290
Permeable Reactive Barrier
original pumps were then successfully replaced by another type of pump.
Owing to these problems, the effort required for proper O&M of the system was much higher than expected. Originally, the test period was planned
only for 1 year. To obtain a sufficient operation period under optimum conditions, the test phase was extended until September 2009 (around 2 years
in total). It was subsequently decided that the system would be extended by
longer funnels and (probably) a second gate for a full hydraulic containment
of the site (Tiehm et al., 2008; Weingran et al., 2009, 2011; Birke et al., 2010;
Birke and Burmeier, 2012a).
13.2.2.7 Rheine
In 1998, a pilot-scale CRB containing two types of ZVI in two separated
segments (total length: 22.5 m) to treat cVOCs (mainly PCE, in 1998: around
10,000 μg/L, in 2012: around 2000 μg/L yet), was installed approximately
400 m downstream from a former dry-cleaning facility located in the small
town of Rheine, about 30 km westward of Osnabrück (Ebert et al., 2001,
2007; Birke et al., 2003, 2004; Parbs and Birke, 2005; Burmeier et al., 2006;
Birke and Burmeier, 2012a,b). Long-term monitoring of the performance
of the PRB was an important part of the mission of the RUBIN network
(RUBIN, 2014): the PRB was extensively used for regular in-depth monitoring campaigns over 12 years (2000 until 2012) including coring both ZVI
types and groundwater modeling to determine performance and predict
the long-term effect (Ebert et al., 2001). The Rheine pilot CRB is 22.5 m long,
0.6–0.9 m thick, and about 6 m deep. A single row of overlapping boreholes
(diameter 0.9 m) was constructed by utilizing caisson installation; these
were then filled with ZVI.
Two types (brands) of ZVI were employed: on the right side (viewed
from upstream), the boreholes were loaded with 69 tons of granular iron
(“Gotthart-Maier”) mixed with pea gravel at a 1:2 volume ratio (34.5 tons each
of iron and gravel) over a length of 10 m. Eighty five tons of “iron sponge”
(ReSponge ® , brand of Mull und Partner GmbH, Hanover, Germany) were
applied on the left side (12.5 m long). A concrete-filled borehole separates the
two segments. The name “iron sponge” is due to the material’s appearance:
the small, dark gray or black pellets (average diameter about 1 cm, Birke
et al., 2004; Parbs and Birke, 2005) resemble a pumice-like material. They
consist of reduced iron oxide and were supplied by the steelworks “ISPAT”
(now Mittal Steel), Hamburg, Germany.
Monitoring results prove an effective performance of the ReSponge section over the whole PRB life span since 1998, with an overall degradation
efficacy >99.5% while no decrease in reactivity has been indicated. In contrast to the efficient iron sponge section, the section containing a mixture of
Gotthart-Maier ZVI and pea gravel showed significantly decreased reactivity only 6 months after installation. Its initial degradation efficacy for PCE
was >98% decreasing to approx. 80% 1 year after installation. Since then, the
Permeable Reactive Barrier
original pumps were then successfully replaced by another type of pump.
Owing to these problems, the effort required for proper O&M of the system was much higher than expected. Originally, the test period was planned
only for 1 year. To obtain a sufficient operation period under optimum conditions, the test phase was extended until September 2009 (around 2 years
in total). It was subsequently decided that the system would be extended by
longer funnels and (probably) a second gate for a full hydraulic containment
of the site (Tiehm et al., 2008; Weingran et al., 2009, 2011; Birke et al., 2010;
Birke and Burmeier, 2012a).
13.2.2.7 Rheine
In 1998, a pilot-scale CRB containing two types of ZVI in two separated
segments (total length: 22.5 m) to treat cVOCs (mainly PCE, in 1998: around
10,000 μg/L, in 2012: around 2000 μg/L yet), was installed approximately
400 m downstream from a former dry-cleaning facility located in the small
town of Rheine, about 30 km westward of Osnabrück (Ebert et al., 2001,
2007; Birke et al., 2003, 2004; Parbs and Birke, 2005; Burmeier et al., 2006;
Birke and Burmeier, 2012a,b). Long-term monitoring of the performance
of the PRB was an important part of the mission of the RUBIN network
(RUBIN, 2014): the PRB was extensively used for regular in-depth monitoring campaigns over 12 years (2000 until 2012) including coring both ZVI
types and groundwater modeling to determine performance and predict
the long-term effect (Ebert et al., 2001). The Rheine pilot CRB is 22.5 m long,
0.6–0.9 m thick, and about 6 m deep. A single row of overlapping boreholes
(diameter 0.9 m) was constructed by utilizing caisson installation; these
were then filled with ZVI.
Two types (brands) of ZVI were employed: on the right side (viewed
from upstream), the boreholes were loaded with 69 tons of granular iron
(“Gotthart-Maier”) mixed with pea gravel at a 1:2 volume ratio (34.5 tons each
of iron and gravel) over a length of 10 m. Eighty five tons of “iron sponge”
(ReSponge ® , brand of Mull und Partner GmbH, Hanover, Germany) were
applied on the left side (12.5 m long). A concrete-filled borehole separates the
two segments. The name “iron sponge” is due to the material’s appearance:
the small, dark gray or black pellets (average diameter about 1 cm, Birke
et al., 2004; Parbs and Birke, 2005) resemble a pumice-like material. They
consist of reduced iron oxide and were supplied by the steelworks “ISPAT”
(now Mittal Steel), Hamburg, Germany.
Monitoring results prove an effective performance of the ReSponge section over the whole PRB life span since 1998, with an overall degradation
efficacy >99.5% while no decrease in reactivity has been indicated. In contrast to the efficient iron sponge section, the section containing a mixture of
Gotthart-Maier ZVI and pea gravel showed significantly decreased reactivity only 6 months after installation. Its initial degradation efficacy for PCE
was >98% decreasing to approx. 80% 1 year after installation. Since then, the