A DECADE OF OPERATING EXPERIENCE AT THE DAVENPORT IOWA AERATED STATIC PILE COMPOSTING FACILITY

The City of Davenport, Iowa constructed a totally enclosed aerated static pile composting facility that was placed in operation in August of 1995. This facility was designed to process 28 dry tons per day (140 wet tons per day or 36,400 wet tons per year) of dewatered digested biosolids on a 5-day per week basis. In addition, over 100,000 cubic yards per year of yard wastes are received and processed to supplement bulking agent needs. Wood chips and ground yard wastes are used as the two bulking agents. The facility includes totally enclosed biosolids receiving, mixing and composting operations with full odor control to treat the exhausts from these operations using biofiltration. Aerated static pile curing, and bulking agent storage is provided under cover. The facility has operated since start-up with no odor problems. Compost and yard waste mulch have been successfully marketed in bulk and bagged form to the public and private enterprises in the Quad City area resulting in a significant reduction in operating costs. Demand for the compost product has outstripped supply.This paper presents historical data regarding the operation and maintenance costs of this composting facility. Detailed operating and maintenance and annualized costs including amortized capital is presented. Utility costs, fuel costs, labor costs, product marketing costs, etc are presented. In addition, costs associated with improvements to the facility since its initial construction cost of 8.6 million will be presented. Key improvements that will be discussed include modifications to the 210,000 cubic feet per minute (CFM) capacity biofilter to incorporate air distribution design changes, rebuilding of the in-pad aeration channel system with longer life materials, improvements and enhancements to facility controls and other aspects of the facility such as coating system performance and aeration system modifications. Facility operating performance including equipment throughput, odor control operating efficiencies, and the consistency of compost product characteristics will also be presented. Compost marketing efforts and program components that have led to marketing success will also be presented.