The　simultaneous　partial　nitrification,　anammox　and　denitrification　(SNAD)　process　for　treating　domestic　wastewater　was　investigated　in　a　sequencing　batch　reactor　(SBR).　The　SBR　was　operated　with　air　flow　rate　of　500　L　h(-1)　at　30　A　degrees　C.　Domestic　wastewater　was　used　as　influent　and　Kaldnes　rings　were　used　as　biomass　carriers.　In　the　beginning,　long　aeration　condition　was　implemented　to　cultivate　nitrification　biofilm.　Afterwards,　intermittent　aerobic　condition　was　conducted　during　the　cycle　operation.　The　influent　organic　matter　loading　rate　was　improved　by　reducing　the　aeration　and　mixing　times.　Consequently,　when　the　SNAD　biofilm　reactor　was　fed　with　the　organic　matter　loading　rate　of　0.77　(kg　COD　m(-3)　d(-1)),　the　bio-bubbles　appeared　in　the　reactor　and　the　total　inorganic　nitrogen　(TIN)　removal　efficiency　decreased.　After　the　organic　matter　loading　rate　decreased　to　0.67　(kg　COD　m(-3)　d(-1)),　the　reactor　showed　excellent　nitrogen　removal　performance.　The　TIN　removal　efficiency　varied　between　80　and　90　%,　and　the　average　TIN　removal　loading　rate　was　0.22　(kg　TIN　m(-3)　d(-1)).　Additionally,　the　scanning　electron　microscope　(SEM)　observation　confirmed　that　the　anammox　bacteria　located　in　the　inner　part　of　the　carriers.　Finally,　the　microbial　community　analysis　of　16S　rRNA　gene　cloning　revealed　that　the　anammox　bacteria　on　the　carriers　consisted　of　three　main　genuses:　Candidatus　Brocadia　sp.,　Candidatus　Brocadia　caroliniensis　and　Candidatus　Brocadia　fulgida.