Evaluation of a Novel Bioremediation Process Coupling An Electrokinetic System with Microbial Fuel Cell Technology

            Electokinetic remediation is a relatively new physicochemical remediation method primarily utilized to mobilize and direct ionic pollutants for recovery or reduction in the subsurface. This technology has been utilized for both organic and heavy metal remediation, and  pilot scale systems have been tested. One of the drawbacks for such systems is the formation of precipitates comprised of the reduced forms of the contaminant. These precipitates require such systems to utilize a washing system for the area surrounding their electrodes or the addition of augmenting fluids to prevent the formation of these precipitates.

            To overcome these drawbacks, integration of a bioelectrochemical system with a laboratory scale electrokinetic system was designed and tested. Bioelectrochemical systems  and in particular microbial fuel cells (MFCs) have generated a large amount of interest and research in the past few years. Large uncertainties exist on the fundamental process governing the operation of these reactor systems. These include transport mechanisms for various species, mechanisms of biocatalysis, dominant members of a mixed community biocatalysis, etc. For these reasons, specific electrochemically active bacteria, Shewanella  spp. and Geobacter spp., have been used as model organisms due to the large amount of information on electron transport already available for these species.

            One aspect of MFC systems currently under investigation is utilizing the reducing potential at the cathode to perform remediation of heavy metals. For example, uranium or chromium reduction has been reported in the literature as possible electron acceptors in MFC systems. Oxidized forms of these metals are soluble and highly mobile. Upon reduction, these metals generally form insoluble precipitates, facilitating their immobilization and preventing their exposure to the environment.

            This study aimed to (1) characterize the behavior of the main factors governing removal by application of the electrokinetic remediation system alone and (2) use an understanding of these phenomena to integrate an MFC system to augment removal and remediation effectiveness. Initial results show that the removal of hexavalent chromium is highly dependent on soil condition, e.g. pH, organic content, etc. as well as the initial concentration of hexavalent chromium.

            Evaluation of the MFC-electrokintic system was performed and is presented. Furthermore, impacts of different operating parameters such as recycle rates and positioning of the fuel cell system are discussed.