PSA - Groundwater Remedy and Quarterly Sampling Plan - Oliver Industrial Park - Hull and Assoc.

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Hull & Associates Inc. Page 17 toxicity to dehalogenating bacteria and to enhance catalytic reductive dechlorination when ferrous iron is added. Further, ferrous iron, itself, may act as an electron donor. Injected, colloidal reactive iron is a promising technology, which may be applied, in a synergistic approach with compatible technologies. There are two primary reactions with CAHs that take place which will consume the iron and require stoichiometric consideration: the anaerobic iron corrosion reaction in which water is disassociated to form hydrogen gas; and • the direct adsorption of a chlorinated hydrocarbon onto the surface of the iron, followed by reductive dehalogenation. Recent research on elemental iron systems suggests that four mechanisms are at work during the reductive process: • First, the Fe' acts as a reductant by supplying electrons directly from the metal surface to an adsorbed halogenated compound. • Second, hydrogen gas is generated by the anaerobic corrosion of the metallic iron by water. • Third, metallic iron may act as a catalyst for the reaction of hydrogen with the halogenated hydrocarbon using the hydrogen produced on the surface of the iron metal as the result of anaerobic corrosion with water. Theoretically, these reactions are not kinetically effective without a catalyst; thus, it is thought that impurities in the iron or surface defects act as that catalyst. • Fourth, solubilized ferrous iron can also act as a reductant, albeit at a rate at least an order of magnitude slower. Hydrogen gas can be used for reductive dehalogenation by the following reaction: Hz + X-CI = X-H + H' + CI' Vitamins: Recent studies suggest that metal — containing coenzymes, found in certain types of anaerobic microorganisms, and can reductively dechlorinate one- and two -carbon solvents. Cobalt -containing corrinoid cofactors such as vitamin B12 mediate the reductive dechlorination of carbon tetrachloride and tetrachloroethene.in these biological systems the rate -limiting step to complete dechlorination to ethylene is the last stage conversion of vinyl chloride. The rate of that process has been found to be significantly enhanced by the presence of vitamin B12, which acts as an electron carrier. It is the core of B12, which contains cobalt, and the various oxidation states the cobalt obtains, which allows for the electron transfer intra-cellularly. The existence of the cobalt core has also been seen to catalyze the surface reaction of the iron lowering the necessary activation energy required for the electron transfer.