Module  6


Example of remediation



Treatment of soil contaminated with mercury through a combination of wet screening and vacuum distillation, France


Mercury contaminated soil and building rubble was treated by a combination of soil washing and vacuum thermal desorption with a vacuum mixer. The soil washing process separates coarse material, which is generally less contaminated, from fine material, which contains the bulk of the contamination and has to be treated in the vacuum mixer. Coarse material was tested and declared as cleaned if it met the quality criteria. If not, it was crushed and treated in the vacuum mixer.


The material treated by the vacuum mixer achieved a final mercury content of less than 1 ppm and leached less than 0.001 mg/l. After the treatment, stabilization was used to reduce the leachability of other heavy metals and the clean material was used for backfilling on site.


Before adopting a soil washing approach, it may be advisable to determine if the concentration of mercury in the contaminated soils is amenable to this type of treatment.


Combination of wet screening and vacuum distillation

flow chart


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