Microbial fuel cells (MFCs) are devices that are expected to be applied to the recovery of electric energy from wastewater. We have recently demonstrated that cassette-electrode MFCs (CE-MFCs) are useful for the treatment of wastewater. A concern about CE-MFCs is however relatively low columbic efficiency that may be caused by oxygen contamination from water surfaces. In the present study, floating boards were installed at the surface of water for minimizing oxygen diffusion from the air, and

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... eir effects on organics removal, electricity generation and microbial communities were analyzed. It was found that the installation of floating boards allowed an average of 10% increases in Columbic efficiency, while organic removal efficiency remained over 80%. The improved electricity generation was associated with changes in microbial communities as analyzed by denaturing gradient gel electrophoresis of 16S rRNA-gene amplicons. These results suggest the utility of floating boards for improving electricity generation in CE-MFCs used for wastewater treatment.