IN-SITU CHEMICAL OXIDATION (ISCO)

At last week's Chemtura Public Advisory Committee (CPAC) meeting in Elmira, Steve Martindale of the Ministry of Emvironment (M.O.E.) handed out a four page phamplet produced by the U.S. Environmental Protection Agency (EPA). Steve was responding to questions about examples of ISCO successes or failures. The four most common ISCO chemicals were described including the chemical reactions involved in the subsurface. Essentially all of them have large amounts of oxygen and they combine with hydrocarbon contaminants present in the subsurface to produce water (H2O) and various other intermediates.

Permanganates, Fenton's Reagant, Ozone and Persulfate are the ISCO chemicals. They each have different strengths and weaknesses including different organic (carbon based) chemicals which they work best upon . Table 2 was very interesting as it described the various hydrocarbons and their reactions with the various ISCO chemicals. One example is chlorinated ethenes which would include Trichloroethylene (TCE). Potassium Permanganate (KMNO4) was used in the Bishop St. community of Cambridge several years back. According to Table 2 all four ISCO chemicals have excellent results on TCE. We were advised by Steve Martindale that Permanganate (KMNO4) however had only mixed results in Cambridge. I can see but two possible reasons for that. Firstly the TCE from Northstar (Bishop St.) is in the Bedrock which may have inhibited its' effectiveness. Conversely the "mixed results" may not reflect success on TCE so much as failure with the other contaminants present, specifically Trichloroethane (TCA). Table 2 makes it clear that for whatever reason none of the four ISCO chemicals have had much success with TCA.

Table 2 does not mention NDMA which allegedly is one of the contaminants it is being used to reduce/destroy in Elmira. N-Nitrosodimethylamine (NDMA) is a hydrocarbon as it includes dimethyl or 2(CH3). NDMA also has abundant Nitrogen in it of various forms as in Nitroso (NO), Nitrogen (N) and finally amines (NH2). Nitrogen including fertilizers are a component of various explosives. While explosives are mentioned in Table 2 as a chemical group which ISCO can destroy, frankly I am skeptical that NDMA is remotely classified under that group. Ammonia is another major contaminant in Elmira which is Nitrogen based (NH3). It is not a hydrocarbon by any definition. It is an inorganic chemical. To date no comments have been forthcoming from Chemtura and their acolytes regarding any possible breakdown of Ammonia.

What is very clear via Table 2 is that chlorobenzenes are an excellent candidate for ISCO treatment with three of the four ISCO chemicals. Interestingly the one ISCO chemical that is ineffective is permanganates (MNO4). Conestoga Rovers advised us early on that they wouldn't be using KMNO4, not due to its' ineffectiveness but due to discoloration of the groundwater and the Manganese precipitate leftover as part of the reaction. Odd?