Partial　denitrification　(PD)　provides　a　promising　approach　of　efficient　and　stable　nitrite　(NO2−-N)　generation　for　annamox.　In　this　study,　the　feasibility　of　short-term　sludge　anaerobic　fermentation　driving　PD　was　evaluated.　It　was　found　that　a　higher　NO2−-N　accumulation　in　nitrate　(NO3−-N)　reduction　was　obtained　with　the　5-days　fermented　sludge　compared　to　8　and　15-days　fermentation.　Moreover,　compared　to　acetate　as　carbon　source,　sludge　fermentation　products　(SFPs)　induced　the　higher　NO2−-N　production　with　nitrate-to-nitrite　transformation　ratio　(NTR)　nearly　100　%.　Denitrification　activity　of　fermented　sludge　were　obviously　improved　with　SFPs　as　electron　donor.　Metagenomic　analysis　revealed　that　Thauera　was　the　dominant　bacteria,　which　was　assumed　to　be　the　key　contributor　to　PD　performance　by　harboring　the　highest　narGHI　and　napAB　but　much　lower　nirS　and　nirK.　Under　the　conditions　of　SFPs　and　fermented　sludge,　Thauera　was　speculated　to　have　higher　resistance　than　other　denitrifiers　attributed　to　versatile　carbon　metabolic　capabilities　utilizing　SFPs　with　the　significantly　improved　genes　for　metabolism　of　complex　organic　carbon　via　glycolysis　after　anaerobic　fermentation.　A　novel　integration　of　sludge　fermentation　driving　PD　and　anammox　for　mainstream　wastewater　treatment　and　sidestream　polishing　was　proposed　to　offer　a　promising　application　with　reduced　commercial　carbon　source　consumption　and　waste　sludge　reduction.　©　2023　Elsevier　B.V.