By Sarah Martynowski
During the summer, EPA hosts several events to provide interns with enriching experiences in the D.C. metropolitan area. Last summer, we visited the Blue Plains Advanced Wastewater Treatment Plant, located along the Potomac River. Designed to treat an average daily flow of 370 million gallons of wastewater per day, Blue Plains is the largest treatment plant of its kind in the world. It’s known globally for its state-of-the-art technology and innovative research.
We began the tour at the point where 1,800 miles of pipes bring both raw sewage and stormwater into the plant from D.C., Maryland, and Virginia. The first step screens and removes grit. Then the wastewater moves through primary and secondary treatment. Primary treatment is a physical process that removes floating materials, while secondary treatment is a biological process that removes organic matter. And while most treatment plants stop after primary and secondary treatment, the advanced system at Blue Plains continues the process to remove nitrogen and phosphorous that can hurt local waterways. The treated water then passes through filters and is disinfected before flowing into the Potomac River.
Blue Plains is currently constructing an anaerobic digestion facility and a thermal hydrolysis process to further treat the solids that are removed in the treatment process. The digesters will produce enough biogas to generate 10 megawatts of electricity: enough to provide one-third of the plant’s own power requirements. The thermal hydrolysis process will create “Class A” biosolids that can be safely applied to land as a fertilizer.
DC Water is also working to improve treatment of its “combined sewer system,” meaning that storm water and wastewater come together when it rains. A massive tunneling project called “the Clean Rivers Project” will capture excess flows. Currently, many of these combined sewers become overloaded during storms and raw sewage overflows into local rivers. When the tunnel system is complete in 2025, most of these excess flows will be captured and conveyed to Blue Plains for treatment. As a result, DC Water expects to reduce overflows by 96 percent.
Our tour was an excellent opportunity to learn about wastewater treatment plants, beyond just the information found in my environmental textbooks. I may never operate a wastewater treatment plant, but I think it’s important to understand how they work and their vital role in keeping our waters clean and healthy.
About the author: Sarah Martynowski is a senior at the University of Cincinnati majoring in environmental studies and political science. She was an intern for EPA’s Office of Water during the summer of 2014.