A foam-enhanced washing technique has been developed to reduce the channeling effect characteristic for soil treatment, thus achieving a homogenous flow, even
in a heterogeneous porous medium. Foam can be successfully created and stabilized
by biosurfactants. Maity et al. (2013) demonstrated a foam-enhanced removal of Cu,
Pb, and Zn from contaminated soil using a plant-based biosurfactant saponin from
soapberry Sapindus mukorossi and surfactin from Bacillus subtilis (BBK006). The
optimized foam-enhanced technology resulted in removing 98%, 95%, and 56% of
Pb, Cu, and Zn, respectively, while the efficiency of simple washing was twice less
efficient.
24.2.4.3 Treatment of Sites Co-contaminated with Heavy Metals
and Hydrocarbons
Industrial areas are often co-contaminated with heavy metals and hydrocarbons.
Remediation of heavy metal- and hydrocarbon-contaminated soil could be difficult
because of the different chemical nature of these two contaminant types. Nevertheless, several recent studies showed the potential of biosurfactants for addressing this
problem. One study on washing soil contaminated with high concentrations of heavy
metals (Fe, Pb, Ni, Cd, Cu, Co, and Zn) and petroleum hydrocarbons using
alipopeptide biosurfactant consisting of surfactin and fengycin originated from
Bacillus subtilis A21 was published by Singh and Cameotra (2013). Bisurfactantbased washing removed significant amounts of both petroleum hydrocarbons
(64.5%) and metals, namely Cd (44.2%), Co (35.4%), Pb (40.3%), Ni (32.2%), Co
(26.2%), and Zn (32.07%). The treated soil exhibited a non-inhibited (100%)
germination of brown Indian mustard (Brassica juncea), whereas the simply washed
soil yielded 0% germination. Maslin and Maier (2000) concluded that the biodegradation of phenanthrene can be rhamnolipid-enhanced in organic-metal
co-contaminated soils by masking (complexing) toxic cadmium. This protective
effect was further improved during the lab-scale simulated degradation of phenanthrene in the aqueous medium and two co-contaminated soils.
24.2.4.4 Long-Term Contaminated Sites—Aged Pollutants
The sorption of pollutants often becomes nearly irreversible over time. Such “aging”
of both types of pollutants, either organic compounds (Ncibi et al. 2007) or heavy
metals (Liang et al. 2016) causes their low bioavailability, thus prolonging the
bioremediation time and decreasing its efficiency. However, it was found that
biosurfactants help to effectively release such “irreversibly” adsorbed PAHs
(Bezza and Chirwa 2016, 2017; Sánchez-Trujillo et al. 2013), pesticides
(Wattanaphon et al. 2008), PCBs (Fava et al. 2003), and heavy metals (Kulikowska
et al. 2015b), making the remediation process shorter and more efficient.
Humic substances extracted from compost were used as a washing agent for a
simultaneous removal of Cu, Cd, Zn, Pb, and Ni from artificially contaminated soils
504
M. Halecký and E. Kozliak
in a heterogeneous porous medium. Foam can be successfully created and stabilized
by biosurfactants. Maity et al. (2013) demonstrated a foam-enhanced removal of Cu,
Pb, and Zn from contaminated soil using a plant-based biosurfactant saponin from
soapberry Sapindus mukorossi and surfactin from Bacillus subtilis (BBK006). The
optimized foam-enhanced technology resulted in removing 98%, 95%, and 56% of
Pb, Cu, and Zn, respectively, while the efficiency of simple washing was twice less
efficient.
24.2.4.3 Treatment of Sites Co-contaminated with Heavy Metals
and Hydrocarbons
Industrial areas are often co-contaminated with heavy metals and hydrocarbons.
Remediation of heavy metal- and hydrocarbon-contaminated soil could be difficult
because of the different chemical nature of these two contaminant types. Nevertheless, several recent studies showed the potential of biosurfactants for addressing this
problem. One study on washing soil contaminated with high concentrations of heavy
metals (Fe, Pb, Ni, Cd, Cu, Co, and Zn) and petroleum hydrocarbons using
alipopeptide biosurfactant consisting of surfactin and fengycin originated from
Bacillus subtilis A21 was published by Singh and Cameotra (2013). Bisurfactantbased washing removed significant amounts of both petroleum hydrocarbons
(64.5%) and metals, namely Cd (44.2%), Co (35.4%), Pb (40.3%), Ni (32.2%), Co
(26.2%), and Zn (32.07%). The treated soil exhibited a non-inhibited (100%)
germination of brown Indian mustard (Brassica juncea), whereas the simply washed
soil yielded 0% germination. Maslin and Maier (2000) concluded that the biodegradation of phenanthrene can be rhamnolipid-enhanced in organic-metal
co-contaminated soils by masking (complexing) toxic cadmium. This protective
effect was further improved during the lab-scale simulated degradation of phenanthrene in the aqueous medium and two co-contaminated soils.
24.2.4.4 Long-Term Contaminated Sites—Aged Pollutants
The sorption of pollutants often becomes nearly irreversible over time. Such “aging”
of both types of pollutants, either organic compounds (Ncibi et al. 2007) or heavy
metals (Liang et al. 2016) causes their low bioavailability, thus prolonging the
bioremediation time and decreasing its efficiency. However, it was found that
biosurfactants help to effectively release such “irreversibly” adsorbed PAHs
(Bezza and Chirwa 2016, 2017; Sánchez-Trujillo et al. 2013), pesticides
(Wattanaphon et al. 2008), PCBs (Fava et al. 2003), and heavy metals (Kulikowska
et al. 2015b), making the remediation process shorter and more efficient.
Humic substances extracted from compost were used as a washing agent for a
simultaneous removal of Cu, Cd, Zn, Pb, and Ni from artificially contaminated soils
504
M. Halecký and E. Kozliak