Evaluation of Two Dual Digestion Processes: Autothermal Thermophilic Aerobic Pretreatment Followed by TPAD Versus MAD
Abstract:Two dual digestion (DD) processes: autothermal thermophilic anaerobic digestion (ATAD) followed by temperature-phased anaerobic digestion (TPAD) and ATAD followed by mesophilic anaerobic digestion (MAD), are evaluated for digestion of thickened combined municipal solids in terms of volatile solids (VS) destruction, and biogas production. Conventional MAD and ATAD-MAD processes achieved better performance with shorter hydraulic retention time (HRT) of 10d when compared to ATAD-TPAD process with 14d HRT for high organic loading rates (OLRs) (up to 6.75 gVS/L/d). On the other hand when OLR reduced to 3.38 gVS/L/d, ATAD-TPAD system was the most efficient process among the processes compared. The ‘apparent’ inhibition for high OLRs was attributed to substrate availability (unionized acetic acid levels) and inhibition in the TPAD 55°C reactor (1.35 and 3.10 mmol/L for OLRs of 5.06 and 6.75 gVS/L/d, respectively) since unionized acetic acid is substrate as well as inhibitor for methanogenesis.
Document Type: Research Article
Publication date: January 1, 2009
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