Achieving　advanced　nitrogen　removal　based　on　anammox　for　treating　mainstream　municipal　wastewater　in　a　single　suspended　sludge　bioreactor　is　a　challenging　research　topic.　In　this　study,　multiple　coupling　nitritation,　denitritation　and　endogenous　denitritation　with　anammox　(PNA-(E)PDA)　was　simultaneously　achieved　in　a　10　L　step-feed　bioreactor,　which　enhanced　stable　nitrogen　removal.　After　223　days　of　operation,　the　total　nitrogen　concentrations　of　the　influent　and　effluent　were　70.7　+/-　6.1　and　4.3　+/-　1.8　mg/L,　respectively,　when　treating　municipal　wastewater　even　at　C/N　ratio　of　2.24　with　only　5　h　of　aerobic　time　(DO:　0.5-0.8　mg/L).　After　the　evolution　of　nitritation/anammox　to　PNA-(E)PDA,　the　contribution　of　anammox　to　nitrogen　removal　increased　to　78.6%　and　the　anammox　activity　increased　from　4.3　+/-　0.2　to　15.2　+/-　0.7　mg　NH4+-N/gVSS/d.　qPCR　results　showed　that　the　abundance　of　anammox　bacteria　increased　from　4.1　x　10(9)　to　4.5　x　10(10)　copies/　(g　VSS).　Highthroughput　sequencing　further　revealed　that　the　relative　abundance　of　Candidatus　Brocadia,　the　dominant　anammox　genus,　increased　from　0.09　to　0.46%.　Based　on　the　strong　competitiveness　of　anammox　on　nitrite,　this　novel　PNA-(E)PDA　process　provides　a　potential　strategy　for　enriching　anammox　bacteria　in　municipal　wastewater　treatment　plants.