Designing for Improved Performance with Staged Anaerobic Digestion

Abstract

Recent research provides ample indication that a conventional, single-stage flow train is not the optimal configuration for realizing the full potential for solids stabilization and pathogen reduction in mesophilic anaerobic digestion--and it is now time to put these research findings into practice. Temperature Phased Anaerobic Digestion, two-phase digestion and other advanced digestion process trains may be too ambitious for some, but simple staging of anaerobic digesters would be a good start in improving digestion performance. Staging coupled with draw-and-fill feeding would be even better. Encouragement to do so is provided by a twostage mesophilic digestion system in Rockford, Illinois that has been beating performance expectations in over four years of operation. This paper discusses the Rockford installation, plus a new two-stage digestion system currently in design for the Minneapolis-St. Paul metropolitan area. The anticipated system operation and the design adjustments required to accommodate future operation in a two-stage mode are reviewed.