Microbial degradation of high molecular weight PAHs and weathered crude oil using marine SMFCS.

Abstract

Sediment Microbial Fuel Cells (SMFCs) are a type of bioelectrochemical systems, based on the Microbial Fuel Cell (MFC) technology, which can be used for bioremediation of various contaminants in aquatic sediments. Recently, there has been a rise in studies targeting applicability of SMFCs for biodegradation of lingering pollutants in sediments, such as petroleum hydrocarbons. The interest in the SMFC technology can be attributed to the overall simplicity of the system when applied as a bioremediation approach. SMFCs can thus provide a passive and a sustainable bioremediation system that does not heavily interfere with the existing environment. However, research targeting SMFCs is still limited, hindering the potential of applying SMFCs for treatment of contaminated sites. For example, existing literature is confined to few specific compounds rather than simulating actual field conditions with a multitude of coexisting contaminants. Additionally, given the importance of ferric iron reducing microbes in the electrochemical performance of the SMFCs, and given that ferric iron reducers are generally lacking in marine sediments, most of the research is focused on freshwater SMFCs. To better understand the technology for bioremediation of marine sediments, we investigated the use of marine SMFCs for the bioremediation of petroleum hydrocarbon contamination. Thus, 2 sets of experiments were conducted utilizing ferric iron stimulated SMFCs for the removal of a mixture of Polycyclic Aromatic Hydrocarbons (PAHs) as well as for the removal of weathered crude oil from the sediments. Volatilization was the major removal mechanism of low molecular weight PAHs (2 and 3 rings). In the case of high molecular weight PAHs, highest removal was observed under iron stimulation when sulfate reducing bacteria (SRB) were inhibited, irrespective of the involvement of anode reduction, compared to the controls. Additionally, significant variation in the microbial community composition was observed, with several electrochemically active