Two-side cathode microbial electrolysis cell for nutrients recovery and biogas upgrading

Here a three-chamber microbial electrolysis cell (MEC) has been developed to couple the CO2 removal from a gas mixture to the ammonium nitrogen recovery. The here proposed MEC adopted an innovative two-side cathode configuration, where two identic cathodic chambers are connected in parallel by a titanium wire and separated from an intermediate anodic compartment by an anion and a cation exchange membrane (AEM and CEM). The two-side configuration has been proposed as a post treatment unit capable to perform the biogas upgrading through the CO2 reduction and removal into the cathodic chambers as well as the ammonium recovery from a liquid waste stream due to its migration for the electroneutrality maintenance of the cell. The experiments have been conducted at two different anodic potential (i.e. +0.2 and −0.1 V vs Standard Hydrogen Electrode SHE), using a synthetic feeding solution and a gas mixture simulating a domestic wastewater and a biogas, respectively. The results obtained using the new configuration have been also compared to the performances reported in a previous work where a three – chamber MEC, characterized by the presence of an intermediate accumulation chamber, was aimed to the CO2 removal and to nitrogen recovery; this comparison highlighted higher performances of the two-side configuration in terms of methane production, CO2 removal and energy consumption, keeping the same anodic performances.