which is an electrochemical technology developed for the electrokinetic transport
coupled to the in situ treatment (Ho et al. 1995), and it involves the placement of a
BES-based biobarrier that intercepts the contaminated plume (Daghio et al. 2017).
For the treatment of halogenated hydrocarbons (e.g., TCE or PCE) it could be
feasible to place a cathodic biobarrier upstream to an anodic biobarrier. This setup
allows the reductive dehalogenation in the cathodic area, followed by the anodic
oxidation of the reduced compounds (Fig. 17.2c). The possibility to apply a sequential reductive–oxidative treatment has been suggested by several lab-scale studies
(Aulenta et al. 2011; Lai et al. 2015, 2017; Lohner and Tiehm 2009). However, a
crucial parameter that has to be considered with this architecture is the spacing
between the electrodes since an excessive energy input may be required with a
distance between the electrodes higher than a few meters (Daghio et al. 2017).
An alternative configuration suggested for the bioremediation of hydrocarboncontaminated groundwater is the so-called “bioelectric well” (Palma et al. 2018)
(Fig. 17.2d). A concentric anode made of granular graphite is placed around a
concentric cathode in order to minimize the spacing between the electrodes and
the resulting energy loss. The two electrodes can be kept physically separated by a
thin layer of plastic material (e.g., polyethylene mesh) that, however, has to ensure
hydraulic connection. This system could be easily installed in wells already placed in
situ (Palma et al. 2018), potentially decreasing the installation cost for the treatment
system.
17.4 Microorganisms Involved in Bioremediation
with Bioelectrochemical Systems
The characterization of the microorganisms able to use electrodes as electron
acceptors/donors during the oxidation/reduction of organic contaminants is pivotal
for the comprehension of the mechanisms involved, and thus for the optimization of
the technology. Unfortunately, not all of the published studies have reported information about the taxonomy of the microorganisms inoculated or enriched in the
reactors.
Pure cultures of Geobacter metallireducens and S. oneidensis were able to
degrade toluene and phenanthrene in a BES (Adelaja et al. 2014; Zhang et al.
2010). However, iron reducers were not the only microorganisms that were successfully inoculated in BES reactors. P. aeruginosa was able to remove phenanthrene
faster than S. oneidensis (Adelaja et al. 2014). Cupriavidus basilensis degraded
phenol with an electrode poised at +325 mV as electron acceptor and an oxidation
peak at +140 mV was observed (Friman et al. 2013).
In one of the first reports that showed the possibility of coupling diesel degradation with current production, facultative anaerobes (i.e., NO 3
À reducing bacteria)
were enriched in a single chamber MFC reactor (Morris et al. 2009). In another
experiment, during the PAHs degradation, microorganisms belonging to Chloroflexi
17 Bioelectrochemical Processes for the Treatment of Oil-Contaminated. . .
381
coupled to the in situ treatment (Ho et al. 1995), and it involves the placement of a
BES-based biobarrier that intercepts the contaminated plume (Daghio et al. 2017).
For the treatment of halogenated hydrocarbons (e.g., TCE or PCE) it could be
feasible to place a cathodic biobarrier upstream to an anodic biobarrier. This setup
allows the reductive dehalogenation in the cathodic area, followed by the anodic
oxidation of the reduced compounds (Fig. 17.2c). The possibility to apply a sequential reductive–oxidative treatment has been suggested by several lab-scale studies
(Aulenta et al. 2011; Lai et al. 2015, 2017; Lohner and Tiehm 2009). However, a
crucial parameter that has to be considered with this architecture is the spacing
between the electrodes since an excessive energy input may be required with a
distance between the electrodes higher than a few meters (Daghio et al. 2017).
An alternative configuration suggested for the bioremediation of hydrocarboncontaminated groundwater is the so-called “bioelectric well” (Palma et al. 2018)
(Fig. 17.2d). A concentric anode made of granular graphite is placed around a
concentric cathode in order to minimize the spacing between the electrodes and
the resulting energy loss. The two electrodes can be kept physically separated by a
thin layer of plastic material (e.g., polyethylene mesh) that, however, has to ensure
hydraulic connection. This system could be easily installed in wells already placed in
situ (Palma et al. 2018), potentially decreasing the installation cost for the treatment
system.
17.4 Microorganisms Involved in Bioremediation
with Bioelectrochemical Systems
The characterization of the microorganisms able to use electrodes as electron
acceptors/donors during the oxidation/reduction of organic contaminants is pivotal
for the comprehension of the mechanisms involved, and thus for the optimization of
the technology. Unfortunately, not all of the published studies have reported information about the taxonomy of the microorganisms inoculated or enriched in the
reactors.
Pure cultures of Geobacter metallireducens and S. oneidensis were able to
degrade toluene and phenanthrene in a BES (Adelaja et al. 2014; Zhang et al.
2010). However, iron reducers were not the only microorganisms that were successfully inoculated in BES reactors. P. aeruginosa was able to remove phenanthrene
faster than S. oneidensis (Adelaja et al. 2014). Cupriavidus basilensis degraded
phenol with an electrode poised at +325 mV as electron acceptor and an oxidation
peak at +140 mV was observed (Friman et al. 2013).
In one of the first reports that showed the possibility of coupling diesel degradation with current production, facultative anaerobes (i.e., NO 3
À reducing bacteria)
were enriched in a single chamber MFC reactor (Morris et al. 2009). In another
experiment, during the PAHs degradation, microorganisms belonging to Chloroflexi
17 Bioelectrochemical Processes for the Treatment of Oil-Contaminated. . .
381