Intermittent　aeration　is　favorable　for　maintaining　a　long-term　sewage　partial　nitrification-anammox　(PN/　A)　process　but　the　underlying　mechanism　is　not　yet　fully　understood.　In　this　study,　mainstream　PN/A　was　established　in　an　integrated　fixed　film　activated　sludge　(IFAS)　PN/A　reactor　and　nitrite　oxidization　bacteria　(NOB)　activity　was　continuously　suppressed.　The　suppression　of　NOB　was　significantly　affected　by　the　dissolved　oxygen　(DO)　concentration　during　the　aeration　period　as　well　as　the　duration　of　anoxic　period.　NOB　was　more　suppressed　in　the　hybrid　system　under　a　low　DO　level　(0.5　mg/L)　than　under　a　high　DO　level　(1.5-1.8　mg/L).　Meanwhile,　shortening　the　anoxic　time　from　40　to　20　min　and　keeping　low　DO　during　the　intermittent　aeration　cycle　could　still　suppress　NOB　activity,　increasing　the　nitrogen　removal　rate　by　40%.　Biomass　segregation　was　also　enhanced　by　low　DO,　which　favors　the　NOB　inhibition　in　IFAS　PN/A　system.　Overall,　under　an　optimized　intermittent　aeration,　a　stable　and　high　nitrogen　removal　efficiency　(80-89%)　with　a　nitrogen　removal　rate　of　0.101　kg-N/(m(3).d).　This　study　is　useful　to　supports　the　application　of　PN/A　in　sewage　treatment.　(C)　2020　Elsevier　Ltd.　All　rights　reserved.