Downstream application of a microbial fuel cell for energy recovery from an Arthrospira maxima fed anaerobic digester effluent

Abstract

Anaerobic digestion of Arthrospira maxima biomass produced an effluent stream that consisted of residual organic compounds not converted into biogas. Further polishing of the effluent presented the opportunity to extract additional energy and improve the overall systems biomass-to-energy efficiency. In this study a microbial fuel cell was placed downstream of a CSTR and AAR anaerobic digester to treat the effluent stream. Feed concentration (C₀) and hydraulic retention time were varied across the MFC, which in turn resulted in a range of OLRs of 2.7–21.6 g TCOD L⁻¹ d⁻¹ being applied. An increase in OLR resulted in lower total chemical oxygen demand (TCOD) removal and Columbic efficiencies (CE). At a C₀ and HRT (2.7 g TCOD L⁻¹ and 12 h), the polishing microbial fuel cell had a CE of 5.2% and removed 63% of the TCOD, which resulted in a maximum energy capture efficiency of 10.4%.