Processes for Landfill Leachate Treatment

Landfill leachate is defined as all water that has been in contact with waste stored in a landfill. It is caught in the drainage system and undergoes special wastewater treatment. Depending on the substances present, appropriate DAS wastewater technology is available.

DAS Technologies for Treatment of Leachate in Landfills and Sewage Treatment Plants

Landfill Leachate arises primarily as rainwater seeps through the landfill body, but also from the moisture inherent to the waste itself or – in the case of inadequately sealed landfills – groundwater ingression. Untreated leachate is a hazard to the environment if it is allowed to enter a body of water. DAS Environmental Expert offers the right technologies for the treatment of landfill leachate, proven in many diverse cases.

These include, for example, biological processes for wastewater treatment such as MBBR, TFR, activated sludge processes, anammox and loop reactors as well as reverse osmosis. If persistent biological compounds remain in the wastewater, activated carbon filters and/or ozonisation are employed to remove these contaminants. These processes are deployed both as stand-alone solutions and in combination.

Properties and Challenges

Landfills generally contain a highly inhomogeneous mixture of materials, which include both a very high organic component as well as soluble mineral substances. Some of the organic substances decompose naturally in the landfill body. Due to these exothermal processes inside the landfill, the temperature of the leachate is usually higher than typical groundwater in the area. Landfill leachate is usually quite turbid, has a very strong odour and a brownish colour.

The composition of landfill leachates differs depending on the type of waste stored, the weather and the holding time in the landfill body. As the landfill holding time increases, so too does the degree of persistent organic pollutants. As the landfill holding time increases, anaerobic decomposition progresses to methane production. In addition to a range of soluble nitrogen and sulphur compounds, sulphates and chlorides, the leachate then contains a high degree of persistent organic pollutants.

It is often sufficient to treat the leachate to the extent that it can be passed off to the next municipal wastewater treatment plant for further processing. If this is not possible, then it is necessary to treat the leachate up to a quality meeting the requirements for direct discharge. In this case, the remaining contaminant load is so low that the treated water may be released into a river, stream or lake. Our Environmental Experts are at your disposal for the planning and construction of such solutions.

DAS Technologies for Landfill Leachate Treatment

A range of technologies are available for the treatment of landfill leachate, proven in many diverse cases. Our experts offer you the right solution for your wastewater. Upon request, we will first analyze the specific composition of your leachate in our laboratory and then recommend an effective and cost-effective solution. The highlighted technologies are deployed both as stand-alone solutions and as part of a process combination.

Landfill Leachate Treatment with Biological Processes as the First Step

Biological treatment has proven itself in many cases as a first step in treatment and is also useful for nitrogen removal. MBBR, TFR, activated sludge processes, anammox and loop reactors are deployed. A downstream ultrafiltration step is used in a great deal of cases to deal with sludge arising from biological processes. If persistent biological compounds remain in the wastewater, activated carbon filters or ionization are employed to remove the biorefractory contaminants.

Chemical-Physical Processes for Landfill Leachate Treatment

Wet oxidation processes, such as ionization, are used if it is possible to oxidize organic contaminants either completely or to convert biorefractory contaminants into biodegradable contaminants.

Activated carbon adsorption is used for cases in which organic pollutants in the leachate cannot be degraded either biologically or using wet oxidation processes. The contaminants are first bound to the carbon through adsorption and then destroyed by incineration.

Precipitation/flocculation and ion exchange processes are less widespread in the field of landfill leachate treatment. Both technologies are used to reduce inorganic ionogenic contaminants.

A Chemical Site and its Contaminated Groundwater

As part of the remediation of a chemical site, DAS is responsible for the treatment of the resulting leachate. Years of chemical production have left their marks: chlorinated hydrocarbons and metals have penetrated into the soil through rainwater and contaminate the groundwater. In order to effectively clean the wastewater, the affected area was separated in the course of the underground treatment and well galleries have been installed. The wells are operated to keep the construction site dry. After pumping the soil is separated and loaded into containers for disposal. The pumped groundwater is first cleaned from metals by precipitation-flocculation, then a inclined lamella clarifier is used for sedimentation before the wastewater is fed to a sand filtration. In the subsequent biological stage (MBBR), nitrification and COD degradation take place. After another sand filtration, an activated carbon adsorbing stage is applied before finally sodium hypochlorite is used to eliminate nitrogen pollution. The wastewater treated in this way achieves a quality that allows direct discharge into a river.