Microbial electrolysis cell to enhance energy recovery from wastewater treatment

Energy intensive activate sludge treatment is the most utilized technology for municipal wastewater treatment. However, an innovative way to harvest part of the energy contained in municipal wastewater is offered by the utilization of microbial electrolysis cells (MECs). In an MEC, through the utilization of electro active microorganism, is possible to couple the oxidation organic matter with the generation of value-added reduced products, such as methane, similar to the anaerobic digestion process. MECs typically consist of a bio-anode and a (bio)-cathode separated by an ion exchange membrane (IEM). The addition of external energy usually is required to make the cathodic reaction thermodynamically feasible. Here, a continuous flow methane- producing MEC equipped with an anion exchange membrane was operated in a continuous flow mode for over 60 d at two different poised anode potentials (+ 0.20 and -0.10 V vs. standard hydrogen electrode, SHE) and with a fixed organic load rate (1.08 gCOD/Ld). The MEC showed a high COD removal efficiency (92 ± 1%), with a net energy recovery (122 ± 3 %, at -0.1 V) and low sludge production (0.09 gCOD/gCOD), making its utilization attractive in the frame of low strength wastewater treatment.