Partial　denitrification/anammox　(PD/A)　processes　have　emerged　as　a　promising　technology　for　efficient　nitrogen　removal　from　wastewater.　However,　these　processes　fail　to　remove　phosphorus　(P),　a　key　pollutant　that　contributes　to　water　eutrophication.　To　address　this　issue,　the　potential　of　inducing　hydroxyapatite　(HAP)　precipitation　in　PD　processes　to　achieve　simultaneous　P　removal　was　investigated　for　the　first　time.　Specifically,　three　SBRs　(R1-R3)　for　PD　were　operated　with　adding　varying　concentrations　of　external　Ca　(30,　60,　and　120　mg/L,　respectively).　Results　demonstrated　significant　P　reduction　in　all　three　SBRs,　particularly　in　R3　with　high　Ca,　which　achieved　an　80　%　removal　efficiency.　Notably,　sludge　granulation　was　observed　during　operation,　with　the　granule　size　in　R3　with　high　Ca　reaching　906.1　μm　during　the　stable　period,　exceeding　those　in　R2　(788.7　μm)　and　R1　(707.1　μm).　This　led　to　good　settle　ability　of　the　PD　sludge,　as　demonstrated　by　the　lowest　SVI5　(20　mL/g　MLSS).　Moreover,　the　decrease　in　the　MLVSS/MLSS　ratio　suggested　that　the　inorganic　content　accumulated,　as　observed　by　confocal　laser　scanning　microscopy　in　the　interior　of　the　granules.　Elemental　composition　analysis　suggested　that　PD　granules　contained　high　P　and　Ca,　while　the　X-ray　diffraction　(XRD)　results　confirmed　the　formation　of　HAP.　Overall,　this　study　demonstrated　that　PD-HAP　coupled　granular　sludge　process　has　potential　as　a　robust　and　efficient　method　for　nitrite　production,　as　well　as　effective　P　removal　and　recovery,　thereby　advancing　the　application　of　anammox　processes　in　wastewater　treatment.　©　2023　Elsevier　B.V.