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-H-2/mg-COD (154 mL-H-2/g-COD versus a maximum possible conversion of 0.126 mg-H-2/mg-COD), with an energy requirement equivalent to 0.0116 mg-H-2/mg-COD, producing an 8% net yield of H-2. 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. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.