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Using microbial fuel cells for the remediation of hydrocarbon-contaminated aquifers Nicolau del Roure Eylerts, Constanza

Abstract

Bio-electrochemical systems (BES) have been proposed as an emerging technology for enhancing groundwater remediation and are an interesting alternative for hydrocarbon-contaminated reducing aquifers where natural attenuation may be slow. BES take advantage of the ability of exoelectrogenic bacteria to transfer electrons from organic substrates to an extracellular electron acceptor, such as the anode of a microbial fuel cell (MFC). An electrical connection between the oxidizing and reducing compartments of the MFC allows reduction of oxygen at the cathode coupled to the oxidation of the reduced contaminant in the reducing compartment, accompanied by electricity production. Electricity production has been proposed as a proxy to monitor the progress of the remediation. The effects of additional electron donors, like ferrous iron, over the contaminant degradation efficiency and electricity production in BES have not been thoroughly studied. This research applied chemical, mineralogical, and microbiological analyses to study the degradation of naphthalene in a series of MFC experiments. The main objective was to test whether a reactor inoculated with native microorganisms from a local contaminated aquifer could successfully remediate naphthalene contamination in a reducing environment where iron was potentially an electron donor. An additional experiment was developed to address naphthalene sorption to electrodes and other reactor materials. The sorption experiment revealed that naphthalene dynamics in the MFC were significantly affected by sorption/desorption to reactor materials, so interpretation of MFC results required the consideration of naphthalene sorption and diffusion processes. The MFC experiments in this study did not find any advantage in providing an electrical connection between reducing and oxidizing zones of the bioreactors in terms of naphthalene degradation achieved in the system. However, the former did show the additional benefit of generating a small current. MFC experiments showed an increased electricity production when iron was available, however, the experiments with no iron achieved higher removal of naphthalene. The results from this study suggest that measuring electricity production is no substitute for direct measurement of contaminant biodegradation, since iron, sulfur, and naphthalene metabolites were involved in electricity production.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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