The　application　of　partial　mainstream　anaerobic　ammonium　oxidation　(anammox)　technology　for　nitrogen　removal　from　low　carbon-to-nitrogen　ratio　municipal　wastewater　offers　significant　technical　and　economic　benefits.　However,　the　lack　of　clear　recurrence　patterns　and　unclear　external　regulation　strategies　has　resulted　a　delay　in　identification　of　the　anammox　phenomenon　in　actual　wastewater　treatment　plants　(WWTPs).　The　further　optimization　and　scaling　up　of　this　technology　face　bottlenecks.　Therefore,　it　is　crucial　to　predict　and　estimate　the　contribution　of　anammox　to　nitrogen　removal　from　the　partial　mainstream　anammox　process.　This　paper　summarizes　the　abundance　and　activity　of　anaerobic　ammonia-oxidizing　bacteria　(AnAOB)　in　WWTPs　and　provides　a　baseline　for　predicting　anammox　contribution　(15.9　%-37.5　%).　Furthermore,　anammox　feature　method,　anammox　absence　method,　and　anammox　presence　method　for　estimating　anammox　contributions　are　introduced.　Meanwhile,　the　advantages,　disadvantages　and　feasibility　of　in-situ　and　ex-situ　testing　are　explained.　In　terms　of　outlook　and　future　trends,　machine　learning,　microfluidic　technology,　and　synthetic　biology　are　proposed　for　accurate　quantification　of　anammox　contributions.