Abstract
Most of the former East-German open cast lignite mines were shut down. To mine the lignite, the ground water table had been lowered up to 100 m. Today, the ground water flow regimen is changing due to the refilling of the depression cones and subsurface acid mine drainage is endangering surface waters and drinking water supply facilities outside the mining areas. Because of the large discharge area, only in situ technology can be used to reduce acid mine drainage. It has been developed on a laboratory scale and is currently being tested in an aquifer which already is contaminated by acid mine drainage. Sulphate reduction and the formation of sulphide minerals are being enhanced by adding bioreactive liquids in the aquifer. To apply the remediation technology to other areas which will soon be endangered, their future ground water quality is being assessed by predictive modelling. A 1-D transport and reaction model based on a hydraulic 3-D model of the study area is being developed. The dump material is described as a two component system consisting of low permeable silt aggregates with a large surface area, with high sulphide and organic contents and a matrix of highly permeable sands with a small surface area and low sulphide and organic contents. The transport and reaction model reflects the process of dump ground water genesis and includes the processes: (i) diffusive interaction between mobile and immobile pore water; (ii) dissolution of minerals according to the dissolution product and the redox state of the solution; (iii) control of the concentration of redox-sensitive species by addition of biodegradable organic material as electron donor (this part of the model is used to represent the remediation technology); (iv) weathering of feldspars; and (v) cation exchange reactions. Most parameters used to describe the processes are based on laboratory experiments with sediments and waters from the site.
Get full access to this article
View all access options for this article.
