Microbial desalination cell based wastewater treatment and resource recovery: Various challenges

The scarcity of freshwater is the force to innovate desalination technology. However, the present desalination technologies are not sustainable due to enormous energy needs and capital costs. Therefore, there is a need to develop sustainable and eco-friendly technologies to diminish the techno-economic restrictions of heat and membrane-based desalination. As a novel technology, microbial desalination cell (MDC) has been paid attention due to its capacity to remove salts from seawater, organics from wastewater with the concurrent recovery of electricity and value-added products. MDC recovers electrical energy from the bacterial degradation of organics. The recovered electrical energy and the potential difference transport the ions, which subsequently generate the value-added products. This chapter presents the prospects of MDC as (i) a sustainable technology for desalination, wastewater treatment and value-added resources (H2O2, H2, NaOH, HCl, humic and fulvic acid) recovery, and (ii) an electrochemical process to remove specified contaminants (i.e., Cu, NH4 +-N, Cr, Ni, Pb, As). Instead of having ecological and economic prospects, the real application of MDC is inadequate due to several engineering challenges. Therefore, this chapter also covers the challenges related to technical factors (reactor design, internal resistance, electrode and membrane materials, controlling fouling) and operating factors (imbalance of pH caused by ion transport, lower rate of ion transport, lower adhesion of biofilms on electrode, and biofilm contamination). Finally, the chapter represents several recently developed MDC reactor designs suitable to mitigate the current challenges. The recent MDC designs can alleviate the pH imbalance and ion transport barriers.