In addition to the frequently applied biological or physical "in situ" methods, classic soil washing is the only technical and economical alternative in many cases. In this method, contaminated soil from former refineries, coking plants or gasworks is removed for treatment just like smaller volumes of soil on which accidents or technical accidents have occurred, resulting in penetration of hydrocarbons containing petroleum, chlorinated hydrocarbons or other contaminants into the soil.
Two groups of chemicals are used in this field of application:
Work steps for soil washing
First, the sand and gravel particles must be free of adherent
contaminants in an aqueous phase. For this purpose, we carry a number
of specially formulated surfactants to provide the best degree of
cleaning efficiency depending on the type of contamination involved.
After washing, the contaminants are highly concentrated in the
ultrafine particle fraction. Since a closed water system is normally
used, this ultrafine fraction must be removed from the aqueous phase
completely. The lamellar clarifiers used for this purpose can be run
with much higher throughput volumes when coagulant are dosed into the
medium beforehand. The outlet section of the lamellar clarifier is
usually dewatered - using polymers or flocculants to obtain a residue
that is solid enough to be spaded and disposed of.