EN
This paper includes the results of research on indicatory microorganisms of contamination (TVC 20°C, TVC 37°C) and sanitary (TC, FC, FS, Clostridium perfringens) states in water-bearing formations (without isolation from the surface) of the Omulewski aquifer in Mazuria, Poland, conducted from 1988 to 1993. Less bacteriological contamination was characteristic of water from wells in a partly (Janowo) or entirely (Sedańsk, Narty) forested area, at a depth of 38-40 m. Greater contamination was discovered in the area of large cattle and hog farms (Dzierzki, Wesołowo, Wielbark, Przezdzięk, Baranowo, Wyżegi). In this area less bacteriological contamination occurred in water from deeper wells (to 64 m), whereas water contamination from shallow boreholes (6.8-23.5 m) was higher. Most well-water samples taken from the forested area fulfilled sanitary and bacteriological requirements for drinking water. The percentage of well-water samples which would fulfill sanitary and bacteriological requirements was smaller for farming areas. The most severe contamination was discovered in water samples from shallow boreholes at a cattle farm in Wesołowo.