Anaerobic digestion of dairy manure in a hybrid reactor with biogas recirculation

A novel anaerobic hybrid reactor (AHR) configuration incorporating floating support media for biomass immobilization and biogas recirculation for enhanced mixing was used for anaerobic digestion of dairy manure. No pretreatment or solid liquid separation was applied. The reactor was operated at high influent volatile solids (VS) and organic loading rates (OLR) of up to 9.87% and 7.30 g VS/l day, respectively. After 149 days of continuous operation the results revealed that a high amount (38.1 g VSS) of biomass was able to attach itself to the support medium being used. The investigated AHR configuration achieved COD, BOD, TS, and VS removal efficiencies of 48-63, 64-78, 55-65, and 59-68%, respectively, at a hydraulic retention time (HRT) of 15 days. The corresponding average methane production value obtained in this study was 0.191 l/g VS added.