The　rapid　growth　of　nitrite-oxidizing　bacteria　(NOB)　in　reactor　prevents　the　application　of　anaerobic　ammonium　oxidation　(anammox)　technology　to　main-stream　wastewater　treatment.　How　to　eliminate　NOB　and　reserve　anaerobic　ammonium　oxidation　bacteria　(AnAOB)　simultaneously　becomes　the　biggest　challenge.　In　this　study　two　coupled　biological　aeration　filters　(BAFs)　were　built　up　to　treat　domestic　sewage.　In　BAF1　nitrogen　removal　concentration　was　21.4　mg/L　via　heterotrophic　denitrification　pathway.　Backwash　was　conducted　to　BAF2　to　improve　nitrogen　removal　performance.　After　backwash　Nitrospira　proportion　declined　from　10.8%　to　2.1%,　while　Candidatus　Kuenenia　percentage　increased　from　5.6%　to　10.2%.　Nitrogen　removal　concentration　improved　from　8.6　mg/L　to　22.8　mg/L　via　anammox　pathway　in　BAF2,　and　total　nitrogen　removal　concentration　reached　to　44.2　mg/L　in　two　coupled　BAFs　during　aeration　process.　These　findings　could　provide　a　new　strategy　for　the　application　of　anammox　technology　to　main-stream　wastewater　treatment.