A case-by-case assessment prior to accepting soils for thermal treatment is required because every contaminated soil brings an individual contaminant composition, a different material matrix, and specific physical properties that directly influence the treatment process. Only through a targeted preliminary assessment can it be ensured that the delivered soil can be treated safely, completely, and in compliance with regulations in the thermal desorption plant. The following sections shed light on which factors play a role and how the assessment process works in practice.
What factors make every contaminated soil unique?
Contaminated soils differ in their type of contaminants, contaminant concentration, particle size distribution, moisture content, and organic fraction. These parameters directly influence how a soil responds during thermal treatment and whether the plant can process it safely. No two remediation projects are alike.
The site of origin plays a decisive role: soils from decommissioned gasworks typically contain PAHs and BTEX compounds, while areas of former industrial facilities are frequently contaminated with chlorinated hydrocarbons, PCBs, or heavy metals such as mercury. Military sites, in turn, often exhibit nitroaromatics or explosive residues. These differing contamination profiles each require adapted treatment parameters.
Added to this are physical properties such as water content and the proportion of coarse material or construction rubble. An excessively high moisture content reduces thermal efficiency, while coarse components affect mechanical pre-treatment and throughput in the rotary kiln. The organic fraction of the soil is also relevant, as it alters energy demand and flue gas composition.
Which types of contaminants require special assessment steps prior to acceptance?
Certain contaminants require an in-depth suitability assessment because they are either poorly volatile, reactive, or particularly complex to treat in combination with other substances. These include in particular mercury (Hg), PFAS/PFOS, PCDD/PCDF, and highly concentrated mixtures of multiple contaminant classes.
Mercury vaporizes at low temperatures and requires precise control of the treatment temperature as well as a high-performance flue gas purification system. PFAS and PFOS are particularly persistent due to their chemical stability and must be completely destroyed at sufficiently high temperatures. PCDD and PCDF — that is, dioxins and furans — can also be newly formed under unfavorable conditions and therefore require thermal post-combustion at defined minimum temperatures as well as multi-stage flue gas purification.
Cyanides, phenols, and nitroaromatics also require precise preliminary analysis, as they influence flue gas behavior and treatment efficiency at certain concentration ranges. In cases of multiple contamination — that is, the simultaneous presence of various contaminant classes — the complexity of the assessment increases considerably, because interactions between the substances must be taken into account.
How does a case-by-case assessment for thermal soil treatment work?
The case-by-case assessment for the acceptance of contaminated soils for thermal soil treatment follows a structured process: first, declaration analyses and existing expert reports are evaluated; then a technical assessment of treatability is carried out; and finally, the admissibility of acceptance is reviewed on the basis of the applicable permits.
In detail, the process is typically divided into the following steps:
- Preliminary inquiry and document review: The client submits analysis results, proof of origin, and available expert reports on the site. These documents form the basis of the initial assessment.
- Technical assessment: Qualified staff review whether the contaminant composition, concentrations, and physical properties of the material are compatible with the plant’s operating parameters.
- Regulatory review: It is checked whether the waste falls under the plant’s existing permits and whether all required disposal certificates are in place.
- Sampling and incoming analysis: If necessary, samples are taken from the delivered batch and analyzed in the laboratory before the material enters treatment.
- Approval or rejection: Acceptance is only approved after a positive evaluation of all assessment steps. In the event of discrepancies, the client is informed and possible alternatives are discussed.
This structured process ensures that the plant operates at all times within its approved operating parameters and that statutory emission limit values are complied with.
What happens if a soil does not meet the assessment criteria?
If a soil does not meet the acceptance criteria, it is not approved for thermal desorption. Instead, alternative disposal routes are examined, such as mechanical-physical pre-treatment, interim storage, or transfer to a suitable partner facility. A rejection does not mean the end of the solution, but rather the beginning of individual alternative planning.
In practice, there are various scenarios that can lead to a rejection:
- Contaminant concentrations exceed the approved acceptance limit values
- The material contains contaminants that are not covered by the plant’s permit
- Physical properties such as extreme moisture or an excessively high coarse material fraction make direct treatment technically impossible
- Documentation is incomplete or the origin of the material is not sufficiently verified
In such cases, mechanical-physical pre-treatment can help prepare the material to meet the requirements of thermal treatment. Alternatively, material flow management is employed to direct the waste to a suitable disposal route. The goal is always to ensure safe and proper disposal, even when the direct route via thermal desorption is not possible.
Which statutory requirements establish the obligation to carry out the assessment?
The obligation to carry out a case-by-case assessment when accepting contaminated soils arises from several statutory frameworks: the Circular Economy Act (KrWG), the Waste Tracking Ordinance (NachwV), the requirements of the Federal Immission Control Act (BImSchG), and the site-specific permit conditions of the plant. These regulations oblige operators of thermal treatment plants to document the origin, composition, and treatability of every accepted waste in a traceable manner.
The Circular Economy Act requires that waste may only be disposed of at facilities that are approved for the respective waste types. The Waste Tracking Ordinance governs the management of disposal certificates and consignment notes for hazardous waste, which contaminated soils typically constitute. The BImSchG and the associated permit notices specify which types of waste may be treated at a plant and at what concentrations.
Operators of thermal desorption plants are also obliged under the quality management system in accordance with ISO 9001 to comply with and document defined assessment processes. As a certified waste management company pursuant to Section 56 KrWG, they are additionally subject to regular external audits that confirm compliance with all requirements. The case-by-case assessment is therefore not a voluntary service, but a statutory prerequisite for proper plant operation.
How ARE Deutzen GmbH handles the case-by-case assessment for your remediation projects
ARE Deutzen GmbH supports clients from the initial inquiry through to completed disposal. With over 30 years of experience in contaminated site remediation and thermal soil treatment, the company possesses the expertise to reliably evaluate even complex contamination profiles and determine the appropriate treatment route. The case-by-case assessment is an integral part of every project.
As part of the acceptance assessment, ARE Deutzen GmbH specifically offers:
- Expert evaluation of declaration analyses and site expert reports
- Technical assessment of treatability in the rotary kiln plant at temperatures of 250 to 560 °C
- Regulatory review on the basis of existing BImSchG permits
- Coordination of alternative disposal routes via material flow management when thermal treatment is not possible
- Complete documentation of all disposal certificates in accordance with the Waste Tracking Ordinance
If you wish to dispose of contaminated soils safely and in compliance with regulations, please contact ARE Deutzen directly. The team will advise you on the acceptance requirements and work with you to initiate the appropriate disposal route.