Rapid start-up of a bioelectrochemical system under alkaline and saline conditions for efficient oxalate removal

• Published in: Bioresource technology Vol. 250; pp. 317 - 327
• Main Authors: Weerasinghe Mohottige, Tharanga N., Ginige, Maneesha P., Kaksonen, Anna H., Sarukkalige, Ranjan, Cheng, Ka Yu
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2018
• Subjects: Alkaline industrial wastewater; Alumina; Bayer process; Bioelectrochemical system; Microbial fuel cell; Oxalotrophic; Microbial fuel cell; Bayer process; Bioelectrochemical system; Alumina; Alkaline industrial wastewater; Oxalotrophic
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2017.11.009

•A bioelectrochemical system (BES) was successfully started up for oxalate removal.•Aerobic oxalotrophic biofilm pre-grown on graphite granules was used as inoculum.•The biofilm could rapidly switch from using oxygen to graphite as electron acceptor.•Highest coulombic efficiency (>70%) for anodic oxalate oxidation in the literature.•Oxalobacteraceae strains became abundant signifying their role in the BES process. This study examined a new approach for starting up a bioelectrochemical system (BES) for oxalate removal from an alkaline (pH > 12) and saline (NaCl 25 g/L) liquor. An oxalotrophic biofilm pre-grown aerobically onto granular graphite carriers was used directly as both the microbial inoculum and the BES anode. At anode potential of +200 mV (Ag/AgCl) the biofilm readily switched from using oxygen to graphite as sole electron acceptor for oxalate oxidation. BES performance was characterised at various hydraulic retention times (HRTs, 3–24 h), anode potentials (−600 to +200 mV vs. Ag/AgCl) and influent oxalate (25 mM) to acetate (0–30 mM) ratios. Maximum current density recorded was 363 A/m3 at 3 h HRT with a high coulombic efficiency (CE) of 70%. The biofilm could concurrently degrade acetate and oxalate (CE 80%) without apparent preference towards acetate. Pyro-sequencing analysis revealed that known oxalate degraders Oxalobacteraceae became abundant signifying their role in this novel bioprocess.