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

J. Annie Modestra, M. Lenin Babu, S. Venkata Mohan

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 (4000 mg/l and 8000 mg/l) on biohydrogen production with simultaneous remediation was studied at 0.2 V and 0.6 V applied potential along with closed circuit (CC) and control operations. Maximum cumulative H₂ production (CHP) and hydrogen production rate (HPR) of 39.35 ml and 0.057 mmol/h was observed at 0.6 V. VFA utilization as substrate was high at 0.6 V (68%) followed by 0.2 V (45%), CC (39%) and control (19%). Dehydrogenase activity, pH profiles, low redox slopes (β_a and β_c) and polarization resistance (R_p) at 0.6 V 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.

Graphical abstract

Keywords: Microbial electrolysis; Bioelectro fuel; Applied potential; Volatile fatty acids; Acid-shock pretreatment.