Effects of precipitation on the amount and quality of raw sewage entering a sewage treatment plant in Wodzisław Śląski

The study presents the effects of precipitation on the amount and quality of raw sewage entering a sewage treatment plant in Wodzisław Śląski. It covers a six-year period between January 2010 and December 2015. The research period was divided into seven classes of precipitation intensity. The classes were characterized for their basic descriptive statistics of the raw sewage entering the investigated sewage treatment plant (STP). Data obtained from the collected material and derived from an analysis indicated a considerable influence of precipitation on the amount of sewage entering the investigated facility. Mean amount of sewage entering the STP was by 10.5% (884.9 m3·d-1) greater in B class and by 69.6% (6,153.9 m3·d-1) greater in G class than during dry weather. Individual classes of precipitation intensity were compared for their mean values of raw sewage contamination. Precipitation intensity was found to significantly affect concentrations of the investigated parameters of raw sewage contamination. Basic parameters of sewage contamination (BOD5, CODCr, total suspended solids) were determined and their basic descriptive statistics, such as median, mean, minimum and maximum value, standard deviation and coefficient of variation were calculated