Microbial electrochemical technologies (METs) represent a promising platform for sustainable wastewater treatment. Thereby, METs may not only allow energy savings by reducing the need for aeration, but may even aim at providing an additional energy gain, for example, as electricity in microbial fuel cells (MFCs). The key element is the anode community, in which complex wastewater constituents are broken down and extracellular electron transfer is performed. So far, most studies exploiting real domestic wastewater for METs have focused on the engineering perspective. In this study, the role of the microbial community of anodes in treating domestic wastewater was investigated. Wastewater of a primary clarifier was regularly fed to 400 mL batch reactors and the systems performance was assessed in terms of chemical oxygen demand removal, current production, and coulombic efficiency, as well as biomass formation and biomass composition. Originating from an identical source and regularly fed with identical wastewaters, microbially diverse but functionally stable electroactive anode biofilms were formed, demonstrating functional redundancy as well as flexibility.