Simultaneous　nitrogen　and　phosphorus　removalcould　be　realized　by　denitrifying　phosphorus　removal　system.　However,　a　shortageof　organic　carbon　for　wastewaters　with　low　COD/N　ratiocan　result　in　adding　carbon　source　to　overcome　the　limitation　of　low　organic　carbon.　By　adding　carbon　sources　to　adjust　influent　COD/N　ratio　around　4.3,the　role　of　various　carbon　source　in　the　A2/O-BCO(anaerobic　anoxic　oxic-biological　contact　oxidation)process　was　investigated.　The　batch　tests　were　used　to　further　research　the　substrate　storage　and　conversion　of　activated　sludge　with　various　additional　carbon　sources.　These　results　showed　that　the　substrate　storage　and　utilization　characteristics　were　influenced　by　the　type　of　influent　carbon,　which　further　effected　the　nitrogen　and　phosphorus　removals.　When　sodium　propionate　was　the　additional　carbon　source,　PO43--P　removal　steadily　maintained　around　94%,　however,　the　removal　efficiency　of　TIN　was　70.82%.　For　sodium　acetate,　TIN　removal　reached　to　74%,　but　the　average　removal　efficiency　of　PO43--P　was　89.90%.　The　conversion　analysis　of　carbon　source　revealed　that　the　content　of　PHA　was　mainly　PHV　with　adding　sodium　propionate　in　the　anaerobic　phase.　On　the　contrary,　the　proportion　of　PHB　increased　with　adding　sodium　acetate.　In　the　anoxic　phase,　the　effect　of　PHB　and　PHV　degradation　by　DPAOs　was　closely　related　to　its　content.　Compared　to　PHB,　PHV　is　liable　to　be　absorbed　by　DPAOs.　When　sodium　propionate　was　used　as　additional　carbon　source,　the　higher　PHV　degradation　rate　and　productivity　efficiency　were　observed,　which　improved　the　phosphorus　absorption　rate.　In　addition,　the　optimal　operation　strategy　of　the　A2/O-BCO　process　with　various　sources　was　proposed.　©　All　Right　Reserved.