Enhanced production of methane from waste activated sludge by the combination of high-solid anaerobic digestion and microbial electrolysis cell with iron–graphite electrode

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2015-01, Vol.259, p.787-794
• Main Authors: Feng, Yinghong, Zhang, Yaobin, Chen, Shuo, Quan, Xie
• Format: Article
• Language: English
• Subjects: Anaerobic digestion; Iron; Methane production; Microbial electrolysis cell (MEC); Waste activated sludge
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2014.08.048

•High production of methane was achieved using iron–graphite electrode with 0.3V.•0.3V also increased the transformation of SCOD and the conversion of VFA.•Energy consumption at 0.3V could be neglected compared to the incremental methane.•Further increase the voltage to 0.6V led to the accumulation of hydrogen.•Iron–graphite electrodes had bioaugmentation effect for both archaea and bacteria. Batch tests were operated to investigate the bioelectrochemical enhancement of methane production from the high-solid anaerobic digestion of waste sludge in the microbial electrolysis cells (MEC) with iron–graphite electrode. Compared with the control tests, methane production in the MEC with iron–graphite electrode increased by 22.4% and VSS removal rate increased by 11% at an applied voltage of 0.3V. However the methane production decreased and hydrogen was cathodically produced when increasing the voltage to 0.6V. At the higher voltage, the excessive utilization of H+ in the cathode led to the alkaline pH to inhibit the methanogenesis. The applied voltages of 0.3V could also enhance the removal of suspended and volatile suspended solids. The input of energy at 0.3V could be neglected compared to the incremental energy generated from the methane. Denaturing gradient gel electrophoresis analysis revealed that the operation at 0.3V had a bioaugmentation effect for both archaea and bacteria in the high-solid anaerobic digestion of waste sludge, which might be useful for enhancing VFA formation and methane production.