Soils Decontamination Services

A particular section of decontamination activities is represented by soil decontamination. Unlike works for decontamination of some industrial installations or tanks, where during analysis the pollutants and waste volume can be accurately identified, within soil decontamination works there is an unforeseen rate.Even with some consistent land studies, the final soil volume to be decontaminated can only be estimated.

In fact, the big difficulty in soil treatment consists in separating the soil from the pollutant. Given the big number of soil types, each of them with specific composition, but also the diversified range of existing pollutants, there is a multitude of possible situations. If we add to these situations the degree of soil contamination, we get an overview of the difficulty in approaching a work for soil decontamination.

The experience gained in this field – as it can partially be seen in the section “Main projects” – leads to the conclusion that the best way to approach such kind of issue depends on the contamination degree.
Within total volume of excavated contaminated soil, we have:

  • abt. 3–5% – soil with high contamination – high cost/m3 for disposal;
  • abt. 20–40% – soil with average contamination;
  • abt. 55–75% – soil with low contamination – low cost/m3 for treatment.

Approaching the work from this point of view involves cost optimization for the entire project, which is to be taken into account that such works, as a rule, are big. For example, for an area of 1000 sqm contaminated in an average depth of 1 m means 1000 m3 contaminated soil, while same contaminated area in an average depth of 5 m means 5000 m3, namely 5 times more. It obliges, as we explained in previous section – “Decontamination of industrial plants and locations” – that initial analysis for the purpose of technical offer release, to be as exact as possible so that to make entire project be feasible.

Main technolgies used by SETCAR for soil decontamination:

Direct thermal desorption (DTD) – applicable especially for soils containing hydrocarbons and/or other pollutants containing volatile components.
Advantages: high productivity of the plant; advanced decontamination; low costs for plant mobilisation; operation flexibility and safety;
Disadvantages: applicable for big quantities of contaminated soil.
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Indirect thermal desorption (ITD) – applicable for soils with lower hydrocarbons contamination, but also for hazardous substances contamination: phenols, HCH, mercury, PCB oils.
Advantages: low costs for plant mobilisation; operation flexibility and safety;
Disadvantages: lower productivity given by smaller thermal transfer rates, compared with DTD.
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Immobilisation (with hydraulic binders) – applicable especially for soils with low pollutant concentrations.
Advantages: high productivity; low costs;
Disadvantages: not applicable for soils with high pollutant concentrations.

Washing – used with good results for sandy soils, gravel or stone and for materials with high granulation resulted from soil screening.
Advantages: high productivity; low costs;
Disadvantages: non applicable for soils containing clay or humus; requires an additional stage for pollutant separation (solubilization, precipitation and filtration etc.) from resulted used washing solutions.

Bioremediation – used with good results for soils with low pollutant concentrations.
Advantages: low costs;
Disadvantages: relatively long treatment duration; requires a controlled climate (moisture, temperature etc.).

Centrifuging (biphase, three-phase) – used to treat sludge containing hazardous waste. It represents a preparatory stage for significant reduction of moisture/ hydrocarbons content/etc., being followed, as the case may be, by any of treating methods described above.