Sand Drying Beds & Belt Filter Presses After most of the organic solids have been digested, the sludge is pumped to sand drying beds or to the belt filter presses. The belt filter presses use a chemical flocculent to separate the water from the solids. The dewatered solids are then squeezed between two belts to further dewater them.
Fertilizer & Soil Conditioner The resulting solids are in the range of 18% - 20% solids. These solids are applied to agricultural land. If agriculture fields are not available, the solids would be taken to a landfill; however, this is expensive and a waste of valuable soil conditioner.
The sludge drying beds also provide a means of drying the sludge treated by the anaerobic digesters. As an alternative, the digested sludge may be pumped to the truck loading station to be hauled to other locations for drying or for use as fertilizer. Sludge is a good soil conditioner as well as fertilizer.
Elmhurst sludge has been approved by the Illinois Environmental Protection Agency for application on agricultural soils, it has very low concentrations of elements which may be toxic to the soil or plants.