MICROBIAL-CONTAMINATION AS AN INDICATOR OF SEWER LEAKAGE

The presence of several physiological groups of microorganisms (general aerobic bacteria, amylolytic bacteria, denitrifying bacteria, actinomycetes and fungi) was investigated in wastewater, seepage water, and soil samples in areas of sewer leakage. The results were compared with the findings for several chemical parameters (pH value, electrical conductivity, and total organic carbon <TOC>) analysed. Wastewater infiltration causes an increase in the TOC concentration of seepage water samples. In the same samples, an increase in general aerobic bacteria and denitrifying bacteria was recorded. General aerobic bacteria, actinomycetes, and fungi were more abundant in contaminated soil samples than in non-contaminated ones. The occurrence of denitrifying bacteria and amylolytic bacteria in the soil samples did not show correlations to sewer leaks. The relationship between results from the chemical and microbiological analyses not only indicates contamination of seepage water and soil due to wastewater exfiltration, but also provides information on the degradation potential of microorganisms and a part of this decomposition process in the underground. The knowledge of the occurrence of various physiological groups of microorganisms is of extraordinary importance for classifying and judging the level of contamination, as well as for choosing a renovation process. In an epidemiological view, the bacteria and viruses pathogenic for humans should be considered in the case of wastewater exfiltration near drinking water supplies.