Heterotrophic　denitrification　is　a　robust　and　reliable　process　for　nitrogen　removal　from　wastewater.　However,　wastewater　often　faces　the　issue　of　lacking　carbon　source.　In　this　study,　the　feasibility　of　using　primary　sludge,　a　by-product　of　wastewater　treatment　plants,　to　support　denitrification　of　high-strength　nitrite　wastewater　was　investigated.　Results　suggest　the　desired　performance　can　be　achieved　with　the　influent　nitrite　concentration　of　400　to　1200　mg　N/L,　and　the　optimal　primary　sludge　dosage　for　the　complete　nitrite　removal　was　3.6　g　VSS/g　N.　Ammonium　removal　was　also　detected　along　with　nitrite　removal.　Microbial　analysis　reveals　various　types　of　denitrifying　bacteria　and　a　large　number　of　macromolecular　organics　degrading　bacteria　existed　in　the　microbial　community.　Notably,　anammox　bacteria,　Candidarus　Brocadia,　was　also　identified　with　an　abundance　of　0.1%.　The　slow　kinetics　of　carbon　source　release　from　primary　sludge　was　likely　the　reason　for　the　existence　of　anammox　process.　This　study　developed　a　promising　nitrogen　removal　process　using　an　alternative　carbon　source　for　denitrification,　and　it　shows　great　potential　to　couple　denitrification　with　anammox　to　reduce　ammonium　residue.　(C)　2020　Elsevier　B.V.　All　rights　reserved.