Improved Properties and Enhancement Strategies of Hydroxyapatite-Based Functional Granular Sludge for a High-Rate Partial Nitritation/Anammox System

/d. After a long-term operation of 870 days, the enhancement strategies underlying the superior performance of the granular sludge were identified. These findings clearly demonstrate that the enhancement strategies are crucial for the superior operating performance of the PNA process, and they can promote the application of the anammox-based process.