The Key Laboratory of Resources and Environmental Systems Optimization;
Ministry of Education;
College of Environmental Science and Engineering;
North China Electric Power University;
Beijing 102206;
China;
CAS Center for Excellence in Biotic Interactions;
University of Chinese Academy of Sciences;
Beijing 100049;
China;
The Key Laboratory of Water and Sediment Sciences;
Ministry of Education;
College of Environmental Sciences and Engineering;
Peking University;
Beijing 100871;
China;
Ammonia-oxidizing bacteria; Ammonia-oxidizing archaea; Transcriptional activity; Community structure; Wastewater treatment system;