HR: 0830h
AN: H51C-1054    [PDF]
TI: Long-Term Monitoring of Post-Aquifer Flushing With Cyclodextrin
AU: Blanford, W J
EM: blanford@lsu.edu
AF: Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70808 United States
AU: * Hinrichs, R M
EM: hinrichs@geol.lsu.edu
AF: Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70808 United States
AU: Brusseau, M L
EM: brusseau@ag.arizona.edu
AF: Department of Soil, Water, and Environmental Science, University of Arizona, Tucson, AZ 85721 United States
AU: McCray, J E
EM: mccray@mail.utexas.edu
AF: Department of Geological Sciences, University of Texas at Austin, Austin, TX 78712 United States
AU: Boving, T
EM: boving@uri.edu
AF: Department of Geosciences, University of Rhode Island, Kingston, RI 02881 United States
AB: Cyclodextrins are benign sugar solutions that have been shown at numerous DoD sites to be effective in removing many different types of organic compounds from aquifers through flushing. Cyclodextrins enhance the solubility of many organic contaminants because the interior cavity of the toroidal shaped molecule has favorable conditions for inclusion of low-polarity compounds. They are also effective for aquifer flushing because the outside of the molecule is highly polar resulting in a high aqueous solubility. Their feasibility as a remedial alternative for many sites is dependent on whether unrecovered cyclodextrin mass left in the aquifer after active remediation leads to adverse results. The potential adverse results could include enhanced potential for spreading of hydrophobic contaminant and complications resulting from biodegradation of large quantities of cyclodextrin altering geochemical conditions. In the summer of 2002, a pilot test was performed at a military base in the Norfolk area of Virginia. Through funding by the Environmental Security Technology Certification Program within the DoD, hydroxyl-propyl-beta-cyclodextrin (HPCD) flushing was evaluated as a remedial technique for a chlorinated solvent contaminated aquifer. At the hazardous waste site there is a trichloroethylene (TCE) and sewage contaminated surficial sand aquifer. During the four months of field activities, tens of thousands of gallons of 20 percent wt./vol. HPCD solution were flushed through the aquifer. During and for 1.5 years after the cessation of flushing activities, the concentration of HPCD, TCE, dissolved oxygen (DO), nitrate, sulfate, and iron were monitored within the aquifer by sampling from the high density of monitoring wells at the site. The results of long-term monitoring have found that HPCD concentration continues to linger above 0.5 percent wt./vol. at the site. But, TCE levels have rebounded only slightly from post-flushing levels. Background dissolved oxygen is low at the site approximately 0.4 mg/L, but we found that the rates of DO depletion during flushing activities increased with exposure of the aquifer to HPCD solutions. Currently, we are examining the potential for HPCD to enhance the mobility of TCE by determining whether the ability of HPCD to enhance the solubility of low-polarity compounds is reduced over the time the HPCD solution resides in the aquifer.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: 2003 Fall Meeting