Capabilities of Modified Microbial Desalination Cell in Sweetening of saltwater

Due to the fresh water scarcity in many parts of the world, desalinating of water and wastewaters has been taken into consideration now. Microbial desalination cell (MDC) is a new technology which can desalinate water, generate electricity, and simultaneously purify wastewaters in a reactor. However, low current generation and deionization are from main challenges of this process. This study aimed to improve the MDCs efficacy. Three-cell MDC consisted of anode, cathode, and middle chambers, was designed. Here, ozone was used as a new electron acceptor in MDC (O3-MDC), and middle chamber solution containing 20 g/L NaCl was pretreated by ultrasonic process. The reactor operated under oxygen diffusion (O2-MDC), and without ultrasonic pretreatment was chosen as control. Biofilm formation on anode surface and dominant bacteria in the O3-MDC reactor were studied using Scanning Electron Microscopy (SEM), and 16S rRNA gene sequencing, respectively.
Findings: saltwater pre-treatment caused to increase the electrical conductivity from 28.1 ms/cm to 35.5 ms/cm. Moreover, the use of ozone in the reactor significantly improved the reactor performance in terms of bioelectricity generation and water desalination, so that O2-MDC and O3-MDC were able to remove 74% and 55.58% of NaCl from water, respectively. Proteobacteria, firmicuites and acidobacteria were dominant microbial communities in the anode biofilm based on 16S rRNA sequencing. Modified MDC can be a good option for water desalination if properly navigated. Although the process is still subject to some limitations, conducting such studies can provide basics of process operationalization and commercialization.