Three-chamber bioelectrochemical system for biogas upgrading and nutrient recovery

Here, an innovative three-chamber bioelectrochemical system configuration is proposed to combine COD, CO2 and NH4+ removal into a single device. In the proposed process, while COD oxidation and CO2 reduction occurred, respectively, in the anodic and cathodic chamber, the consequent current generation promoted the migration of target ionic species towards an intermediate accumulation chamber, across cation and anion exchange membranes, respectively. Under this configuration, COD removal proceeded in the anode chamber with an average removal rate of 841 mgCOD L–1 d–1 while the cathode was able to remove 2.1 gCO2 L–1 d–1 and produce 60 meq L–1 d–1 of CH4. Around 90% of the removed CO2 was contained in the concentrated spill (at around 20 g L–1 of bicarbonate), which was recovered from the intermediate accumulation chamber and also contained the removed nitrogen as ammonium ion (around 32% removal and around 4-fold concentration with respect to the anode influent). Methane generation allowed a partial recovery of energy of overall energy consumption costs of both COD and CO2 removal. This study confirms the possibility to combine three processes into a single bioelectrochemical device.