Effect of hydrodymamic force and prolonged oxygen exposure on the performance of anodic biofilm in microbial electrolysis cells

In this work, the significance of Reynolds number (N_Re) in evaluating the performance of hydrogen production in MECs was demonstrated. Experiments performed with the same anode under the same operating conditions (applied potential, pH, stirring speed and substrate concentration) showed different performances when operated with different stirrers. An average increase of 30% in hydrogen production was obtained by increasing the diameter of the stirring bar from 1.2 cm to 2.8 cm. This increased the N_Re from ≈900 to ≈4900. The anodic bacteria communities on MEC's anodes were also shown to be unaffected when exposed to oxygen for a prolonged period of time outside the reactor by storing them in buffer solution. This however was not enough to get rid of methanogenic bacteria which were still active on the electrodes after exposing them to oxygen in the air for 24 h and in buffer solution for 5 days.