By Chris Peot, P.E.
District of Columbia Water and Sewer Authority
The District of Columbia Water and Sewer Authority (DC WASA) Blue Plains Advanced Wastewater Treatment Plant in Washington, DC, recycles 1,200 tons per day of biosolids to agriculture, restoration projects, and composting production in Virginia and Maryland. Rather than sending biosolids to a landfill, recycling the nutrient-rich material to land in need of nutrients aids the environment. We, along with our colleagues in this profession, work hard every day to examine issues, conduct research, and improve techniques to ensure we are producing the highest-quality, safest product within our power.
The use of biosolids in urban settings can be misunderstood by some. Recently, there have been some negative comments about the First Family garden on the lawn of the White House, which has received some biosolids compost within the past 20 years. For the record, the tests showed approximately 90 parts per million (ppm) lead in the garden soil. Lead occurs naturally in soils up to 50 ppm. The U.S. Environmental Protection Agency (EPA) has set actions levels for urban soils set at 1200 ppm for regular use and 400 ppm for children’s play areas. Lead levels of 90 ppm in the garden pose no known health risk, and are considered extremely low for an urban setting, where levels from atmospheric deposition can exceed 10,000 ppm. DC WASA biosolids contains lead levels that are considered naturally occurring and well below EPA limits for reuse, at approximately 30 ppm lead. Biosolids compost can, as researched by the U.S. Department of Agriculture (USDA) and others (“Heavy Metals in the Environment” by Brown and others, Journal Environmental Quality, 2003, and “Biosolids Compost Amendment for Reducing Soil Lead Hazards” by Farfel and others, Science of the Total Environment, 2005) help reduce the availability of lead in urban soils, making them safer for our children.
This concept was misrepresented in an AP story last year, prompting AP to write a more balanced follow-up article, stating that the original story was “inaccurate and misleading."
Also see a more in-depth look at the inaccuracies.
Land application of biosolids helps protect the Chesapeake Bay by managing the nutrients generated in an urban setting in an environmentally sustainable manner. It is Mother Nature at work (slightly modified by mankind)—-an essential and important part of the nutrient cycle. DC WASA’s land application program employs the latest technology and research, but we continue to seek out cutting-edge solutions through research and education. For example, we are considering investing in technology to improve the product, produce energy, and reduce biosolids output. This technology would increase our options for reuse of the residual and also produce 10 megawatts of renewable energy.
DC WASA will continue to support returning nutrients and carbon to the soil from which it came, unless scientific evidence indicates we ought to move in a different direction.