Sewage sludge is a byproduct of the wastewater treatment process in which solid constituents are removed from the liquid wastewater effluent before it is discharged to the environment. When these solids, which include organic matter, inorganic minerals, and nutrients beneficial to plant growth are treated to EPA and state standards for pathogen control and to minimize other potential pollutants, they are considered to be ‘biosolids’.
In metropolitan Washington region, biosolids from the more than 37 municipal wastewater treatment plants (WWTPs) are managed primarily through beneficial recycling programs, such as land application or composting. These biosolids are applied to farmland, used in mine land reclamation, or further processed for public use as a soil amendment for lawns and gardens (e.g. compost). Several WWTPs in the region incinerate their sewage sludge. Several of the incinerators and several of the other solids processing systems that produce biosolids generate electricity and heat that are used at the plants to reduce the use of purchased energy supplies, thereby improving their carbon footprint by reducing the production of greenhouse gases.
COG staff works with biosolids program managers at the region’s major WWTPs in various ways. COG staff coordinates regional research on beneficial uses of biosolids and tracks legislative and regulatory issues. It also coordinates efforts by the Chesapeake Bay Program to accurately model the impact of biosolids land application on nutrient loss to the bay. In support of these efforts, COG collects information on biosolids master plans and other management studies and maintains a database on how biosolids are managed in the region.
COG staff also coordinates biosolids management efforts among the parties of the Blue Plains 2012 Intermunicipal Agreement. This support addresses specific issues that arise from the management of Blue Plains’ biosolids by the DC Water and Sewer Authority and the Washington Suburban Sanitary Commission and their respective contractors.