Flow field design for zero-gap microbial electrolysis cells using synthetic and real wastewater

Increasing performance in microbial electrolysis cells (MECs) requires the development of optimized reactor configurations with minimal internal resistance and capable to operate with real wastewater. Here, the impact of two different flow fields (serpentine and circular) was examined in zero-gap MECs with synthetic and real wastewaters. The serpentine flow field enabled a uniform distribution of the electrolyte in the anode chamber, resulting in larger current densities at lower flow rates compared to the circular flow field. Electrochemical tests using synthetic media with high buffer capacity revealed more stable and higher performance with the serpentine flow field compared to the circular flow path, producing larger current density (23.7 +/- 0.8 A/m(2) vs 21.9 +/- 5.6 A/m(2)), hydrogen production rate (75.8 +/- 4.1 L/L-d vs 54.3 +/- 2.4 L/L-d), cathodic coulombic efficiency (>91 % vs >50 %), and an overall lower internal resistance (12.5 +/- 0.5 m Omega m(2) vs 14.8 +/- 3.7 m Omega m(2)). Continuous operation for over 30 days with real wastewater indicated higher tolerance of the MECs with serpentine flow field toward media with large concentration of suspended solids, producing a current density of 5.4 +/- 1.1 A/m(2) and a hydrogen production rate of 22.2 +/- 6.2 L/L-d. The results presented here underscore the importance of reactor design and architecture in optimizing MEC performance for hydrogen production from liquid wastes.