Composting Success at Spotsylvania County

In response to a wastewater residuals management planning study, Spotsylvania County, Virginia began composting wastewater residuals and yard wastes in 2001 on a demonstration basis. Through the success of the demonstration project, modest improvements were made in 2003-2004 followed by expansion of a state-of the art aerated static pile facility designed by CH2M HILL in 2007. Construction of the expansion was completed in 2009 and the new facility commissioned in early 2010. The 80 wet ton per day capacity biosolids composting facility includes several innovative design features. Batch mixing is followed by aerated static pile composting utilizing below ground aeration piping and aeration risers with grates to deliver aeration to the compost piles. Supervisory Control and Data Acquisition (SCADA) temperature feedback controls blowers which provide continuous aeration for optimal process control. Odorous process offgas is captured and treated through a state of the art biofiltration system. The solids receiving, mixing, composting, screening and curing facilities have a roof cover instead of totally enclosed building. This design concept was a breakthough approach which saved $3M in capital costs over a totally enclosed facility while providing even better odor control than an enclosed facility.In the planning stage it was estimated that the processing of wastewater residuals through composting would cost between $25 and $30 per ton after compost sales. The actual net per ton cost of management in FY 2012 was $26.51 per ton. This O&M cost is being realized at the current wastewater residual processing rate, roughly 50 percent of the facility capacity. As residual production increases the processing cost will further decrease realizing even more savings through economies of scale. The USEPA Class A compost is marketed by County staff under the Livingston Blend trademark. The USCC STA certified product provides customers a high quality soil amendment that is routinely sold out. In recognition of the outstanding operational success, this facility received the Solid Waste Association of North America's highest honor by winning the Composting System Gold Excellence Award in 2012. Visitors from around the country and around the world have come to tour the facility to learn from its successes.