accessible for microorganisms and thus easily biodegradable. Water solubility of
aromatic compounds is higher in comparison with alkanes with the same number of
carbon atoms (Table 5.2). Biodegradability of hydrocarbons is strongly related to
structure (Gargouri et al. 2014). Compounds with simple chemical structure such as
benzene, toluene, ethylbenzene, and xylenes (BTEX) and low molecular weight
aromatic hydrocarbons are normally easily biodegraded in comparison to more
complex molecules such as PAHs, particularly those with more than four fused
aromatic rings (Zappi et al. 1996; Straube et al. 1999; Sakulthaew et al. 2014).
However, monoaromatic hydrocarbons can be more recalcitrant than PAHs if
additional long alkyl chains are present. The long-chain alkylated monoaromatic
hydrocarbons (LAMAs), which are present in diesel oil, are less water soluble than
short-chain alkylated PAHs and thus less biodegradable. This finding was reported
in the experiment performed by Mao et al. (2009), in which long-chain alkylated
monoaromatic hydrocarbons were a dominant fraction after 20 weeks of bioremediation of a diesel oil-contaminated soil.
5.1.2 How to Overcome the Limitations of Biodegradation
Process?
Remediation of soils polluted with TPH may occur naturally, this process is called
“natural attenuation” (Tang et al. 2012). However, this process is slow and thus,
application of additional practices is needed to enhance the remediation efficiency.
Within soil treatment strategies, bioremediation represents an environmentalfriendly solution in comparison with conventional physical treatments such as
thermal extraction, solvent extraction, steam stripping, hot-air stripping, immobilization, and chemical treatments such as chemical oxidation (Gan et al. 2009; Tang
et al. 2012). Time needed for soil cleanup vary significantly between treatments.
Solvent extraction methods can be completed within few hours, chemical oxidation
last from 1 day to few weeks, thermal extraction treatments last around a month
while immobilization strategies depends on sorption and desorption kinetics and last
from few days to several months (Gan et al. 2009). In case of bioremediation, time
needed for soil treatment varies from few months to few years depending on the
characteristics of contaminated sites (Gan et al. 2009). Application of physical and
chemical treatments can be fast and in great extent decrease soil contamination level;
however, residual concentrations may still remain in soil causing toxicity. Due to
low concentration of contaminants, physical and chemical treatments may not be
longer profitable, and thus bioremediation may be selected as an additional treatment
(Lin et al. 2017).
In contrast to bioremediation, conventional remediation methods are not always
specific in terms of contaminants and are strongly invasive for the treated soils,
which may result in environmental perturbations. In most cases, bioremediation has
also an economic advantage over physical and chemical treatments. However, the
5 Potential Use of Waste-to-Bioenergy By-Products in Bioremediation of Total. . .
245
aromatic compounds is higher in comparison with alkanes with the same number of
carbon atoms (Table 5.2). Biodegradability of hydrocarbons is strongly related to
structure (Gargouri et al. 2014). Compounds with simple chemical structure such as
benzene, toluene, ethylbenzene, and xylenes (BTEX) and low molecular weight
aromatic hydrocarbons are normally easily biodegraded in comparison to more
complex molecules such as PAHs, particularly those with more than four fused
aromatic rings (Zappi et al. 1996; Straube et al. 1999; Sakulthaew et al. 2014).
However, monoaromatic hydrocarbons can be more recalcitrant than PAHs if
additional long alkyl chains are present. The long-chain alkylated monoaromatic
hydrocarbons (LAMAs), which are present in diesel oil, are less water soluble than
short-chain alkylated PAHs and thus less biodegradable. This finding was reported
in the experiment performed by Mao et al. (2009), in which long-chain alkylated
monoaromatic hydrocarbons were a dominant fraction after 20 weeks of bioremediation of a diesel oil-contaminated soil.
5.1.2 How to Overcome the Limitations of Biodegradation
Process?
Remediation of soils polluted with TPH may occur naturally, this process is called
“natural attenuation” (Tang et al. 2012). However, this process is slow and thus,
application of additional practices is needed to enhance the remediation efficiency.
Within soil treatment strategies, bioremediation represents an environmentalfriendly solution in comparison with conventional physical treatments such as
thermal extraction, solvent extraction, steam stripping, hot-air stripping, immobilization, and chemical treatments such as chemical oxidation (Gan et al. 2009; Tang
et al. 2012). Time needed for soil cleanup vary significantly between treatments.
Solvent extraction methods can be completed within few hours, chemical oxidation
last from 1 day to few weeks, thermal extraction treatments last around a month
while immobilization strategies depends on sorption and desorption kinetics and last
from few days to several months (Gan et al. 2009). In case of bioremediation, time
needed for soil treatment varies from few months to few years depending on the
characteristics of contaminated sites (Gan et al. 2009). Application of physical and
chemical treatments can be fast and in great extent decrease soil contamination level;
however, residual concentrations may still remain in soil causing toxicity. Due to
low concentration of contaminants, physical and chemical treatments may not be
longer profitable, and thus bioremediation may be selected as an additional treatment
(Lin et al. 2017).
In contrast to bioremediation, conventional remediation methods are not always
specific in terms of contaminants and are strongly invasive for the treated soils,
which may result in environmental perturbations. In most cases, bioremediation has
also an economic advantage over physical and chemical treatments. However, the
5 Potential Use of Waste-to-Bioenergy By-Products in Bioremediation of Total. . .
245