Phosphate

Abstract

The element phosphorus exists in nature as compounds with oxygen, the phosphates. Phosphates are omnipresent in nature: in the lithosphere, biosphere, hydrosphere and atmosphere. Because of their unique physico-chemical properties phosphates are essential and indispensable for all organisms. This fact demonstrates that phosphates are non-toxic. The majority of phosphate deposits in four continents of the world consists of marine-sedimentary apatite, a calcium phosphate. About ninety per cent of the steadily increasing phosphate rock production is used in food production. The rest of the raw phosphate rock is used in technical applications in many different fields e.g. water softening, detergents, cleaning agents, food industry, toothpastes, flame retardants, phosphatization, anticorrosion. Also raw phosphates are the basis of many other phosphorus containing products of the chemical industry. Organisms not only take in vital phosphates with their food but they also continuously release them. Thus, phosphates concentrated in deposits are distributed over the world and find their way into surface waters. In former times phosphate contents of surface waters were limiting for plant growth by being too low in proportion to other nutrients. Increasing phosphate concentrations can promote the growth ofwater organisms, which can finally overburden the limited oxygen content of waters, especially lakes. Existing phosphate elimination processes effectively control phosphate loads of sewage and water inputs of lakes. By using phosphate elimination processes it is possible to recycle phosphates, thus helping the preservation of phosphate resources e.g. by the agricultural use of sewage sludges.