 IN SITU TREATMENT OF LEACHATE-IMPACTED GROUNDWATER: SEPARATING FACT FROM FICTION |
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| Robert D. Mutch, Jr., P.Hg., P.E. and Gary J. DiPippo, P.E. |
Abstract:In situ treatment of leachate-contaminated groundwater has been successfully employed at a number of landfills in lieu of conventional approaches, such as groundwater extraction and treatment with or without subsurface barrier walls. Often these systems have cost a small fraction of the cost of conventional approaches. A variety of specific in situ treatment technologies have been used including enhanced reductive dechlorination, permeable reactive barriers, and recirculating, in situ treatment wells. The principle advantage of all these techniques is that groundwater is treated in situ without the need for extraction systems or expensive groundwater treatment facilities. However, each of the many emerging in situ treatment technologies has specific limitations, as well as, distinct advantages and disadvantages. Significant questions have arisen regarding the ability of such systems, even when combined in the subsurface in the form of a subsurface treatment train, to cope with the variability and shear number of different constituents commonly associated with MSW leachate. This presentation looks this issue as well as the economic advantages of in situ versus conventional ex situ treatment using case studies as examples. The presentation also reviews the key technical and practical limitations associated with the principal in situ treatment technologies, including specific contaminants that are resistant to treatment, incomplete treatment resulting in untreated "daughter products" that are in some cases more hazardous than their parents, and aquifer or reactive barrier "plugging" due to accumulation of byproducts. |
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