BIOSOLIDS COMPOSTING FACILITY EXPANSION

Fredericksburg, Virginia

The Spotsylvania County Department of Utilities/Public Works has achieved 100 percent biosolids diversion from the county's landfill, thanks to expansion of its composting facility. Originally opened in 2001 as a pilot project, the program was progressively expanded to process more than 12,000 tons/year of biosolids and ground mulch by 2008, according to a news article in the Biosolids Technical Bulletin. The new facility, which opened this past spring, incorporates negative aeration with process air treated in a biofilter and automated control of aeration fans based on temperature feedback. Highlights of the operation include the following: Brush collected within the county is ground and transported to a covered storage area. The mixing area is separated from the compost aeration piles by a concrete push wall to avoid cross-contamination of fresh and composting material. Two Kuhn-Knight stationary mixers blend biosolids and wood chips in a 1:1 ratio; the mixers discharge onto a conveyor that carries the material over the push wall and into a bucket loader, which transport the mixed feedstocks to the aeration bay of the compost hall.

Two biofilter structures are connected to the composting hall through a series of pipes and headers. Each has a humidification and irrigation system to ensure the media - made from screened mulch - is maintained at 60 percent moisture. After 21 days in the aerated bays, the compost is screened in a trommel with. 375 inch holes; overs are added back into the raw mix. Material passing through the screen is cured under roof for 30 days. Finished compost, named Livings ton Blend, is sold in buik to landscapers, landscaping suppliers and residents.