This paper presents a study focused on the process of water contamination as a consequence of human activities at the limit of man made disaster, concerning pollutant diversification as a result of the development of manufacturing processes. The investigations were focused on the evaluation of the pollution level as well as the self-purification (eutrophication) capacity of the Bahlui river waters in Iaşi, Romania, by means of quantitative assessment of certain ecophysiological groups of bacteria involved in organic residue recycling, also by determining of sanitary-bacteriological attributes describing the quality of water.