Impact of heavy metals on the viability of activated sludge

With 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.