Try Before You Buy – Bench-Scale Digestion Evaluation of Potential Co-Digestion Waste Streams

摘要

With limited digester capacity and the desire to increase digester gas production, GwinnettCounty Department of Water Resources initiated a research project with Hazen and Sawyer andGeorgia Institute of Technology to evaluate various fats, oils, and grease (FOG) and highstrength waste (HSW) streams for co-digestion. The bench-scale evaluation included wastestream characterization, ultimate digestibility, continuous flow bench scale digester andbiological modeling with BioWin. During waste stream characterization, the solidsconcentration, carbonaceous oxygen demand (COD), along with pH and nutrient (nitrogen andphosphorus) concentration were measured. During the ultimate digestibility test, the CODconcentration and methane production was determined after a 90-day residence time. Theultimate digestibility was used to compare the multiple waste streams to identify the streams thatproduced the most methane per volume of waste digested. Two waste streams, FOG and chewinggum wastes, was used in the continuous, anaerobic, bench scale reactor. The waste streams wereco-digested with the plant’s primary and waste activated sludges at similar organic loading tosimulate the full-scale digestion process. Each waste stream was co-digested individually andthen both waste streams were co-digester together. With each waste stream, the COD destructionand methane production exceeded the expected values of each individual waste stream from theultimate digestibility tests. The continuous bench scale reactor was modeled using a calibratedBioWin model by EnviroSim that matched the theoretical and underestimated the observed CODdegradation and methane production.