NGWA Event and Education Recordings Archive

Background/Objectives: The remediation of dense non-aqueous phase liquids (DNAPLs) can be complicated by the associated physical and chemical properties of the contaminants. The potential effectiveness of ZVI for remediation of groundwater impacted by chlorinated solvents has been documented since the early 1990s. The chemical transformation with ZVI occurs via aqueous-phase reactions on particle surfaces and therefore involves at least three steps: (a) contaminant adsorption on the ZVI particle surface, (b) reaction at the surface, and (c) desorption of the transformation product. The ZVI mediated transformation processes described above are relevant for dissolved phase contaminant destruction, as the ZVI requires a hydrogen donor (e.g. H2O) for the abiotic reactions to proceed. Because DNAPL is not in the dissolved phase and has a hydrophobic physical chemistry, injection of ZVI slurries into source areas will not provide direct destruction of source material.

Approach/Activities: Emulsified ZVI (EZVI) technology provides a solution to these problems. First, it is engineered to enable maximum contact with source materials, while including ZVI suspended within water (hydrogen donor) so that direct DNAPL destruction is possible using ZVI technology. EZVI also combines food grade vegetable oil (VO) with a surfactant, elemental iron and water in a specific physical structure to enable direct DNAPL destruction utilizing a combination of abiotic and biotic processes while leveraging contaminant physical chemistry. The key innovation surrounding genuine EZVI technology is the structure of the emulsion. The structure of the EZVI technology enables; Miscibility with DNAPLs in situ; Continuous Sequestration (phase partitioning) of COI into outer VO membrane (decreased COI mass flux); Encapsulates ZVI so that it only reacts with COIs with hydrophobic physical chemistry; and Provides a long term hydrogen source for biostimulation downgradient from the source area.