Composting Success Continues at Spotsylvania County

In response to a wastewater residuals management planning study and loss of viable landfilling and land application options, Spotsylvania County 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 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. SCADA temperature feedback controls blowers which provide continuous aeration for optimal process control. Odorous process off gas is captured and treated through two 54,000 cfm capacity biofilters with automated inlet temperature control. The solids receiving, mixing, composting, screening and curing facilities have a roof cover instead of a totally enclosed building. This design concept was a breakthrough approach which saved $3M in capital costs over a totally enclosed facility while providing a zero discharge operation and even better odor control than a totally enclosed facility.In the planning stage CH2M HILL estimated that the processing of wastewater residuals through composting would cost approximately $30 per ton after compost sales. The actual net operating and maintenance (O&M) cost of management in fiscal years 2012 and 2104 averaged approximately $26 per wet ton of dewatered wastewater residuals processed, lower than originally projected. The USEPA Class A EQ compost is marketed by County staff under the Livingston Blend trademark. The USCC STA certified product provides customers a high quality fertilizer product 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 toured the facility to learn from its successes.Capital and O&M costs are presented as well as lessons learned from this composting facility expansion and operations over the past 5 years. Throughput in 2012 was roughly half the 29,250 wet ton design capacity at 14,900 wet tons. In 2014 the throughput increased to nearly full capacity at 22,940 wet tons. Actual operating costs for both 2012 and 2014 are provided. This case study provides valuable information to other communities considering composting as a biosolids management solution.