Partial　nitrification　(PN)　and　high　glycogen　accumulating　metabolism　(GAM)　activity　are　the　basis　for　efficient　nitrogen　(N)　and　phosphorus　(P)　removal　in　simultaneous　nitrification　endogenous　denitrification　and　phosphorus　removal　(SNDPR)　systems.　However,　achieving　these　processes　in　practical　operations　is　challenging.　This　study　proposes　that　light　irradiation　is　a　novel　strategy　to　enhance　the　nutrient　removal　performance　of　the　SNDPR　system　with　low　carbon　to　nitrogen　ratios　(C/N　of　3.3–4.1)　domestic　wastewater.　Light　energy　densities　(Es)　of　55–135　J/g　VSS　were　found　to　promote　the　activity　of　ammonia-oxidizing　bacteria　(AOB)　and　GAM,　while　inhibiting　the　activity　of　nitrite-oxidizing　bacteria　(NOB)　and　polyphosphate　accumulating　metabolism　(PAM).　Long-term　exposure　to　different　light　patterns　at　Es　of　55–135　J/g　VSS　revealed　that　continuous　light　rapidly　achieved　PN　by　inhibiting　NOB　activity　and　promoted　the　growth　of　glycogen　accumulating　organisms　(GAOs),　allowing　the　removal　of　above　82　%　N　and　below　80　%　P.　Intermittent　light　maintained　stable　PN　by　inhibiting　the　activity　and　growth　of　NOB　and　promoted　the　growth　of　polyphosphate　accumulating　organisms　(PAOs)　with　high　GAM　activity　(Accmulibacer　IIC-ii　and　IIC-iii),　allowing　the　removal　of　above　82　%　N　and　95　%　P.　Flow　cytometry　and　enzyme　activity　assays　showed　that　light　promoted　GAM-related　enzyme　activity　and　the　metabolic　activity　of　partial　Accmulibacer　II　over　other　endogenous　denitrifying　bacteria,　while　inhibiting　NOB　translation　activity.　These　findings　provide　a　new　approach　for　enhancing　nutrient　removal,　especially　for　achieving　PN　and　promoting　GAM　activity,　in　SNDPR　systems　treating　low　C/N　ratio　domestic　wastewater　using　light　irradiation.　©　2023