Nitrite　oxidizing　bacteria　(NOB)　outcompeting　anammox　bacteria　(AnAOB)　poses　a　challenge　to　the　practical　implementation　of　the　partial　nitrification/anammox　(PN/A)　process　for　municipal　wastewater.　A　granules-based　PN/A　bioreactor　was　operated　for　260　d　with　hydroxylamine　(NH2OH)　added　halfway　through.　qPCR　results　detected　the　different　amounts　of　NOB　among　granules　and　flocs　and　the　dynamic　succession　during　operation.　CLSM　images　revealed　a　unique　layered　structure　of　granules　that　NOB　located　inside　led　to　the　inhibition　effect　of　NH2OH　delayed.　Besides,　the　physical　and　morphological　characteristics　revealed　that　anammox　granules　experienced　destruction.　AnAOB　took　the　broken　granules　as　an　initial　biofilm　aggregate　to　reconstruct　new　granules.　RT-qPCR　and　high　throughput　sequencing　results　suggested　that　functional　gene　expression　and　community　structure　were　regulated　for　the　AnAOB　metabolism　process.　Correspondingly,　the　rapid　proliferation　(0.52　→　1.99%)　of　AnAOB　was　realized,　and　the　nitrogen　removal　rate　achieved　a　nearly　quadruple　improvement　(0.21　→　0.83　kg-N/m3·d).　This　study　revealed　that　anammox　granules　can　self-reconstruct　in　the　PN/A　system　when　granules　are　disintegrated　under　NH2OH　stress,　broadening　the　feasibility　of　applying　PN/A　process.　©　2023　Elsevier　Ltd