Three‐chamber Bioelectrochemical System for Biogas Upgrading and Nutrient Recovery

Abstract

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.

Electron Recycle Concept in a Microbial Electrolysis Cell for Biogas Upgrading

“…All the parameters evaluated in this work have been already described in previous research, namely, electrodic reactions efficiencies [28,29], CO 2 removal and its mass balance [25], potential evolution description [30], and energy consumption evaluation [31]. Tab.…”

“…Indeed, the migration of ionic species different from protons and hydroxyls transport across ion exchange membranes promoted the protons accumulation in the anodic chamber and the accumulation of hydroxyl ions in the cathodic chamber with the consequent pH split in the two bioelectrochemical reactor chambers [17,18]. Continuous generation of acidity and alkalinity, along with the electroosmotic phenomenon, can be used as a strategy to increase the capacity removal and or the recovery of target compounds like ammonium from liquid effluents [19,20] or phosphorus remobilization [21].…”

Ammonium Recovery and Biogas Upgrading in a Tubular Micro-Pilot Microbial Electrolysis Cell (MEC)

“…The utilization of the bioelectromethanogenesis reaction requires the utilization of a microbial electrolysis cell (MEC), in which, by the application of an external potential, partial energy support is supplied by the anodic bioelectrochemical oxidation of organic waste streams [ 33 , 34 ]. Several authors proposed the utilization of MECs for biogas upgrading into biomethane with different configurations, including the direct treatment of biogas [ 35 , 36 ] or separate conversion of the residual CO 2 from the upgrading step in the biocathode [ 37 ]. Moreover, in an MEC biocathode, the main CO 2 removal mechanism along with the bioelectromethanogenesis reaction is represented by the CO 2 sorption as HCO 3 − promoted by alkalinity generation, which directly depends on the transport of ionic species different from protons and hydroxyls for the maintenance of electroneutrality [ 38 ], i.e., the alkalinity generation in an MEC biocathode permits the removal of up to 9 moles of CO 2 for each mole of CH 4 produced [ 39 ].…”

Bioelectrochemical Systems for Removal of Selected Metals and Perchlorate from Groundwater: A Review

“…In BESs, both oxidation and reduction reactions can occur, respectively at the anode and at the cathode [45][46][47], and thus oxidized contaminants such as nitrate, vanadium, perchlorate or chromium can be reduced in the cathodic environment, while arsenic and/or organic matter can be oxidized in the anodic environment (Figure 1), with possible complete groundwater remediation due to the integration in a single treatment sequence. Energies 2018, 11, x FOR PEER REVIEW 2 of 22 as being able to produce energy from more complex substrates such as domestic and industrial wastewater: dairy [15-18], food-processing [19], leachate [20,21], pharmaceutical [22], brewery [23,24], winery [25], oil [26] and petroleum refinery wastewater [27] are amongst the principal examples.After the initial exclusive interest as possible net energy producers from organic matter degradation, which had somehow disappointed researchers' initial development expectations [28][29][30][31][32], BES technology has been used as a flexible platform for fulfilling several other tasks: brackish water desalination in microbial desalination cells (MDC) [33,34], hydrogen production in the microbial electrolysis cell (MEC) setup [35,36], microbial electrosynthesis (MES) of valuable chemicals and commodities [37,38], power-to-gas energy storage [39], nutrient recovery [40,41], and biosensing [42,43] are some notable examples.Due to the intrinsic characteristics of the technology, BES has been identified as a promising technology for groundwater bioremediation [44]. In BESs, both oxidation and reduction reactions can occur, respectively at the anode and at the cathode [45][46][47], and thus oxidized contaminants such as nitrate, vanadium, perchlorate or chromium can be reduced in the cathodic environment, while arsenic and/or organic matter can be oxidized in the anodic environment (Figure 1), with possible complete groundwater remediation due to the integration in a single treatment sequence.…”

“…After the initial exclusive interest as possible net energy producers from organic matter degradation, which had somehow disappointed researchers' initial development expectations [28][29][30][31][32], BES technology has been used as a flexible platform for fulfilling several other tasks: brackish water desalination in microbial desalination cells (MDC) [33,34], hydrogen production in the microbial electrolysis cell (MEC) setup [35,36], microbial electrosynthesis (MES) of valuable chemicals and commodities [37,38], power-to-gas energy storage [39], nutrient recovery [40,41], and biosensing [42,43] are some notable examples.…”