The　substantial　discharge　of　ferroferric　oxide　nanoparticles　(Fe3O4　NPs)　into　sewage　threatens　the　survival　of　functional　microorganisms　in　wastewater　treatment.　This　study　elucidated　responses　of　anaerobic　ammonium　oxidation　(anammox)　consortia　to　inhibition　from　high　Fe3O4　NPs　concentration　and　recovery　mechanisms.　The　nitrogen　removal　efficiency　decreased　by　20.3　%　and　recovered　after　55　days　under　1000　mg/L　Fe3O4　NPs　concentration.　Toxicity　was　attributed　to　reactive　oxygen　species　(ROS)　production.　The　excessive　ROS　damaged　membrane　integrity,　nitrogen　metabolism,　and　DNA　synthesis,　resulting　in　the　inhibition　of　anammox　bacteria　activity.　However,　recovery　mechanisms　of　anammox　consortia　activity　were　activated　in　response　to　1000　mg/L　Fe3O4　NPs.　The　increase　of　heme　oxygenase-1,　thioredoxin,　and　nicotinamide　adenine　dinucleotide-quinone　oxidoreductase　genes　alleviated　oxidative　stress.　Furthermore,　the　activation　of　metabolic　processes　associated　with　membrane　and　DNA　repair　promoted　recovery　of　anammox　bacteria　activity.　This　study　provided　new　insights　into　NPs　contamination　and　control　strategies　during　anammox　process.