Groundwater Standards

Vast reserves of water are in the ground in many areas of the world. Little is known about the quality of this groundwater, except in areas where aquifers are being exploited. In Europe and the United States, where groundwater represents a significant source of fresh water, between 5 and 10 percent of all investigated wells have nitrate levels higher than the maximum recommended value of 45 mg/L(A). Many organic pollutants find their way into groundwater as seepage from dumps, leakage from sewers and fuel tanks, and runoff from agricultural land or paved surfaces.

Because groundwater is cut off from the atmosphere's oxygen supply, its capacity for self-purification is low. The microbes that perform this function in surface waters need oxygen to function. Microbes that do not use oxygen are in groundwater, but their destruction of pollutants is slow. Thus, although the pollution of rivers and lakes can be rapidly reversed, pollution of groundwater is not easily reversed. Generally, the only practical control for ground-water pollution is to eliminate sources of contamination, particularly in areas of rapid aquifer recharge from the surface.

For regulatory purposes, groundwaters are classified according to use, generally potable and nonpotable. In some areas, such as Florida, almost all drinking water comes from groundwater. They have four classes of groundwa-ter, with the additional discrimination based on levels of dissolved solids. Because of Florida's strong dependence on groundwater, it has developed some of the most sophisticated regulations and standards to manage the resource. For this reason, this section focuses on the current regulation of groundwater in Florida as a model that may become more common in the next century.

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