Keywords Chlorinated hydrocarbons · Electrokinetics · Chemical reduction ·
Nanoremediation · nZVI · Tracer test
6.1 Introduction
The use of nZVI for contaminated groundwater remediation is nowadays one of
standard methods for in situ treatment or stabilization of chlorinated hydrocarbons,
selected inorganic anions, heavy metals and others. The effectiveness of this method
depends on the geological and hydrogeological conditions, which affect both the
reactivity of nanoparticles with contaminants and their spreading in the subsurface.
In the case of low permeability environment, the migration of nanoparticles is very
limited and the efficiency of the method might be therefore reduced. The application
of nanoparticles supported by direct current (DC) electric field of certain field
intensity leads to a significant increase of lifetime and total efficiency of this
combined remediation technique.
The site selected for the pilot test of nZVI enhanced by electrokinetics is located
in canton of Aargau, Switzerland. The site is situated a few hundred meters from the
river Rhine. Until 2004 a mercury cell chlor-alkali electrolysis plant operated at the
site, and chlorinated solvents were produced in a dedicated production unit from
1940s to 1970s. The soil and groundwater around this production and storage units
have been contaminated by accidentally spilled chlorinated products or by contaminated wastewater leaching from the sewer. The main contaminants found in the area
are tetrachloroethene (PCE), trichloroethene (TCE), hexachloroethane (HCA), and
hexachlorobutadiene (HCBu).
Within the site, the groundwater flows to the west towards the river. The pilot test
area consists of unconfined alluvial sediments of sand and gravel, but stones and
boulders are also abundant. The marlstone bedrock (Opalinus Clay) is found at
16.5 m bgl and the average water table at 13 m bgl. The hydraulic conductivity is
high causing groundwater flow velocity in order of meters per day (as determined
based on the tracer test).
6.2 Materials and Methods
The monitoring system on the Aargau site consisted of nine monitoring/application
wells and three wells equipped by micropump system (Fig. 6.1). Each micropump
well had two sampling horizons. The monitoring/application wells were approximately 16–17 m deep and had an open screen only at the bottom 70–100 cm.
Micropump wells collected water from different depth horizons between 15 and
16.5 m below the ground level. The wells and their use in the monitoring campaigns
are listed in Table 6.1.
As the diameter of the monitoring wells is only 50 mm DIN, it was necessary to
install permanent sampling pumps into the wells together with electrodes. The
106
V. Stejskal et al.
Nanoremediation · nZVI · Tracer test
6.1 Introduction
The use of nZVI for contaminated groundwater remediation is nowadays one of
standard methods for in situ treatment or stabilization of chlorinated hydrocarbons,
selected inorganic anions, heavy metals and others. The effectiveness of this method
depends on the geological and hydrogeological conditions, which affect both the
reactivity of nanoparticles with contaminants and their spreading in the subsurface.
In the case of low permeability environment, the migration of nanoparticles is very
limited and the efficiency of the method might be therefore reduced. The application
of nanoparticles supported by direct current (DC) electric field of certain field
intensity leads to a significant increase of lifetime and total efficiency of this
combined remediation technique.
The site selected for the pilot test of nZVI enhanced by electrokinetics is located
in canton of Aargau, Switzerland. The site is situated a few hundred meters from the
river Rhine. Until 2004 a mercury cell chlor-alkali electrolysis plant operated at the
site, and chlorinated solvents were produced in a dedicated production unit from
1940s to 1970s. The soil and groundwater around this production and storage units
have been contaminated by accidentally spilled chlorinated products or by contaminated wastewater leaching from the sewer. The main contaminants found in the area
are tetrachloroethene (PCE), trichloroethene (TCE), hexachloroethane (HCA), and
hexachlorobutadiene (HCBu).
Within the site, the groundwater flows to the west towards the river. The pilot test
area consists of unconfined alluvial sediments of sand and gravel, but stones and
boulders are also abundant. The marlstone bedrock (Opalinus Clay) is found at
16.5 m bgl and the average water table at 13 m bgl. The hydraulic conductivity is
high causing groundwater flow velocity in order of meters per day (as determined
based on the tracer test).
6.2 Materials and Methods
The monitoring system on the Aargau site consisted of nine monitoring/application
wells and three wells equipped by micropump system (Fig. 6.1). Each micropump
well had two sampling horizons. The monitoring/application wells were approximately 16–17 m deep and had an open screen only at the bottom 70–100 cm.
Micropump wells collected water from different depth horizons between 15 and
16.5 m below the ground level. The wells and their use in the monitoring campaigns
are listed in Table 6.1.
As the diameter of the monitoring wells is only 50 mm DIN, it was necessary to
install permanent sampling pumps into the wells together with electrodes. The
106
V. Stejskal et al.