[Microbiologic studies of in situ removal of iron and manganese].

While undoubtedly a good understanding of soil microbiology in terms of pedology exists, little is presently known about unsaturated subsoils, and aquifers. Yet, in the North German Basin, such underground environments contain to a 90 m depth up to 10(4) g-1 dry wt of heterotrophic bacteria, oligocarbophilic bacteria, denitrifying bacteria, nitrate reducing bacteria, iron precipitating and reducing bacteria, manganese oxidizing and reducing bacteria and other physiological groups of microorganisms. These bacteria are facultative anaerobes. When estimating microscopically, their counts reach up to 10(7) g-1 dry wt. In an oxygen free aquifer which received an oxygenated water for 10 years to remove iron and manganese, the counts of heterotrophic bacteria increased 1-2 orders of magnitude. The counts of nitrifying bacteria also increased whereas those of desulfurizers remained non-affected. In general, the oxidizing bacteria benefited more from the treatment than the reducing bacteria. The soil Eh value was increased, and BOD 5, 10 or 20 values were diminished in comparison to the oxygen free aquifer.