A direct approach for enhancing the performance of a microbial electrolysis cell (MEC) combined anaerobic reactor by dosing ferric iron: Enrichment and isolation of Fe(III) reducing bacteria

• A new approach was developed to enrich exoelectrogens via dosing Fe(III) in MEC-anaerobic reactor.
• A novel Aeromonas hydrophila was isolated from the anodic biofilm of MEC-anaerobic reactor.
• The isolated strain was capable of Fe(III) reduction, decolorization and electro-activity.

Enrichment of microbial functional consortium is critical to strengthen the performance of bio-electrochemical devices for treating industrial wastewaters. This study described a newly enrichment approach for electrochemically active iron reducing bacteria (IRB) through dosing Fe(III) into a MEC combined anaerobic reactor (R1) for dye wastewater treatment. After 51 days operation, reactor R1 presented the highest performance for the degradation of organic matter and dye as compared to the reference reactors without Fe(III). Subsequently, five isolates were obtained from the anodic biofilm of R1, in which a novel IRB related to Aeromonas hydrophila was selected as a model strain due to its highest Fe(III) reducing ability cyclic voltammetry and microbial fuel cell (MFC) technology showed that the model strain has the electrochemical activity and electricity generation capability. After inoculating this model strain, the decolorization of three dyes also reached over 90% at an initial concentration of 100 mg/L. This study might provide a novel method to enrich electrochemically active IRB in the bio-electrochemical reactor for treating industrial wastewater.