Challenges　in　obtaining　stable　nitrite　have　impeded　the　use　of　anammox　in　municipal　wastewater　treatment.　This　study　explored　the　feasibility　of　using　sludge　fermentation　products　as　carbon　source　and　selective　nitrification　inhibitor　to　supply　nitrite　via　partial　nitrification　(PN)　and　partial　denitrification　(PD).　PD　was　initiated　within　15　days,　achieving　nitrite　transformation　rate　of　over　90　%　with　a　carbon/nitrogen　ratio　of　3　and　a　reaction　time　of　0.75　h.　The　dominant　genus,　Romboutsia,　increased　in　relative　abundance　from　4.1　to　35　%.　Organic　acids　in　sludge　fermentation　products,　like　acetate　(200　mg/L)　and　propionate　(400　mg/L),　selectively　suppressed　nitriteoxidizing　bacteria　(NOB)　more　than　ammonia-oxidizing　bacteria　(AOB),　leading　to　PN.　Combining　anaerobic　exposure　with　sludge　fermentation　products　addition　achieved　PN　with　over　80.0　%　nitrite　accumulation.　AOB　increased　tenfold　in　the　long　term,　significantly　outpacing　NOB　growth.　This　strategy　simplifies　difficulty　of　anammox　application　and　shows　broad　application　potential　in　municipal　wastewater　treatment.