Impact of the rotational speed and counter electrode configuration on the performance of a rotating disc bioelectrochemical reactor (RDBER) operated as microbial electrolysis cell

Abstract

Abstract A 10 L Rotating Disc Bioelectrochemical Reactor (RDBER) was operated as a microbial electrolysis cell (MEC) under different rotational speeds and counter electrode configurations. Increasing the anode’s speed from 0.25 to 1 rpm raised the anodic current density from 55 ± 14 to 100 ± 7 A m -3 while increasing hydrogen production rates from 0.05 ± 0.01 to 0.18 ± 0.01 . Higher speeds provided no further benefit. Moving the counter electrodes to the upper reactor half reduced observed hydrogen shuttling. The modified RDBER reached current densities of 1.98 ± 0.11 A m -2 and 0.99 ± 0.03 hydrogen production. Optical coherence tomography confirmed biofilm morphology changes but no significant increase in biovolume or substratum coverage. Hydrogen recovery remained below 50%. While the RDBER achieved high volumetric current densities and volumetric hydrogen production rates compared to other MEC pilots, improvements in anodic current density and cathodic hydrogen recovery are required for practical application. Graphical Abstract Highlights 10 L RDBER was operated as MEC in batch experiments at different rotational speeds hydrogen shuttling was reduced through cathode displacement Current densities of 198 ± 11 A m -3 and H 2 -production rates of 0.99 ± 0.03 L L R -1 d -1 Anodic biofilm parameters were not significantly altered by cathode modification

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Identifiers

DOI

10.1101/2025.03.06.641858

Journal

bioRxiv (Cold Spring Harbor Laboratory)

Year

2025