Denitrifying　phosphorus　removal　(DPR)　technology　is　one　of　the　most　effective　approach　to　simultaneously　realize　nitrogen　(N)　and　phosphorus　(P)　removal　from　low　COD/N　ratio　wastewater.　Identifying　the　interaction　of　denitrifying　phosphate-accumulating　organisms　(DPAOs),　denitrifying　glycogen　organisms　(DGAOs)　and　denitrifying　ordinary　heterotrophic　organisms　(DOHOs)　is　critical　for　optimizing　denitrification　and　anoxic　P　uptake　efficiency　in　DPR　processes.　In　this　study,　a　novel　DPR　system　of　anaerobic　anoxic　oxic　-biological　contact　oxidation　(AAO-BCO)　was　employed　to　dispose　actual　sewage　with　various　influent　COD/N　ratios　(3.5-6.7).　High　efficiency　of　TIN　(76.5%)　and　PO43--P　(94.4%)　removal　was　observed　when　COD/N　ratio　was　between　4.4　and　5.9.　At　the　COD/N　ratio　of　5.7　+/-　0.2,　prominent　DPR　performance　was　verified　by　the　superior　DPR　efficiency　(88.7%)　and　anoxic　phosphorus　uptake　capacity　(PUADPAOs/Delta　TIN　=　1.84　mg/mg),　which　was　further　proved　by　the　preponderance　of　DPAOs　in　C,　N　and　P　removal　pathways.　GAOs　have　a　competitive　advantage　over　PAOs　for　COD　utilization　at　low　COD/N　ratio　of　3.7　+/-　0.2,　which　further　limited　the　N　removal　efficiency.　High　proportion　of　N　removal　via　DOHOs　(21.2%)　at　the　COD/N　ratio　of　6.5　+/-　0.2　restrained　the　DPR　performance,　which　should　be　attributed　to　the　outcompete　of　DOHOs　for　NO3-.　The　nutrient　removal　mechanisms　were　explicated　by　stoichiometric　calculation　methodology　to　quantify　the　contribution　of　diverse　functional　microorganisms,　contributing　to　improving　the　robustness　of　AAO-BCO　system　when　facing　the　fluctuation　of　influent　carbon　source　concentration.　(C)　2021　Elsevier　B.V.　All　rights　reserved.