Microbial Electrochemical Technologies: Coupling Wastewater Treatment with Resource Recovery

Microbial electrochemical technologies (METs) are a promising approach in the context of global warming and circular economy. The achievement of the so-much-desired carbon neutrality can be a reality by coupling carbon capture METs with other electrochemical or not electrochemical bioprocesses. Wastewaters are nowadays considered a potential source of energy (electricity, hydrogen, and methane) and platform molecules (volatile fatty acids, alcohols, biopolymers, etc.) that can be upgraded with METs such as microbial fuel cells (MFCs), microbial electro-synthesis (MES), and microbial electrolysis cells (MECs). METs rely on the use of whole microbial cells as biocatalysts. The microorganisms used in such systems are called electroactive microorganisms (EAMs) and have the outstanding ability to perform extracellular electron transfer processes for energy metabolism. EAM can use electrodes either as terminal electron acceptors (exoelectrogens) or as electron sources (electrotrophs). In this chapter, the principles of technologies such as MFC, MES, and MEC employed for wastewater treatment and energy recovery are discussed. Furthermore, the main technical bottlenecks encountered such as scalability, process yields, and electron transfer interaction limitations between EAM and electrodes are addressed. Lastly, ongoing approaches and perspectives to overcome critical issues to upscale METs for wastewater treatment and resource recovery are discussed.