EN
There were run comparative investigations over water samples coming from different water drains of Nida river by Korczyn Stary and of Koszarawa river by Żywiec, gathered between November 2005 and May 2006. The rivers differ each other by microbiological purity level, but both were the water source for water treatment process, subsequently a potable water source for consumers. In the water samples there was determined numerosity of mesophilic, psychrophilic and coli group bacteria, respecting the Polish Standards. At both locations water samples were taken in the first place from rivers, later at particular treatment steps, the last sampling point was located at final consumers'. It was stated that water treatment process was run correctly, proved by decreasing number of investigated microorganisms, at particular water treatment steps for both water treatment plants.