria, similar to what you’d find in the stomach of a cow. When organic waste goes into the digester tanks, the bacteria devour it and produce a biogas, which is mostly methane. The methane drawn off the four digester tanks will power three turbines that together can generate up to 10 megawatts of clean electricity. D.C. Water estimates that it will save $10 million each year on its electricity bill after the system is completed this summer. The digesters will also help reduce the overall carbon footprint of the facility.

“At the turn of the century, we looked at wastewater just as a public health issue, it was all about keeping people from getting sick” said Lauren Fillmore, Senior Program Director at the nonprofit Water Environment Research Foundation. “And then in the 1970s, with the Clean Water Act, we started dealing with everything else in the water besides pathogens that was damaging the environment. Now, we are just starting to look at wastewater management as really water resource recovery.”

Longer term, there are also plans being considered to install 50 acres of solar panels on top of the Blue Plains treatment plant. The solar panels could generate an additional 8 megawatts of electricity. D.C. Water is currently the largest consumer of electricity in the District.

Elsewhere in the country, the Philadelphia Water Department is using heat recovery technology and anaerobic digesters to reduce its reliance on the grid. In Gloversville-Johnstown, New York, a small wastewater treatment plant not only uses a digester to generate energy from its own biosolids, it takes the waste byproducts of a yogurt producer nearby and generates energy from them too. There are similar projects at wastewater facilities in Sheboygan, Wisconsin, Ithaca, New York, and Oakland, California.

“In terms of climate readiness, it doesn’t get any more basic than protecting water,” said Fillmore. “And D.C. Water is really leading the nation in making the most of the opportunities preparing for the future provides, to become better at what they do.”