A new approach to in situ sediment remediation based on air-cathode microbial fuel cells

Purpose As an attempt to remove the back color and odor of the organic-rich sediment, a novel tubular air-cathode MFC (TAC-MFC) was constructed and employed for in situ sediment remediation. The biodegradation of organic matter in sediment was stimulated by providing anodic electrode as an electron acceptor. The TAC-MFC was more favorable for application than typical sediment-type MFCs, whose performances are strongly limited due to the drawbacks such as low oxygen availability of cathodes, big electrode spacing, and fouling of cathodes. Materials and methods The TAC-MFC was constructed with a cloth cathode assembly (CCA) structure that consisted of a conductive, catalytic, and waterproof layer to replace the cathode and ionic exchange membrane in a typical MFC. By simply inserting TAC-MFC into the sediment, a whole electrochemical biosystem was established for simultaneous organic matter oxidization and electricity generation. The MFC performance for power generation and sediment bioremediation were evaluated under various external loadings, in terms of power density and the sediment quality parameters including loss on ignition (LOI), readily oxidizable organic matter (ROOM), and acid volatile sulfide (AVS). Results and discussion The highest power density (107.1 +/- 8.6 mW/m(2)), coulombic efficiency (17.9%), and the lowest internal resistance (20 Omega) were obtained from the TACMFC that was loaded with an external resistance of 30 Omega. At the same time, LOI was decreased by about 33.1%, ROOM was decreased by about 36.0%, and AVS was decreased by about 94.9% in the sediment. Under closed circuit conditions, the oxidation and reduction potential value in the sediment increased from -162.5 to +245.7 mV, suggesting that an improved environment of sediment was achieved upon MFC treatment. Conclusions A higher power output was achieved in the proposed TAC-MFC compared with sediment-type MFCs reported in previous literature, indicating that the TAC-MFC with a CCA was a desirable configuration. From the analysis of sediment quality parameters, the proposed MFC was demonstrated to be a potential means for the sediment remediation coupled with electricity production.