The　biotransformation　of　triclosan　(TCS)　during　wastewater　treatment　occurred　frequently,　while　little　researches　are　known　the　identity　of　microorganisms　involved　in　the　biodegradation　process.　In　this　work,　DNA-based　stable　isotope　probing　(DNA-SIP)　was　occupied　to　investigate　the　TCS　assimilation　microbes　originated　from　a　full-scale　cyclic　activated　sludge　system　in　Beijing.　Results　of　TCS　removal　pathway　showed　that　the　TCS　removal　in　nitrification　process　was　mainly　contributed　by　the　metabolism　of　heterotrophic　bacteria,　accounting　for　about　18.54%.　DNA-SIP　assay　indicated　that　Sphingobium　dominated　the　degradation　of　TCS.　Oligotyping　analysis　further　indicated　that　oligotype　GCTAAT　and　ATGTTA　of　Sphingobium　played　important　roles　in　degrading　TCS.　Furthermore,　the　Kyoto　Encyclopedia　of　Genes　and　Genomes　functional　abundance　statistics　based　on　PICRUSt2　showed　that　glutathione　transferase　was　the　most　prevalent　enzyme　involved　in　TCS　metabolism,　and　TCS　might　be　removed　through　microbial　carbon　metabolism.　Metagenomics　made　clear　that　Sphingobium　might　play　irrelevant　role　on　the　propagation　of　antibiotics　resistance　genes　(ARGs),　even　though,　it　could　degrade　TCS.　Thauera　and　Dechloromonas　were　identified　as　the　key　hosts　of　most　ARGs.　This　study　revealed　the　potential　metabolic　pathway　and　microbial　ecology　of　TCS　biodegradation　in　nitrification　process　of　wastewater　treatment　system.　©　2020　Elsevier　B.V.