Tuesday, September 10, 2024
9:15 AM - 9:45 AM
Location Name
FUD’s Biosolids Dewatering Alternatives Evaluation and Implementation

First Utility District (FUD), responsible for wastewater treatment in the Town of Farragut and southwest Knox County, initiated its wastewater treatment operations in 1975 with a compact package plant situated on the shores of Fort Loudoun Lake. Responding to the rapid growth of Farragut and West Knoxville in the late 80s and early 90s, a new plant was established in 1995, with significant upgrades in 2007, resulting in a permitted capacity of 15 million gallons per day (MGD). In line with strategic planning, FUD recently devised a 25-year facility improvements plan for its Water Resource Recovery Facility. This comprehensive plan aimed to determine the hydraulic and treatment capacity of the existing facility and propose alternatives to accommodate projected flow, loads, and regulatory effluent limits for the year 2043. Additionally, the plan documented previously identified process improvements earmarked for near-term implementation. A crucial near-term improvement involved upgrading the aging dewatering facility, which featured gravity thickeners and belt filter presses. The dewatered sludge (15-16% solids) was disposed of in a local landfill. FUD conducted a thorough dewatering evaluation, seeking cost-effective process and technology improvements to optimize the facility while considering future landfill limitations. The evaluation encompassed: • Assessment of thickening and dewatering technologies • Analysis of nonmonetary advantages and disadvantages of each technology • Economic evaluation of six scenarios incorporating current industry technologies • Economic evaluation of six scenarios considering drying for achieving Class A biosolids in the future The evaluation identified gravity thickening and centrifuge dewatering as the preferred alternative, primarily due to its cost-effectiveness and the ability to produce a dryer cake solid between 20-22%, a critical factor for potential solids dryer implementation. In 2022, FUD implemented this selected alternative, replacing the existing belt filter press with two horizontal, solid-bowl Andritz centrifuges and five shaftless screw conveyors. The resulting % solids consistently ranged between 21-22%, leading to significant annual landfill disposal savings and overall operational and maintenance improvements. Post-implementation, FUD observed a notable change in odors within the solids storage bays. The centrifuge's shearing of solids induced biological activity, causing strong odors. Through detailed analysis, FUD replaced the existing odor control chemical with a misting agent, proving effective with minimal cost impact. Additionally, an odor control study was conducted to identify specific odorant compounds and explore potential alternative, more cost-effective chemicals that could offer operational benefits. This presentation will provide a comprehensive overview of the project's success, encompassing initial facility planning related to the dewatering process, the dewatering evaluation, design, construction, and post-odor control efforts.