concentration of ClE was reduced mainly only over the first 20 days after the
injection, the values of the degree of dechlorination greatly increased (above
pre-application values for whole 146 days of the field test). The sharpest increase
after the injection was observed in the borehole AW5–58, where the degree of
dechlorination rose from 51% to 60% during the first 20 days. After that, the degree
decreased gradually and leveled off at around 55%.
5.4 Discussion
5.4.1 Effects on E H
On the basis of the decrease in E H after the injection, the application of NANOFER
STAR seems to be the most effective. The reductive process was observed in four
out of six boreholes and had the strongest course. The effect of this injection lasted
up to 30 days, after that E H remained constant. The NZVI-C3 application had almost
no influence on the reduction potential. A significant decrease was registered only in
the borehole AW5–60, which is located to the west of the injection centre. The
NANOCOMPOSITE with the CMC application caused a dip of reduction potential;
however, the reduction was not as strong as during the NANOFER STAR application. In this case, the reductive conditions lasted for 13 days.
5.4.2 Evaluation of the Contaminant Reduction
The main contaminants in the pilot test area were TCE and DCE. After each
application, concentrations of ClE plummeted immediately; however, the decrease
in the ClE concentration was usually not long-term. It seems that the decrease in
TCE caused production of DCE molecules. Therefore, in most of the boreholes, the
concentration of DCE rose gradually after the injection.
After the NANOFER STAR application, the sharpest decrease in ClE was
monitored in AW5–57 and AW5–58 boreholes and lasted for 7 days. The NZVIC3 application caused a sharp, short-term drop in ClE in AW5–58, AW5–60, and
AW5–62 boreholes. After 7 days, the values of ClE recovered quickly. The
NANOCOMPOSITE with CMC application had the smallest impact on the ClE
concentrations. There was a slight fall in TCE after the injection, accompanied with a
drop in DCE 20 days after the injection.
Table 5.1 shows the efficiency of each nZVI application in the ClE reduction
(counted for concentrations of all boreholes). The concentration of 4926 μmol/L of
ClE, which is the sum of ClE on the pilot test area measured before the injections
started, was considered as 100%.
We can see that the NANOFER STAR application was the most efficient because
of the 39% decrease in the total ClE concentrations. The nZVI application showed
100
V. Stejskal and N. Vacková
injection, the values of the degree of dechlorination greatly increased (above
pre-application values for whole 146 days of the field test). The sharpest increase
after the injection was observed in the borehole AW5–58, where the degree of
dechlorination rose from 51% to 60% during the first 20 days. After that, the degree
decreased gradually and leveled off at around 55%.
5.4 Discussion
5.4.1 Effects on E H
On the basis of the decrease in E H after the injection, the application of NANOFER
STAR seems to be the most effective. The reductive process was observed in four
out of six boreholes and had the strongest course. The effect of this injection lasted
up to 30 days, after that E H remained constant. The NZVI-C3 application had almost
no influence on the reduction potential. A significant decrease was registered only in
the borehole AW5–60, which is located to the west of the injection centre. The
NANOCOMPOSITE with the CMC application caused a dip of reduction potential;
however, the reduction was not as strong as during the NANOFER STAR application. In this case, the reductive conditions lasted for 13 days.
5.4.2 Evaluation of the Contaminant Reduction
The main contaminants in the pilot test area were TCE and DCE. After each
application, concentrations of ClE plummeted immediately; however, the decrease
in the ClE concentration was usually not long-term. It seems that the decrease in
TCE caused production of DCE molecules. Therefore, in most of the boreholes, the
concentration of DCE rose gradually after the injection.
After the NANOFER STAR application, the sharpest decrease in ClE was
monitored in AW5–57 and AW5–58 boreholes and lasted for 7 days. The NZVIC3 application caused a sharp, short-term drop in ClE in AW5–58, AW5–60, and
AW5–62 boreholes. After 7 days, the values of ClE recovered quickly. The
NANOCOMPOSITE with CMC application had the smallest impact on the ClE
concentrations. There was a slight fall in TCE after the injection, accompanied with a
drop in DCE 20 days after the injection.
Table 5.1 shows the efficiency of each nZVI application in the ClE reduction
(counted for concentrations of all boreholes). The concentration of 4926 μmol/L of
ClE, which is the sum of ClE on the pilot test area measured before the injections
started, was considered as 100%.
We can see that the NANOFER STAR application was the most efficient because
of the 39% decrease in the total ClE concentrations. The nZVI application showed
100
V. Stejskal and N. Vacková