A　promising　technology　for　partial　nitritation/anammox　(PN/A)　processes　to　treat　ammonium　wastewater　is　integrated　fixed-film　activated　sludge　(IFAS).　For　practical　applications,　achieving　efficient　enrichment　of　anammox　bacteria　(AnAOB)　remains　a　challenge.　In　this　study,　membranes　were　temporarily　used　to　separate　solid　and　liquid　components　to　induce　changes　in　the　mixed　liquor　suspended　solids　of　the　flocs.　With　membrane　separation,　AnAOB　proliferated　rapidly　with　a　seven-fold　increase　in　the　maximum　specific　growth　rate　(mu)　(from　0.009　to　0.072　d-1)　and　a　three-fold　increase　in　the　nitrogen　removal　rate　(from　0.91　to　3.20　kg　N/(m3　&　sdot;d)).　Moreover,　microbial　community　analysis　showed　significant　changes　in　bacterial　species　richness　and　diversity　with　and　without　membrane　separation.　Overall,　the　regulation　of　flocs　significantly　influenced　the　microbial　community　structure　of　both　flocs　and　biofilms　leading　to　improved　nitrogen　removal　efficiency　in　the　IFAS-PN/　A　system.