Use of a graphite-cement composite as electrode material in up-flow constructed wetland-microbial fuel cell for greywater treatment and bioelectricity generation

Abstract The main goal of this study was to examine the removal performance of an up-flow constructed wetland-microbial fuel cell (CW-MFC) for greywater treatment using for the first time a graphite-cement composite as electrodes material. Organic matter, nitrogen and solids removal as well as bioelectricity production were monitored for a period of 7 month and compared with a simple up-flow CW (without electrodes). A mean COD removal of about 93% were recorded in both examined systems when the applied OLR was 20.6 g COD m−2 d−1. The average NH4+-N removal efficiency was ranged from 75% to 80% while TSS removal was higher than 95% in any cases. The application of higher OLR and longer period of feeding had as a result a dramatically increase of bioelectricity production (from 6.9 mV to 60.8 mV). The mean power density and coulombic efficiency of the CW-MFC at higher OLR was 11.6 ± 3.0 mW m−3 and 0.48 ± 0.22%, respectively. These findings shown that the examined graphite-cement electrodes could be successfully applied in CW-MFCs for bioelectricity production. In addition, the proposed system could remove very efficiently the organic pollutants from greywater. However, the presence of complex and possible toxic for electroactive bacteria organic compounds in greywater had as a result the generation of relatively low bioelectricity in comparison with low molecular weight carbon sources.