Novel Recirculating Treatment Cell Achieves Substantial Reduction in Soil Lead in a Single Growing Season
(Dulles, VA, 6 June 2001) Edenspace Systems Corporation announced today the conclusion of its phytoremediation demonstration at the U.S. Army’s Ft. Dix, in central New Jersey. The preliminary results of the demonstration indicate that phytoextraction of ionic lead, combined with physical separation to remove bullet fragments, can successfully reduce lead levels in firing range soil to desired concentrations.
Lead at thousands of military, police, and private firing ranges around the world poses a significant environmental cleanup challenge. Sponsored by the U.S. Army TACOM-ARDEC at Picatinny Arsenal, New Jersey, the RangeSafe Technology Demonstration Initiative program that funded the Ft. Dix project seeks to develop new technologies to address this challenge. Concurrent Technologies Corporation served as prime contractor on the project. The demonstration was conducted with authorization by the New Jersey Department of Environmental Protection and under the observation of the U.S. Environmental Protection Agency.
Field operations for the demonstration began in 1999. Late that year, Brice Environmental Services Corporation excavated and processed sand from Range 24 at the New Jersey Army base, using a modified placer mining technology to remove bullet fragments. Edenspace then placed approximately 2,100 cubic yards of sand on a 1.25-acre (5,100 square meter) geomembrane liner, with embedded pipes draining to a lined catchment basin. Storage tanks and a pump-fed irrigation system allowed drainage water to be recirculated.
Beginning in April 2000, Edenspace sequentially planted three treatment crops on the cell, consisting of Indian mustard, sunflower, and rye mixed with barley. Edenspace purchased irrigation water through June, then added extra storage tanks in July and August to capture unusually heavy rainfall. The site received approximately 18 inches of rain from late July through September, almost twice the average level. Repeated recirculation of the rainfall and drainage water, including fertilizer, amendments and soluble lead, increased the efficiency of Edenspace’s standard techniques by promoting continuous phytoextraction with minimal use of amendments. During the last three months of field operations the project recirculated and concentrated a total column of about 4.3 feet of water – approximately 1,800,000 gallons – through the soil in the treatment cell. The Ft. Dix project represents the first time that a recirculating treatment cell has been used in the field for metal phytoextraction.
The analytical results from soil samples collected from the treatment cell indicate that lead concentrations before phytoremediation averaged 516 milligrams per kilogram (mg/kg), which exceeded the New Jersey standard of 400 mg/kg for soil intended for residential use. Final lead concentrations averaged 290 mg/kg, well under the residential standard. The final TCLP extract concentration (a measure of leachable lead) of the treated sand was approximately 1 milligram per liter (mg/L), which was less than the project goal of 5 mg/L. Lead in the recirculated drainage water remaining at the end of the demonstration represented a soil lead concentration of 30 mg/kg, comparable to the amount of water-soluble lead in the soil at the beginning of the joint demonstration (25mg/kg). The project showed that the use of solubilizing amendments to make lead available for plant uptake can also contribute to downward migration of lead, so that care must be taken to minimize leaching of lead when such amendments are applied in situ (without a liner), particularly in sandy, well-drained soils. The project also identified several techniques using cropping strategies and amendments that can minimize or eliminate leaching.
Average plant lead concentrations in the crops ranged from 1,430 mg/kg to 4,400 mg/kg, representingbioconcentration factors of up to ten. Harvested plants were disposed of in a landfill at substantially less cost than disposing of the contaminated soil.
Dr. Michael J. Blaylock, Edenspace’s Project Scientist on the Ft. Dix project, said, “We are delighted that our phytoremediation cleanup results at Ft. Dix met target levels. We are especially proud that, with the strong support of the Army and CTC, we were able to compensate for the unusually heavy rainfall.” Mr. John Cefaloni, U.S. Army RangeSafe manager on the Ft. Dix project, commented: “The new concentration and containment techniques demonstrated in, and derived from, this project should be extraordinarily helpful to future phytoextraction projects.”
Headquartered in Dulles, Virginia, Edenspace Systems Corporation is a leader in the use of live plants to protect and clean the environment. Its proprietary techniques employ plants to concentrate and remove lead, arsenic, radionuclides, chlorides (salts) and other minerals from water and soil. With expertise in plant science, soil science and agronomy, Edenspace is developing new markets for the restoration and enrichment of our surroundings.