Membrane configuration influences microbial capacitive desalination performance

Abstract

A microbial capacitive desalination cell (MCDC) is a new bioelectrochemical reactor for energy-positive wastewater treatment and desalination. So far, MCDCs have only used two cation exchange membranes (CEMs) to separate three chambers (CC-MCDC), and in this study we investigated how and why different membrane setups can impact system performance. Three types of MCDCs were developed by using different combinations of CEMs and anion exchange membranes (AEMs). In addition to the CC-MCDC, a CA-MCDC used a CEM to separate the anode chamber from the middle chamber and an AEM to divide the middle and cathode chambers, and an AA-MCDC used two AEMs to separate the three chambers. Results showed that the membrane effects are significant due to the different ion transfer mechanisms. The CA-MCDC shows higher performance by removing salts from all three chambers, with anode, middle, and cathode chamber desalination efficiencies of 14.5%, 44.4%, and 5.3%, respectively. The performance of the reactors decreased by 7–12% after a 5-month operation, and the AA-MCDC showed the lowest membrane scaling potential during the long-term operation.