Endogenous　denitrification　(ED)　is　an　effective　approach　to　achieve　advanced　nitrogen　removal　for　low　COD/N　(C/N)　municipal　wastewater,　in　which　internal　carbon　sources　are　used　for　denitrification.　However,　phosphorus-accumulating　organisms　(PAOs)　and　denitrifying　ordinary　heterotrophic　organisms　(DOHOs)　outcompeting　glycogen-accumulating　organisms　(GAOs)　for　carbon　sources　decreases　total　inorganic　nitrogen　(TIN)　removal　efficiency.　This　study　proposed　a　novel　side-stream　sludge　treatment　strategy,　i.e.,　through　phosphorus　famine,　to　selectively　strengthen　GAOs.　Two　sequencing　batch　reactors　(SBR)　were　used,　with　one　served　as　an　anaerobic/aerobic/anoxic　SBR　(AOA-SBR)　and　the　other　as　a　side　SBR.　Side-stream　phosphorus　famine　treatment　was　conducted　three　times　during　140　days’　experiment,　of　which　20–30%　of　the　sludge　collected　from　the　AOA-SBR　was　imposed　to　phosphorus　famine　condition　in　the　side　SBR　for　4　days　(24　cycles).　Results　showed　that　the　average　TIN　and　phosphorus　removal　efficiencies　were　88.76%　and　95.31%,　and　the　average　TIN　and　phosphorus　in　the　effluent　were　8.01　and　0.30　mg/L,　respectively,　treating　low　C/N　(~3.25)　municipal　wastewater　in　the　AOA-SBR.　The　relative　abundance　of　PAOs　decreased　from　3.23%　to　2.15%　and　that　of　DOHOs　reduced　by　62.78%.　In　contrast,　the　abundance　of　GAOs　increased　from　3.09%　to18.25%,　which　should　be　the　key　reason　for　the　improvement　of　the　ED　efficiency.　Moreover,　the　enrichment　of　GAOs　promoted　ED　simultaneously　using　glycogen　and　poly-β-hydroxyalkanoates　(PHA)　as　carbon　sources.　The　strategy　of　side-stream　treatment　proved　the　potential　of　rapid　proliferation　of　GAOs　while　achieving　improved　nitrogen　removal.　©　2021　Elsevier　B.V.