The aim of the present work was to assess the functioning of the integrated treatment process of surface water in the Water Treatment Plant (ZUW) in Jarosław between 2008–2015. The application of factor analysis made it possible to reduce the number of random variables down to the set described by four principal components, including two variables related to the bacteriological quality of water. It was observed that the removal of the component bacteria in 2011–2015 (after the modernization of the Water Treatment Plant), during the filtration and disinfection process, was 100% effective. Microfiltration membranes with a nominal pore size of 0.1 μm proved effective in removing both protozoa and pathogenic bacteria from the captured water. The use of the microfiltration technique in the coagulation-integrated system has increased the effectiveness of the conventional disinfection of surface water.