There is a need for quality control of wastewater introduced into drainage systems. Physical and chemical analyses of wastewater inform only about the situation existing at the moment of sampling. The analysis based on bioindication methods allows to evaluate the existing state before sampling and so to recognize a drop of excessive loads or harmful substances for activated sludge. This refers to the moment preceding the sample taking at least by the generation time of the species with the lowest reproduction rate. For these reasons, the possibility of using microfauna representatives (feeding on organic pollutions) for bioindication was evaluated. The estimation was made of the usefulness of indicator species from the Kolkwitz-Marssori system, the Shannon-Wiener index based on species abundance and the latter based on abundances of morphological-functional organism groups. The study results showed that the ShannonWiener index calculated for morphological-functional groups (easiest to determine) was accurate enough for bioindication.