The　anaerobic/anoxic/oxic　(AAO)　process　remains　a　common　nutrient　removal　process　in　municipal　wastewater　treatment,　yet　research　focusing　on　concurrent　optimization　of　process　performance　and　N2O　emissions　reduction　is　scarce.　This　study　aimed　to　investigate　the　mitigation　of　N2O　emissions　and　enhance　nitrogen　removal　efficiency　in　an　AAO　system　treating　low　C/N　domestic　wastewater　by　establishing　a　fully　enclosed　gas-collecting　continuous　flow　reactor　and　implementing　carbon　supplementation　and　dissolved　oxygen　(DO)　control　strategies.　The　results　indicated　that　carbon　supplementation　in　the　anoxic　zone　effectively　reduced　nitrate　concentrations　and　mitigated　the　accumulation　of　dissolved　N2O　below　0.1　mgN/L.　The　moderate　DO　control　(1–2　mg/L)　could　ensure　the　nitrification　efficiency　while　reducing　the　gaseous　N2O　emission　rate　to　63.48　mgN/d,　and　decreasing　the　dissolved　N2O　concentration　in　the　effluent　to　below　0.01　mgN/L.　Both　too　high　and　too　low　DO　levels　were　detrimental　to　N2O　emission　mitigation.　The　optimized　AAO　process　achieved　a　significant　reduction　in　the　N2O　emission　factor　to　0.85　%　and　an　increase　in　nitrogen　removal　efficiency　to　81.81　%.　Additionally,　the　enrichment　of　anammox　bacteria,　Candidatus　brocadia　(0.15　%),　positively　contributed　to　the　improvement　in　nitrogen　removal　efficiency.　In　conclusion,　this　study　provides　valuable　insights　into　optimizing　AAO　process　to　mitigate　N2O　emissions,　enhance　nitrogen　removal,　and　lower　carbon　footprints　associated　with　wastewater　treatment.　©　2025