Contaminated soil may not be deposited directly at a landfill when pollutant levels exceed the legally defined assignment values. In this case, pre-treatment is required by law before landfill disposal is permitted at all. The following article answers the most important questions about treatment methods, thermal desorption, and the practical process of disposal.
When may contaminated soil not be deposited at a landfill?
Contaminated soil may not be deposited directly at a landfill when its pollutant levels exceed the assignment values of the Landfill Ordinance (DepV). The DepV establishes binding limit values for each landfill class. If these values are exceeded, pre-treatment of the material is legally mandatory.
The Landfill Ordinance distinguishes between classes DK 0 to DK IV as well as underground landfills. The higher the pollutant load, the stricter the requirements. Soils with high concentrations of organic pollutants such as polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), or volatile hydrocarbons (BTEX) frequently exceed the limit values of the available landfill classes and therefore cannot be deposited without treatment.
Added to this are practical and economic considerations: landfill capacities for highly contaminated materials are limited and disposal costs are correspondingly high. Targeted treatment of contaminated soil can not only make it suitable for landfill disposal, but can also significantly reduce the quantity of material that actually needs to be deposited.
What treatment methods are available for heavily contaminated soil?
For heavily contaminated soil, biological, chemical-physical, and thermal processes are essentially available. The choice of the appropriate method depends on the type of pollutants, their concentrations, and the requirements for the treated material.
- Biological methods: Microorganisms break down organic pollutants. This method is particularly suitable for easily biodegradable compounds such as mineral oil hydrocarbons (MKW) at moderate concentrations. At high pollutant levels or with hard-to-degrade compounds, biological methods reach their limits.
- Chemical-physical methods: These include soil washing processes, in which pollutants are dissolved out of the soil material. These methods are suitable for certain pollutant classes, but require complex water treatment and are not universally applicable.
- Thermal methods: Thermal desorption and incineration are the most powerful methods for complexly contaminated soils. They are also suitable for pollutants that cannot be reliably removed by other methods, such as PCB, PCDD/PCDF (dioxins and furans), or PFAS.
- Mechanical-physical pre-treatment: A mechanical pre-treatment is frequently used to separate foreign matter, homogenize particle size, and prepare the material for a subsequent process.
In the remediation of complex contaminated sites, several methods are often used in combination to effectively treat different pollutant classes.
How does thermal desorption work for contaminated soil?
In thermal desorption, contaminated soil is heated in a rotary kiln under exclusion of oxygen to temperatures of up to approximately 600 °C, depending on the material and pollutant load. The heat drives organic pollutants out of the soil material or destroys them, without the soil material itself combusting.
The process can be divided into three main phases:
- Mechanical pre-treatment: The delivered material is first screened, crushed, and brought to a suitable particle size. Interfering substances such as metals or plastics are separated out.
- Thermal treatment in the rotary kiln: The prepared material passes through the rotating kiln. The temperature is set according to the pollutant profile. Under exclusion of oxygen, volatile pollutants are transferred to the gas phase; poorly volatile compounds are directly destroyed.
- Multi-stage exhaust gas purification: The resulting process gas undergoes multi-stage purification: dedusting, thermal post-combustion at high temperatures, flue gas scrubbing, and activated carbon filters. This process ensures that the statutory emission limit values are reliably maintained.
The result is a largely pollutant-free mineral material that can subsequently be assessed and directed toward appropriate recovery or landfill disposal. More about the entire process is explained on the page for thermal soil treatment.
For which pollutants is thermal desorption suitable?
Thermal desorption is suitable for a wide range of organic pollutants, particularly those that are volatile or thermally degradable. It is one of the few methods that delivers reliable results even with particularly persistent or mixed pollutant contaminations.
Typical pollutants for which the process is approved and proven:
- Mineral oil hydrocarbons (MKW)
- Volatile aromatic compounds (BTEX: benzene, toluene, ethylbenzene, xylene)
- Polycyclic aromatic hydrocarbons (PAH)
- Polychlorinated biphenyls (PCB)
- Mercury (Hg)
- Phenols and cyanides
- Nitroaromatics
- Per- and polyfluoroalkyl substances (PFAS/PFOS)
- Dioxins and furans (PCDD/PCDF)
- Further chlorinated hydrocarbon compounds
Particularly in cases of mixed contamination, as frequently found at decommissioned industrial, gasworks, or military sites, thermal desorption is superior to other methods, as it can address several pollutant classes in a single treatment step.
What happens to the soil after thermal treatment?
After thermal treatment, a mineral material is obtained that is largely free of organic pollutants. This material is sampled and analytically assessed to determine its further disposal route. Depending on the result, it can be recovered or deposited at a suitable landfill.
Well-treated material with low residual contamination may under certain circumstances be used in earthworks, as fill material, or in other technical applications. The prerequisite is that the applicable limit values of the Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV) and the Substitute Building Materials Ordinance are met.
Materials that do not meet the assignment values for recovery after treatment are properly landfilled. However, as a result of thermal treatment they are significantly less contaminated than before, which enables deposition at a lower landfill class and reduces disposal costs. The material flow management ensures that every material stream is directed to the optimal disposal route.
How does the delivery and disposal of contaminated soils work?
The delivery of contaminated soils follows a regulated process that begins with the preliminary inquiry and characterization of the material. Without a complete waste characterization, contaminated soil may not be accepted for treatment. The process typically involves the following steps:
- Preliminary inquiry and material characterization: The client submits available analysis data and information on the origin and composition of the material. On this basis, it is assessed whether and under what conditions acceptance is possible.
- Quotation and approval: After reviewing the documents, a quotation is prepared. Where applicable, official transport permits or accompanying documents pursuant to the Evidence Ordinance are required.
- Transport and delivery: Transport is carried out by certified waste management companies. Upon delivery, the material is weighed, visually inspected, and sampled if necessary.
- Interim storage and treatment: If immediate treatment is not possible, the material can be stored in a secured interim storage facility before being fed into the rotary kiln.
- Documentation and proof of disposal: After treatment, the client receives all required disposal certificates and analysis documents.
Early contact and complete material information are essential to avoid delays and ensure smooth processing.
How ARE Deutzen GmbH helps with the disposal of contaminated soils
ARE Deutzen GmbH has specialized in the thermal treatment of contaminated mineral waste since 1994 and operates one of the most powerful thermal desorption plants in Germany. With over 30 years of experience and more than 2.5 million treated tons, ARE Deutzen offers concrete solutions for demanding remediation projects.
The range of services includes:
- Thermal soil treatment in a rotary kiln at temperatures of up to approximately 600 °C, depending on the material and pollutant load, under exclusion of oxygen
- Acceptance and treatment of a wide range of pollutants, including PAH, PCB, PFAS, dioxins, mercury, and MKW
- Mechanical-physical pre-treatment for material preparation
- Secured interim storage for contaminated materials
- Complete material flow management including proof of disposal and documentation
- Certification as a specialist waste management company (EfB) as well as to ISO 9001, 14001, 50001, and 18001
Whether a decommissioned industrial site, former gasworks, or contaminated military area: ARE Deutzen develops individual solutions for complex contaminations. Get in touch early to assess your project together and determine the optimal treatment route. The ARE Deutzen contacts are available for expert initial consultation.