Hydraulic retention time drives changes in energy production and the anodic microbiome of a microbial fuel cell (MFC)

The fish -canning industry generates large quantities of wastewater that typically contains high concentrations of organic matter and salts. However, little is known about the potential valorization of this type of industrial wastewater using the microbial fuel cell (MFC) technology operated in a continuous flow mode. This study investigated the impacts of three different hydraulic retention times (HRT) on the performance, energy production, and prokaryotic and eukaryotic anodic microbiome of a two -chambered H -cell type MFC inoculated with activated sludge from a seafood industry. The HRT determined changes in voltage, current density, and power density of an MFC. Decreases in the efficiency of removal of organic compounds in the range of 20-40 % and increases in the abundance of archaeal communities were related to decreased energy production (from 970 mV at HRT of 1 day to 639 mV and 578 mV at HRTs of 3 and 6 days, respectively) at greater HRTs. Increases in the relative abundance of electroactive microorganisms such as those belonging to the genera Geobacter, Shewanella, Arcobacter, and Clostridium was related to increased energy production at lower HRT. This study shows there is a critical balance between the HRT and prokaryotic microorganisms contributing to organic removal rate and increases and decreases in energy production in an MFC treating wastewater from the fish -canning industry and operated in a continuous mode.