2010 Annual Meeting

(723c) Evaluation of a Novel Bioremediation Process Coupling An Electrokinetic System with Microbial Fuel Cell Technology

Authors

Lewis Hsu - Presenter, University of Southern California
Ryan Thacher - Presenter, University of Southern California
Aditi Yokota-Joshi - Presenter, University of Southern California
Andrea Wong - Presenter, University of Southern California
Kenneth H. Nealson - Presenter, University of Southern California
Massoud Pirbazari - Presenter, University of Southern California

           
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.