Аннотация:The aim of this study was the identification of activated sludge algae and
cyanobacteria as biomarkers for the state of the activated sludge at biological treatment plants in the territory of the Republic of Bashkortostan. We have identified changes in dominating species complexes. We have identified 11 species at two or more treatment plants. 4 groups have been identified at biological treatment plants in the Republic of Bashkortostan: Cyanobacteria (Microcystis, Oscillatoria, Phormidium, Spirulina, Synechocystis); Diatoms (Cyclotella, Stephanodiscus, Diatoma, Navicula); Euglena (Euglena, Trachelomonas); the Green
(Chlamydomonas, Chlorella, Oocystis). Our results were compared with those of assessing the state of the activated sludge using bioestimators.