Since　the　influent　flux,　components,　contamination＇s　variety　and　concentration　of　municipal　wastewater　treatment　processes　(WWTPs)　is　passive　acceptance,　the　operation　of　municipal　WWTPs　always　stay　in　the　non-stationary　state,　which　frequently　leads　to　terrible　abnormal　conditions,　such　as　sludge　bulking.　Once　abnormal　conditions　happen,　it　will　decrease　the　efficiency　of　municipal　WWTPs　and　bring　the　problem　of　unqualified　effluent.　In　serious　cases,　the　collapse　of　municipal　WWTPs　and　even　accidents　are　caused.　Thus,　it　is　also　a　crucial　task　to　reduce　the　occurrence　of　abnormal　conditions　and　ensure　security　and　stability　of　municipal　WWTPs.　In　this　paper,　the　researches　with　respect　to　identification　and　suppression　of　abnormal　conditions　in　municipal　WWTPs　are　reviewed.　First,　we　introduce　the　back-ground　of　municipal　WWTPs　and　characteristics　of　abnormal　conditions.　Second,　the　overview　of　methods　that　identify　and　suppress　the　abnormal　conditions　is　presented.　Finally,　we　realize　the　analysis　and　summary　of　this　paper,　and　point　out　the　future　research　direction　of　identification　and　suppression　methods　for　abnormal　conditions　in　municipal　WWTPs.　Copyright　©　2018　Acta　Automatica　Sinica.　All　rights　reserved.