Landfill leachate is produced when precipitation or surface water seeps through deposited waste, absorbing dissolved organic and inorganic substances in the process. Depending on the age and composition of the landfill, this water can contain high concentrations of ammonium, heavy metals, chlorinated hydrocarbons, humic substances, and persistent organic compounds.
Since untreated leachate poses significant risks to groundwater and surface water, landfill operators are legally required to treat it using complex processes. Activated carbon adsorption is considered a particularly effective method for removing persistent pollutants, as it reliably binds even substances that are difficult to degrade.
Legal framework in Germany and the EU
The treatment of landfill leachate is subject to strict legal requirements in order to minimize the introduction of pollutants into soil and water ecosystems and to ensure the long-term protection of humans and the environment. The most important legal bases are:
- Waste Water Ordinance (AbwV), Annex 51 "Landfill Leachate“
Regulates binding discharge limits for parameters such as chemical oxygen demand (COD), total nitrogen, ammonium nitrogen, heavy metals (e.g., cadmium, mercury), and adsorbable organically bound halogens (AOX).
- Exemplary guideline values (varying depending on the federal state):
- COD: < 75 mg/l
- Total nitrogen: < 20 mg/l
- Ammonium N: < 5 mg/l
- AOX: < 0,2 mg/l
- Water Resources Act (WHG)
Requires that all discharges into water bodies must be designed in such a way that they do not adversely affect the public interest (Sections 57 ff. WHG)).
- EU Water Framework Directive (2000/60/EC)
Requires member states to achieve "good chemical and ecological status" for all water bodies. This means that operators are required to treat landfill leachate in such a way that there is no deterioration in the status of water bodies.
- Landfill Ordinance (DepV)
Specifies that leachate must be collected and "treated in such a way that its discharge or introduction does not lead to harmful changes in the soil or groundwater.“
These requirements make it clear that landfill operators must reliably achieve very low residual concentrations of pollutants, even when leachate volumes fluctuate greatly.
Properties and mode of action of activated carbon
Activated carbon, such as our
Hydraffin, is a carbonaceous material with an extremely large internal surface area (up to 1,000 m²/g) and a highly porous structure consisting of micro-, meso- and macropores. This structure enables the physical adsorption of a large number of organic molecules and certain inorganic compounds.
- Micropores (<2 nm): particularly effective for small, difficult-to-degrade organic molecules.
- Mesopores (2–50 nm): important for larger molecules such as humic substances.
- Macropores (>50 nm): serve as transport channels and facilitate diffusion.
The adsorption capacity depends on factors such as temperature, pH value, competition from other substances, and the specific pore profile of the carbon used.
Reasons for use in landfill leachate treatment
Activated carbon is used to remove persistent pollutants as well as colorants and odorous substances, ensuring compliance with legal limits.
- Elimination of poorly degradable organic compounds
Biological treatment stages primarily reduce easily degradable substances. Complex aromatics, organochlorines, or traces of pesticides often remain – this is where activated carbon acts as a "polishing" stage.
- Reduction of COD and TOC
Adsorption on activated carbon can significantly reduce chemical oxygen demand (COD) and total organic carbon (TOC), ensuring reliable compliance with regulatory discharge limits.
- Color and odor removal
Humic substances and other coloring substances are adsorbed, making the wastewater clearer and less odorous.
Process variants: powdered vs. granular activated carbon
Granular activated carbon (GAC) is primarily used in landfill leachate treatment because it produces less sludge and is easier to handle in continuous operation. Powdered activated carbon (PAC) can be used as an alternative, especially when flexible dosing is required.
- Powdered activated carbon (PAC)
- Function: Dosed directly into the wastewater stream; separation via sedimentation or filtration.
- Advantage: Flexible dosing, ideal for fluctuating loads.
- Disadvantage: Generation of additional sludge and higher operating costs due to handling and disposal.
- Granulated activated carbon (GAC)
- Function: Used as a granulate in fixed-bed filters or adsorbers.
- Advantage:
- Less sludge formation
- Simple handling
- Practice: Due to these advantages, GAC is standard in landfill leachate treatment. Continuous operation over weeks to months.
Integration of activated carbon adsorption into the overall process
Landfill leachate is usually treated in several stages:
- Preliminary clarification and mechanical filtration to remove solids.
- Biological treatment (e.g., activated sludge, SBR, membrane biology) to reduce easily degradable organic substances and nitrogen compounds.
- Activated carbon adsorption as a final polishing stage to eliminate residual COD, micropollutants, and color components.
This combination optimizes operating costs and protects the activated carbon from rapid overload.
Operation and replacement of GAC Filters
Operating granular activated carbon systems require continuous monitoring and timely reactivation or replacement to maintain performance.
- Loading and breakthrough curves: Performance is typically monitored via online COD/TOC measurements. When breakthrough increases, reactivation or carbon replacement is required
- Reactivation: GAC can be thermally reactivated several times, improving cost efficiency.
- Cost factors: Depend on raw water quality, flow rate, carbon type, and reactivation intervals
Read also: Activated carbon: reuse or disposal?
Practical examples and outlook
In Germany, GAC adsorbers are widely used at landfills. When particularly stringent discharge limits must be met, many operators combine GAC with reverse osmosis. Emerging technologies—such as impregnated activated carbons or combined ozone/activated carbon processes—further enhance adsorption capacity and reduce fresh carbon consumption.
Conclusion: Activated carbon in landfill leachate treatment
The legal requirements of the Waste Water Ordinance, WHG, DepV, and EU Water Framework Directive set strict standards for the discharge of landfill leachate.
Activated carbon adsorption is a proven, technically mature, and economically efficient technology to reliably meet these requirements. It removes even persistent organic pollutants and reduces COD, AOX, and micropollutants to the required limit values.
Activated carbon thus remains a cornerstone of modern landfill leachate treatment – supporting both environmental protection and regulatory compliance.
Donau Carbon offers suitable solutions for this:
activated carbon filters from the LT series and high-quality activated carbon grades from
the Hydraffin WR series support operators in the reliable and long-term implementation of these requirements.