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

Abstract

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 nonchlorinated 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 1 year. Operation of the treatment system was optimized to maintain catalyst activity and to prevent formation of intermediate compounds.

Hydraulics Analysis for Groundwater Flow Through Permeable Reactive Barriers

“…The barrier also prevents groundwater contaminants from migrating to uncontaminated aquifer, which may be difficult to locate and remediate. The most common contaminants that have been treated through the use of PRBs involve organic compounds [6][7][8][9][10], nitrate [11][12][13][14][15], heavy metals [16][17][18][19][20] and acidic wastes [21][22][23]. The main advantage of PRBs over the ex situ or other in situ methods of groundwater remediation is the passive nature of the treatment.…”

Ex-Situ Remediation Technologies for Environmental Pollutants: A Critical Perspective

“…In many studies, microbiological reductive dechlorination of chlorinated organic molecules is proved to be important for bioremediation of polluted groundwater (McNab and Ruiz 2000 ). There exists an electrochemical dehalogenation mechanism where chlorinated hydrocarbons and chlorofl uorocarbons are dechlorinated by electrolysis using appropriate solvents.…”

Tratamiento de efluentes acuosos contaminados con compuestos organoclorados

“…En un primer grupo de trabajos (Lowry & Reinhard, 1999;Lowry & Reinhard, 2000;McNab et al, 2000;Schreier & Reinhard, 1995), se ha centrado mayoritariamente la investigación en la hidrodecloración catalítica de compuestos organoclorados presentes en aguas subterráneas y en agua de grifo, es decir, con bajas concentraciones de los contaminantes, empleando siempre Pd como catalizador soportado sobre distintos materiales, como alúmina (el más utilizado), carbón o zeolitas. Entre todos los compuestos estudiados, los más empleados han sido el TCE y el TTCE.…”

“…Y, por último, como trabajo aplicado a un caso real, en McNab et al (2000) se detalla la destrucción in-situ de distintos organoclorados mediante un sistema de tratamiento instalado en un acuífero para aguas subterráneas. De igual manera a las anteriores, el agente reductor es H 2 y el catalizador empleado es Pd/Al 2 O 3 , con el fin de transformar los organoclorados en hidrocarburos no clorados.…”