Investigation of modified microbial desalination cell performance in sweetening of saltwater

Abstract

BACKGROUND AND OBJECTIVE: Lack of enough fresh water is a global challenge. Water sweetening can be done using thermal or membrane systems that each of them requires significant energy. 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: In this experimental study, 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: Based on the results of this study, modified MDC with ozone and ultrasound waves could be an appropriate option for desalinating salt water. © 2018, Babol University of Medical Sciences. All rights reserved