In situ oxidation

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In situ chemical oxidation (ISCO) is a technique used to clean up (remediate) certain types of environmental contamination below the ground surface. Strong chemical oxidants, such as sodium permanganate or potassium permanganate may be applied to a contaminated site to destroy harmful compounds, especially certain organic compounds which are resistant to natural degradation. The most common organic chemicals targeted for remediation via ISCO are sites with chlorinated solvent (e.g. trichloroethene and tetrachloroethene) or gasoline-related compounds (e.g. benzene, toluene, ethylbenzene, or xylene). Some contaminants can be made less toxic through chemical oxidation. Other common oxidants used are persulfate, modified Fenton's Reagent, and ozone gas. The effectiveness of the oxidation is contingent primarily upon the geology, the residence time of the oxidant, the amount of oxidant used, and the effective contact the oxidant has with the contaminant(s). Some ISCO compounds (particularly Fenton's Reagent) can react aggressively with organic contaminants and must be used with care.

The primary delivery mechanism for ISCO is through perforated, hollow metal rods hammered with a mechanical hammer into the ground. The general term for this mode of delivery is "direct-push." Typically a truck mounted direct-push rig is used.

The oxidant is delivered as a water-based solution. Often the oxidant is injected into ground water wells (monitoring wells or injection wells) instead of direct-push rods. This enables multiple injections to be made into the same location.

Typically, the soil and groundwater are tested both before and after oxidant application to verify the effectiveness of the process. Monitoring of gases given off during oxidation can also help determine if contaminants are being destroyed. Elevated levels of CO₂ are an indicator of oxidation.