The　effect　of　sludge　retention　time　(SRT)　on　the　continuous-flow　system　with　enhanced　biological　phosphorus　removal　(EBPR)　granules　at　different　COD　loading　was　investigated　during　the　operation　of　more　than　220　days.　And　the　results　showed　that　when　the　system　operated　at　long　SRT　(30　days)　and　low　COD　loading　(200　mg.L-1),　it　could　maintain　excellent　performance.　However,　long　SRT　and　high　COD　loading　(300　mg.L-1)　deteriorated　the　settling　ability　of　granules　and　the　performance　of　system　and　resulted　in　the　overgrowth　of　filamentous　bacteria.　Meanwhile,　the　transformation　of　poly-beta-hydroxyalkanoates　(PHAs)　and　glycogen　in　metabolism　process　was　inhibited.　Moreover,　the　results　of　pyrosequencing　indicated　that　filamentous　bacteria　had　a　competitive　advantage　over　polyphosphate-accumulating　organisms　(PAOs)　at　high　COD　loading　and　long　SRT.　The　PAOs　specious　of　Candidatus_Accumlibater　and　system　performance　increased　obviously　when　the　SRT　was　reduced　to　20　days　at　high　COD　loading.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.