WORK PLANS - Laserfiche WebLink

Home Browse Search

IN-SITU CHEMICAL OXIDATION By James Jacobs, P.G., C.H.G., Clearwater Group In-Situ Chemical Oxidation CISCO) relies on the destructive capacity of oxidants to chemically destroy the bonds of the hydrocarbons. Complete chemical oxidation of gasoline would produce carbon dioxide and water. Chemical oxidants work by producing free radicals, such as the hydroxyl radical, which oxidize the gasoline. Several commonly used chemical oxidants have been used for in-situ applications on gasoline and MTBE, including hydrogen peroxide, Fenton's Reagent (hydrogen peroxide with an iron catalyst, frequently performed at a low pH), sodium persulfate and ozone. In-situ chemical oxidizers rapidly treat soils contaminated with gasoline and MTBE. Chemical oxidation of impacted soil or groundwater involves injecting an oxidizing agent, such as hydrogen peroxide (11202), activated persulfate or other oxidant, into the subsurface to break down the contaminants from toxic to non-toxic. ISCO has been used by EPA to remediate groundwater contaminated by petroleum products at service stations and demonstrated to effectively oxidize free product and to reduce dissolved contaminant concentrations. This technology not only destroys dissolved-phase contaminants in groundwater, but also desorbs contaminants from the soil matrix so that supplementary chemical oxidation may destroy these desorbed contaminants. Delivery of the oxidants will be through the existing and new monitoring wells or Geoprobe wellports. Chemical compatibility of the injection equipment components and safety procedures become critical with the injection of strong acids, bases, oxidants and other chemicals. Commonly-used-in-sitrroxidants-for-petroleum-hydrocarbon-treatment are-Fenton' Reagent (hydrogen peroxide and ferrous iron), ozone, and persulfate. Due to the high cost of the delivery system required by ozone, only combinations of hydrogen peroxide (with modifications) and persulfate are the two oxidants considered for this site and discussed in detail below. The proposed technology is In-situ Chemical Oxidation CISCO) using hydrogen peroxide (two cases) and one case with sodium persulfate and an iron catalyst: • Hydrogen Peroxide (Classic Fenton's Reagent) with pH adjustment • Hydrogen Peroxide with Sodium Persulfate and amendments • Sodium persulfate with iron EDTA Catalyst with no pH adjustment Hydrogen Peroxide 11202is one of the most powerful oxidizers known, stronger than chlorine. Despite its power, H2O2 is a natural metabolite of many organisms, which decompose the H2O2 they produce into oxygen and water (211202 - 2112O + 02). Hydrogen peroxide is a powerful oxidant, but at low concentrations (<O. 1%) its reaction kinetics are too slow to degrade many contaminants of concern. However, the addition of a ferrous iron dramatically increases the oxidative strength of peroxide. This increase is attributed to 1