Like　the　lethal　cardiovascular　embolism　in　humans,　the　serious　blockage　of　the　mass　transfer　channel　can　inactivate　anammox　granular　sludge　(AnGS).　Also　like　the　therapeutic　thrombolysis　in　humans,　the　remediatory　dredging　of　the　mass　transfer　channel　can　sustain　the　function　of　AnGS.　In　this　study,　the　ultrasound　was　thus　explored　to　remediate　the　embolism　of　AnGS.　It　turned　out　that　Low-Intensity　Ultrasound　(LIU)　with　an　energy　density　of　5.6　kJ/(g-VSS·cm2)　was　optimal　to　achieve　an　obvious　increase　in　specific　anammox　activity　of　AnGS　by　34.8%　to　420.3　mg-N/(g-VSS·d).　The　improved　mass　transfer　of　AnGS　and　cell　membrane　permeability　of　anammox　bacteria　(AnAOB)　was　revealed　to　mainly　contribute　to　the　enhanced　activity.　After　treatment　with　LIU　under　optimal　conditions,　the　mass　transfer　efficiency　of　AnGS　was　improved　by　26.9%　with　enhanced　permeability,　and　the　proportions　of　pores　larger　than　50　μm　in　the　surface　layer　of　AnGS　increased　by　13.7%　evidenced　by　the　micro-CT　observation.　Correspondingly,　the　permeability　of　AnAOB　was　increased　by　inducing　instantaneous　pores　on　the　cell　membrane,　thus　stimulating　the　metabolism　by　6.9%.　Further　analysis　demonstrated　that　LIU　was　capable　of　breaking　the　hydrogen　bonds　of　protein　in　the　EPS　and　loosening　its　spatial　structure,　which　would　benefit　the　partially　exfoliation　and　dissolution　of　EPS　and　resulted　in　enlarging　and　dredging　pores,　thus　relieving　the　embolism　of　AnGS.　Consequently,　the　results　of　this　study　could　deepen　the　understanding　of　granules　treated　by　ultrasound　and　also　provide　a　promising　technique　for　raising　the　ceiling　of　nitrogen　removal　performance　by　AnGS.　©　2022