Planning offices should clarify at least six questions before selecting a treatment method for contaminated soils: what contaminants are present, which methods are technically suitable, what materials can be treated, what credentials the provider must demonstrate, what output quality is expected, and when the provider should be involved. The answers to these questions determine not only the technical suitability of a method, but also the costs, schedule, and legal security of a remediation project. The following sections provide a direct, practical answer to each of these questions.
Which contaminants determine the choice of treatment method?
The type and concentration of pollutants in the soil are the central criterion when selecting a method for soil remediation. Not every treatment method is suitable for every contaminant. Planning offices must therefore first have reliable contaminant analysis results before comparing or tendering methods.
Volatile organic compounds such as BTEX, TPH, or chlorinated hydrocarbons can be reliably removed from soil by thermal desorption, as they transition into a gaseous state at elevated temperatures. Semi-volatile compounds such as PAH, PCB, PCDD/PCDF, or PFAS/PFOS require higher treatment temperatures or specific process management. Mercury (Hg) and cyanides can also be treated thermally, but place special demands on exhaust gas purification.
Biological methods are ruled out for many of these compounds, as they are either not biologically degradable or are present at too high a concentration. A thorough preliminary investigation of the contaminant spectrum is therefore not optional, but mandatory. Based on the analysis results, planning offices should evaluate whether a single method is sufficient or whether a combination of mechanical pre-treatment and thermal treatment is appropriate.
What are the differences between thermal desorption, incineration, and biological treatment?
Thermal desorption, incineration, and biological treatment differ fundamentally in their working principle, area of application, and output quality. The choice of the right method depends on the type of contaminant, the desired output quality, and the regulatory requirements.
Thermal Desorption
In thermal desorption, contaminated soil is heated to temperatures of up to approximately 600 °C under exclusion of oxygen. Contaminants are vaporized or destroyed without incinerating the mineral carrier material. The result is a treated soil material that can be reused or landfilled depending on the contaminant load and quality requirements. This method is particularly suitable for organic contaminants and is more resource-efficient than complete incineration.
Incineration
In incineration, the contaminated material is completely oxidized at significantly higher temperatures. The carrier material is lost in the process. Incineration is appropriate for very highly concentrated organic contaminants or for materials that are not suitable for desorption. Disposal costs are generally higher, and the treated material is not available for recycling.
Biological Treatment
Biological methods use microorganisms to break down organic contaminants. They are cost-effective but limited to biologically degradable compounds such as TPH at low concentrations. Biological methods fail with PAH, PCB, PFAS, or heavy metals. In addition, treatment times are significantly longer, which is a disadvantage for time-critical projects.
What types of waste and materials can a thermal desorption plant treat?
In addition to contaminated soils, a thermal desorption plant can also treat construction debris, dredged material, and process residues such as slags, ashes, sludges, and dusts, provided they are mineral in nature and contain the approved contaminants. The suitability of a material depends on its grain size, moisture content, and contaminant spectrum.
Typical input materials for thermal desorption plants include:
- Contaminated soils from brownfield remediation and construction projects
- Construction debris with organic contaminant loads
- Dredged material from harbor basins, canals, or industrial waterways
- Process residues such as filter ashes, sludges, and dusts from industrial processes
- Industrial wastewater with mineral fractions
Materials with very high moisture content or too fine a grain size may require mechanical pre-treatment before being fed into the rotary kiln. Planning offices should therefore clarify at an early stage whether the material arising can be treated directly without pre-treatment or whether additional processing steps are necessary. Information on treatable materials and process steps can be found at thermal soil treatment.
What credentials and certifications must a treatment provider demonstrate?
A reputable treatment provider for contaminated mineral waste must demonstrate at minimum certification as a specialist waste management company (Entsorgungsfachbetrieb, EfB) under the Circular Economy Act, as well as the required permits under the Federal Immission Control Act (BImSchG). Without these credentials, legally compliant disposal is not possible.
In addition, the following certifications and credentials are relevant when selecting a provider:
- ISO 9001 for a proven quality management system
- ISO 14001 for a systematic environmental management system
- ISO 50001 for energy management
- ISO 45001 / OHSAS 18001 for occupational health and safety management
- BImSchG permit for the operation of the plant and the approved waste types
- Records of regular emissions measurements and compliance therewith
As part of a soil treatment tender, planning offices should systematically request these documents and verify whether the provider’s permit actually covers the specific contaminants of the project. A permit that does not include certain contaminants renders the provider unsuitable for the respective project. More information on quality management is available on the ARE Deutzen website.
How does the output quality of the treated material influence the treatment decision?
The output quality of the treated material determines whether it can be recycled or must be landfilled after treatment. The higher the achievable purity, the greater the potential for recycling and, as a rule, the lower the overall disposal costs for the project.
Thermal desorption generally produces a mineral product that, upon compliance with the relevant limit values, can be used as a recycled material, for example as fill material in civil engineering. The achievable output quality depends on the input contamination level, the treatment temperature, and the plant control system. Planning offices should therefore clarify in advance what limit values the treated material must meet and whether the provider demonstrably achieves this quality.
When selecting a treatment method, output quality should be considered an equally weighted decision criterion alongside treatment costs. A cheaper method that only allows landfilling of the output can be significantly more expensive for large quantities of material than a method with higher output quality and recycling potential. Material flow management plays a decisive role in the overall economic assessment of a project.
When should a planning office involve a treatment provider at an early stage?
A treatment provider should be involved no later than planning phase 2 or 3, that is, when the first results of the preliminary investigation are available. The earlier the provider is included in the planning process, the better the method suitability, capacities, and logistics can be coordinated with one another.
Early involvement offers concrete advantages:
- The provider can give a method recommendation based on the contaminant analysis before the tender is formulated.
- Capacity bottlenecks at the plant can be identified and planned for at an early stage.
- Requirements for material processing or interim storage can be integrated into the detailed planning.
- Cost estimates become more reliable because they are based on actual quotes.
- Permit-relevant questions, such as those relating to transport logistics or waste classification, can be clarified in advance.
For complex remediation projects, such as those at former industrial sites or gasworks sites, early coordination with the treatment provider is often decisive for project success. Anyone who only begins searching for a suitable provider after construction has started risks delays and additional costs.
How ARE Deutzen supports planning offices in selecting a treatment method
ARE Deutzen GmbH is the experienced specialist for the treatment of contaminated mineral waste in Germany. With over 30 years of operational experience and more than 2.5 million treated tons of mineral materials, ARE Deutzen offers planning offices a reliable basis for method selection and tender planning. Support specifically includes:
- Expert consultation on method suitability based on the available contaminant analysis
- Treatment of a broad contaminant spectrum: Hg, TPH, BTEX, PAH, PCB, PFAS/PFOS, PCDD/PCDF, cyanides, nitroaromatics, and other chlorinated hydrocarbons
- Thermal desorption in a rotary kiln at temperatures of up to approximately 600 °C, depending on the material and contaminant load, under exclusion of oxygen with multi-stage exhaust gas purification
- Acceptance of soils, dredged material, construction debris, and process residues within the framework of material flow management
- Certified specialist waste management company (EfB), BImSchG-approved, certified to ISO 9001, 14001, 50001, and 45001
- Early involvement in project planning possible to coordinate capacities and logistics
If you are a planning office preparing a remediation project and need a well-founded assessment of the treatment method selection, contact the experts at ARE Deutzen directly. Contact us for a no-obligation initial expert consultation.