Chemical-physical and biological physical cleaning of soil - comprises mixing with water, coarse material is separated, and sludge is sedimented and biologically treated using fluidised bed procedure

摘要

In a new procedure for cleaning contaminated soil: the soil is mixed with water in a reactor (1) in a ratio of 1:2 to 1:10 by means of at least two air/water agitation operations (2), so that the impurities are transferred to the resulting sludge or artificial sludge substitute; sludge and microorganisms are separated from the coarser material by reducing the turbulence (3, 5) and by changing the direction of flow, the resulting clean coarse material is removed (4); suspended materials are removed (6) from just below the liquid surface and are taken to a settling tank (7) with a dwell time of about 1 hr., in which the suspended material flows upwards through a bed of the separated sludge and is filtered by it; the water which is free of suspended materials is withdrawn (14) at about 20 cm below the liquid surface and is returned to the inlet of the washing system; floating materials and oils are removed (13); the sedimented foam and microorganisms (12) are introduced into an aerobic fluidised bed in which organic contaminants are broken down by microorganisms specific to them; if heavy metals are present, the sludge from the settling tank or reactor undergoes an elution procedure by which the heavy metals are separated; and the clean sludge is mixed with the previously separated coarse material. Also claimed is an appts. for carrying out this procedure. USE/ADVANTAGE - For cleaning soils or other granular materials which have a grain size less than 20 mm and are contaminated with organic materials, nutrients or heavy metals. The cost of on-site and off-site soil cleaning is reduced while maintaining the required cleaning effect, and the appts. has a high degree of mobility.