Bioremediation of PAH-contaminated marine sediments using sediment microbial fuel cells -

Abstract

Contamination of marine sediments with polycyclic aromatic hydrocarbons (PAHs) poses a significant concern due to the contaminants toxicity and resistance to biodegradation. Current bioremediation studies suggest that degradation of PAHs in marine sediments occurs under anaerobic conditions using terminal electron acceptors (TEAs) such as sulfate, nitrate or iron (III), with sulfate reduction being the most dominant pathway due to the sulfate abundance in marine sediments. Nevertheless, in addition to being a slow rate process, degradation of PAHs under anaerobic conditions is impeded by depletion of indigenous sulfate, which requires its frequent replenishment. Microbial Fuel Cells (MFCs) are controlled biochemical systems emerging as a viable alternative to traditional anaerobic processes with the benefit of direct electric power generation and enhanced contaminant removal efficiency. In Sediment Microbial Fuel Cells (SMFCs), a conductive anode embedded in the marine sediment is perceived as an inexhaustible TEA that is thermodynamically favorable over sulfate and nitrate. This study evaluates the efficiency of SMFCs for enhanced in situ bioremediation of PAHs contaminated marine sediments. For this purpose, biodegradation of PAHs was tested in laboratory-scale marine sediment-seawater microbial fuel cells under different experimental conditions. SMFCs were operated under four operating conditions after spiking the sediments with three PAHs (naphthalene, 2-methylnaphthalene and phenanthrene). The change in the concentration of naphthalene and 2-methylnaphthalene did not vary appreciably among the SMFCs as they exhibited a similar fast drop in concentration aided by their volatility and not by microbial degradation. On the other hand, the drop in the concentration of phenanthrene, a more stable and less volatile PAH, showed a significant difference between the treatment conditions. Under controlled autoclaved SMFCs conditions, abiotic losses of phenanthrene contributed to a slight drop from 20 to 16 mg-Kg of