Production of hydrogen from domestic wastewater using a bioelectrochemically assisted microbial reactor (BEAMR)

Hydrogen production from domestic wastewater was examined using a plain carbon electrode or graphite-granule packed-bed bioelectrochemically assisted microbial reactors (BEAMRs) capable of continuous or intermittent hydrogen release. When graphite granules were added to the anode chamber (packed-bed mode) current density was increased when the domestic wastewater had a high initial chemical oxygen demand (COD > 360 mg / L), and produced a maximum Coulombic efficiency of 26% (applied voltage of 0.41 V) and a maximum hydrogen recovery of 42% (applied voltage of 0.5 V). The packed-bed system successfully treated the wastewater, with removal efficiencies of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and dissolved organic carbon (DOC) in the range of 87-100%. The final BOD of the treated wastewater was always reduced to less than 7.0 ± 0.2 mg / L. Overall hydrogen production based on COD removal was a maximum of 0.0125 mg - H₂ / mg - COD (154 mL - H₂ / g - COD versus a maximum possible conversion of 0.126 mg - H₂ / mg - COD), with an energy requirement equivalent to 0.0116 mg - H₂ / mg - COD, producing an 8% net yield of H₂. These results demonstrate that a wastewater treatment based on a BEAMR reactor is feasible, but improvements are needed in hydrogen recoveries and Coulombic efficiencies to increase the overall hydrogen yield.