Stable　nitritation　is　the　major　challenge　for　short-cut　nitrogen　removal　from　municipal　wastewater.　This　paper　demonstrated　a　rapid　achievement　of　partial　nitrification　(PN)　in　an　enhanced　biological　phosphorus　removal　(EBPR)　reactor　treating　domestic　wastewater.　Polyphosphate　accumulating　organisms　(PAOs)　were　enriched　operated　at　a　short　aerobic　HRT　(2.0　h)　and　SRT　(10　d),　with　satisfactory　phosphorus　removal　efficiency　(95.9%).　Both　of　ammonia　oxidizing　bacteria　(AOB)　and　nitrite　oxidizing　bacteria　(NOB)　were　elutriated　simultaneously.　Interestingly,　AOB　recovered　much　faster　than　NOB　by　a　subsequent　extension　of　aerobic　HRT　and　SRT,　resulting　in　a　rapid　development　of　PN　within　15　days.　Ammonia　oxidation　rates　of　AOB　significantly　increased　by　44.2%,　facilitating　a　high　nitrite　accumulation　rate　(NAR)　of　95.8%.　Genus　Tetrasphaera,　Halomonas,　Paracoccus　and　Candidatus_Accumulibacter　belonging　to　PAOs　accounted　for　4.6%.　The　proliferation　of　heterotrophs,　typically　as　PAOs,　maximized　the　microbial　competition　against　NOB　by　favoring　AOB　activity　and　synergy　with　functional　bacteria.