Remediation Approaches – In Situ Chemical Oxidation (ISCO), Part 1

Is ISCO a good choice for your site?

Many contaminants and site conditions are difficult to treat with conventional remediation technologies such as soil vapor extraction, air sparging, bioremediation, or pump and treat. In addition, conventional technologies are often costly and time-consuming. For the past 15 years oxidation has become a common alternative for in situ remediation. But is it a good technology for your site? This series of blog posts provides a framework for answering this question.

When chemical oxidation is considered for a site, there are many screening criteria to see if it is a good choice.

  • What are the contaminants of concern
  • What is the best oxidant to address the contamination and the geologic conditions?
  • What is the optimal delivery method?

The following four oxidants are typically applied for in situ oxidation systems:  permanganate (MnO4-), hydrogen peroxide (H2O2), sodium persulfate (Na2S2O8), and ozone (O3).

Permanganate is frequently used for site affected by chlorinated volatile organic compounds. It reacts well with chlorinated ethene compounds and their aerobic degradation components and can be mixed to provide a site-specific balance of dose, hydraulic loading, and environmental persistence.

While Permanganate alone is frequently used for chlorinated VOC compounds, hydrogen peroxide should also be considered. Hydrogen peroxide and permanganate are the preferred oxidants for treating commonly found VOCs, especially benzene, toluene, ethylbenzene, and xylene (BTEX), and chlorinated ethenes such as perchloroethene (PCE), trichloroethene (TCE), dichloroethene (DCE), and vinyl chloride. Permanganate has an advantage over hydrogen peroxide in that it does not rapidly decompose and thus can provide residual oxidation potential. Both of these soluble oxidants can also oxidize a number of smaller PAHs and phenolic compounds.

Persulfate is the preferred oxidant for remediation of recalcitrant organics and mixed contaminants such as chlorinated volatile organics, chlorinated ethanes (e.g., DCA and TCA), oxygenates, and polynuclear aromatic hydrocarbons (PAH).

Ozone is the preferred oxidant for recalcitrant organic compounds such as PAHs, pesticides, plasticizers, phenolics, and polychlorinated biphenyls (PCBs). It can also be used to treat VOCs.

Each of the four oxidation systems is compatible with other treatment technologies and can be effectively used in treatment trains or integrated systems. Chemical oxidation systems can be effectively used for pretreatment, primary treatment, or polishing.