Microbial core communities in activated sludge plants are strongly affected by immigration and geography

The study is the first comprehensive investigation of WWTPs in a confined geographical area providing new insights in our understanding of activated sludge microbiology by introducing a concept of combining immigration and growth calculation with identifying core and CRAT to reveal the true ecosystem-critical organisms. Additionally, the clear biogeographical pattern on this scale highlights the need for more region-level studies to find regional process-critical taxa (core and CRAT), especially at species and amplicon sequence variant (ASV) level.