Preliminary evaluation of microbial fuel cells applicability to bioremediate marine sediments contaminated by polycyclic aromatic hydrocarbons

This study reports a preliminary evaluation of applicability of sediment microbial fuel cells (SMFCs) to bioremediate marine sediments contaminated by phenanthrene, a polycyclic aromatic hydrocarbon (PAH). The anodic compartments of two SMFCs were batch-fed with a slurry (5% w/w real dry sediment in artificial seawater) contaminated with phenanthrene (200 mg/kgdw), while the corresponding cathodic compartments were filled with 0.5 M K3[Fe(CN)6]. Both anode and cathode consisted of a piece of conductive graphite felt (4 cm2). A cation-permeable membrane was used to separate the compartments. SMFC-1 was operated in static conditions, whereas mechanical stirring was applied in SMFC-2. Good phenanthrene removals were achieved in SMFC-1 (61%) and SMFC-2 (88.5%) after 20 days of operation; mechanical stirring played a role in accelerating phenanthrene degradation. Biocatalytic activity was characterized by linear sweep voltammetries: maximum power densities and optimal current densities in SMFC-1 and -2 were 9.2 and 38.4 ?W/cm2, and 26.2 and 142.7 ?A/cm2, respectively. Such promising results are putatively associated to the capability of electroactive microorganisms to promote phenanthrene degradation at the anodes. The use of electrodes as electron sink in electrochemical remediation of contaminated slurries deserves further investigation, since it represents a cost-effective alternative to conventional treatments requiring energy-consuming aeration.