The organic matter present in urban solid waste (MSW) degrades forming a polluting liquid, black in color and with a very penetrating odor, called leachate. In addition, this liquid carries all kinds of harmful substances: Up to 200 different compounds have been found, some of them toxic and even carcinogenic. Moisture from waste and rain are the two main factors that accelerate leachate generation.

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Proper treatment of these toxic fluids should be a fundamental part of MSW management. If not properly controlled, leachates can contaminate soils and surface and groundwater ( aquifers ). As it is a polluting process that occurs slowly, its effects are usually not perceived until several years later.

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For this problem, collection systems are installed to guarantee the storage of all the accumulated leachates on the sanitary landfill system, therefore leachate lagoons are important to avoid the penetration of toxic substances into the environment.

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