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IN SITU CHEMICAL OXIDATION (ISCO) IS A TECHNIQUE USED TO DECONTAMINATE SOILS IN SITU.
- WHAT DOES IT? It reduces the concentrations of the existing contaminants in groundwater and/or soil down toacceptable levels for the environment.
- HOW DOES IT WORK? It cleans the soil and removes pollutants from it.
- HOW IS IT PERFORMED? A product (oxidant agent) is introduced into the subsurface, goes through its mass and produces the chemical destruction (oxidation) of pollutants into less harmful chemical species. Those compounds are extracted to the surface for their treatment.
The behaviour of a pollutant in soil and the efficiency of a remediation technology are determined by a number of factors that interact in a complex way and depend on the characteristics of the pollutant itself and those of the soil.
To select a technology with good prospects of success it is crucial to take into account the characteristics of both, the pollutant and the polluted site.
The following PHASES are carried out to implement the technique on site:
1. SELECTION OF THE PERFORMANCE AREA AND BASIC INFRASTRUCTURES: The success of the technique depends on the optimal location. Likewise, if there are not, drillings and wells to inject, to extract and to monitor the test must be carried out in the selected pilot area.
2. INJECTIONS: After the drill a solution with an oxidising agent is injected in a well. That solution breaks the C-C bonds of the organic compounds. The chemical oxidation of pollutants turns them into less hazardous and more treatable compounds.
3. RECIRCULATION: The oxidation of pollutants depends on the time of permanence of the oxidant in the subsoil. When the contact time (oxidant-bedrock) is considered sufficient, the solution is pumped through a well and injected again, if necessary. The recirculation process will be carried out until the oxidation capacity of the agent decreases.
4. EXTRACTION: The performance will be stopped when the oxidant becomes inefficient and the contaminants concentration shows a decreasing trend. Then, the solution is pumped and treated in an adequate water treatment plant.
5. MONITORING: To evaluate the progress (initial, middle and final conditions) and the global performance of the test, it is crucial to monitor parameters such as the oxidation-reduction potential, conductivity, temperature, oxidants and sub-products or concentration of targeted pollutants.