CleanLeachate – Electrochemical treatment of landfill leachate

Highly contaminated landfill leachate

The most frequently employed method of waste management is disposal of waste on a landfill site. However, a major disadvantage of landfill operations is the generation of contaminated leachate caused by rainfall. Water contained in the waste and water released by biological degradation processes also adds to the landfill leachate. Together with the leachate, contaminants are released which come from biological decomposition processes of the landfill material, or are simply washed out. The leachate therefore has toxic properties and contains substances that are not easily biodegradable. Treatment plants with biological processes can only treat the wastewater to a limited extent. Above all, persistent organic substances (measured as chemical oxygen demand, COD), ammonium and halogenated organic substances (measured as dissolved organic halogens, AOXs) are present in the landfill leachate in critical concentrations and have to be removed before discharge into the aquatic environment or transfer to a municipal, biological wastewater treatment plant.

Project information

Project title

CleanLeachate – Combined anode and cathode process to treat landfill leachate

 

Project duration

December 1, 2010 – November 31, 2012

 

Coordinated by

  • Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V., Deutschland

 

Project partners

  • Eilenburger Elektrolyse- and Umwelttechnik GmbH, Eilenburg
  • MAGNETO special anodes B.V., Schiedam, Netherlands
  • ASIO spol. s r.o., Brno, Czech Republic | Initial Projects Limited, Wolverhampton, UK
  • Centre de Recerca i Innovació de Catalunya, S.A., Barcelona, Spain

Processing landfill leachate

Activated sludge tank of a plant for the treatment of landfill leachate.

The treatment of landfill leachate is a considerable cost factor for the landfill site operator. Contaminated leachate requiring treatment is generated even decades after the closure of a landfill site. Membrane and adsorption processes (e.g. with activated carbon) are frequently used. However, these have the disadvantage that the contaminants are not eliminated but are merely concentrated. Subsequently the concentrate has to be disposed of or further processed. On a worldwide scale the quantity of landfill waste is increasing, while at the same time the legislation is becoming more stringent. This results in a growing demand for cost- and energy-efficient as well as reliable processes for the treatment of landfill leachate.

Combination of electrochemical oxidation and reduction

Leachate samples during the electrochemical treatment.

Within the EU-funded project CleanLeachate and together with European partners from industry and research, the Fraunhofer IGB has developed an electrochemical process that permits the reliable treatment of landfill leachate without the need to add auxiliary substances to the wastewater. Both ammonium and dissolved organic substances can be eliminated from the landfill leachate by means of electrochemical oxidation at the anode of the reactor and dissolved organic halogens by the subsequent reduction at the reactor cathode. In contrast to membrane filtration, electrochemical treatment completely degrades the dissolved substances. There is no need for the disposal of residues.

Divided electrolytic cell

Electrolytic cell on a laboratory scale.

For oxidation and reduction reactions, the electrolytic cell is separated into two chemical reaction compartments by means of an ion exchange membrane; the water passes through them one after another, but nevertheless the two compartments form one electric circuit. The contaminants in the water are thus subjected to two treatment processes. The basis for developing the process was first established in laboratory experiments. The divided electrolytic cell was then developed in cooperation with our project partner Eilenburger Elektrolyse- und Umwelttechnik GmbH (EUT, Electrolysis and Environmental Technology). Six different anode materials provided by our project partner MAGNETO were tested in the lab with a view to the degradation of organic substances and ammonium by anodic oxidation. Stainless steel cathodes with varying geometries were tested to investigate the dehalogenation of the AOX.

Pilot plant – test operation at a landfill site

Schematic view of the prototype plant.

A pilot plant with a throughput of 20 L/h was designed in accordance with the laboratory findings, and built by our project partner EUT. Continuous operation tests were carried out by our project partner ASIO at a landfill site in the Czech Republic. The process was successfully optimized and able to reduce the COD concentration in the landfill leachate to below 200 mg/L and the total nitrogen concentration to below 70 mg/L. This means compliance to the legal requirements for COD and overall nitrogen concentration in the treated landfill leachate. The energy requirement for the removal of contaminants was 43 kWh to degrade one kilogram of COD and 22 kWh to eliminate one kilogram of ammonium.

Outlook

An automated and transportable prototype plant is now available for further development in view of market introduction. It could be demonstrated that the electrochemical treatment of landfill leachate meets pollutant discharge limits. The technology will now be further tested and demonstrated in a variety of industrial wastewaters.

Funding

The research leading to results in this project received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 262335.

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