In　an　anammox　biofilm　reactor,　long-term　operation　inevitably　leads　to　the　repeated　formation　of　localized　dead　zones.　Once　these　dead　zones　(DZs)　occur,　the　anammox　reactor＇s　nitrogen　removal　efficiency　is　severely　reduced.　However,　the　mechanisms　and　intrinsic　reasons　for　the　transformation　of　DZs　remain　unexplored.　In　this　study,　the　pilot-scale　biofilters　were　classified　into　biologically　active　zones　(BZs),　transition　zones　(TZs),　and　DZs.　The　results　indicated　that　microbial　communities　undergo　accelerated　succession　from　the　TZ.　Biofilms　respond　to　environmental　stress　from　the　DZs　by　altering　the　levels　of　signaling　molecules,　triggering　a　series　of　cascading　reactions.　These　reactions　alter　the　abundance　of　genes　involved　in　nitrogen　removal,　promote　substance　transformation,　and　speed　up　the　succession　of　microbial　communities.　This　study　demonstrates　the　objectives　and　self-healing　mechanisms　of　the　anammox　biofilm　process　in　the　presence　of　dead　zones,　which　could　support　the　long-term　application　of　anammox　technology.　©　2024　Elsevier　Ltd