High　levels　of　organics　negatively　affect　Anammox　for　treating　landfill　leachate.　To　enhance　the　ability　of　Anammox　to　survive　against　adverse　environments,　a　lab-scale　two-stage　Anammox　system　using　a　Sequencing　Biofilm　Batch　Reactor　was　applied　to　treat　mature　landfill　leachate　under　35　degrees　C.　Over　107　days,　with　influent　total　nitrogen　(TN)　and　chemical　oxygen　demand　(COD)　concentrations　of　3000　+/-　100　and　3000　+/-　100　mg/L,　effluent　TN　was　below　20　mg/L.　For　extracellular　polymeric　substance　(EPS)　of　Anammox,　slime-EPS　and　loosely-bound-EPS　of　floccules　were　both　higher　than　biofilm,　while　tight-bound-EPS　of　biofilm　was　significantly　higher,　contributing　to　biofilm　formation.　Quantitative　microbial　analysis　showed　that　as　influent　COD　increased,　Anammox　gene　ratios　of　biofilm　increased　from　1.34%　to　13.28%;　the　gene　ratios　of　floccule　first　increased,　then　decreased　to　3.88%.　This　indicated　that　Anammox　and　heterotrophic　bacteria　could　coexist　because　of　the　biofilm,　leading　to　stable　nitrogen　removal　performance,　even　when　organics　were　present.　(C)　2016　Published　by　Elsevier　Ltd.