Case Histories from Eight Years of Successful Testing and Remediation Using Aerobic Soy-based Cometabolism for Removal of Chlorinated Hydrocarbons from Groundwater

摘要

During the period from 2000 through 2008, an aerobic cometabolism technology has been successfully tested and employed at more than ten field pilot test locations and full scale remediation sites in several states. The technology has been suc- cessfully utilized for remediation of common halogenated hydrocarbons including tri- chloroethene, dichloroethene, tetrachloroethene, carbon tetrachloride, and chloroform, as well as several less common hydrocarbons and fluorocarbon compounds present in groundwater. In nine of the first ten applications conducted through 2007, the technology resulted in rapid, cost effective reduction in overall halogenated groundwater constituents of concern (COC). Concentration reductions typically exceed 95% and have resulted in “no further action” (NFA) approval at several sites. In the single unsuccessful applica- tion, a high pH (>11) precluded the establishment of adequate microorganism populations to support the cometabolic process. In situ cometabolism was initially evaluated in 2000 at a Union Carbide Corporation (UCC) site in West Virginia in an effort to simulate a toluene oxygenase enzyme co- metabolic process observed elsewhere on site at a mixed toluene and halogenated hydro- carbon plume. Various biodegradable vegetable based mixtures were tested on the bench scale to evaluate delivery methods and dispersion/migration characteristics under simu- lated aquifer conditions. A soy methyl ester and a biodegradable surfactant blend has been tested and used extensively for full scale field application. Results from the applications have been documented in reports to USEPA and State regulatory agencies, and indicate that the technology has reduced concentrations of chlo- rinated hydrocarbon and fluorocarbon compounds at the sites to levels meeting target cleanup criteria. Long term data from the first two site-wide remediation projects indicate that site-wide average COC reductions greater than 96 % were achieved within six to eight months and re-sampling of site groundwater more than two years after the conclu- sion of active remediation indicated that only minimal rebound had occurred, with overall post rebound COC reductions exceeding 95% compared to pre-remediation concentra- tions. Comprehensive site information, including COC concentration data, indicator field parameters, and microbiological population counts from numerous sites where the tech- nology has been successfully applied over the past six years have been compiled, with representative examples provided below. The process described within this paper combines several proven technologies, in- cluding air sparging, liquid/liquid extraction, and biological cometabolism. Field applica- tion of the technique during the past six years at several pilot and full scale remediation sites has resulted in rapid and dramatic decreases in groundwater COC concentrations with cleanup goals being achieved at several of the sites.