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A theoretical model that describe the effect of design and operational conditions on current density distribution in a bioelectrochemical reactor used as microbial electrolysis cell (MEC) is described in this study. This model is proposed considering an approach where a direct electron transfer mechanism from the biofilm to the electrode surface takes place (mechanism present in most of microbial systems) and is governed by a dual donor-acceptor Nernst-Monod bioelectrochemical kinetic expression. The bioelectrochemical reactor is modelled considering two flow electrochemical reactor designs (a reactor design based in literature reports and a modified system proposed by the authors) operating at different flow inlet velocities and electrical overpotentials. Results obtained from the numerical solution shows that flow distribution is an essential aspect that impact the reactor performance, since concentration profiles and electrical potential-current distributions are strongly dependent on flow regime. Modified inlet configuration displays a more homogeneous fluid distribution and this behavior directly affects the mass transport and current density performance, as a result higher current density values are obtained for such configuration. Finally, it is expected that the information obtained from the analysis carried out in this report will provide us with a theoretical basis to realize the construction of a bioelectrochemical reactor prototype to develop the MEC concept.

Electrochemical reactors with a flat parallel plate electrode configuration and diverse flow channel designs have been extensively used in the study of different electrochemical processes at lab and bench scales, and they have been scaled up for some electrosynthesis and energy-storage processes at semipilot and industrial levels. Progress in the electrochemical process applications demands the use of different computer and experimental-assisted techniques to design novel electrochemical reactors. The objective of this work is to evaluate the hydrodynamic performance of different electrochemical reactor designs and quantify their effect on velocity magnitude through numerical and experimental studies using computational techniques like computational fluid dynamics (CFD) and digital image treatment. For local velocity magnitude measurements, a digital imaging treatment, based on the use of an optical flow algorithm, to try the validation of velocity profiles obtained by CFD is implemented. This experimental technique determined reliably that the problems associated with the use of the empty channel in the flow pattern are mainly associated with high velocities and recirculation zones, which are not detected by CFD simulations in the first instance. Also, the findings associated with the velocity behavior using this proposed technique agreed with those obtained by the traditional experimental flow characterization technique like residence time distribution, nevertheless, further work will be needed to refine the measurements and perform its comparison with other most employed velocimetry techniques.

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