Mitsumi Kaneko

MICROBIAL POLLUTION OF SURFACE WATERS

ABSTRACT In order to evaluate the microbial quality of surface waters, the microbial flora of water samples collected from rivers, lakes and seasides was examined. Vibrio cholerae non 0–1, Salmonella, Staphylococcus aureus and Welchii ( Clostridium perfringens ) were selected as pathogenic microorganisms. The distribution pattern of microorganisms was much different among samples, but waters collected from the lower reaches of rivers had a similar one, indicating relatively high density levels of fecal coliforms and fecal streptococci. Water samples more than 50 % contained the pathogenic microorganisms except Welchii . A very few indicies of microorganisms had relatively high mutual relationships with only Welchii . However, it is not so difficult to find the density levels of indicator microorganisms below which pathogenic microorganisms were seldom detected. These density levels can be standard levels to ensure sanitary safety of surface waters and were around 101-102/100 ml for many indicator microorganisms, 0/100 ml for fecal coliforms by the EC method, 10/100 ml for Welchii and 103/100 ml for spore-forming bacteria.