The present sludge management plan of the Metropolitan Sanitary District of Greater Chicago is referred to as the “Dry Solids Program.” This nrogram meets the criteria for being environmentally acceptable and cost-effective. The program includes several unique unit operations in what would otherwise be considered a conventional sludge processing train that consists of thickening, stabilization, dewatering, and drying. Among the unique unit operations are thickening the raw sludge by centrifugation, thickening ana dewatering the stabilized sludge in centrifuges or lagoons, atmospheric air drying of the dewatered sludge on paved surfaces, and continuous use of mechanical agitating equipment during the drying season to enhance the atmospheric drying rate of the sludge. Final disposal of air-dried sludge is administered under a “Controlled Distribution” permit issued by the Illinois Environmental Protection Agency. End usages of the air-dried sludge include: landfill cover; soil conditioner/fertilizer for sod farms, tree nurseries, golf courses, and highway right-of-ways; and land reclamation work.

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