In Situ Destruction of Chlorinated Hydrocarbons in Groundwater Using Catalytic Reductive Dehalogenation in a Reactive Well: Testing and Operational Experiences

A groundwater treatment technology based on catalytic reductive dehalogenation has been developed to efficiently destroy chlorinated hydrocarbons in situ using a reactive well approach. The treatment process utilizes dissolved H2 as an electron donor, in the presence of a commercial palladium-on-alumina catalyst, to rapidly reduce common chlorinated aliphatics such as trichloroethylene and tetrachloroethylene into non-chlorinated hydrocarbons such as ethane. Rapid reaction rates permit the deployment of a treatment unit within a dual-screened well bore, allowing contaminated groundwater to be drawn from one water-bearing zone, treated within the well bore, and discharged to an adjacent zone with only one pass through the system. A demonstration groundwater treatment system based on this concept was evaluated in a chlorinated hydrocarbon contaminated aquifer at a major Superfund site. The system rapidly destroyed a variety of common contaminants such as TCE and PCE and maintained its performance for a test period of one year. Operation of the treatment system was optimized to maintain catalyst activity and to prevent formation of intermediate compounds. Introduction. Groundwater contamination by trichloroethene (TCE), tetrachloroethene (PCE), and other chlorinated hydrocarbons is a well-recognized environmental problem. Conventional treatment technologies such as air-stripping with activated carbon adsorption require the construction of surface treatment facilities and produce secondary waste streams. To whom correspondence should be addressed. Telephone: (925)422-0061; fax (925)422-9203; E-mail: [email protected].