Phosphate

Phosphorus compounds – in particular ortho-phosphate PO₄^3- – are considered to be the limiting nutrients in most stagnant and flowing waters. An increase in their concentration caused by higher input (wastewater, avulsion etc.) results directly in increasing eutrophication of the water with known effects such as increased growth of algae, oxygen depletion as far as anoxia in the deeper regions, etc.

Phosphorus occurs in 3 compounds in natural waters:

• Inorganic, dissolved ortho-phosphate
• Dissolved organic phosphorus compounds
• Particulate phosphorus (bound in biomass or attached to particles),

They add up to the total of phosphorus content P_Total, an important parameter in monitoring wastewater treatment plant effluents.