In　order　to　analyze　the　nitrogen　(N)　and　phosphorus　(P)　removal　characteristics　of　simultaneous　partial　nitrification-endogenous　denitrification　and　phosphorus　removal　(SPNED-PR)　systems　and　to　elucidate　the　contribution　and　competitive　relationships　between　phosphorus　and　glycogen　accumulating　organisms　(PAOs　and　GAOs)　in　the　nutrient　removal,　an　extended　anaerobic　(150min)/low　aerobic　(180min,　dissolved　oxygen　(DO)　concentration　for　0.5~0.7mg/L)　operated　sequencing　batch　reactor　(SBR)　fed　with　domestic　wastewater　(C/N:　around　4)　was　studied　by　investigating　the　effects　of　different　DO　(0.5~2.0mg/L),　nitrite　(4.7~39.9mg/L)　and　nitrate　(5.0~40.0mg/L)　concentrations　on　the　nutrient　removal　and　intracellular　carbons　transformation.　Results　showed　that　DO　had　barely　effects　on　the　aerobic　metabolisms　of　both　PAOs　and　GAOs,　and　almost　no　PAOs-GAOs　competition　was　detected　at　various　DO　concentrations.　GAOs　had　a　competitive　advantage　over　PAOs　at　the　presence　of　nitrite,　and　nitrite　was　mainly　removed　by　GAOs　(about　58%);　GAOs　had　a　greater　tolerance　to　nitrite　than　PAOs,　which　alleviated　the　nitrite　inhibition　on　PAOs　at　high　nitrite　concentrations　(26.2~39.9mg/L)　and　assured　the　nutrient　removal　in　the　SPNED-PR　system.　PAOs　had　a　competitive　advantage　over　GAOs　when　nitrate　was　present,　and　it　contributed　to　about　61.2%　of　total　nitrate　removal.　Additionally,　PAOs　preferred　to　utilize　DO　over　nitrite　and　nitrate　for　P　uptake　(PUR　DO　>PUR　nitrate　>PUR　nitrite　),　which　assured　the　efficient　P　removal　at　low　aerobic　conditions.　Highly　active　GAOs　ensured　the　efficient　N　removal　in　the　SPNED-PR　system　via　endogenous　nitrite　denitrification.　©　2018,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.