Electro-fermentation of real-field acidogenic spent wash effluents for additional biohydrogen production with simultaneous treatment in a microbial electrolysis cell

Abstract

Real-field acidogenic effluents rich in short chain carboxylic acids/volatile fatty acids (VFA) were obtained from biohydrogen (H2) producing reactor operated with spent wash as substrate. A single chambered microbial electrolysis cell (MEC) was designed to electro ferment the effluents towards additional H2 production with simultaneous treatment using acid pretreated biocatalyst. The effect of VFA concentration (4000mg/l and 8000mg/l) on biohydrogen production with simultaneous remediation was studied at 0.2V and 0.6V applied potential along with closed circuit (CC) and control operations. Maximum cumulative H2 production (CHP) and hydrogen production rate (HPR) of 39.35ml and 0.057mmol/h was observed at 0.6V. VFA utilization as substrate was high at 0.6V (68%) followed by 0.2V (45%), CC (39%) and control (19%). Dehydrogenase activity, pH profiles, low redox slopes (βa and βc) and polarization resistance (Rp) at 0.6V corroborated well with the H2 production at both the VFA concentrations operated. Additional H2 recovery utilizing VFA rich effluents demonstrates the sustainability of this integrated approach through electro fermentation in a single chamber MEC.