Autotrophic　denitrification　has　become　the　main　contributor　to　the　nitrogen　removal　from　wastewater　due　to　its　high　efficiency,　safety　and　economy.　Effect　of　Fe　on　sulfur　autotrophic　denitrification　coupled　to　heterotrophic　denitrification　was　investigated　to　enhance　the　nitrogen　removal.　Under　the　substrate　ratios　of　S2O32-:Fe　(II):CH3COO–　of　1:1:3,　1:3:1　and　3:1:1,　the　microorganisms　were　wrapped　by　Fe　minerals,　and　the　normal　metabolic　pathways　were　blocked.　By　adjusting　the　substrate　ratios　of　S2O32-:CH3COO–　of　1:3,　2:2　and　3:1　without　Fe　(II),　the　denitrification　recovered　with　the　removal　efficiency　of　NO3–-N　to　99%.　Insufficient　addition　of　S2O32-　and　CH3COO–　promoted　the　production　of　NO2–-N　and　N2O　with　high　percentage　of　N2O　of　5.70%.　When　S2O32-　and　CH3COO–　were　sufficient,　the　nitrogen　removal　was　effective　and　N2O　production　was　low　(1.35%).　Modified　Blotzman　model　and　Logistic　model　were　suitable　to　describe　the　removal　of　NO3–-N,　modified　Logistic　model　was　suitable　to　reveal　the　generation　of　SO42-.　Dechloromonas　acted　as　denitrifying　bacteria　in　substrate　ratios　of　S2O32-:CH3COO–　of　1:3　and　3:1　up　to　58%　and　56%　at　the　genus　level.　Autotrophic　Thiobacillus　bacteria　decreased　from　19%　(inoculated　sludge)　to　1%　(1:3),　16%　(2:2)　and　17%　(3:1),　respectively.　Thauera　was　corresponded　to　the　heterotrophic　denitrification　which　was　successfully　enriched　from　0　(inoculated　sludge)　to　13%　(1:3),　49%　(2:2)　and　2%　(3:1).　The　different　substrate　ratios　promoted　the　coexistence　of　autotrophic　and　heterotrophic　bacteria　and　cooperated　with　Fe　minerals　to　improve　nitrogen　removal　from　wastewater.　©　2021　Elsevier　B.V.