The　occurrence　of　denitrifying　phosphate　accumulating　organisms　(DNPAOs)　and　the　contribution　of　DNPAOs　to　biological　nutrient　removal　performance　were　investigated　in　a　bench-scale　A(2)O　system.　Moreover,　the　effect　of　excessive　aeration　on　biological　phosphorus　removal　(BPR)　was　studied.　The　experimental　results　suggested　that　anoxic　phosphorus　uptake　could　occur　in　the　A　20　process,　as　compared　with　the　conventional　A　20　process.　Good　COD,　phosphorus,　ammonia　nitrogen　and　total　nitrogen　removal　efficiency　(92.3%,　95.5%,　96%　and　79.5%　respectively)　could　be　achieved.　Furthermore,　sludge　analysis　demonstrated　that　the　ratio　of　anoxic　P　uptake　rate　to　aerobic　P　uptake　rate　reached　69%　in　such　a　system　and　nitrate　concentration　in　the　anoxic　phase　and　different　organic　substrate　introduced　into　the　anaerobic　phase　had　significant　effects　on　the　anoxic　P　uptake.　It　was　also　found　that　if　the　air　supply　was　not　adjusted　properly　wider　good　anoxic　P　uptake　conditions,　excessive　aeration　of　activated　sludge　at　the　end　of　aerobic　zone　could　lead　to　the　deterioration　of　BPR.