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
Bioengineering and Environmental Sciences (BEES), CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad 500 007, India.
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 (βaand βc) and polarization resistance (Rp) 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.
Keywords: Microbial electrolysis; Bioelectro fuel; Applied potential; Volatile fatty acids; Acid-shock pretreatment.