Hydroxyapatite-microbe coupling confers Cu²⁺ resilience and functional recovery in partial denitrification granules.
Partial denitrification (PD) regulates nitrite supply in partial denitrification-anammox (PD/A) systems and is therefore central to stable, low-carbon nitrogen removal. In practice, however, PD/A performance is highly vulnerable to toxic heavy metals, particularly Cu². Here we engineer a hydroxyapatite-coupled PD granu...