The paper presents an analysis of sewage susceptibility to biodegradation on an example of sewage treatment plant in Wodzisław Śląski in the Śląskie province. For this purpose, dependencies between selected indices of domestic sewage pollution were applied. Descriptive statistics of the respective indices rations COD/BOD5, BOD5/TN, BOD5/TP were presented. Moreover, an analysis was conducted on the composition of raw sewage flowing into the treatment plant, pre-treated sewage and sewage leaving the studied treatment plant. The analysis was carried out on the basis of three basic indices of sewage pollution (BOD5, COD and total suspended solids) and two biogenic indices (total nitrogen and total phosphorus). Tests on the sewage composition were conducted in the years 2010-2015. Basic descriptive statistics were compiled for the values of the studied indices of sewage pollution and the obtained results were interpreted. On the basis of collected material it may be said that sewage reaching the treatment plant in Wodzisław Śląski revealed a good susceptibility to biodegradation, whereas the BOD5/TN and BOD5/TP ratios were below the optimum value. ...
