Under these conditions a group of heterotrophic bacteria, called polyphosphate-accumulating organisms (PAO) are selectively enriched in the bacterial community within the activated sludge.
In the subsequent aerobic phase, these bacteria can accumulate large quantities of polyphosphate within their cells and the removal of phosphorus is said to be enhanced.
[2] EBPR can also integrate biological nitrogen removal through the addition of an anoxic zone where nitrate is present due to the denitrification capabilities of some PAO.
[3] Generally speaking, all bacteria contain a fraction (1-2%) of phosphorus in their biomass due to its presence in cellular components, such as membrane phospholipids and DNA.
If additional chemical precipitation takes place, for example to reach discharge limits, the P-content could be higher, but that is not affected by EBPR.