Membrane Configuration Influences Microbial Capacitive Desalination Performance

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 the 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 and middle chambers and an AEM to divide the middle and cathode chamber, 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 the anode, middle, and cathode chamber desalination efficiency of 14.5%, 44.4%, and 5.3%, respectively. The performance of reactors decreased by 7-12% after 5-month operation, and the AA-MCDC showed the lowest membrane scaling potential during long-term operation.