The　feasibility　of　achieving　nitritation　and　phosphorus　removal　using　bio-augmentation　was　investigated　in　a　continuous-flow　anaerobic/oxic　(A/O)　reactor　treating　sewage.　The　results　indicated　that　nitritation　could　be　quickly　start-up,　and　reconstructed　with　an　increase　in　the　nitrite　accumulation　rate　(NAR)　from　1%　to　89%　within　15　days　by　using　bio-augmentation　and　controlling　DO　at　0.96　mg/L.　Biological　phosphorus　removal　could　be　achieved　with　the　average　phosphorus　removal　efficiency　of　96.43%　when　the　NAR　was　maintained　above　78.60%.　Meanwhile,　sludge　settleablity　was　good　with　a　sludge　volume　index　(SVI)　of　between　62　and　102　mL/g　even　under　high　NAR.　After　nitritation　and　biological　phosphorus　removal　were　achieved,　this　A/O　reactor　has　the　potential　to　supply　appropriate　influent　for　the　anammox　UASB　reactor.　(c)　2013　Published　by　Elsevier　Ltd.