Abstract: Vor dem Hintergrund einer planmäßigen Tagebauentwicklung muss der das Gewinnungsfeld in Nord-Süd-Richtung durchquerende Fluss Inde Ende 2005 bergbaulich in Anspruch genommen werden. Als Ersatz wurde auf Grundlage des Planfeststellungsbeschlusses vom 10.09.1998 eine neue Inde auf einer Länge von rd. 12 km erstellt. Rund 10 km der neuen Inde liegt innerhalb des Tagebaufeldes. Hierzu musste eine Flusslandschaft angelegt werden. Im Gegensatz bisher anthropogen geprägten Inde, ist eine naturnahe und weiträumige Flusslandschaft vorgesehen. Die Gestaltung soll, in Verbindung mit den zahlreichen eingebrachten Landschaftselementen wie Flutmulden, Altarmansätzen und Kolke, eine artenreiche und ökologisch hochwertige Auenlandschaft ermöglichen. Die Flutung der neuen Inde erfolgt auf Grundlage eines dreiphasigen Gewässerumschlusskonzeptes. Im Anschluss an die Flutung soll ein Monitoring- Programm zur Dokumentation der hydrodynamischen, morphologischen und landschaftsökologischen Entwicklung der Indeflur durchgeführt werden. Against the background of the scheduled eastward development of the Inden opencast mine, the Inde river which runs there must make way for mining operations at the end of 2005. Prior to this, as a replacement for the riverbed, which is some 4.5 km long, a riverscape has had to be created as a bypass in the west, mainly within the scope of rehabilitation measures. The model built for this purpose based on historical records provides for a close-to-nature and spacious riverscape with hand- and soft-wood meadows, unlike the anthropogenically marked Inde of today, with a meandering mean water bed. This design, in conjunction with the many installed landscape elements, like flood hollows, creeks and potholes, aims at creating a diverse and ecologically high-quality meadow landscape. The main factors impacting the river's route were the opencast mine's geometry and progress, as well as the planned and existing utilization of the land surfaces outside the opencast field. Besides these constraints, there were stipulated vertical points due to hydraulic requirements. The Inde plains, taking account of the planned route, were created on the basis of a design template, which provides for a stable level, a sealing layer and a cultivatable meadow substrate layer. In addition, the meadow substrate layer protects the sealing layer from erosion thanks to its medium- and coarse-grained gravel content. The Inde was constructed in the opencast field within the scope of rehabilitation in spreader operations, meaning that it was possible to dump the material to be installed in line with the design template and given elevations. The flooding of the 'new' Inde was based on a three-phase waterway rerouting concept and provided for increasing discharge quantities. This enabled a bottom covering layer to be formed successively, and ailowed the aquatic fauna to gently adapt to the changed living conditions and further seed material to be flushed in.

Abstract: Acid-mine drainage can contain high concentrations of heavy metals and release of these contaminants into the environment is generally avoided by lime neutralization. However, this classical treatment is expensive and generates large amounts of residual sludge. The selective precipitation of metals using H2S produced biologically by sulfate-reducing bacteria has been proposed as an alternative process. Here, we report on experiments using real effluent from the disused Chessy-les-Mines mine-site at the laboratory pilot scale. A fixed-bed bioreactor, fed with an H2/CO2 mixture, was used in conjunction with a gas stripping column. The maximum rate of hydrogen transfer in the bioreactor was determined before inoculation. kLa was deduced from measurements of O2 using Higbie and Danckwert's models which predict a dependence on diffusivity. The dynamic method of physical absorption and desorption was used. The maximum rate of H2 transfer suggests that this step should not be a limiting factor. However, an increase in H2 flow rate was observed to induce an increase in sulfate reduction rate. For the precipitation step, the gas mixture from the bioreactor was bubbled into a stirred reactor fed with the real effluent. Cu and Zn could be selectively recovered at pH=2.8 and pH=3.5, respectively. Other impurities such as Ni and Fe could also be removed at pH=6 by sulfide precipitation. Part of the outlet stream from the bioreactor was used to regulate and maintain the pH during sulfide precipitation by feeding the outlet stream back into the bioreactor. The replacement of synthetic medium with real effluent had a positive effect on sulfate reduction rate which increased by 30-40%. This improvement in bacterial efficiency may be related to the large range of oligo-elements provided by the mine-water. The maximum sulfate reduction rate observed with the real effluent was 200 mgl-1 h-1, corresponding to a residence time of 0.9 day. A preliminary cost estimation based on a treatment rate of 5 m3 h-1 of a mine effluent containing 5 gl-1 SO42- is presented.