Achieving　nitrite　accumulation　via　partial　denitrification　(PD)　is　a　novel　technique　to　supply　sufficient　nitrite　for　the　anammox　process　which　is　used　to　treat　carbon-limited　wastewater.　Rapid　initiation　of　PD　through　pH　control　was　developed　in　this　pilot-scale　study　and　the　optimum　C/N　ratio　was　investigated.　The　startup　strategy　is　proposed　based　on　a　lab-scale　experiment　reported　in　this　work　in　which　a　high　rate　of　nitrate　reduction　and　an　efficient　nitrate-to-nitrite　transformation　ratio　(NTR)　could　be　simultaneously　achieved　at　the　pH　of　9.0.　Two　pilot-scale　reactors　(100　L),　with　one　serving　as　an　experimental　reactor　and　the　other　as　a　control,　were　used　to　determine　the　pH　effect　on　the　start-up　of　the　PD　process.　In　the　experimental　reactor,　the　initial　pH　of　9.0　was　applied　at　the　beginning　of　mixing　in　each　cycle.　Results　showed　that　the　PD　process　was　rapidly　established　within　100　cycles　with　an　average　NTR　of　83.86%,　whereas　the　control　reactor　achieved　PD　after　250　cycles.　Moreover,　the　effect　of　C/N　ratios　on　the　PD　process　was　investigated　and　the　result　showed　that　the　optimum　C/N　ratio　was　2.5　with　both　the　NTR　and　nitrate　reduction　ratio　(NRR)　exceeding　80%.　High-throughput　sequencing　results　demonstrated　that　Thauera,　possibly　a　functional　bacterium　for　the　partial　denitrification　process,　was　dominant　on　the　genus　level　and　accounted　for　over　65%　of　the　microbial　community　in　both　PD　reactors.　The　strategy　for　establishing　the　partial　denitrification　process　can　be　easily　achieved　through　long-term　stable　nitrite　accumulation.　PD　can　be　integrated　with　anammox　to　improve　nitrogen　removal　in　an　energy-saving　mode.