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

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 anodes 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 [Formula]. 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 [Formula] 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 O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=87 SRC="FIGDIR/small/641858v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@f8e054org.highwire.dtl.DTLVardef@14fbaaeorg.highwire.dtl.DTLVardef@1692978org.highwire.dtl.DTLVardef@121b116_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LI10 L RDBER was operated as MEC in batch experiments at different rotational speeds C_LIO_LIhydrogen shuttling was reduced through cathode displacement C_LIO_LICurrent densities of 198 {+/-} 11 A m-3 and H2-production rates of 0.99 {+/-} 0.03 L LR-1 d-1 C_LIO_LIAnodic biofilm parameters were not significantly altered by cathode modification C_LI