Design and evaluation of an in-situ ground water treatment wall composed of zero-valent iron

Abstract

An in-situ permeable treatment wall using zero-valent iron for the remediation of ground water affected by chlorinated volatile organic compounds (VOCs) was recently constructed in Sunnyvale, California. Because this site was the first full-scale application of this technology as a final remedy of VOC-affected ground water, it provides a framework for assessing the factors that must be considered when moving from laboratory studies of this treatment technology to design and construction of a full-scale treatment system. Experience from this case study is valuable for both practical design considerations and as incentives for future research. The patented treatment process, licensed by Environmental Technologies Inc., utilizes granular zero-valent iron as a porous medium to enhance the degradation of VOCs dissolved in ground water. The dissolved VOCs, such as 1,1,1-trichloroethylene (TCE), that pass through the granular iron matrix are transformed through the oxidation of the iron and reductive dechlorination of the organic compound to a final end product consisting chiefly of chloride and ethylene. The degradation process appears to be abiotic and half-lifes of the transformations are several orders of magnitude faster in the presence of zero-valent granular iron than observed in the ambient environment.