Rapid　start-up　of　partial,　nitrification　is　of　great　significance　for　subsequent　denitrification　and　the　anammox　process;　however,　slow　nitritation　hinders　the　application　of　these　processes.　The　current　study　presents　a　novel　strategy　for　achieving　nitritation　using　aerobic　starvation　and　controlling　sludge　retention　time　(SRT).　Activated　sludge　with　a　high　level　of　complete　nitrification　was　introduced　into　an　aerated　reactor　without　feeding　to　start　the　aerobic　starvation.　The　results　showed　that　nitritation　was　rapidly　achieved,　while　the　shorter　SRT　(15　days)　guaranteed　the　stability　of　nitritation　with　an　average　nitrite　accumulation　ratio　(NAR)　of　More　than　95%.　The　activity　recovery　rates　of　ammonium-oxidizing　bacteria　(AOB;　from　0.20　+/-　0.00　d(-1)　to　0.29　+/-　0:08　d(-1))　were　higher　than　those　of　nitrite-oxidizing　bacteria　(NOB;　-0.11　+/-　0.02　d(-1)　to　0.16　+/-　0.05　d(-1))　during　the　reactivation　periods.　Furthermore,　the　transcriptional　responses　of　amoA　and　hao　mRNA　after　aerobic　starvation　were　faster　than　that　of　the　nxrB　gene,　which　explained　the　fast　occurrence　of　nitritation　after　the　aerobic　starvation　period.　The　quantitative　real-time　PCR　(qPCR)　analysis　showed　that　the　cell　number　of　nitrifying　bacteria　remained　stable　during　the　starvation　process,　whereas　the　AOB　population　gradually　became　dominant　over　that　of　NOB　in　the　reactivation　period.　These　observations　strongly　supported　the　feasibility　of　accelerating　the　establishment　of　nitritation　using　aerobic　starvation.