LEACHATE CONTROL FOR SANITARY LANDFILLS

Percolated rainwater and liquefied waste materials in sanitary landfills, if not controlled, seep to the bottoms and the lateral edges of refuse piles and migrate into surrounding soil and usable groundwater. Such escape without control is now almost universally forbidden. Controls are discovered, improved, and applied; but leachate continues to form, leaching persists, and barriers or treatments are neither fool-proof nor complete.

Virtually by definition, leachate has been considered to be the waterborne, dissolved organic and inorganic pollutants seeping in liquid form through solid waste landfills into surrounding porous soil materials and potentially to nearby, down-gradient, usable groundwater. The moisture may be derived from the waste materials placed in the landfill, but predominantly the volume is contributed by infiltrating and seeping runoff from local rainstorms. Gounaris, et al., however, have learned that about 40% of the total organic carbon and 50% of the total iron in leachate are in the colloidal, solid but unsettleable particles carried in the liquid leachate (4:18).

The mechanisms of leaching -- extraction of pollutants from solid materials into a passing fluid -- have been studied in detail by Webster and Loehr (12). The principal mechanism for extraction of metals from a solid, such as concrete or Portland cement, appears to be acidic solubilization (12:72

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Category: Science - L