Towards upscaling microbial desalination cell technology: A comprehensive review on current challenges and future prospects

Abstract

Shortage of potable water is the driving force behind desalination practices mainly performed by conventional thermal and membrane-based technologies. However, conventional desalination technologies are unsustainable due to their high energy requirements. This highlights the necessity of developing more sustainable and eco-friendly alternatives. As an emerging technology, microbial desalination cell (MDC) has attracted a great deal of attention due to its ability to desalinate seawater, treat wastewater, and recover electricity and value-added products in a single reactor. The technology produces electricity through the biodegradation of organics present in wastewater. The recovered electricity derives the migration of ions, and is subsequently collected as value-added product. The present review summarizes the prospects of MDC as (i) a sustainable green desalination technology, (ii) a cost-effective approach for simultaneous wastewater treatment and recovery of value-added products (i.e., HCl, NaOH, H2O2, H2, humic and fulvic acid), and (iii) an electrochemical process for + removal of targeted pollutants (i.e., NH4+-N, Cu, Cr, Pb, Ni, As). Despite the favorable environmental and economic attributes of MDCs, large-scale application of those technology is limited due to a number of engineering and operational challenges. Therefore, this review carefully summarizes all the challenges associated with engineering parameters (i.e., reactor design, internal resistance, cost-effectiveness of electrodes and membranes, membrane fouling), and operating factors (i.e., pH imbalance due to ion migration, low ion transport rate, growth and adhesion of electroactive biofilms, and biofilm inhibition). The interrelationships between the engineering/operational challenges and MDC performances are also concisely explained. Finally, research needs to scale up MDCs for simultaneous desalination, wastewater treatment, and energy-resource recovery are proposed.