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Chemical oxidation
In-situ chemical oxidation (ISCO) has the potential to effectively treat a wide range of organic contaminants. Essentially, oxidants are applied to the ground using a sufficient number of wells to allow overlap of treatment zones and therefore contact with the contaminants. However, due to subsurface heterogeneities, obstructions, etc., it is common practice to use a phased approach to oxidant applications. This allows re-treatment of contamination hotspots without delivery of excess oxidant to other areas of the site.
Delivery of oxidant to the required treatment zone is critical to the success of ISCO. Generally oxidant is delivered under pressure using Geoprobe or similar, or delivered by gravity to previously installed screened boreholes. The method adopted depends on site-specific factors including geological conditions, presence of hardstanding, proximity of buildings and underground services.
The rates of oxidation reactions depend on a range of variables including oxidant concentration, pH, catalysts, temperature, reaction by-products and none-target compounds (e.g. oxygen scavengers, natural organic matter, etc.). Application of the technology is therefore site specific and requires determination of a number of parameters prior to full scale use.
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