Biosolids- and Yard-Waste-to-Energy Feasibility Study in St. Petersburg, FL

摘要

The City of St. Petersburg, FL (City) produces an average of 41,000 wet tons per year (WTpY) ofClass-B biosolids and 40,000 WTpY of yard waste. The City operates four Water ReclamationFacilities (WRFs): Albert Whitted WRF, NEWRF, NWWRF, and SWWRF. Plans are underway todecommission the Albert Whitted WRF and pump that service area’s wastewater to the SWWRF fortreatment. The Biosolids- and Yard-Waste-to-Energy Feasibility Study (Study) was driven by theState of Florida’s “effective ban” on Class-B biosolids land application (Florida AdministrativeCode Chapter 62-640) and the City’s desire to produce renewable power from currently under-usedresources.During the feasibility study, the team (City of St. Petersburg and Brown and Caldwell staff)investigated over 35 options and determined that a 2-phase approach could save the city up to $33million over the next 20 years. The two phases consist of:Phase 1. Consolidate all solids processing at the SWWRF through a combination of sludgeforcemains and the existing collection system. Add primary clarifiers to “catch” theconveyed solids and other settleable solids at the SWWRF and upgrade the digestion at thatplant to Class-A, temperature-phased, anaerobic digestion (TPAD). Digester gas would beused to fuel new engines for production of 1.2MW of power and the heat needed for Class-Adigestion. Additional thickening and dewatering capacity would also be required.Phase 2. Develop a yard-waste-fueled thermal process to produce additional power; this iscurrently envisioned as gasification with syngas-to-internal-combustion-engine powergeneration. Depending on the selected thermal process and its final configuration, biosolidsmay also be burned in this system.The Phase 1 improvements are moving forward while the Phase 2 efforts have been deferred untilcertain technical and economic conditions have been met. The two phases have been coordinated sothat all Phase 1 improvements will have benefit/be integrated into the Phase 2 improvements.