Ionescu, IoanaIoanaIonescuTiron, OlgaOlgaTironBumbac, CostelCostelBumbacBadescu, ValeriuValeriuBadescuCosma, CristianaCristianaCosma2017-04-042017-04-0420151311-5065http://hdl.handle.net/123456789/690Journal of Environmental Protection and Ecology Volume 16 Issue 4With an ever increasing population, biological wastewater treatment process has a crucial importance in the world. Activated sludge can be defied as a microbial community and consists of free, flocculated and filamentous bacteria, protozoa, rotifers and other invertebrates. Many studies on the relationships between protozoa and physico-epresent an important indicator of the wastewater treatment process efficiency. At a certain concentration, heavy metals and other pollutants are toxic to most microorganisms. The protozoa community is represented by interacting organisms, including species that are sensitive, intermediate or resistant in their tolerance to pollutants. The focus of the research was to determine the effect of 3 metals (copper, chromium and zinc) on the activated sludge viability. Experiments were conducted in a continuous flow bioreactor (simulating the conditions of a WWTP) fed with real wastewater and inoculated with activated sludge obtained from a local wastewater treatment plant. Microscopic determinations were used to evaluate the diversity and dynamics of the activated sludge biocenosis community. The study emphasized that all three metals had a more or less impact on the protozoa community highlighting both the most sensitive and the most resistant species.en-USActivated sludgeWastewater treatmentHeavy metalsBiocenosisArticle