Carbon nanotubes simultaneously as the anode and microbial carrier for up-flow fixed-bed microbial fuel cell

•A novel fixed-bed MFC for electricity generation and wastewater treatment.•Carbon nanotubes were used simultaneously as the anode and microbial carrier.•Overloading of MFC was first observed with increased organic loading.•Overloading was confirmed by electrochemical and biochemical analysis.

A novel up-flow fixed-bed microbial fuel cell (FBMFC) using carbon nanotubes (CNTs) as the anode and microbial carrier was developed for continuous treatment of wastewater and electricity generation. A maximal power density of 590 mW m−3 was achieved with a maximal chemical oxygen demand (COD) removal rate of 90% at an organic loading rate (OLR) of 3.94 g COD l−1 d−1. An OLR of up to 10.27 g COD l−1 d−1 caused the overloading of FBMFC, accompanied with an unexpected decrease in voltage generation below 0.1 V and a sudden accumulation of volatile fatty acids (VFAs) up to 1.82 g l−1. The overloading also led to a rapid decline in COD removal rate (72%) and a morphology change of microbial consortia confirmed by scanning electron microscope (SEM). These results demonstrated the feasibility of Carbon nanotubes simultaneously as the anode and microbial carrier for up-flow fixed-bed microbial fuel cell. The overloading of MFC suggesting that further researches are still needed on improving the performance of FBMFC for energy production and wastewater treatment.