In-Situ Chemical Oxidation (ISCO) Applications at MGP Sites

摘要

This paper will focus on two refinements to the application of in-situ chemical oxidants at MGP sites; pulsed ozone technology, and the use of persulfate reagent. Shaw’s experience with ozone has led to the development of pulsed ozone technology (patent pending) for the treatment of PAH contamination. Testing with this technique has demonstrated the ability to destroy PAHs using up to an order of magnitude less ozone than traditional continuous application technology. In other technology development tests using permanganate reagents on soils contaminated with PAHs, Shaw has demonstrated the ability for the reagent to oxidize PAHs and reduce soil concentrations. This has been observed with soils spiked with PAHs and contaminated soil from a MGP site. However, soil from MGP sites typically has a fairly high organic content, which may also react efficiently with permanganate and result in high dose requirements and reagent costs for treatment. Fenton’s Reagent technology has been used at a few MGP sites with good success being reported. However, Fenton’s Reagent may be less effective at some sites due to high organic background or high rates of decomposition due to soil constituents and subsurface conditions. A more recent oxidant alternative to permanganate ion and Fenton’s Reagent is persulfate ion. Persulfate ion is a stronger oxidant than permanganate, capable of oxidizing PAHs, and at the same time is typically much less sensitive than permanganate to chemical demand from natural organic and other petroleum (TPH) compounds found in MGP soils. Under these conditions, persulfate reagent may be preferred over Fenton’s reagent for treatment. There are potential MGP site applications that may be well suited to the use of these reagent technologies. They include PAH contaminated groundwater and saturated zone soils or potentially shallow soils that can be treated by an infiltration gallery. Chemical oxidant behavior and characteristics are compared to MGP site characteristics to select which, if any, chemical oxidation technologies are appropriate for consideration at a site. Bench and pilot-scale testing are also helpful tools to select the appropriate oxidant prior to field implementation of the site remedy.