Phosphorus　(P)　removal　occurred　in　heterotrophic　nitrification　process,　but　its　mechanism　has　not　been　fully　explored.　In　this　study,　the　P　removal　performances,　pathways,　and　mechanisms　in　heterotrophic　nitrification　processes　of　different　microbial　aggregates　(activated　sludge　and　biofilm)　were　investigated.　The　results　showed　that　the　biofilm　reactor　had　more　efficient　total　nitrogen　removal　(98.65%)　and　phosphate　removal　(94.17%).　Heterotrophic　nitrification　and　denitrification　processes　generated　alkalinity　for　biologically　induced　phosphate　precipitation　(BIPP),　which　contributed　to　64.12%-78.81%　of　the　overall　P　removal.　The　solid　phase　P　content　reached　48.03　mg/gSS　with　hydroxyapatite　and　calcium　phosphate　formation.　The　study　clarified　that　biofilm　was　beneficial　to　BIPP　because　of　the　nitrogen　removal　metabolism　and　extracellular　polymeric　substance　(EPS).　Heterotrophic　nitrogen　removal　metabolism　was　the　driving　force　of　BIPP,　while　EPS　with　abundant　carboxyl　and　amide　groups　promoted　the　precipitation.　The　study　would　provide　new　insights　into　simultaneous　nutrients　removal　and　P　recovery　from　wastewater.