In a German-Romanian joint project feasible and cheap techniques for a safe storage of mine waste to prevent acid rock drainage were tested. A percolator, consisting of 4 sep. leaching chambers, was installed in the main waste dump of Ilba Mine, Maramures, Romania. Each unit contains 65 m3 of sulfidic waste material. The inhibitory effect of SDS on the activity of leaching bacteria and on metal mobilization was studied in a long term expt. SDS was proven to have an inhibitory, however transient, effect on leaching bacteria. In the course of the expt., it became possible to quantify the potential for environmental pollution resulting from microbial leaching in mine waste using microcalorimetric activity measurements.