In model experiments carried out in the laboratory the survival of bacteria in groundwater kept at 10±l °C was tested. Only two of the tested bacteria species did not survive longer than 10 - 30 days. Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa and other pathogenic or facultative pathogenic bacteria survived up to 100 days or even more in ground-water with or without the addition of sand from an aquifer. These results can be of importance for determining groundwater protection zones.

Chlorinated organic solvents - such as tetrachloroethene, trichloroethene and 1.1.1-trichloroethane - are the most frequently used compounds e.g. for degreasing in all branches of industries. Due to their widespread use, their large consumption quantities (Fed.Rep.of Germ. 180 × 103 t/a) and their physical properties, these organic solvents are the most important point-source of groundwater contamination. A serious case of soil, soil air and groundwater contamination by these organic solvents (maximum concentrations detected were 500 mg/kg, 7g/m3, 50 mg/l respectively) is reported, caused by the metal industry, rendering plant and paper production. A special effect is the comparatively rapid degradation sequence of tetrachloroethene to trichloroethene to cis-1,2-dichloroethene and to vinyl chloride. Concentrations of cis-1,2-dichloroethene observed in groundwater were up to 1600 µg/l and of vinyl chloride up to 120 µg/l, respectively, although none of these substances were primary pollutants in the investigated area. Results of laboratory tests give rise to the suggestion that degradation of chlorinated hydrocarbons in contaminated areas is mainly by microbiological means. This effect is of special hygienic relevance, due to the fact that one of the metabolites, vinyl chloride, is known to be a human carcinogen and the polluted area (approx. 4 km2) is located in a catchment area of a waterworks.

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In Germany there is much legislation to guarantee adequate protection of groundwater quality and quantity. The main objective of the legislation is to maintain the natural high quality of groundwater. The most important Act in this context is the Water Resources Policy Act. One aspect of German groundwater protection is the possibility to delineate up to four wellhead protection zones in the recharge area of a drinking‐water well. The time‐distance integrated protection zone concept, with bans and limitations on use increasing towards the well, was developed in the 1930s. It has guaranteed for decades a safe drinking water supply from the point of view of quality. However, recent scientific investigations have shown gaps especially with regard to (a) the importance of the 50‐days line, (b) the behaviour of micro‐organisms and (c) the mobility and persistence of man‐made pollutants.