Leachate is the liquid produced when water percolates through any permeable material. It can contain either dissolved or suspended material, or usually both. This liquid is most commonly found in association with landfills where result of rain percolating through the waste and reacting with the products of decomposition, chemicals and other materials in the waste to produce the leachate. If the landfill has no leachate collection system, the leachate can enter groundwater, and this can pose environmental or health problems as a result. Typically, landfill leachate is anoxic, acidic, rich in organic acid groups, sulfate ions and with high concentrations of common metal ions especially iron. Leachate has a very distinctive smell which is not easily forgotten. Water (from the Old English waeter; c. ... Landfill is a waste disposal site for the deposit of the waste onto or into land including: internal waste disposal sites (i. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of geologic formations. ... For other uses, see Acid (disambiguation). ... An organic acid is an organic compound that is an acid. ... In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. ... // An ion is an atom or a group of atoms (a chemical substance), or subatomic particle, with a net electric charge. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ...

The risks from waste leachate are due to pathogenic micro-organisms and toxic substances that might be present in it. These risks are greatly mitigated by properly designed and engineered landfill sites. For example, sites that are constructed on geologically impermeable materials or sites that use impermeable liners made of geotextiles or clay. The use of linings is now mandatory within both the United States and the European Union except where the waste is genuinely impermeable. In addition, toxic materials such as cadmium and toluene cannot be disposed of in landfills. A geotextile is a synthetic permeable textile. ... The Gay Head cliffs in Marthas Vineyard are made almost entirely of natural clays. ... General Name, Symbol, Number cadmium, Cd, 48 Chemical series transition metals Group, Period, Block 12, 5, d Appearance silvery gray metallic Atomic mass 112. ... Toluene, also known as methylbenzene or phenylmethane is a clear, water-insoluble liquid with the typical smell of paint thinners, reminiscent of the sweet smell of the related compound benzene. ...

In older landfills, the leachate was directed to the sewers, but this caused problems. One of these was the contamination by toxic metals that passed through the sewage treatment plant and eventually entered the environment. Another problem was that if the landfill contained large amounts of organic material then methane was produced, some of which dissolved in the leachate. This could be released in poorly ventilated areas in the treatment plant and lead to an explosion. Finally, it can contain high concentrations of ammonia which can pose a health hazard to treatment plant workers, particularly in acidic leachate. The simplest hydrocarbon, methane, is a gas with a chemical formula of CH4. ... Ammonia is a compound of nitrogen and hydrogen with the formula NH3. ...

Leachate can also be produced from land that was contaminated by chemicals or toxic materials used in industrial activities such as factories, mines or storage sites.

External links

• An introduction to leachate
• Landfill Leachate