Using microbial fuel cells (MFCs) to power a capacitive deionization (CDI) process enables simultaneous removal of salinity and organic matter in wastewater. The desalination performance of an MFC-CDI system can be influenced by not only the capacity of individual components but also the arrangement and operation of the MFC-CDI circuit. Five typical circuits (consisting of serial- or parallel-connected MFCs or CDIs) and two ion-desorption modes (short-circuit and reverse-voltage desorption) were compared. Results showed that the MFC-CDI system could be reasonably modeled (R-2 > 0.967) by a first-order resistor-capacitor circuit. The optimal arrangement of the MFC-CDI circuit depended on the electrical characteristics of selected MFCs and CDIs as well as operating conditions. When the system was powered by two MFCs of a larger internal resistance (146 Omega), the highest salt removal after 60 min (m(60); 7.5 mg) was achieved by paralleling the two MFCs; with MFCs of a smaller resistance (12 Omega) being used, the highest m(60) (16.5 mg) was obtained when the two MFCs were connected in series. Further analysis revealed that the MFCs internal resistance and open-circuit voltage, along with the CDI's internal resistance and capacitance, were the chief factors affecting the charge transfer and accordingly desalination on the CDI electrodes. (C) 2015 Elsevier B.V. All rights reserved.