Fundamentals of Microbial Desalination Cell

Abstract

Microbial desalination cells (MDCs) are bioelectrochemical tools which exploit organic matter in wastewater to use as an energy source for desalinating salt water. These cells desalinate water by expending the electric potential gradient established by exoelectrogenic bacteria to drive ion transport through a series of ion exchange membranes (Kim and Logan 2013). This device has the potential to solve the world’s freshwater crisis. As such, a significant increase in the number of installed desalination capacities were noticed since the 1980s (Greenlee et al. 2009). However, conventional technology of desalination consumes high amounts of energy which is a matter of concern as the stocks of fossil fuels are rapidly depleting. Theoretically, if we consider a thermodynamically reversible process at 50% water recovery, the minimum energy required for desalination of typical sea water is approximately 1 kWh m−3. The most efficient systems of seawater desalination using reverse osmosis have achieved an energy requirement of only 1.8–2.2 kWh m−3. However, considering the energy needs for pre-treatment, pumping, etc., the overall consumption stands at about 3–4 kWh m−3, which is not efficient at all (Liu et al. 2011). MDCs have emerged as a solution to this problem because they accomplish environment friendly wastewater treatment and at the same time they drastically diminish the energy expenditure for desalination (Cao et al. 2009).