Influence of ionic conductivity in bioelectricity production from saline domestic sewage sludge in microbial fuel cells

This study aimed at manipulating ionic conductivity (EC) to harvest the maximum electrical energy from seawater-based domestic wastewater sewage sludge (SWS), unique to only a few cities, through microbial fuel cell (MFC). SWS has never been investigated as a MFC substrate before, and thus the influence of high in-situ EC on the energy recovery was unknown. In this study, the EC of the SWS was reduced through mixing it with fresh water-based domestic wastewater sewage sludge (FWS) or diluted 50% using deionized water while FWS and SWS were individually served as reference treatments. SWS:FWS mix (1:1) exhibited a maximum Coulombic efficiency of 28.6 ± 0.5% at a COD removal of 59 ± 3% while the peak power density was 20-fold higher than FWS. The improved performance was due to the lower ohmic internal resistance (36.8 ± 4.2 Ω) and optimal conductivity (12.8 ± 0.2 mS cm−1). Therefore, dilution with FWS could enhance energy recovery from SWS.