Davenport Compost Facility Odor Control Improvements

The City of Davenport, Iowa has been successfully composting wastewater residuals and yard wastes for 18 years at their enclosed aerated static pile composting facility. This facility has won numerous design and operations awards. One of the core values of this operation has been to provide a valuable service to the Scott County, Iowa communities while being a good neighbor by controlling odors. The original facility was sized to process 140 wet tons per day of wastewater biosolids on a 5-day per week basis. The facility routinely processes 100,000 cubic yards of yard wastes annually as well. Odor control is provided through 8 biofilter cells with a combined capacity of 210,000 cubic feet per minute of odorous process air. During this 18 year period only one odor complaint has been received (due to a broken odor collection duct that was quickly repaired) owing to the ability of the original biofiltration technology to perform and the high degree of operational controls provided by the operations staff.The biofiltration system requires periodic media replacement. With the original design of air distribution laterals in gravel, media replacement is time consuming and expensive. In recent years, there has been a lack of supply of organic wood based media due to the economic downturn. As a result, the City contracted with CH2M HILL to perform a feasibility study to evaluate alternatives for upgrading the biofiltration system. Eight different arrangements were evaluated for both cost effectiveness and operator preferences. A system consisting of high density polyethylene pipes imbedded in a concrete pad was selected and a design for replacement of the existing filters is completed and construction of the replacement biofilters is in progress.This paper and presentation will provide valuable information on the evaluation process used for various state-of-the art odor control biofiltration options including capital, operating and life-cycle cost comparisons.