Microorganisms as Sanitary State Bioindicators of Flowing Waters in Poland

Abstract

The article presents changes in the quantitative and qualitative composition of indicator bacteria in three Polish rivers – Vistula, Oder, and Łyna River – in the last 30 years. The analyzed rivers are situated in the catchment area of the Baltic Sea, and they play important economic, tourist and environmental roles. The sanitary and bacteriological status of these ecosystems was determined based on the counts of total coliform bacteria (TCB), fecal coliform bacteria (FCB), fecal enterococci bacteria (FEB), and Escherichia coli. The study involved a review of the literature and the reports published by Polish inspectorates of environmental protection. Water samples collected from all rivers in urban areas were characterized by the highest TCB, FCB, FEB, and E. coli counts throughout the analyzed period. High contamination levels contributed to epidemiological risks in rivers, in particular in the proximity of discharge points of treated effluents. As a result, most of the analyzed water samples were graded as purity class III and/or as non-class (polluted beyond permissible standards) waters. Since 2003, Polish laws have been harmonized with the provisions of the Water Framework Directive (2000/60/EC), and the range of indicator bacteria was restricted to FEB and E. coli only in water bodies used as sources of water for human consumption and/or for bathing. In Poland, treated wastewater does not have to be disinfected before it is discharged to surface waters. For this reason, contamination with indicator bacteria (TCB, FCB, FEB, and E. coli) continues to be high in water bodies that act as receptacles of wastewater despite considerable reduction of microbiological contamination (97–99%) in treated effluents. The above applies particularly to rivers where contamination spreads. For this reason, the concentration of indicator bacteria should be the main criterion in evaluations of river water purity.