The　characteristics　of　removal　of　nitrogen　and　phosphorus　were　investigated　by　using　denitrifying　phosphorus　activated　sludge　taken　from　an　anaerobic/anoxic/oxic　(A2/O)-biological　contact　oxidation　(BCO)　system.　Different　concentrations　of　NO2--N　and　NO3--N　(NO2--N　+　NO3--N=30　mgL-1)　were　used　to　evaluate　the　influence　of　different　electron　acceptor　ratios　(NO2--N:NO3--N=0,　0.2:0.8,　0.4:0.6,　0.5:0.5,　0.6:0.4)　on　nitrogen　and　phosphorus　removal　of　denitrifying　polyphosphate　accumulating　organisms　(DPAOs).　The　results　showed　that　sodium　acetate　was　the　ideal　carbon　source　for　DPAOs　to　denitrify　phosphorus　removal　and　the　best　concentration　was　200　mgL-1.　The　more　appropriate　additive　amount　of　NO3--N　was　30　mgL-1　when　NO3--N　was　the　electron　acceptor　in　anoxic　phosphorus　absorption　reaction.　It　was　hard　for　the　DPAOs　that　using　NO3--N　as　electron　acceptor　and　untamed　with　NO2--N　to　use　NO2--N　in　a　short　time,　but　a　low　NO2--N　concentration　(6　mgL-1)　did　not　affected　nitrogen　and　phosphorus　removal　by　DPAOs　when　NO3--N　was　the　electron　acceptor.　Additionally,　the　effect　of　NO2--N　on　phosphorus　absorption　was　more　significant　than　that　of　denitrification　by　NO3--N,　and　the　reaction　of　phosphorus　absorption　almost　ceased　when　the　concentration　of　NO2--N　achieved　18　mgL-1.　Furthermore,　high　NO2--N　concentration　would　inhibit　the　decomposition　and　utilization　of　PHA　(polyhydroxyalkanoate),　and　more　energy　from　PHA　decomposition　would　use　for　glycogen　storage,　where　PHB　(poly-β-hydroxybutyrate)　accounted　for　more　than　90%　of　the　PHA　decomposition　and　utilization.　©　All　Right　Reserved.