Wastewater Treatment

Historically the wastewater industry has focused on protecting water quality through relatively high energy treatment technologies and chemical use. WSSC and other “Utilities of the Future” are moving towards ever increasing levels of resource recovery while returning high quality treated effluent to the environment. Initiatives include continuous improvements in energy use, nutrient recovery, water reuse, and use of alternative energy sources.

WSSC operates and maintains six water resource recovery facilities (WRRFs). The Western Branch, Piscataway, Parkway, Seneca, Damascus and Hyattstown WRRFs have a total design capacity to handle 95.6 million gallons of wastewater per day, and they treat an annual average of approximately 65 million gallons of wastewater daily.  The remainder of the wastewater from our service area is treated at the Blue Plains WRRF in the District of Columbia. Attached is a 5-year annual average performance summary showing influent and effluent concentrations, flows, biosolids generated, and major chemicals used for WSSC’s WRRFs.  You can also take a tour of the WSSC WRRFs.  We accomplish our mission safely, cost-effectively, and in a manner that serves our customers well and protects the environment.

View a brief movie on wastewater treatment (.wmv)

Wastewater treatment plant process


At the WRRFs, wastewater goes through physical, chemical and biological processes.  The “secondary treatment” process is a biological process that relies on bacteria and other microorganisms to remove wastes. In the process, the bacteria grow and create new bacteria.  To maintain steady treatment, a portion of these are constantly removed from the process - and we refer to this portion as the biosolids.  At WSSC the biosolids are typically thickened, dewatered, and then treated with lime to raise the pH level to stabilize them (i.e., to eliminate pathogens and minimize odors). In the future, the Bio-Energy project will process the dewatered solids from the WRRFs to produce high-quality Class A biosolids and generate renewable energy.

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