Key Parameters - Phosphorus

The element phosphorus is necessary for plant and animal growth. Nearly all fertilizers contain phosphates (chemical compounds containing the element, phosphorous). When it rains, varying amounts of phosphates wash from farm soils into nearby waterways. Phosphates stimulate the growth of plankton and water plants that provide food for fish. This may increase the fish population and improve the waterway’s quality of life.

However if too much phosphate is present the process of eutrophication will be advanced. In such circumstances algae and water plants grow wildly, choke the waterway, and use up large amounts of oxygen. Many fish and aquatic organisms may die as a secondary effect, despite phosphates not being directly toxic to fish.
Phosphates come from fertilizers, pesticides, industry and cleaning compounds. Natural sources include phosphate-containing rocks and solid or liquid wastes.

Phosphates enter waterways from human and animal wastes (the human body releases about a pound of phosphorus per year), phosphate-rich rocks, wastes from laundries, cleaning and industrial processes, and farm fertilizers. Phosphates also are used widely in power plant boilers to prevent corrosion and the formation of scale.
Phosphates exist in three forms: orthophosphate, metaphosphate (or polyphosphate) and organically bound phosphate. Each compound contains phosphorus in a different chemical formula. Ortho forms are produced by natural processes and are found in wastewater.

Poly forms are used for treating boiler waters and in detergents; they can change to the ‘ortho’ form in water. Organic phosphates are important in nature and also may result from the breakdown of organic pesticides, which contain phosphates. Some values for total phosphate-phosphorus are given.

Phosphate-phosphorus levels and effects