Anaerobic　ammonium　oxidation　(anammox)　has　great　potential　to　be　applied　to　the　process　of　nitrogen　removal　from　mainstream　wastewater.　However,　directly　applying　complete　anammox　to　the　mainstream　is　typically　hindered　by　low　temperatures,　a　low　ammonia　concentration,　and　high　organic　matter　concentrations.　Directly　integrating　anammox　into　mainstream　treatment　by　enhancing　the　in-situ　enrichment　of　anammox　bacteria　in　wastewater　treatment　plants　(WWTPs)　could　effectively　improve　the　nitrogen　removal　efficiency　and　reduce　the　treatment　cost.　A　certain　anammox　bacteria　abundance　in　full-scale　WWTPs　provides　the　feasibility　of　directly　integrating　anammox　into　mainstream　treatment　and　realizing　partial　mainstream　anammox.　The　technical　development　status　of　partial　anammox　and　the　mechanisms　of　achieving　partial　mainstream　anammox　by　aeration　and　organic　control　are　summarized.　This　review　provides　an　enhanced　understanding　of　this　novel　technical　route　of　partial　mainstream　anammox　treatment　for　improving　the　quality,　performance,　and　prospects　for　this　technology　to　be　used　in　upgrading　WWTPs.　©　2022　Elsevier　Ltd