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Evaluation of Mixing in Anaerobic Digesters Using Hydraulic Recirculation

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Anaerobic digesters at the City of Sioux Falls, South Dakota were originally designed to be mixed by the hydraulic recirculation of sludge and the recirculation of biogas through gas compressors. The compressors are currently at the end of their useful life and are scheduled to be replaced in the next 3-4 years. Tracer analyses were conducted to evaluate the effectiveness of mixing the primary digesters strictly through hydraulic recirculation. The effectiveness was measured by computing the active volume of the digesters with various mixing schemes and measuring biogas. The results showed that the digesters being fed (recirculated) through the top resulted in a higher active volume than those digesters being fed into the side. This study showed that the Sioux Falls Water Reclamation Plant (SFWRP) was able to effectively mix their primary digesters using only hydraulic recirculation in a system that was designed to use both hydraulic and gas recirculation.

Keywords: Active Volume; Anaerobic Digestion; Hydraulic Residence Time; Initial; Mixing Energy; Velocity Gradient

Document Type: Research Article


Publication date: January 1, 2009

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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