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Updated: Apr 12, 2026

Continuously-stirred Anaerobic Digester to Convert Organic Wastes into Biogas: System Setup and Basic Operation
Published on: July 13, 2012
Semi-continuous mesophilic anaerobic digester performance under variations in solids retention time and feeding
Nathan D Manser1, James R Mihelcic1, Sarina J Ergas1
1Department of Civil and Environmental Engineering, University of South Florida, 4202 E Fowler Avenue, ENB 118, Tampa, FL 33620, United States.
Abstract:
The goal of this research was to understand the effect of solids retention time (SRT) and feeding frequency on the performance of anaerobic digesters used to recover bioenergy from swine waste. Semi-continuous mesophilic anaerobic digesters were operated at varying SRTs and feeding frequencies. Performance metrics included biogas and methane production rates, biomass robustness and functionality and removals of volatile solids, soluble chemical oxygen demand, the fecal-indicator bacteria Escherichia coli, and the human pathogen Salmonella. Biochemical methane formation potential and specific methanogenic activity assays were used to demonstrate biomass robustness and functionality. Results indicated that anaerobic digesters fed weekly had higher average methane yields (0.20 vs. 0.18m(3)CH4/kg-VSadded), specific methanogenic activities (40 vs. 35ml/day), and fecal indicator bacteria destruction (99.9% vs. 99.4%) than those fed every-other day. Salmonella, soluble COD, and VS destruction did not change with varied feeding frequency; however, higher removals were observed with longer SRT.
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