Under　organic　stress,　the　limited　filamentous　bulking　(FB)　was　demonstrated　to　improve　anammox　capability　by　inhibiting　granule　disintegration　and　washout.　The　accumulation　of　internal　stress　played　a　more　important　role　than　the　adverse　physicochemical　properties　(low　viscoelasticity　and　hydrophobicity)　of　granules　in　limiting　granular　strength　by　consuming　the　granular　elastic　energy.　Different　from　the　floc-forming　heterotrophic　bacteria　(HB)　that　stored　its　growth　stress　as　internal　stress　by　pushing　the　surrounded　anammox　micro-colonies　outwards　under　the　spatial　constraint　of　elastic　anammox　＂shell＂,　the　filamentous　HB　grew　into　a　uniform　network　structure　within　granules,　endowed　granules　low　internal　stress　and　acted　as　the　granular　skeleton　due　to　its　rich　amyloid　substance,　which　was　benefited　from　the　elimination　of　inhomogeneous　growth　and　the　consequent　expansion　competition　for　living　space.　Combined　with　the　mechanical　instability　and　sticking-spring　models,　controlling　FB　at　limited　level　was　effective　for　improving　granular　strength　without　affecting　sludge　-water　separation.