Phosphates are chemical compounds containing phosphorus. Phosphorus is a non-metallic element which is necessary for life and is found in rock as inorganic phosphates. As water runs over and through rocks it carries off small amounts of minerals such as calcium, magnesium, and phosphates. Inorganic phosphates are a plant nutrient and are taken in by plants with water and incorporated into organic phosphate compounds. Animals obtain their essential phosphorus from phosphates in water and plant material. Natural waters have a phosphorus concentration of approximately 0.02 parts per million (ppm) which is a limiting factor for plant growth. On the other hand, large concentrations of this nutrient can accelerate plant growth.

Phosphates enter waterways through manmade sources also. Per capita we contribute approximately 3.5 pounds of phosphate yearly to our environment (1). The addition of large quantities of phosphates to waterways accelerates algae and plant growth in natural waters; enhancing eutrophication and depleting the water body of oxygen. This can lead to fish kills and the degradation of habitat with loss of species. Large mats of algae can form and in severe cases can completely cover small lakes. As a result, water can become putrid from decaying organic matter. When the concentration of phosphates rises above 100 mg/liter the coagulation processes in drinking water treatment plants may be adversely affected. Manmade sources of phosphate include human sewage, agricultural run-off from crops, sewage from animal feedlots, pulp and paper industry, vegetable and fruit processing, chemical and fertilizer manufacturing, and detergents.

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1. Groundwater Contamination: Sources, Control, and Preventative Measures. 1989. Chester D. Rail. pub by Technomic Publishing Co., Inc., Lancaster, PA. pp 17.

2. Aquatic Pollution. 2nd Ed. 1993. E.A. Laws. John Wiley & Sons, Inc., New York, NY. pp 148-149.

This page was prepared by T.L. Pedersen , UCD EXTOXNET FAQ Team.
June 1997