Acidic lignite mining lakes – a typical case for remediation? Tagebaurestseen – schon bei dar Entstehung ein Sanierungsfall

Abstract

The formation of lakes after sudden termination of opencast lignite mining in eastern Germany is influenced by massive hydrological problems in the mining area. In spite of restricted surface water availability flooding from external sources is preferable to slow re-ascension of ground-water for geochemical, technological and socio-economical reasons. However, the water quality of the newly formed lakes poses subsequent problems which include eutrophication, salinization, contamination by toxic substances and predominantly acidification. The geological situation in the eastern German mining areas promotes acidification by pyrite oxidation. As a result, biological colonisation of the lakes is poor and use for fishery and recreation is restricted or impossible. Strategies for abatement of acidification include limitation of further pyrite oxidation, restriction of acidity inflow into lake water and neutralisation of already existent lakes by chemical or biotechnological processes. Their current state of the art is discussed. A method which is not yet intensively studied in full scale application but possibly of economic interest as a low price technology is the stimulation of bacterial sulphate reduction with the aid of organic additions. Experiences from various pilot scale applications with different carbon sources are reviewed. The contribution of other processes, for example iron reduction, for biological neutralisation is also discussed.