LEACHED: definition, examples and treatment - summary

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The increase in the generation of waste is a reality and the landfills do not stop filling up, producing in them a mixture of different waste such as, for example, decomposing organic matter, leftover detergents, other liquids and oxidized metals, among others. This mixture causes a by-product to be generated in the form of a liquid, called leachate, which is found circulating through the rest of the waste. These leachates have serious consequences, mainly because they cause contamination of streams and groundwater. That is why it is so necessary to reduce and recycle waste, in short, to do a good management of it to avoid the increase of leachate. In addition, it is also important to have methods to treat them.

If you want to know more about leachates and about the treatments used to control them, continue reading this interesting article by Ecologist Verde in which we talk about the definition of leachate, examples and its treatment.

What are leachates and leaching - definition

Leachates are the liquids that circulate between the waste found in landfills. The leaching process occurs during processes of fermentation and decomposition of organic matter, as a consequence of the filtration of water from the rains that seep through the waste and carry chemical compounds and biological materials. They are very polluting and a danger to the environment and the health of living beings, that is why they must be treated correctly.

The quality of these in a landfill depends on the time it is in them and the type and quantity of waste that is had. For example, the quality of leachate from a developed country is not the same as one that is still developing, since, in developed countries, there is a waste management (recycling) that prevents more waste from reaching landfills. However, most developing countries do not have good waste management.

Leachate: examples

Did you know that worms produce a nutrient-rich leachate, also called earthworm humus, while decomposing organic matter? Yes, in addition, thanks to its concentration of nutrients, it is used as a fertilizer for cultivation. Although it is 100% natural and non-toxic, it is composed of a large amount of minerals and nutrients, so it is important to dilute it before use, since its high concentration could be harmful to plants.

Therefore, mainly, as examples of leachate we can distinguish between two types:

  • Landfill leachates: Liquids that circulate between the waste from the landfills and are given by the leaching process when decomposition and fermentation of these take place.
  • The leachate of the worms: liquids produced in a totally natural way by these animals in the earth and the subsoil by feeding on organic matter and decomposing it.

Leachate treatment

All polluting liquids in landfills must be treated before being dumped on a surface. In the treatment process, the characteristics of the leachate must be taken into account, as well as the location of the landfill. Well, they don't get the same treatment leachate from a landfill new than those of a landfill that has been exploited for a long time, or those of an RNP or hazardous waste landfill. To perform the treatment for avoid contamination by leachate, its characteristics, as well as the location of the landfill, must be taken into account.

As we have mentioned before, the leachates are stored in ponds before their final treatment, these differ depending on the type of landfill. The hazardous waste (RP) landfills are deposited in ponds that must be waterproofed with polyethylene to prevent leaks, leachates from non-hazardous waste landfills (RNP) They are collected in concrete rafts.

The technologies to treat leachate are as follows:

Heat treatment (evaporation)

In this, the energy of the biogas generated in the landfill is used to evaporate the leachates. This technology controls leachate emissions and, finally, a sludge remains that is deposited back into the landfill. Here you can learn more about what evaporation is.


Aerobic or anaerobic treatments can be chosen, depending on the characteristics of the leachate. Aerobic biological treatments consist of using microorganisms in the presence of oxygen and agitation, to purify the organic compounds present in the leachate. On the other hand, the anaerobic process has the same principle, although the microorganisms are in conditions characterized by a lack of oxygen.

Membrane systems

The technology using membranes is used more and more frequently, and it is being included for the treatment of leachate. The applications that are given are the following: ultrafiltration, reverse osmosis, microfiltration, nanofiltration and direct osmosis.

Physical-chemical treatments

This treatment removes coagulant particles, that is, metal salts and polyelectrolytes. Coagulation, flocculation and sedimentation processes are involved. Treatments are classified into chemical precipitation, reverse osmosis, NH3 stripping, chemical oxidation, and activated carbon absorption.

Natural systems

Some systems that can function naturally, such as lagoons or wetlands, are proposed for the management of leachates, as an alternative to the other treatments, and placing them where it is needed artificially so that they then function naturally. However, with these systems a large amount of territory is required for the processes.

Learn more about leachate and its contamination with this other Green Ecologist article in which we talk about Garbage Pollution: causes and consequences.

If you want to read more articles similar to Leachates: definition, examples and treatment, we recommend that you enter our Pollution category.

  • Corena, M.J, 2008. Treatment systems for leachate generated in landfills. Comprehensive solid waste management deepening line.
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