[Microbiologic/hygienic evaluation of the risk potential of bacteria from soil and water sources in combination with biotechnologic risks of soil restoration].

Biological cleanup-processes removing contaminations from soil and ground-water can be carried out "ex-situ" or "in situ". The pollutants are mineralized (totally or partly) by microorganisms. The successful application of bioremediation techniques often leads to an increase of aerobic and facultatively anaerobic bacteria in soil and/or groundwater, a fact that triggered discussions about a potential biological risk originating from these microorganisms. In this study the identification results of 10,200 microorganisms isolated from 109 ground-water- and 152 soil-samples of different sites contaminated with mineral oil or chlorinated aromatics are evaluated with respect to a possible biological risks originating from these microorganisms. According to their biological risk potential, 19.2% (1958) of the isolated organisms can be grouped into risk-groups II, that means they they are able o cause human disease but it is unlikely that they are spread to the community and there is effective prophylaxis or treatment available. The majority of isolates (81.8%) are grouped into risk group I, meaning that it is very unlikely that they cause a human disease. All these microorganisms are either adsorbed to the soil-matrix or within a closed system of a water-treatment-plant, so that the risk of infection is very unlikely for healthy individuals (regarding possible pathways of infection). The risk potential in waste-water-treatment-plants is regarded to be significantly higher than in biological soil-cleanup processes, because of the specific origin of the bacteria and the possible formation of aerosols.