What primarily drives the growth and reproduction of Polyphosphate Accumulating Organisms (PAO)?

Polyphosphate Accumulating Organisms (PAOs) primarily thrive in environments where they can efficiently utilize polyhydroxybutyrate (PHB). The consumption of PHB is a critical metabolic process for these organisms. PAOs typically utilize PHB as a carbon source during anaerobic conditions, allowing them to store intracellular polyphosphate which they can then utilize during subsequent aerobic conditions.

The ability to store carbon in the form of PHB directly supports their growth and reproduction. When PHB is consumed, it not only serves as a source of energy but also facilitates the subsequent uptake of phosphate from the environment, which is essential for PAOs to grow and reproduce effectively.

In contrast, while nitrogen levels, oxygen presence, and phosphate recycling play roles in the broader context of wastewater treatment and the cycles of nutrient availability, it is the consumption of PHB during anaerobic conditions that specifically drives the growth and reproduction of PAOs. This mechanism is fundamental to the enhanced biological phosphorus removal (EBPR) processes used in wastewater treatment facilities.