An interim remediation measure (IM) conducted in 2002 and 2003 atSpace Launch Complex 15, located at Cape Canaveral Air Force Station in Florida, testedthe remediation potential of combined thermal remediation followed by injection of 2%by weight of zero-valent iron (ZVI). The site was defined as the volume containinggroundwater with a trichloroethylene (TCE) concentration in excess of 10 ppm and wasbelieved to contain DNAPL of TCE and Freon 113 in some locations. The remediationprocess was implemented by large diameter auger (LDA) in situ soil mixing at depthsfrom 20 ft to 55 ft.An optional task was designed to evaluate the use of micron-sized EZVI combinedwith thermal treatment in an area not believed to contain DNAPL and to compare it withthe use of the -50 mesh ZVI powder, the majority of whose particles ranged between 200and 300 microns. The EZVI iron size ranged from 1 to 10 microns with an average of3 microns. It cost approximately 10x that of the –50 mesh iron. The decision to evaluatethe use of micron iron rather than nano-iron (nominally 0.1 micron) for the EZVI test wasbased upon cost; nano-iron costs 5 times as much as the micron iron. The loading ofmicron iron was 0.18% or 190 pounds per cell and cost approximately that of the–50 mesh at 2% loading. It was decided to also test a larger loading in case the chosenamount was insufficient. Thus, a second test was implemented using 570 lb per cell.The Work Plan called for treatment of four 7-ft-diameter cells for a total volume of204 cubic yards. Two cells were injected with the two EZVI concentrations. Two cellswere preheated to an offgas temperature of 150°F before injection of the EZVI, and twocells were not preheated. The four cells were located in an overlapping, hexagonal close-packed pattern.The four optional task cells clearly demonstrated that the micron EZVI remediatedthe chlorinated VOC. This was shown by the almost complete removal of VOC fromboth the soil and groundwater 3.5 months after treatment with the EZVI. This was alsodemonstrated by the continued reduction of the VOC concentration after the thermaltreatment is stopped. The data also suggest that the remediation is speeded up by increasedtemperature. The increased values of cis-1, 2 dichloroethylene as the remediationprogresses followed by a decrease are believed an indicator of the reductive dechlorinationof TCE and PCE by EZVI.
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