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Several oxidizers provide an effective first step in groundwater and soil remediation.
As innovative treatment technologies to remediate groundwater and soil become widely accepted, agencies are focusing on technologies that facilitate natural attenuation later in the remediation process. In situ chemical oxidation (ISCO) is an effective way of remediating soil and groundwater contaminated with chlorinated solvents such as perchloroethylene (PCE), trichloroethylene (TCE), vinyl chloride (VC) and benzene, toluene, ethylbenzene and xylene (BTEX). ISCO can be applied using different types of oxidizers such as ozone, Fenton's reagent, potassium permanganate and sodium permanganate. The advantages of ISCO include:
. The ability to oxidize dense non-aqueous phase liquids (DNAPLs).
. A reduction in overall treatment time, allowing the site to reach closure sooner.
. The elimination of capital-intensive pump-and-treat systems.
. The ability to treat contaminated areas without disturbing above-ground structures.
. The elimination of costly excavation and handling of contaminated soil.
ISCO can be used as a stand-alone treatment or in conjunction with other technologies such as bioremediation. The nature and location of the contamination, size of the contaminated area, type of soil and hydrogeology play a significant role in choosing the most effective type of ISCO treatment. In situations where contamination covers a vast area, economics will dictate the extent to which ISCO is used. In many cases, ISCO is a cost-effective precursor to bioremediation and natural attenuation.
Before considering an ISCO treatment scheme, it is best to become familiar with specific state underground injection control (UIC) programs that have specific permitting requirements. Information listed in 40 Code of Federal Regulations (CFR), Parts 144 to 148, should be reviewed.
application methods
There are two primary injection methods for ISCO treatment. The first method injects the oxidant on one side of the contaminated zone while extracting groundwater on the other side. Extraction creates a negative pressure zone, causing the oxidant to migrate more quickly through the contaminated zone. Injection can be accomplished either upgradient or downgradient of an aquifer.
The second method uses injection without extraction. The oxidant is injected into the contaminant and allowed to migrate through the contaminated zone. This can be done in a horizontal or radial configuration. Monitoring wells throughout the treatment area are used for tracking oxidant migration and for...