Combined　nutrient　removal　and　phosphorus　recovery　are　pivotal　for　advancing　sustainable　wastewater　treatment　technologies.　Despite　the　proven　efficacy　of　anammox　granular　sludge　systems　in　nutrient　removal,　the　long-term　structural　development,　microbial　dynamics,　and　resource　recovery　potential　of　these　systems　remain　insufficiently　understood,　particularly　under　municipal　wastewater　conditions　at　the　microscopic　level.　Addressing　this　gap　is　critical　to　optimizing　reactor　performance　and　enhancing　sustainability.　In　this　study,　we　investigated　the　impact　of　phosphorus　enrichment　on　granular　sludge　characteristics　using　two　reactors.　The　phosphorus-free　reactor　(R1)　facilitated　the　rapid　formation　of　hollow　granular　sludge,　with　particle　sizes　growing　rapidly-yet　with　significant　variability-and　total　nitrogen　(TN)　removal　efficiencies　ranging　between　74.86　%　and　86.24　%.　In　contrast,　the　phosphorus-enriched　reactor　(R2)　was　supplemented　to　promote　hydroxyapatite　(HAP)　nucleation,　resulting　in　slower　but　more　organized　growth　of　dense　granules　with　a　narrower　size　distribution　and　consistently　higher　nitrogen　removal　efficiencies　(75.17　%-91.97　%).　Notably,　phosphorus　removal　efficiency　in　R2　peaked　when　granules　reached　approximately　800　mu　m,　attributable　to　HAP-mediated　adsorption　and　precipitation.　Furthermore,　the　relative　abundance　of　key　anammox　bacteria,　such　as　Candidatus　Brocadia,　increased　dramatically　from　1.28　%　in　R1　to　18.32　%　in　R2,　while　Denitratisoma　also　proliferated.　Despite　structural　differences,　similar　amounts　of　floating　sludge　were　observed　in　both　reactors,　likely　due　to　gas　entrapment　and　extracellular　polymeric　substances　(EPS)　production.　These　findings　demonstrate　that　phosphorus　enrichment　not　only　enhances　nitrogen　removal　and　phosphorus　recovery　but　also　modulates　microbial　community　composition　and　granule　morphology.