NATO/CCMS Pilot Study Evaluation of Demonstrated and ... - CLU-IN

NATO/CCMS Pilot Project on Contaminated Land and Groundwater (Phase III) January 2002
Water samples collected on 11 days were tested for numerous parameters; on the whole, over 1,600
individual results were obtained for water samples taken during pilot operation. The determined
concentrations for dissolved organic carbons (DOC) ranged between 80 and 160 mg/l at the inlet. The
DOC values correlate well with the CSB and TOC concentrations. No contaminant breakthrough was
detected in samples from the outlets of the two columns over a period of almost half a year.
The pilot tests with Columns 1 and 2 confirm that putting up an adsorbent wall is feasible.
With respect to contaminant retention, results of the pilot tests indicate that the long-term effectiveness
would be much higher than the estimated period of 30 years in the feasibility study.
4. RESULTS AND EVALUATION
The pilot tests confirm the findings of the feasibility study, to the effect that the site is suited to put up an
adsorbent wall. The following statements can be made with respect to the present tests:
The pilot tests show good contaminant retention in the activated carbon, in fact much higher than what
was assessed in the feasibility study. Contaminant breakthrough for toluene and trichloroethylene was
determined at sampling point S2P50 (i.e., after flow through 50 cm), Column 2, only at the end of the 5month
pilot test operation. By this time, throughput had reached 600 times the bed volume.
The pilot tests indicate that the durability of the wall given a 70 cm-thick activated carbon layer would be
much higher than the 30 years estimated in the feasibility study. The thickness of the carbon layer should
therefore be reduced when the wall is put up.
The DOC concentrations established during the pilot tests can almost entirely be traced to the
contaminants detected at the site. It is therefore to be expected that the adsorbing potential of the activated
carbon will not be impaired by natural organic compounds, such as human.
Data pertaining to the contaminant breakthrough suggest that the depletion of the adsorbing capacity of
the activated carbon is accompanied by a sharp peak in the concentration of volatile substances. A
suitable monitoring system should therefore be set up when the adsorbent wall is erected.
The fact that the activated carbon could be regenerated after disassembling the plant suggests economic
operation of the adsorbent wall.
Laboratory analyses of the water and activated carbon samples indicate that iron and manganese
precipitation will be insignificant and will not block the adsorbent wall.
Microbial activity could not be detected in the gravel filter or in the activated carbon; it may be concluded
that under the given site conditions, the build-up of bacterial film does not pose a risk.
Preliminary laboratory tests to determine the choice of activated carbon as well as pilot tests must be
carried out in all cases prior to setting up an adsorbent wall given the variance in site conditions.
5. COSTS
The costs for conducting the field tests have been EURO 50.000,--. The overall costs to erect the wall
system and then fill it with activated carbon are estimated to be EURO 750.000,--. Included are additional
costs for monitoring the water quality for 30 years, which is as long as the minimum performance time of
one single filling will be.
In comparison with traditional pump-and-treat groundwater remediation costs, the proposed permeable
reactive barrier system will be at least 25% less expensive.
6. REFERENCE
Eberhard Beitinger and Eckart Bütow. Machbarkeitsstudie zum Einsatz einer Adsorberwand -
”Schönebecker Schlucht” in Essen, Internal Report, WCI, Wennigsen, 1997 (not published)
21