LANDFILLS, SANITARY

Sanitary landfills are one of the most popular forms of waste disposal, primarily because they are the least expensive way to dispose of waste. More than four-fifths of municipal solid waste is disposed of in landfills. Landfills are rapidly filling up all around the country, however and the majority of them will close by 2010. Also, many have waste problems that are serious health threats. As of 1983, there were 184 landfills listed, or proposed to be listed, on the Superfund National Priorities List (NPL).

A sanitary landfill is an engineered means of disposing of waste. In a sanitary landfill, waste is spread in layers on a piece of property, usually on marginal or submarginal land. The objective is to spread the layers and then compact them tightly, greatly reducing the volume of the waste. The waste is then covered by soil.

Problems that are encountered in open dumping, including insects, rodents, safety hazards, and fire hazards, can be avoided with landfilling. A landfill should not be located in areas with high groundwater tables. Leachate migration control standards must be followed in the design, construction, and operation of landfills during the use of the facility and during the postclosure period.

Much of the waste in a sanitary landfill will decompose through biological and chemical processes that produce solid, liquid, and gaseous products. Food wastes degrade rapidly, whereas plastics, glass, and construction wastes do not. The most common types of gas produced by the decomposition of the wastes are methane and carbon dioxide. Methane, which is produced by anaerobic decomposition of landfilled materials, is hazardous because it is explosive. Depending on the landfill composition, gases can be recovered and utilized in the generation of power or heat. Landfill recovery science is a new technology that is utilized in many parts of the United States. Sadly, in many places, wetlands and other lands considered to be marginal were used for landfills. Only now are people becoming aware of the value of wetlands and other areas that were used—especially with regard to sensitive habitats, biodiversity, and impacts on groundwater.

After a landfill has reached capacity, it is closed for waste deposition and covered. In some cases it can be used as pasture, as cropland, or for recreational purposes. Maintenance of the closed landfill is important to avoid soil erosion and excess runoff into desirable areas.

Mark G. Robson

(see also: Groundwater; Municipal Solid Waste; Sanitation )

Bibliography

Herman, K., and Bisesi, M. (1996). Handbook of Environmental Health and Safety, 3rd edition, Vol. II. Boca Raton, FL: Lewis Publishers.

Morgan, M. T. (1997). Environmental Health. Madison, WI: Brown and Benchmark.