Anaerobic　ammonium　oxidation　(anammox)　combined　with　partial　nitrification　(PN)　is　expected　to　achieve　energy　self-sufficiency　in　wastewater　treatment,　while　its　advantages　have　not　been　fully　revealed.　An　anaerobic/　aerobic/anoxic　(AOA)　system　was　established　to　treat　low　chemical　oxygen　demand　(COD)-total　inorganic　nitrogen　(TIN)　(C/N)　ratio　(3.08)　municipal　wastewater.　Anammox　bacteria　were　enriched　from　7　x　106　to　3　x　108　copies/gSS　during　partial　denitrification　coupling　with　anammox　(PDA)　phase.　With　the　PN　achievement,　the　anammox　hotspot　zone　transformed　from　the　anoxic　zone　through　PDA　(37%)　to　the　aerobic　zone　by　partial　nitrification　coupled　with　anammox　(PNA)　(12%).　As　the　nitrite　accumulation　rate　increased　to　97%,　the　TIN　removal　efficiency　and　rate　increased　to　95%　and　0.12　kgN/(m3.d).　Although　anammox　performance　weakened　after　this　transformation,　the　carbon　sources　saved　by　PN　drove　more　nitrogen　removal.　PNA　was　beneficial　for　advanced　and　efficient　nitrogen　removal　in　carbon-limited　wastewater　treatment　and　was　less　dependent　on　higher　anammox　contribution.