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Historical information on phosphorus load ings to the environment and the effect on water quality are summarized in this report, which was produced as part of the U.S. Geological Survey’s National Water-Quality Assessment (NAWQA) Program. Phosphorus is a water-quality constit uent of concern because it is often the limiting nutrient responsible for accelerated eutrophica tion in water bodies. Phosphorus inputs to the environment have increased since 1950 as the use of phosphate fertilizer, manure, and phosphate laundry deter gent increased; however, the manufacture of phos phate detergent for household laundry was ended voluntarily by the industry in about 1994 after many States had established phosphate detergent bans. Total phosphorus concentrations in raw wastewater effluent contained about 3 milligrams per liter of total phosphorus during the 1940’s, increased to about 11 milligrams per liter at the height of phosphate detergent use (1970), and have currently declined to about 5 milligrams per liter. However, in some cases, tertiary wastewater treatment still is needed to effectively improve water quality of streams. Downward trends in phosphorus concentra tions since 1970 have been identified in many streams, but median total phosphorus concentra tions still exceed the recommended limit of 0.1 milligram per liter across much of the Nation. Data from the NAWQA Program are representa tive of a variety of phosphorus-control measures and, therefore, may be used to evaluate the effects of various control strategies. Current areas of concern include: evaluation of the effects of increased manure loadings of phosphorus on soil phosphorus and, subsequently, on ground water and subsurface runoff; determination of pointsource and nonpoint-source components of phos phorus loads by geographic modeling and hydro logic separation techniques; and development of methods or indices to evaluate nutrient impair ment in streams and rivers to serve as a basis for developing phosphorus criteria or standards.

Review of Phosphorus Control Measures in the United States and Their Effects on Water Quality