How are PAOs removed from the system in biological phosphorus removal systems?

In biological phosphorus removal systems, phosphorus-accumulating organisms (PAOs) are effectively removed through the waste activated sludge (WAS). PAOs absorb phosphates during the biological treatment process, particularly in anaerobic and aerobic conditions where they convert stored energy into polyphosphate. As the treatment process continues, these PAOs are separated from the treated water in the form of sludge.

During the normal operation of a wastewater treatment plant utilizing biological phosphorus removal, some of the biomass, which includes PAOs, is periodically removed from the system as part of the activated sludge process. By doing this, the concentration of phosphorus in the treated effluent is reduced, as the PAOs, along with the phosphorus they have accumulated, are effectively removed. This method is particularly efficient because it harnesses the natural metabolic processes of these organisms to sequester phosphorus, making it a sustainable choice for reducing phosphorus levels in wastewater.