Hazardous Remediation of Waste Sites with In Situ Chemical Oxidation (ISCO)

According to the United States Environmental Protection Agency (USEPA), 80% of all hazardous waste sites in the United States have contaminated groundwater. The most common contaminants are chlorinated organic solvents including: trichloroethylene (TCE) and perchloroethylene (PCE). Conventional "pump and treat" methods have limited success in remediating sites where dense non-aqueous phase liquids (DNAPLs) are present, and therefore, lead to the development of in-situ chemical oxidation (ISCO) with permanganate as one of the optimal technologies for DNAPL treatment.

The merits of any type of treatment technology can be assessed in terms of effectiveness, ease of use, and cost. The use of permanganate (MnO4) for In-Situ Chemical Oxidation (ISCO) is fast, effective and results in the complete mineralization of TCE and PCE. Permanganate is readily available from Carus Corporation who will instruct and supply information how it can be safely handled. Permanganate can be mixed and injected at the site and the equipment needed is moderately inexpensive compared to other technologies.

The most important factor in the success of ISCO Remediation is the ability of the oxidant to reach the contamination. This is relatively easy in sandy soil, but can be a challenge in dense silt and clay. There have been successful In-Situ Chemical Oxidation applications in silt and in clay soil. However, it takes longer for the oxidant to migrate through the treatment zone. As long as there is contact, oxidation reaction will take place.

RemOx ® S ISCO Reagent potassium permanganate (KMnO4) has been used in drinking water and wastewater treatment for several decades to oxidize raw water contaminants. Within the past few years, its solubility characteristics have contributed to making it a more frequently oxidant for use with ISCO Remediation technology. Thus, RemOx ® S ISCO Reagent technology is becoming increasingly popular in the remediation industry due to its overall effectiveness and performance at the site.

RemOx ® S ISCO Reagent is an extremely effective oxidant for chlorinated solvents such as PCE, TCE and other chlorinated ethylenes, and can be used over a wide pH range. Also, it is effective on alkenes, phenols, sulfides, and many other contaminants. Unlike other in-situ oxidants, soils with a high carbonate or bicarbonate content will have no impact on permanganate's ability to oxidize TCE/PCE. Also, contaminants in the soil will not lead to the exothermic decomposition of the oxidant and release the reagents oxidizing power as gaseous oxygen. Handling permanganate is relatively safe compared to other oxidants and the use of permanganate as the ISCO oxidant is compatible with post-treatment biological processes.

RemOx ® L ISCO Reagent sodium permanganate (NaMnO₄) is an oxidant that performs chemically in a fashion analogous to RemOx ® S ISCO Reagent. The significant advantage of RemOx ® L ISCO Reagent is its high solubility in water, allowing it to be a more convenient form of permanganate as applied to ISCO. The higher solubility also allows for greater flexibility in applying the permanganate ion at much higher concentrations.

To get the greatest impact , it is important to determine the scope and limits of permanganate's use. Time, resources, plume size, climate, concentration of contaminants and oxidant availability are some of the variables that will factor into where and for how long ISCO should be used at a site. If contamination is limited to a small area – for instance under a former dry cleaner site – ISCO may be considered for the entire project. If the contaminated area stretches over several acres, it may be economically viable to treat the DNAPL zone with ISCO and follow up with bioremediation or natural attenuation for the dissolved phase.

The goal for every remediation project is site closure. With ISCO becoming more widely accepted as a commercial remediation technology, property owners realize that they have another tool with which to achieve their goals in an economical and timely fashion. With the practice of risk-based corrective action (RBCA), property owners have embraced innovative technologies such as ISCO as an alternative to the expensive “dig-and-haul” or “pump-and-treat” methods used in decades past.