Achieving　low-cost　advanced　nitrogen　(N)　removal　from　municipal　wastewater　treatment　plants　(WWTPs)　remains　a　challenge.　A　plug-flow　anaerobic/oxic/anoxic　(AOA)　system　with　a　mixtures　bypass　(MBP)　integrating　partial　nitrification　(PN),　endogenous　carbon　denitrification　(EnD),　partial　denitrification　(PD),　and　anaerobic　ammonium　oxidation　(Anammox),　was　constructed　to　treat　actual　sewage　with　a　low　C/N　ratio.　The　effluent　concentrations　and　removal　efficiency　of　total　inorganic　nitrogen　(TIN)　during　stable　operation　were　2.9　+/-　0.9　mg/L　and　93.1　+/-　2.0　%,　respectively.　EnD　was　enhanced　by　the　MBP　through　the　efficient　utilization　of　polyhydroxyalkanoates　generated　in　the　anaerobic　zone.　PD　was　promoted　by　the　addition　of　carries　and　sodium　acetate　to　the　anoxic　tank　and　the　subsequent　implantation　of　the　Anammox　biofilm　successfully　coupled　PD/A.　Stable　PN　was　obtained　with　a　satisfactory　nitrite　accumulation　ratio　of　92.6　%,　facilitated　by　carriers　and　the　introduction　of　hydroxylamine　in　the　oxic　zone.　Mass　balance　analysis　revealed　that　EnD　and　Anammox　contributed　40.8%　and　48.2　%　of　TIN　removal,　respectively.　The　enrichment　and　synergistic　effects　of　ammonia-　oxidizing　bacteria,　denitrifying　bacteria,　glycogen-accumulating　organisms,　and　anaerobic　ammonia-oxidizing　bacteria　formed　a　diverses　bacterial　basis　for　the　establishment　of　PN,　EnD,　PD,　and　Anammox　(PNEnD/A)　in　the　AOA　system.　The　successful　integration　of　PNEnD/A　into　the　AOA　process　provides　an　innovative　approach　for　low-cost　advanced　N　removal　in　WWTPs.