The West Central Wisconsin Biosolids Facility (WCWBF) is a regional biosolids processing facility in Ellsworth, Wisconsin, serving Ellsworth and over 20 neighboring communities. The biosolids are dewatered by centrifuges to 20-24% total solids. The dewatered sludge enters an alkaline stabilization system that mixes the sludge with lime and fly ash to yield a Class A product. The treated biosolids are stockpiled in a 37,000-square-foot covered storage building, and beneficially reused semi-annually by local farmers.
In 2008, WCWBF decided to upgrade the lime stabilization process, with the main goals being to contain cost and maintain air quality and odor control. The existing mixer used open hoppers; between that and the fly ash, the system generated a lot of dust. Furthermore, the facility received periodic complaints from neighbors about the odor.
WCWBF chose a Schwing-Bioset system employing a closed hopper, screw conveyors, and pressurized piping system to contain dust and odors. To avoid costly contract hauling charges, WCWBF had to achieve demolition of the old system and installation of the new Schwing-Bioset system within 10 days of shutting down the old system. Demolition and preparation took three days; Schwing Bioset's team installed the new equipment, including the electrical, within the remaining seven days.
With a few minor modifications to adapt it to the winter weather, the Schwing-Bioset system has performed within expectations since commissioning, achieving its goals of managing cost, dust, and odors.