This　study　proposed　a　novel　strategy　for　achievement　of　partial　denitrification　driven　by　endogenous　car-bon　sources　in　an　anaerobic/anoxic/aerobic　activated　sludge　system.　Results　showed　that　in　the　steady-stage,　the　nitrate-to-nitrite　transformation　ratio　(NTR)　was　kept　at　around　87%　without　nitrate　in　the　effluent.　During　the　anaerobic　period,　exogenous　carbon　sources　was　completely　taken　up,　accompanied　by　the　consumption　of　glycogen　and　production　of　polyhydroxyalkanoates　(PHAs).　During　the　anoxic　per-iod,　nitrate　was　reduced　to　nitrite　by　using　PHAs　as　carbon　sources,　followed　by　the　replenishment　of　glycogen.　Thus,　the　phenotype　of　denitrifying　GAOs　was　clearly　observed　and　endogenous　partial　denitrification　(EPD)　occurred.　Furthermore,　results　showed　the　nitrate　reduction　was　prior　to　the　nitrite　reduc-tion　in　the　presence　of　nitrate,　which　led　to　the　high　nitrite　accumulation.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.