example, Singh and Sharma (2003) observed that Brevibacterium sp. degraded the
pesticide fenamiphos that was intercalated into the cationic-surfactant-modified
montmorillonite clay (CTMA–Mt–fenamiphos complex). It seems that this process
is less significant within bioremediation practice.
The sorption processes depend on a number of properties of the contaminants to
be removed, the used organic substrates, and the contaminated soil, and they may be
caused by several mechanisms, such as hydrogen and ionic bonds, van der Waals
forces, hydrophobic interactions, and trapping in cavities of organic or inorganic
matter (Pignatello and Xing 1995). A number of publications deal with the topic of
sorption of the individual substances to particles of soil and humic substances
(Chefetz and Xing 2009; Xing et al. 1996). However, in practice, complex mixtures
of various contaminants that mutually influence their sorption properties are found in
most of the contaminated localities. For example, Luthy et al. (1993) showed that the
transfer of PAHs contained in tar into water, and thus also to microorganisms, may
be considerably reduced by consolidated interfaces of non-aqueous-phase liquids
(NAPLs), such as tar oils. According to the Raoult’s law, the chemical activity,
which is the force causing the transfer from the non-aqueous to the aqueous phase, is
significantly higher in the case when only one substance is present than in the case
with a diverse mixture (Eberhardt and Grathwohl 2002; Ghoshal et al. 1996; Kästner
2000; Lee et al. 1992; Luthy et al. 1994; Wehrer et al. 2013). Further, NAPLs, in
view of their hydrophobic properties, absorb hydrophobic substances present in their
surroundings, such as, fatty acids, waxes, and resins. NAPL enrichment by these
molecules usually results in reduction of NAPL viscosity on its interface with the
water phase, which further reduces the transport of mass into the water phase, and its
bioavailability (Kästner and Miltner 2016). In many localities influenced by coal gas
production, PAHs dissolved in tar oils occur in forms bound to coal or coke as a
consequence of their joint disposal (Luthy et al. 1994, Rein et al. 2016; Wiesmann
1994). These bonds reduce the PAH bioavailability considerably, and may cause
considerable problems during the decontamination of materials contaminated in
this way.
Similar interactions occur between the individual components of contaminant
mixtures, for example, also in the case of petroleum substances and explosives.
On the other hand, the presence of water-soluble compounds, such as humic and
fulvic acids as well as small biomolecules, such as peptides and fatty acids may
cause desorption, solubilization, and/or complexation of organic contaminants,
which usually results in increasing their mobility (Mayer et al. 2005, 2007;
Pignatello et al. 2006; Smith et al. 2009, 2011; Vacca et al. 2005). Further, these
processes cause the increase in bioavailability, and thus accelerate the biodegradation of the mobilized contaminants (Haderlein et al. 2001; Ortega-Calvo and SaizJimenez 1998; Puglisi et al. 2007). Within the framework of the biodegradation
techniques, this process has to be controlled because if excessive contaminant
mobilization occurs, unwanted toxic effects on the degradation organisms might
appear (Puglisi et al. 2007).
Certain bacteria, for example Actinobacteria of the orders Nocardia, Gordona,
Rhodococci, and Mycobacteria have markedly hydrophobic cell wall, causing
23 Composting Practices for the Remediation of Matrices Contaminated by. . .
479
pesticide fenamiphos that was intercalated into the cationic-surfactant-modified
montmorillonite clay (CTMA–Mt–fenamiphos complex). It seems that this process
is less significant within bioremediation practice.
The sorption processes depend on a number of properties of the contaminants to
be removed, the used organic substrates, and the contaminated soil, and they may be
caused by several mechanisms, such as hydrogen and ionic bonds, van der Waals
forces, hydrophobic interactions, and trapping in cavities of organic or inorganic
matter (Pignatello and Xing 1995). A number of publications deal with the topic of
sorption of the individual substances to particles of soil and humic substances
(Chefetz and Xing 2009; Xing et al. 1996). However, in practice, complex mixtures
of various contaminants that mutually influence their sorption properties are found in
most of the contaminated localities. For example, Luthy et al. (1993) showed that the
transfer of PAHs contained in tar into water, and thus also to microorganisms, may
be considerably reduced by consolidated interfaces of non-aqueous-phase liquids
(NAPLs), such as tar oils. According to the Raoult’s law, the chemical activity,
which is the force causing the transfer from the non-aqueous to the aqueous phase, is
significantly higher in the case when only one substance is present than in the case
with a diverse mixture (Eberhardt and Grathwohl 2002; Ghoshal et al. 1996; Kästner
2000; Lee et al. 1992; Luthy et al. 1994; Wehrer et al. 2013). Further, NAPLs, in
view of their hydrophobic properties, absorb hydrophobic substances present in their
surroundings, such as, fatty acids, waxes, and resins. NAPL enrichment by these
molecules usually results in reduction of NAPL viscosity on its interface with the
water phase, which further reduces the transport of mass into the water phase, and its
bioavailability (Kästner and Miltner 2016). In many localities influenced by coal gas
production, PAHs dissolved in tar oils occur in forms bound to coal or coke as a
consequence of their joint disposal (Luthy et al. 1994, Rein et al. 2016; Wiesmann
1994). These bonds reduce the PAH bioavailability considerably, and may cause
considerable problems during the decontamination of materials contaminated in
this way.
Similar interactions occur between the individual components of contaminant
mixtures, for example, also in the case of petroleum substances and explosives.
On the other hand, the presence of water-soluble compounds, such as humic and
fulvic acids as well as small biomolecules, such as peptides and fatty acids may
cause desorption, solubilization, and/or complexation of organic contaminants,
which usually results in increasing their mobility (Mayer et al. 2005, 2007;
Pignatello et al. 2006; Smith et al. 2009, 2011; Vacca et al. 2005). Further, these
processes cause the increase in bioavailability, and thus accelerate the biodegradation of the mobilized contaminants (Haderlein et al. 2001; Ortega-Calvo and SaizJimenez 1998; Puglisi et al. 2007). Within the framework of the biodegradation
techniques, this process has to be controlled because if excessive contaminant
mobilization occurs, unwanted toxic effects on the degradation organisms might
appear (Puglisi et al. 2007).
Certain bacteria, for example Actinobacteria of the orders Nocardia, Gordona,
Rhodococci, and Mycobacteria have markedly hydrophobic cell wall, causing
23 Composting Practices for the Remediation of Matrices Contaminated by. . .
479