Physico-chemical treatment: washing polluted soil

The choice of treatment techniques for a polluted site requiring remediation because it poses a risk to the environment, or for treating polluted spoil as part of site development work, must take into account the best available techniques at the time, without entailing excessive costs.

No methodology for determining the best available treatment techniques has yet been developed in France, as is the case in the United States, the Netherlands and Belgium, or in England, where a "cost-benefit" analysis has been developed.

In order to optimally determine the most appropriate treatment technologies, it is advisable to establish the feasibility, effectiveness and financial evaluation of available treatment techniques as early as the phase of in-depth diagnosis and detailed risk assessment. For example, certain physico-chemical soil parameters (water content, particle size, etc.) not directly related to the risk of remediation should be investigated as part of the field investigation program during the diagnostic phases, in preparation for this analysis.

Physico-chemical treatment techniques are undergoing rapid development in Northern European countries, due to their highly economical nature, while at the same time making it possible to achieve residual concentrations that are tolerable for public health and the environment. This type of treatment has been developed through applications of mineral processing techniques. The equipment used is commonly found in a large number of mining industry processes, such as sand and gravel washing, coal washing, ore separation and hydrometallurgical extraction.

Physico-chemical treatment is suitable for the remediation of soils contaminated by organic and/or inorganic contaminants. In France, it has only recently been introduced, usually ex-situ, in specialized centers. Only a dozen or so companies use the soil washing technique on a marginal basis. In Europe, on the other hand, there are some thirty soil recycling companies, mostly based in Germany, Belgium and the Netherlands, operating some fifteen soil washing plants.