Clean-up of contaminated sites: experiences in the netherlands

The number of more or less strongly contaminated sites in the Netherlands amounts to about 100,000. For more than ten years soil treatment techniques have been developed and used to clean-up those contaminated sites. The major clean-up techniques for excavated soil are extraction/wet classification, thermal treatment and biological treatment by landfarming. With extraction/wet classification experience is available with the treatment of sandy soils with a clay or humus percentage of less than 20%. The type of pollutants which have been removed with extraction/classification varies strongly: PAH, hydrocarbons, mineral oil, cyanides, Cd, Zn, Cr, Cu, Pb and Ni. With thermal treatment, experience is available with all types of soil, contaminated with cyanides, PAH, mineral oil, hydrocarbons, gasoline and HCH. With landfarming, experience is limited to the treatment of sandy soils polluted with easily biodegradable components such as gasoline hydrocarbons, low molecular PAH and mineral oil. Up to now more than 4,000,000 tonnes of soil have been treated with these methods. The major in situ clean-up methods are liquid extraction, soil vapour extraction and biorestoration. However, in comparison with the clean-up of excavated soils the practical experience with these in situ methods is still limited. Research and development is still going on and is especially focused on the improvement of the clean-up techniques for excavated soil, and the improvement and further development of in situ treatment techniques, especially in situ biorestoration.