Traditional environmental remediation methods of cleaning up soil and ground water contaminated with chlorinated solvents, such as soil excavation and disposal or ground water pumping and treatment, are often prohibitively expensive or impractical due to site conditions.  An alternative environmental remediation method used to cleanup chlorinated solvents, known as in-situ chemical oxidation, is growing in popularity and gaining industry and regulatory acceptance as it is proven to be a cost-effective, time-efficient and less intrusive alternative remedial method to achieve compliance with environmental cleanup standards.
  
In general, chlorinated solvent contaminants exist in the subsurface in multiple phases; vapor, dissolved, adsorbed and liquid, which is known as DNAPL.  When the original chlorinated solvent liquid is lost into the subsurface, portions of it may volatilize and become a component of the air in the vadose zone (dry soil), dissolve into and become a component of the ground water, become adsorbed (molecularly bound or “stuck”) to individual soil particles, or remain as a liquid.

The in-situ chemical oxidation remediation process used to treat chlorinated compounds in the subsurface is straight forward from a chemical standpoint but complicated in practice, due to complex subsurface environments and various subsurface chemical contaminants.  The major oxidants available for in-situ application are: 

• Fenton’s Reagent,                                                        
• Ozone
• Modified Fenton’s Reagent,                 
• Permanganate
• Persulfate                                             
• Catalyzed persulfate

These oxidants have varying oxidation potentials, or “oxidation strength”, and the most suitable one for treatment of a particular contaminant plume is dependent upon a wide range of site-specific factors.  In simple terms, the oxidant contacts with the solvent and the solvent molecule is oxidized, gives up an electron, and forms new benign compounds from the original elements, thus rendering a hazardous contaminant plume into contaminant levels that are below regulatory cleanup standards.  For example, Trichloroethylene (TCE) oxidizes into carbon dioxide and chlorine ions.

To determine if a chlorinated solvent contaminant plume at a particular site is suitable for in-situ chemical oxidation remediation, two studies must be performed.  First a laboratory study is performed on a representative sample from a site, which consists of a laboratory test of various chemical oxidants and how effectively they remediate the chlorinated solvent.  If the laboratory study is successful in remediating the chlorinated solvent, then an on-site pilot study is performed, which consists of a test injection of chemical oxidants to determine the effectiveness and rate of reaction of the selected oxidant in real world conditions.  Upon completion of the pilot study, a full scale in-situ chemical oxidation remediation program is formulated to address the chlorinated solvent contaminant plume to bring it within regulatory cleanup levels.

For More Information and Case Histories Contact:  In-Situ Oxidative Technologies, Inc. (http://www.insituoxidation.com/)