Inorganic phosphates are compounds of phosphorus and oxygen that occur in many forms and are usually combined with other elements. Phosphoric acid, the common acid of phosphorus, is the main commercial source of inorganic phosphate compounds. Phosphoric acid is made by treating calcium phosphate rock, such as apatite, with sulfuric acid.
Phosphoric acid is usually stored and sold as a solution. It is a brown/green viscous liquid with a slight acid odour. It is tribasic, having three replaceable hydrogen atoms. Phosphates are products formed by the replacement of some or all of the hydrogen of phosphoric acid by metals, such as sodium, potassium, calcium and aluminium.
Phosphoric acid is primarily used in the production of phosphate compounds. It is also used in a wide range of processes, including for rust proofing metals, in sugar refining, and in soft drinks. The major use of phosphorus compounds is in fertilisers, especially in a mixture called superphosphate. This is a particularly important compound given the importance of fertilisers for world-wide agricultural production. Phosphorus compounds are also used commercially in detergents, water softeners, pharmaceuticals, and toothpaste and as food additives. Specific inorganic compounds include ammonium phosphate which is an important compound in the manufacture of certain fertilisers. Trisodium phosphate is used in detergents, for softening water and for preventing boiler scale and corrosion of pipes and boiler tubes. Calcium phosphate is used to produce fine chinaware and to produce monocalcium phosphate used in baking powder. It is also an ingredient in fertilisers.
Phosphorus and inorganic phosphates are present in all living organisms and phosphorus is an essential nutrient. For example, calcium phosphate is the principal material in bones and teeth. The main source of release into the environment is from anthropogenic sources particularly from fertilisers from agricultural land, and cleaning detergents containing phosphates. Other sources include human sewage, fruit and vegetable industries, and pulp and paper manufacture.
Impacts on human health and environment
Excessive exposure to some chemicals in this diverse group may affect health, with the possible effects depending on the particular chemical.
The release of large quantities of phosphates into the aquatic environment can have significant adverse effects. Algae rapidly absorb inorganic phosphates, primary nutrient for such plant life, which causes them to grow rapidly. When they eventually die, aerobic bacteria decompose them, consuming oxygen in the process. Lowered levels of oxygen in the aquatic environment can seriously threaten aquatic organisms. This process is known as eutrophication. Large mats of algae can form and in severe cases can completely cover water bodies. Water can also become putrid due to the large amount of decaying organic matter. A major problem with phosphate pollution is that it persists for a long time within aquatic environments. Phosphates are simply released back into the environment when plants die to be subsequently re-used by other plants.
No major significant global impacts are considered likely. However, phosphates found in the marine environment can lead to algae blooms known as 'red tides' which can harm marine life in surrounding countries' waters.
Emission to water reporting threshold: 5000 kg/year
Data source: European Pollutant Emission Register