Ozone-cathode microbial desalination cell; An innovative option to bioelectricity generation and water desalination

Abstract

Microbial desalination cell (MDC) is a new approach of water desalination methods, which is based on ionic species removal from water in proportion to the electric current generated by bacteria. However, the low current generation and insufficient deionization in this technology have created challenges to improve the process. Here, the performance of MDC using ozone as a new electron acceptor (O3-MDC) was evaluated versus another operated independently with oxygen (O2-MDC). Results showed the maximum open-circuit voltages of 628 and 1331 mV for 20 g L−1 NaCl desalination in O2-MDC and O3-MDC, respectively. The O3-MDC produced a maximum power density of 4.06 W m−2 (about 11 times higher than O2-MDC) while at the same time was able to remove about 74% of salt (55.58% in the O2-MDC). Each cycle of O2-MDC and O3-MDC operation lasted about 66 and 94 h, respectively, indicating a more stable current profile in the O3-MDC. Moreover, sequencing test based on 16S rRNA gene showed that the anode biofilm had more diverse microbial community than anolyte sample. Proteobacteria, Firmicutes and Acidobacteria were from dominant microbial communities in anode biofilm sample. Accordingly, the results revealed that ozone can enhance MDC performance either as a desalination process or as a pre-treatment reactor for downstream desalination processes.