Candidatus　Accumulibacter　has　been　identified　as　dominant　polyphosphate-accumulating　organisms　(PAOs)　in　enhanced　biological　phosphorus　(P)　removal　(EBPR)　from　wastewater.　This　study　revealed　the　relevance　of　community　structure,　abundance　and　seasonal　population　dynamics　of　Candidatus　Accumulibacter　to　process　operation　of　wastewater　treatment　plants　(WWTPs)　in　China　using　ppk1　gene　as　phylogenetic　marker.　All　sludge　samples　had　properties　of　denitrifying　P　removal　using　nitrate　as　an　electron　acceptor.　Accumulibacter　abundance　in　the　anaerobic-anoxic-oxic　(A(2)O)　process　was　the　highest　(26%　of　total　bacteria),　and　higher　in　winter　than　in　summer　with　a　better　EBPR　performance.　Type-II　was　the　dominant　Accumulibacter　in　all　processes,　and　type-I　accounted　for　a　small　proportion　of　total　Accumulibacter.　The　abundance　of　Clade-IIC　as　the　most　dominant　clade　reached　2.59　x　10(9)　cells/g　MLSS　and　accounted　for　87.3%　of　total　Accumulibacter.　Clade　IIC　mainly　contributed　to　denitrifying　P　removal.　Clades　IIA,　IIC　and　IID　were　found　in　all　processes,　while　clade-IIF　was　only　found　in　oxidation　ditch　process　through　phylogenetic　analysis.　High　proportion　of　clade　IID　to　total　Accumulibacter　led　to　poor　performance　of　aerobic　P-uptake　in　inverted　A(2)O　process.　Therefore,　Accumulibacter　clades　in　WWTPs　were　diverse,　and　EBPR　performance　was　closely　related　to　the　clade-level　community　structures　and　abundances　of　Accumulibacter.　(C)　2017　The　Research　Center　for　Eco-Environmental　Sciences,　Chinese　Academy　of　Sciences.　Published　by　Elsevier　B.V.