An　integrated　process　of　sludge　in-situ　fermentation,　biological　phosphorus　removal　and　endogenous　denitrification　(ISFPR-ED)　was　developed　to　treat　low　ratio　of　chemical　oxygen　demand　to　nitrogen　(COD/N)　wastewater　and　waste　activated　sludge　(WAS)　in　a　single　reactor.　Nutrient　removal　and　WAS　reduction　were　achieved　due　to　Tetrasphaera-dominated　sludge　fermentation　provided　organic　carbon　in　extending　the　anaerobic　duration.　The　WAS　reduction　efficiency,　effluent　orthophosphate　(PO43--P)　and　total　inorganic　nitrogen　reached　28.1　%,　less　than　0.4　and　7.2　mg/L,　respectively.　While　organic　carbon　was　reduced　by　67　%.　Tetrasphaera,　conventional　polyphosphate　accumulating　organisms　(PAOs)　stored　glycogen,　amino　acids,　and　PHA　for　nutrient　removal.　Excess　energy　from　fermentation　enhanced　anaerobic　PO43--P　uptake　by　Tetrasphaera.　Tetrasphaera　was　the　dominant　PO43--P　removal　and　fermentation　bacteria,　working　synergistically　with　conventional　PAOs　and　fermenting　microorganisms.　This　integrated　process　improves　nutrient　removal　efficiency　and　reduces　operating　costs　for　carbon　addition　and　WAS　disposal　in　wastewater　treatment.