Aim of the study:
The aim of the study was to assess the effectiveness of biological wastewater treatment in the process of eliminating sanitary indicators at the Biological Sewage Treatment Plant in Piwniczna Zdrój.

Material and methods:
The microbiological analyses included determinations of the following types of bacteria: the coliforms, Escherichia coli, faecal enterococci, Salmonella spp., Shigella spp. and Clostridium perfringens. The standard dilution method was used for determination of indicator bacteria (using from seven to ten dilutions).

Results and conclusions:
The degree of contamination of raw sewage with sanitary indicators was comparable during all research series. During biological wastewater treatment, the elimination of the studied indicators was very high and remained at the level of 85-100%. The conducted analyzes indicate that the tested sewage treatment plant works at a high level of elimination of microbial contaminants.