Cyclodextrin-Enhanced In Situ Removal of Organic Contaminants from Groundwater at Department of Defense Sites

摘要

Nonaqueous phase liquid (NAPL) spills in the subsurface are considered the single most important factor limiting remediation of military and industrial organic-contaminated sites. The generally limited performance of conventional groundwater pump-and-treat (P&T) systems has led to consideration of chemically enhanced flushing methods such as cyclodextrin enhanced flushing (CDEF). Cyclodextrins are nontoxic, modified sugars that form complexes with hydrophobic pollutants such as trichloroethylene (TCE). Because of its nontoxicity, CDEF technology is an attractive alternative to other chemical flushing agents, such as many surfactants or cosolvent formulations. CDEF generally begins with the injection of a water-based cyclodextrin solution. This solution is flushed through the contaminated aquifer and then extracted. Conventional injection and extraction wells can be used to control the flowfield of the flushing solution. This application scheme is in principle similar to conventional P&T systems, but due to the advantageous solubility enhancing properties of the cyclodextrin solution, mass removal rates are faster and, consequently, remediation times should be shorter. Funded by the Environmental Security Technology Certification Program (ESTCP), this technology demonstration was intended to show the potential of CDEF under near full-scale operational conditions. The particular objectives of this demonstration were (1) evaluation of the cost and performance of cyclodextrin- enhanced removal of dense nonaqueous phase liquids (DNAPL) from polluted groundwater, (2) test unrefined liquid cyclodextrin (CD) as a substitute for CD powder, (3) evaluate membrane technology for recovering and reusing CD, (4) identify the most appropriate wastewater treatment technologies, and (5) conduct partition tracer test (PTT) for mass balancing.