Advanced nitrogen removal from landfill leachate via Anammox system based on Sequencing Biofilm Batch Reactor (SBBR): Effective protection of biofilm.

•Anammox was enriched in carriers to enhance ability against adverse environment.•As influent TN was 3000mg/L, effluent TN was below 20mg/L with TN removal of 95%.•The ratio of NO3−:NH4+ fell below 0.1 in Anammox process treating real leachate.•TB-EPS of biofilm and floccule were 46% and 28%, respectively, helped form biofilm.•Anammox gene ratio of biofilm increased to 13.28%, yet floccule decreased to 3.88%.