the contaminant. However, studies with
14 C-labeled toluene and benzene and isotopic analysis demonstrated that the biodegradation of hydrocarbons is not negatively
affected by adsorption on the electrodes (Rakoczy et al. 2013; Zhang et al. 2010).
Another important advantage that can be linked to the use of bioelectrochemical
technologies is the possibility of adjusting the energy level adapting it to the
environmental conditions. The optimal circumstances for the reaction can thus be
achieved (Daghio et al. 2017). The importance of this aspect has been discussed in
relation to the bioelectrochemical stimulation of the reductive dehalogenation.
Indeed, in this process, the electron’s delivery rate is pivotal to maintain the H 2
concentration and to avoid the unwanted side reactions (e.g., methanogenesis)
(Aulenta et al. 2009, 2010b, 2011). Another aspect linked to the control of the
process is the selectivity of the biological treatments that, in some conditions, could
prevent the formation of unwanted end products (Daghio et al. 2017). As an
example, it is possible to consider the removal of nitrobenzene by
bioelectrochemical reduction. Almost 99% of the nitrobenzene was reduced to
aniline (more degradable compared to nitrobenzene) without production of toxic
nitrosobenzene, which was detected in abiotic conditions (Wang et al. 2011).
Some authors also suggested the possibility of using pre-colonized electrodes to
facilitate the bioaugmentation (Venkidusamy et al. 2016), which could be limited
by the environmental conditions and competition with indigenous bacteria
(Gkorezis et al. 2016).
The use of BESs during the bioremediation of contaminated environments could
be also beneficial for the process monitoring. The generated current can be correlated
to the microbial activity (Daghio et al. 2017; Tront et al. 2008a; Williams et al. 2010)
or it could be used to power sensors (Lovley 2006; Shantaram et al. 2005). Several
studies have investigated the correlation between the electrical signal produced in a
BES and the degradation of the organic substrates, and have demonstrated that the
current production can be correlated to the chemical oxygen demand (COD) and to
the biochemical oxygen demand (BOD) by Monod-type kinetics (Franzetti et al.
2017; Kim et al. 2003; Kumlanghan et al. 2007; Min and Logan 2004). The electrical
current is proportional to the charge exchanged per time unit [1 A (Ampere) ¼ 1 C
(Coulomb) /1 s (second); C ¼ n F where n is the number of electrons and F is the
Faraday constant (i.e., 9.64853 Â 10
4 C/mol)]. It should be therefore proportional to
the rate at which the electrons are transferred to/from the electrode by the oxidation/
reduction reaction. The electrical signal produced in a BES can thus be exploited for
the real-time monitoring of the microbial activity and of the pollutants’ concentration
during the bioremediation of the contaminated sites (Daghio et al. 2017).
The relation between current production and substrate concentration has been
studied in MFCs inoculated with pure cultures of G. sulfurreducens and of
S. oneidensis where easily degradable substrates (i.e., acetate and lactate, respectively) were provided (Tront et al. 2008a, b). Acetate concentration (in the range
0–2.3 mM) and lactate concentration (in the range 0–41 mM) correlated with the
current (Tront et al. 2008a, b), suggesting that the process is governed by a first-order
kinetics.
17 Bioelectrochemical Processes for the Treatment of Oil-Contaminated. . .
385
14 C-labeled toluene and benzene and isotopic analysis demonstrated that the biodegradation of hydrocarbons is not negatively
affected by adsorption on the electrodes (Rakoczy et al. 2013; Zhang et al. 2010).
Another important advantage that can be linked to the use of bioelectrochemical
technologies is the possibility of adjusting the energy level adapting it to the
environmental conditions. The optimal circumstances for the reaction can thus be
achieved (Daghio et al. 2017). The importance of this aspect has been discussed in
relation to the bioelectrochemical stimulation of the reductive dehalogenation.
Indeed, in this process, the electron’s delivery rate is pivotal to maintain the H 2
concentration and to avoid the unwanted side reactions (e.g., methanogenesis)
(Aulenta et al. 2009, 2010b, 2011). Another aspect linked to the control of the
process is the selectivity of the biological treatments that, in some conditions, could
prevent the formation of unwanted end products (Daghio et al. 2017). As an
example, it is possible to consider the removal of nitrobenzene by
bioelectrochemical reduction. Almost 99% of the nitrobenzene was reduced to
aniline (more degradable compared to nitrobenzene) without production of toxic
nitrosobenzene, which was detected in abiotic conditions (Wang et al. 2011).
Some authors also suggested the possibility of using pre-colonized electrodes to
facilitate the bioaugmentation (Venkidusamy et al. 2016), which could be limited
by the environmental conditions and competition with indigenous bacteria
(Gkorezis et al. 2016).
The use of BESs during the bioremediation of contaminated environments could
be also beneficial for the process monitoring. The generated current can be correlated
to the microbial activity (Daghio et al. 2017; Tront et al. 2008a; Williams et al. 2010)
or it could be used to power sensors (Lovley 2006; Shantaram et al. 2005). Several
studies have investigated the correlation between the electrical signal produced in a
BES and the degradation of the organic substrates, and have demonstrated that the
current production can be correlated to the chemical oxygen demand (COD) and to
the biochemical oxygen demand (BOD) by Monod-type kinetics (Franzetti et al.
2017; Kim et al. 2003; Kumlanghan et al. 2007; Min and Logan 2004). The electrical
current is proportional to the charge exchanged per time unit [1 A (Ampere) ¼ 1 C
(Coulomb) /1 s (second); C ¼ n F where n is the number of electrons and F is the
Faraday constant (i.e., 9.64853 Â 10
4 C/mol)]. It should be therefore proportional to
the rate at which the electrons are transferred to/from the electrode by the oxidation/
reduction reaction. The electrical signal produced in a BES can thus be exploited for
the real-time monitoring of the microbial activity and of the pollutants’ concentration
during the bioremediation of the contaminated sites (Daghio et al. 2017).
The relation between current production and substrate concentration has been
studied in MFCs inoculated with pure cultures of G. sulfurreducens and of
S. oneidensis where easily degradable substrates (i.e., acetate and lactate, respectively) were provided (Tront et al. 2008a, b). Acetate concentration (in the range
0–2.3 mM) and lactate concentration (in the range 0–41 mM) correlated with the
current (Tront et al. 2008a, b), suggesting that the process is governed by a first-order
kinetics.
17 Bioelectrochemical Processes for the Treatment of Oil-Contaminated. . .
385