The course is designed for students with an interest in the world of microorganisms and the methods used to study them using microscopy. The aim of the course is to practise methods of sampling and assessing the abundance of ciliated protozoa; observation of live protozoa; culturing and staining methods; silver impregnation and permanent preparations; identification of major groups of protozoa; microphotography and computer image analysis. Use of protozoa to assess the degree of water pollution, in laboratory experiments, in school biology classes. Assessment of the quality of activated sludge based on the composition of the biocenosis and the presence of filamentous bacteria, using the Madoni biotic index and the Eikelboom method.