Performance of the Induced Bed Reactor Anaerobic Digester at Mesophilic and Thermophilic Temperatures
2011
Dustin, J.S. | Hansen, C.L.
The induced bed reactor (IBR) was developed at Utah State University (USU) to apply high-rate anaerobic digestion techniques to high-suspended-solids content substrates (3% to 12% total solids) such as food waste and dairy manures. This technology has been successfully implemented at full-scale multiple installations in the U.S. and Canada as a waste treatment and energy production technology. The objective of this study was to provide a baseline understanding of the performance of the IBR at a range of temperatures and loading rates. Bench-scale reactors (58 L volume) were operated at 35°C, 45°C, and 55°C under three organic loading rates and three corresponding hydraulic retention times for each reactor using a dairy manure starter culture and a dextrose/yeast extract substrate at 30.6 g L-1 COD. Influent and effluent streams were monitored for parameters including solids composition, VFAs, gas quality and quantity, and chemical oxygen demand (COD). Results were integrated with those from a previously published study on operation of the IBR at thermophilic temperatures (55°C). The IBRs were successfully operated for over 180 days, demonstrating a peak COD removal rate of 89% at 35°C. Development of granulated sludge beds comprising settled sludge volumes of 500 mL L-1 (35°C), 250 mL L-1 (45°C), and 120 mL L-1 (55°C) was evident. Operational data regarding reactor performance in terms of COD, VFAs, and biogas are reported. The IBR was demonstrated to operate at all three temperature levels, although the 45°C reactor was susceptible to process upset, and the 55°C reactor produced consistently poor-quality gas compared to the other reactors.
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