In the course of a German-Romanian scientific project, large lysimeters with a vol. of up to 65 m3 were used for up to 3 years long expts. on controlling acid rock drainage formation in three different types of pyritic mine waste: (A) weathered 6 years old waste rock material, (B) sorted, freshly broken, low-grade ore, and (C) unweathered tailings material. An addn. of sodiumdodecylsulfate (SDS) partly reduced the activity and no. of metal sulfide oxidizing bacteria of the type Acidithiobacillus ferrooxidans but did not kill the bacteria. Consequently, the release of metals and sulfate from mine waste was not significantly reduced. The application of the biocide isothiazolinone (Kathon RH 886) reduced the release of Cu, Zn, Fe and sulfate between 5% and 50% for different types of mine waste. A cover of org. material only achieved a moderate redn. of the heavy metal and sulfate release from the weathered 6 years old waste rock material: Cu was reduced by 50%, Zn by 30%, Fe by 90%, and sulfate by 40%.