Management of Electric Currents in Cable Bacteria

Sediment microbial fuel cells (SMFCs) can be used to generate electricity and remove organic contaminants. For electricity generation and contaminant removal, the anode material is one of important factors influencing the performance of SMFCs. In this study, graphene (GR), graphene oxide (GO) and carbon nanotubes (CNTs) were applied to modify the graphite felt (GF) anode in SMFCs during 110 d operation. An economical and easy modification method with the carbon nanomaterials was applied. The carbon nanomaterials increased the electrochemically active surface areas and biomass content of the anodes and correspondingly effectively enhanced the generation of electricity and the removal rates of loss on ignition (LOI) and polycyclic aromatic hydrocarbons (phenanthrene and pyrene). During the steady period from 50 d to 110 d, the GO-SMFCs favored the enrichment of EAB and thus output the highest voltages of 30.60–48.61 mV. The GR-SMFCs and GO-SMFCs generated high electric power of approximate 0.98 ± 0.14 kJ and 0.87 ± 0.04 kJ, followed by CNT-SMFCs (0.57 ± 0.06 kJ) and GF-SMFCs (0.49 ± 0.07 kJ) during the 110 d operation. The PAH degradation was not directly related to the electric current in the SMFCs. Near the anodes, the order of the phenanthrene removal rates was CNT-SMFCs (78.1%) > GR-SMFCs (73.0%) ≈ GO-SMFCs (71.2%) > GF-SMFCs (45.6%), and the order of the pyrene removal rates was GO-SMFCs (69.6%) ≈ GR-SMFCs (68.2%) ≈ CNT-SMFCs (66.7%) > GF-SMFCs (42.3%). The three carbon nanomaterials increased the microbial community diversity and slightly changed the microbial community distribution of biofilms on the anodes. Correlation analysis indicated that the degradation of phenanthrene was positively correlated with the abundances of Pseudomonas, Thauera, Diaphorobacter, Tumebacillus and Lysobacter. Pyrene degradation was strongly correlated with LOI degradation.