Environmental Engineering Reference
In-Depth Information
an operational life of 50 years, the site owner expects up to 2 million € more
to be spent, mainly on changing the GAC and on monitoring. The Federal
State of Baden-Württemberg covered 3.5 million € of the total costs.
Over the first 3 years of operation, the Karlsruhe PRB cleanup results did
not meet remediation goals. The main issues were groundwater bypassing
the barrier at its northern edge and insufficient retardation of contaminants
at some gates. In early 2004, an overflow of some gates was identified as a
major issue, and therefore, all gates were equipped with extensions on their
tops to raise the GAC layer above groundwater level, thus avoiding further
overflow. That repair could be performed relatively readily because of the
high accessibility of the design of the PRB. Shortly after that issue had been
fixed, monitoring data revealed a consistently good cleanup performance
for the first time. The remediation goal for benzene (1 μg/L) was met. The
remediation goal for PAHs excluding naphthalene (0.2 μg/L) was still being
exceeded at some gates but overall, since summer 2004, measurements dem-
onstrate a good performance by the entire PRB installation. An overall deg-
radation rate of 99% was achieved in August 2004.
Since April 2003, PAH concentrations at the northern edge have been
decreasing and reached the remediation target value at the beginning of 2005.
A modeling study carried out in 2004 proved that the circumvention of the
northern edge of the funnel was caused by drainage measures in the course
of a sewer construction 1 km north of the PRB over 2 years. Since April 2004,
the cleanup efficacy achieved by the entire system has been close to 100%.
A monitoring campaign recently (2007-2010) conducted by the RUBIN R&D
program (Birke et al., 2010; Birke and Burmeier, 2012a,b) revealed an ongo-
ing high performance regarding the adsorption of PAHs and BTEX as well
as showing, for the first time, that NSO-PAHs were also removed from the
groundwater successfully (Figure 13.5).
13.2.2.6 Offenbach
A pilot scale PRB was designed, erected, and investigated within the RUBIN
R&D program in 2007 for the removal of tar oil pollutants from contami-
nated groundwater at an abandoned tar factory site in the city of Offenbach,
Germany (Schad et al., 2005; Tiehm et al., 2008; Birke et al., 2010; Weingran
et al., 2011). A three-step process was used, wherein the contaminated
groundwater was treated inside the PRB comprising (i) sedimentation of
ferric iron, (ii) aerobic biodegradation of the aromatic hydrocarbons (HCs)
and heterocyclic compounds, and (iii) a subsequent zone packed with GAC
for removing the remaining pollutants. Owing to the high pollutant concen-
tration in the groundwater encountered at this site, hydrogen peroxide was
selected as an oxygen carrier due to its higher water solubility compared to
oxygen. Also, nitrate was added as an alternative electron acceptor.
Up to 180 mg/L hydrogen peroxide (H
2
O
2
) were added and did not have
any toxic effect on the remedial bacteria. The feasibility of the concept was
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