A　UASB　inoculated　with　PDA　sludge　initiated　by　anammox　bacteria　self-enrichment　was　used　to　gradually　increase　the　influent　nitrogen　concentration　from　20mg/L　to　100mg/L　at　25°C　down　to　19°C　(the　nitrogen　load　increased　from　3.2g/(m3·d)　to　4.0g/(m3·d)).　The　reactor　was　operated　for　115　days　with　a　maximum　total　nitrogen　removal　efficiency　of　89.9%.　16S　rRNA　gene　sequencing　results　showed　that　Candidatus　Brocadia　as　the　main　anammox　functional　bacterium　reached　3.7%　abundance　in　the　bio-carriers　and　the　partial　denitrifying　functional　bacterium　Thaurea　reached　a　maximum　abundance　of　15.7%　in　the　floc　sludge.　Metagenomic　analysis　showed　that　the　genes　Nar　and　Nap,　associated　with　partial　denitrification,　and　Nir,　Hzs　and　Hdh,　associated　with　anammox,　were　fully　expressed.　©　2024　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.