Low Substrate Loading Limits Methanogenesis and Leads to High Coulombic Efficiency in Bioelectrochemical Systems

Kuntke³

et al. 2017

ChemistrySelect

Ion transport through ion exchange membranes in Bioelectrochemical Systems (BESs) is different from other electrochemical cells as a result of the complex nature of the electrolyte, as the electrolytes in BESs contain many other cations and anions than H+ and OH−. Moreover, these other cations and anions are generally present in high concentrations and therefore determine the ion transport through the membrane. In this work, we provide a theoretical framework for understanding ion transport across ion exchange membranes in BESs. We show that the transport of cations and anions other than H+ and OH− determines the pH gradient between anode and cathode, and on top of that, also determines the membrane potential. Experimental data for microbial electrolysis cells with cation and anion exchange membranes are used to support the theoretical framework. In case of cation exchange membranes, the total potential loss consists of both the pH gradient and the concentration gradient of other cations, while in case of anion exchange membranes, the total potential loss is lower because part of the pH gradient loss can be recovered at the membrane. The presented work provides a better theoretical understanding of ion transport through ion exchange membranes in general and in BESs specifically.

Section: Introductionmentioning

confidence: 99%

Membrane Selectivity Determines Energetic Losses for Ion Transport in Bioelectrochemical Systems

Sleutels¹,

Kuntke³

et al. 2017

ChemistrySelect

“…Acetate was always fed in excess to allow sufficient electron donors for current generation. At the same time, an excess of acetate leads to methane formation . The impact of methanogens can be minimized by limiting the dosing of influent and thereby decreasing the substrate loading to the system .…”

Section: Resultsmentioning

confidence: 99%

Prototype of a scaled‐up microbial fuel cell for copper recovery

Motos

Molina²,

J of Chemical Tech & Biotech

et al. 2017

Self Cite

BackgroundBioelectrochemical systems (BESs) enable recovery of electrical energy through oxidation of a wide range of substrates at an anode and simultaneous recovery of metals at a cathode. Scale‐up of BESs from the laboratory to pilot scale is a challenging step in the development of the process, and there are only a few successful experiences to build on. This paper presents a prototype BES for the recovery of copper.ResultsThe cell design presented here had removable electrodes, similar to those in electroplating baths. The anode and cathode in this design could be replaced independently. The prototype bioelectrochemical cell consisted of an 835 cm2 bioanode fed with acetate, and a 700 cm2 cathode fed with copper. A current density of 1.2 A/−2 was achieved with 48 mW m−2 of power production. The contribution of each component (anode, electrolytes, cathode and membrane) was evaluated through the analysis of the internal resistance distribution. This revealed that major losses occurred at the anode, and that the design with removable electrodes results in higher internal resistance compared with other systems. To further assess the practical applicability of BES for copper recovery, an economic evaluation was performed.ConclusionAnalysis shows that the internal resistance of several lab‐scale BESs is already sufficiently low to make the system economic, while the internal resistance for scaled‐up systems still needs to be improved considerably to become economically applicable.© 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

“…In a BES, the current density depends on the oxidation of organic matter (COD) by microorganisms. The oxidation of organic matter by microorganisms, in turn, depends on the amount and nature of organic compounds, anode potential and other factors also affecting the microorganisms, such as pH . At the same time, the COD:TAN ratio of a certain wastewater is fixed, so manipulating the TAN loading rate also would affect the COD loading and therefore the current density.…”

Section: Introductionmentioning

confidence: 99%

The concept of load ratio applied to bioelectrochemical systems for ammonia recovery

Arredondo

Kuntke²,

J of Chemical Tech & Biotech

et al. 2019

BACKGROUND The load ratio is a crucial parameter to optimize the current driven recovery of total ammonia nitrogen (TAN) from urine. The load ratio is the ratio between the current density and the TAN loading rate. It is currently not known if the load ratio concept applies to a bioelectrochemical system (BES) because the current density and TAN loading rate cannot be controlled independently. RESULTS We found a clear increasing trend in TAN removal efficiency with respect to load ratio in the BES for both human and synthetic urine. The maximum TAN removal efficiency was 60.9% at a load ratio of 0.7, corresponding to a TAN transport rate of 119 gN m−2 day−1 at an electrical energy input of 1.9 kWh kgN−1 (synthetic urine). Low load ratios (<1) were obtained, indicating that the current was not enough to transport all the TAN across the membrane. CONCLUSIONS BES and ES show the same general relationship between TAN removal efficiency and load ratio. Therefore, given a stable current density, the concept of load ratio can also predict the TAN removal efficiency in BES. Higher current densities, and insights into the factors limiting current, are needed to increase the load ratio and therefore the TAN removal efficiency. © 2019 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.