Enhanced biological phosphorous removal (EBPR) is a biotechnology used to remove excess or remaining P from municipal or industrial waste streams. This process takes advantage of a group of organisms called phosphate accumulating organisms (PAO), such as Candidatus Accumulibacter phosphatis. These interesting organisms are notable for being capable of accumulating/storing large amounts of phosphate within their cells.

(Simplfying greatly,) EBPR processes typically involve passing waste/mixed liquor through two stages, anaerobic and aerobic, sequentially.

Anaerobic Cycle

Under anaerobic conditions these PAOs are capable of importing a number of simple organic carbon compounds and converting/storing them as polyhydroxyalkanoates (PHA). During this process PAOs break down polyphosphate (Poly-P) stored within thier cells and export orthophosphate to the extracellular medium.

Aerobic Cycle
In aerobic conditions PAO metabolism shifts dramatically reversing the previous processes. PHAs are consumed to support cell growth and maintenence as well as replenishing Poly-P reserves by importing orthophosphate.

The consecutive and aggregate action of these two cycles is the removal of orthophosphate from a waste stream by concentrating it within PAO cells which are then easily removed from suspension via settling.

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