ecosystems. Therefore, it is generally required to remove these contaminants from
the underground environment.
Among the possible remediation strategies that can be implemented, bioremediation is one of the most frequently used because of its lower equipment demand and
labor and energy requirements compared with classical physicochemical techniques.
This concept results in lower costs and increased sustainability of the remediation
works (US EPA 2012). Comprehensive characterization of site-specific biodegradation processes is essential to verify whether in situ biodegradation is feasible and to
determine whether these processes could be efficient enough or can be enhanced in
order to replace conventional clean-up technologies (Bombach et al. 2010).
This work is focused on the assessment of the possibilities to enhance in situ
biodegradation of mono-aromatic solvents via injection of three different injectable
oxygen sources on a typical environmental burden site in the Czech Republic.
19.2 Materials and Methods
19.2.1 The Locality
The studied locality is situated on the premises of an old chemical and pharmaceutical plant where chemical production began almost 100 years ago. The entire site is
highly contaminated mainly by mono-aromatic solvents including
monochlorobenzene (MCB), benzene (B), and toluene (T) as well as other contaminants. The field study was carried out on one of the most contaminated spots in the
area. The aquifer is developed in Quaternary sandy gravels with a clayey admixture
with saturated thickness of approximately 4 m. The hydraulic conductivity of the
aquifer ranges from 1.4 Â 10
À3 to 2.2 Â 10
À4 m/s, based on the Mallet-Pacquant
method (Chery and de Marsily 2007). The base of the aquifer consists of clays with a
sand admixture with a hydraulic conductivity below 1.9 Â 10
À7 m/s. The groundwater is characterized by elevated mineralization (specific conductance ranging from
127 to 1053 mS/m), slightly acidic to neutral pH (6.5–7.0), oxidation–reduction
potentials ranging from À45 to +45 mV, dissolved oxygen below 0.2 mg/L, and a
temperature of approximately 14.2
C. The concentrations of the contaminants just
before the test varied as follows—B 6.7–57.2 μg/L, T 41.3–3245 μg/L, and MCB
451–2840 μg/L. Old monitoring wells installed approximately 15 years prior to the
test were utilized for monitoring the process. The wells had long screen interval
along the whole aquifer thickness.
19.2.2 Site Investigation
A membrane interface probe (MIP) (Geoprobe Systems®, USA) was used for the
investigation of the contamination close to the particular monitoring wells. One MIP
412
O. Lhotský
the underground environment.
Among the possible remediation strategies that can be implemented, bioremediation is one of the most frequently used because of its lower equipment demand and
labor and energy requirements compared with classical physicochemical techniques.
This concept results in lower costs and increased sustainability of the remediation
works (US EPA 2012). Comprehensive characterization of site-specific biodegradation processes is essential to verify whether in situ biodegradation is feasible and to
determine whether these processes could be efficient enough or can be enhanced in
order to replace conventional clean-up technologies (Bombach et al. 2010).
This work is focused on the assessment of the possibilities to enhance in situ
biodegradation of mono-aromatic solvents via injection of three different injectable
oxygen sources on a typical environmental burden site in the Czech Republic.
19.2 Materials and Methods
19.2.1 The Locality
The studied locality is situated on the premises of an old chemical and pharmaceutical plant where chemical production began almost 100 years ago. The entire site is
highly contaminated mainly by mono-aromatic solvents including
monochlorobenzene (MCB), benzene (B), and toluene (T) as well as other contaminants. The field study was carried out on one of the most contaminated spots in the
area. The aquifer is developed in Quaternary sandy gravels with a clayey admixture
with saturated thickness of approximately 4 m. The hydraulic conductivity of the
aquifer ranges from 1.4 Â 10
À3 to 2.2 Â 10
À4 m/s, based on the Mallet-Pacquant
method (Chery and de Marsily 2007). The base of the aquifer consists of clays with a
sand admixture with a hydraulic conductivity below 1.9 Â 10
À7 m/s. The groundwater is characterized by elevated mineralization (specific conductance ranging from
127 to 1053 mS/m), slightly acidic to neutral pH (6.5–7.0), oxidation–reduction
potentials ranging from À45 to +45 mV, dissolved oxygen below 0.2 mg/L, and a
temperature of approximately 14.2
C. The concentrations of the contaminants just
before the test varied as follows—B 6.7–57.2 μg/L, T 41.3–3245 μg/L, and MCB
451–2840 μg/L. Old monitoring wells installed approximately 15 years prior to the
test were utilized for monitoring the process. The wells had long screen interval
along the whole aquifer thickness.
19.2.2 Site Investigation
A membrane interface probe (MIP) (Geoprobe Systems®, USA) was used for the
investigation of the contamination close to the particular monitoring wells. One MIP
412
O. Lhotský