Increasingly　stringent　discharge　standards　make　it　necessary　to　research　and　develop　a　new　processes　that　have　the　advantages　of　relatively　high　efficiency,　less　land　occupation,　investigated　savings,　easy　management,　and　maintenance　for　nutrient　removal　from　the　domestic　sewage.　An　enhanced　denitrifying　phosphorus　removal　system　was　developed　to　treat　domestic　sewage,　especially　for　the　sewage　with　comparatively　low　carbon　source　and　high　nitrogen　and　phosphorus　concentration.　The　system　included　an　integrating　anaerobic/anoxic/oxic　(A2/O)　reactor　and　a　biological　contact　oxidation　(BCO)　(A2/O　-　BCO　for　short).　The　A2/O　unit　consisted　of　four　compartments　in　sequence　with　a　working　volume　of　40L.　It　was　mainly　used　for　the　removal　of　organic　compounds　and　nutrients　without　ammonium　oxidation,　while　the　BCO　unit　was　mainly　responsible　for　nitrification.　The　BCO　unit,　with　24L　working　volume,　consisted　of　three　compartments　in　sequence,　where　suspended　carriers　were　filled　in　it,　with　packing　rates　of　45%　in　each　zone.　The　removal　of　biological　nitrogen　(N)　and　phosphorus　(P)　were　investigated　in　an　A2/O　-　BCO　nitrogen　and　phosphorus　removal　process　when　treating　domestic　sewage.　The　experiment　was　carried　out　with　the　influent　flow　at　a　rate　of　5L/h,　total　hydraulic　retention　time　(HRT)　of　A2O　about　8　h,　sludge　reflux　ratio　of　100%,　sludge　retention　time　(SRT)　of　12d,　MLSS　maintained　at　3500　mg/L,　total　HRT　of　BCO　about　1.9　h,　DO　should　be　controlled　within　a　reasonable　range,　and　nitrate　recycling　ratios　were　set　as　100%,　200%,　300%,　and　400%　respectively.　Based　on　the　experimental　data　under　steady　state　operating　conditions　of　different　nitrate　recycling　ratios,　the　equations　for　calculating　material　balances　of　COD,　nitrogen,　and　phosphate　were　established.　These　three　material　distributions　in　the　system　were　also　evaluated.　The　result　indicated　that　the　process　has　an　advantage　of　making　full　use　of　the　raw　water　carbon　and　removing　biological　nitrogen　and　phosphorus　deeply.　With　the　nitrate　recycling　ratios　of　100%,　200%,　300%,　and　400%　conditions,　the　system　COD　was　mainly　utilized　in　the　anaerobic　stage　in　A2/O　reactor,　and　removal　percentages　of　total　COD　were　78.5%,　71.8%,　57.9%,　and　71.1%　respsectively.　Nitrogen　removal　was　mainly　achieved　by　denitrifying　in　the　phosphorus　removal　process　by　denitrifying　phosphorus　bacteria.　The　denitrification　removal　ratios　of　the　total　amount　were　28.0%,　35.7%,　48.5%,　and　33.9%,　respectively.　Phosphorus　removal　was　mainly　achieved　by　the　discharge　of　excess　sludge,　where　the　amount　of　phosphorus　percentages　of　total　were　78.0%,　88.4%,　84.3%,　and　85.4%　respectively.　Under　the　different　nitrate　recycling　ratios,　COD　balance　ratios　were　96.4%,　99.6%,　98.7%,　and　98.3%,　nitrogen　balance　ratios　were　99.7%,　98.2%,　99.2%,　and　96.5%,　and　phosphorus　balance　ratios　were　92.0%,　98.1%,　93.3%,　and　90.4%.　Fluorescence　in　situ　hybridization　showed　that　the　anammox　bacteria　existed　in　the　biofilm　of　BCO,　and　its　proportion　of　the　total　bacterial　number　was　0.6~2.7%.　The　nitrogen　loss　may　be　due　to　the　occurrence　of　the　anammox　reaction.　The　amount　of　denitrifying　phosphorus　increased　slightly　with　the　nitrate　recycling　ratio　improved.　But　it　is　essential　to　control　nitrate　recycling　ratio　in　the　appropriate　range　to　ensure　nitrogen　removal　efficiency.　The　system　achieved　the　best　removal　efficiencies　of　nitrogen　and　phosphorus　when　the　nitrate　recycling　ratio　was　set　as　300%,　in　which　the　average　concentrations　of　TN　and　TP　were　14.96　mg/L　and　0.49　mg/L　respectively　in　the　effluent,　which　met　the　class　of　a　limit　(GB18918-2002)　of　the　discharge　standards.　This　study　not　only　contributes　to　a　better　understanding　and　analysis　of　distribution　and　changes　about　organics,　nitrogen　and　phosphorus　in　process　systems,　but　also　provides　a　theoretical　basis　and　guidance　for　the　reliability　evaluation　of　the　of　the　experimental　data　by　building　a　mathematical　model.　The　combined　A2/O　-　BCO　process　will　get　a　better　promotion　in　treating　domestic　wastewater,　especially　the　rural　domestic　wastewater　with　the　universal　features　of　small　quantity,　scattered　distribution,　and　water　fluctuation.