Cyclodextrin-enhanced vertical flushing of a trichloroethene contaminated aquifer

Pilot-scale testing of an innovative ground water remediation technology wa s conducted in a source zone of a trichloroethene-contaminated Superfund si te in Tucson, Arizona. The technology is designed to enhance the removal of low-solubility organic contaminants from heterogeneous sedimentary aquifer s by using a dual-screened vertical circulation well to inject and extract solutions containing a complexing sugar (hydroxypropyl-beta-cyclodextrin (H PCD]). Prior to initiating the pilot test, tracer tests were conducted to d etermine hydraulic characteristics of the vertical now field and to evaluat e trichloroethene-elution behavior during water flushing. The pilot test in volved injecting approximately 4 m(3) of a 20% HPCD solution into the upper screened interval of the well and extracting from the lower screened inter val. The results of the pilot test indicate that the cyclodextrin solution increased the rate of trichloroethene removal from the aquifer. The concent rations of trichloroethene in the ground water extracted from the lower scr eened interval of the well increased by a factor of three (similar to 750 m ug/L) in the presence of the cyclodextrin pulse, compared to concentrations obtained during previous water flushing (similar to 250 mug/L). Furthermor e, the concentration of trichloroethene in water collected from the circula tion well under static conditions was reduced to 6% of the levels measured prior to the test.