B139, this well was used for calculating the aquifer thickness in time. The groundwater level in the well is decreasing in time, mean value for the interval of
measurement is 3.5 m.
The inflow groundwater velocity was defined by a tracer test performed in the
summer 2018—0.7 m/day between B149 and B139. Effective porosity of sand/
gravel Quaternary aquifers was about 30% (0.3), this value was used for mass
balance calculation. The total inflow in m
3 /day into each segment was calculated
by multiplication of width, thickness, inflow velocity, and effective porosity.
Calculated mass balance gives the following results. In the B149 segment, there
was injected 100 kg (two application wells) of nZVI degraded 18.9 kg of CHC. In
B148 segment, there was only one application well, and therefore only 50 kg of
nZVI applied, which degraded approximately 8.5 kg of CHC—about a half of what
was degraded in the B149 segment. In the northern part of the pilot site, there was
injected 100 kg of nZVI and if we assume a similar efficiency of electrokinetically
enhanced nZVI, total degraded amount is about 45.5 kg of CHC on the whole site.
6.6 Conclusions
The combined technology of nanocomposite and electrokinetics was successfully
applied on Aargau site in northern Switzerland in November 2017.
After creation of a diffused reactive barrier, there was a significant increase of
CHC concentration in the inflow area observed. A continual increase lasted 75 days,
and the CHC concentration increased from 12 mg/L to 69 mg/L.
With the aim to track the water flow of such contaminated water, we conducted a
tracer test. The applied tracer was found in B152 and further in B139 confirming a
contaminated groundwater flow from B149 through the RB to B139 with the
estimated velocity of 0.7 m/day.
The reduction process of CHC on the nZVI reactive barrier lasted for the first
6 months after the RB installation and the values of CHC reduction were in the range
of 87–97%. In July 2018, (8 months after the application) reduction of about 46%
was still observed. The CHC composition shows that while the inflowing groundwater was contaminated mainly with PCE (90%), the outflowing groundwater was
contaminated with DCE (53%). The concentrations of the nontoxic degradation
products of the in situ chemical reduction increased up to 2500 μg/L in the RB
area, that means 19 times higher compared with the state prior to the test.
On the basis of the results of the performed tracer test and the measured reduction
of CHC contamination, the mass balance of degraded CHC was estimated. As the
tracer test described well only the southern part of the pilot test area, the calculation
of the contamination mass balance was performed only in this part, where 150 kg of
nZVI was applied. The principal result from the southern part is that each 50 kg of
the injected nZVI degraded 9.1 kg of CHC, thus degrading approximately 45 kg of
CHC in total.
116
V. Stejskal et al.
measurement is 3.5 m.
The inflow groundwater velocity was defined by a tracer test performed in the
summer 2018—0.7 m/day between B149 and B139. Effective porosity of sand/
gravel Quaternary aquifers was about 30% (0.3), this value was used for mass
balance calculation. The total inflow in m
3 /day into each segment was calculated
by multiplication of width, thickness, inflow velocity, and effective porosity.
Calculated mass balance gives the following results. In the B149 segment, there
was injected 100 kg (two application wells) of nZVI degraded 18.9 kg of CHC. In
B148 segment, there was only one application well, and therefore only 50 kg of
nZVI applied, which degraded approximately 8.5 kg of CHC—about a half of what
was degraded in the B149 segment. In the northern part of the pilot site, there was
injected 100 kg of nZVI and if we assume a similar efficiency of electrokinetically
enhanced nZVI, total degraded amount is about 45.5 kg of CHC on the whole site.
6.6 Conclusions
The combined technology of nanocomposite and electrokinetics was successfully
applied on Aargau site in northern Switzerland in November 2017.
After creation of a diffused reactive barrier, there was a significant increase of
CHC concentration in the inflow area observed. A continual increase lasted 75 days,
and the CHC concentration increased from 12 mg/L to 69 mg/L.
With the aim to track the water flow of such contaminated water, we conducted a
tracer test. The applied tracer was found in B152 and further in B139 confirming a
contaminated groundwater flow from B149 through the RB to B139 with the
estimated velocity of 0.7 m/day.
The reduction process of CHC on the nZVI reactive barrier lasted for the first
6 months after the RB installation and the values of CHC reduction were in the range
of 87–97%. In July 2018, (8 months after the application) reduction of about 46%
was still observed. The CHC composition shows that while the inflowing groundwater was contaminated mainly with PCE (90%), the outflowing groundwater was
contaminated with DCE (53%). The concentrations of the nontoxic degradation
products of the in situ chemical reduction increased up to 2500 μg/L in the RB
area, that means 19 times higher compared with the state prior to the test.
On the basis of the results of the performed tracer test and the measured reduction
of CHC contamination, the mass balance of degraded CHC was estimated. As the
tracer test described well only the southern part of the pilot test area, the calculation
of the contamination mass balance was performed only in this part, where 150 kg of
nZVI was applied. The principal result from the southern part is that each 50 kg of
the injected nZVI degraded 9.1 kg of CHC, thus degrading approximately 45 kg of
CHC in total.
116
V. Stejskal et al.