Potential microbiological threat to the Vistula waters by its tributaries in the vicinity of Kraków

The Vistula is the longest river in Poland. It stretches from the Silesian Beskids to the Gulf of Gdańsk. Water from the Vistula is the source of drinking water for many cities and is used in industry, and therefore its quality and microbiological purity is an important issue. The quality of water in the Vistula depends, among others, on the quality of water in its basin. The aim of this study is to assess microbiological hazard to the Vistula waters from its tributaries in the vicinity of Kraków. The analyses were carried out on 10 tributaries of the Vistula: Prądnik, Dłubnia, Drwina Długa, Drwinka, Raba, Uszewka, Szreniawa, Uszwica, Kisielina, and Dunajec. The examinations were carried out in four series, from May 2012 to March 2013. The numbers of coliforms, faecal coliforms, Enterococcus faecalis, and sulphate reducing Clostridium were determined using the membrane filtration method, while the serial dilutions method was used to determine the numbers of mesophilic and psychrophilic bacteria, Staphylococcus and Salmonella. There was a large variation in the number of microorganisms in the examined watercourses, however in most cases the water could be classified as clean, whereas waters of the Vistula in the vicinity of Kraków are microbiologically contaminated. Thus, the examined watercourses do not pose a serious threat to the quality of the Vistula. Among the analyzed tributaries, the waters of the Prądnik were characterized by the worst sanitary condition, while the best microbiological quality was observed in the Dunajec.