Investigation of Modified Microbial Desalination Cell performance in Sweetening of Saltwater

BACKGROUND AND OBJECTIVE: Regarding fresh water scarcity rake up controversies in many parts of the world, desalinating of water and wastewaters has now been taken into consideration. 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. METHODS: A modified three-cell MDC consisted of anode, cathode, and middle chambers, was designed in order to water desalination (20 g/L NaCl). Here, the cathode solution was diffused via ozone (O3-MDC) and the middle saline solution was pretreated into an ultrasonic bath. Subsequently, the results achieved in O3-MDC in terms of water desalination and current generation were compared against those of another reactor operated under oxygen diffusion (O2-MDC), and without ultrasonic pretreatment (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; and then current generation from 191 to 131 mV after 24 hr operation. 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. CONCLUSION: 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