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This study focuses on improving the treatment capacity and current output of electrochemically active microorganisms (EAM) during real wastewater treatment. A multi‐carbon‐source artificial wastewater consisting of several carbon sources, which represent typical fermentation and hydrolysis products derived from the otherwise myriad wastewater constituents, was developed as a more realistic simulation thereof. An electrochemically preselected inoculum was obtained by means of re‐suspension of a well‐established EAM biofilm, which was subsequently used to inoculate sterile electrodes. Repeating this procedure yielded increasingly enriched and conditioned biofilms with improved performance. After cultivation in the complex artificial medium, highly efficient fourth generation EAM biofilms were fed real wastewater (i. e. effluent after primary settling) and outperformed those cultivated using a single substrate (i. e. acetate) in terms of current output and chemical oxygen demand (COD) degradation rates.

In this study, electrochemically active microbial biofilms were cultivated and studied at continuously alternating electrode potentials. Compared to cultivation and operation at a single constant potential, this method enhanced microbial turnover and maximum current densities. Electrochemically active microbial biofilms were cultivated in a multi‐carbon source culture for several biofilm generations and were subsequently fed with real, domestic wastewater. Compared to constant potential cultivation, average (N=12) biofilm limiting current density at +0.2 V vs. Ag/AgCl increased from 0.350±0.101 to 0.508±0.099 mA cm−2 with a significant reduction in the time required until the maximum current output was reached from 2.01±0.79 to 1.36±0.71 d. The relative increase in maximum current density and decrease in the time required to reach it are similar. The relative differences of higher over lower values are both approximately 45 %. Biofilm community analysis showed a dominance of Geobacteraceae spp. in the electrochemically active biofilms, which is in accordance with the formal potentials derived from cyclic voltammetry. The overall increase in performance is related to the selection of electrochemically active microorganisms, which exhibit local maxima in their electron transfer kinetics between −0.3 and −0.2 V vs. Ag/AgCl.

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