Environmental Engineering Reference
In-Depth Information
11.3.4.3 Reactive Barrier in Brunn am Gebirge (Austria)
The plume direction of the PRB in Brunn am Gebirge (Austria) was focused
on gate 2 with a very high total concentration of approximately 5600 μg/L.
Total concentrations at the neighboring gates 1 and 3 were a factor 100 (gate 3)
and factor 1000 (gate 1) lower, respectively. The fraction of NSO-heterocycles
at gate 2 was found to be approximately 7%, predominantly determined by
benzothiophene (180 μg/L), dibenzothiophene (120 μg/L), and carbazole
(50 μg/L).
Effluent concentrations were found to be below detection limits for all
compounds, and the efficiency of the PRB was >99% after more than 9 years
of operation. Using the minimum flow for the whole barrier (0.5 L/s) as an
assumed value for gate 2 and a maximum total concentration of 5600 μg/L,
the mass inflow at gate 2 was in the range of 50-100 kg/year. This mass is
valid for gate 2 with approximately 6 tonnes of activated carbon. Hence, the
estimated load for all compounds on activated carbon based on an operating
time of 9 years of the PRB was approximately 7%-15%. The loads for gates 1
and 3 were much lower and assumed to be below 1%.
In agreement with the measurements at the PRB in Karlsruhe (Germany)
and in contrast to organic compounds, the retardation for cyanide was low
and the cyanide concentrations in the influent and effluent were comparable.
11.4 Conclusions
Analytical methods and extraction procedures were developed to investi-
gate a complex spectrum of aromatic compounds that are typically found in
groundwater samples. In addition to BTEX and the 16-EPA PAH, these include
phenols, NSO-heterocycles, and further-related aromatic compounds, such as
alkylated PAHs. This spectrum of compounds was detected in the analysis of
tar oils and groundwater from different contaminated sites. However, in addi-
tion to a basic set (including 16-EPA PAH, NSO-heterocycles, BTEX, and phe-
nols), the spectrum of compounds analyzed varied during the investigation.
In the field campaigns, BTEX, indane and indene, and several PAHs (e.g.,
naphthalene, acenaphthene, fluorene, and phenanthrene) were present.
Methylnaphthalenes and dimethylnaphthalenes were found in high concen-
trations and should be included in sampling programs. However, concen-
trations of 1,8-dimethylnaphthalene were usually below the detection limit.
The most commonly found heterocycles were benzothiophene, benzofuran,
dibenzofuran, 2-methylquinoline, carbazole, acridine, and phenanthridi-
none. High molecular PAHs were generally found in low concentrations (for
instance concentrations of dibenzo(a,h)anthracene were below the detection
limit in all samples). Remarkable concentration differences were detected
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