Management of passive biological water treatment systems for mine effluents

This contribution describes the approach of WISUTEC, a subsidiary of the mine remediation company WISMUT, to passive biological water treatment as a long-term solution to water contamination problems at former uranium mining and milling sites. We introduce the WISMUT project, with special emphasis on water management and treatment at site closure, and the subsequent remediation process of decommissioned mining and milling sites, and discuss a variety of water-related problems within this framework. A peculiarity of mining and milling operations in Germany, as in Europe in general, compared to other typical mining regions worldwide, is the relatively high population density in the affected mining areas and the relative scarcity of land. As a consequence, strict requirements with respect to technical solutions are applied to mine closures, in particular relating to restrictions on the land surface available for semi-natural and constructed wetlands. The regulatory expectations with respect to compliance with discharge standards and long-term stability are high, and demand highly effective solutions on a small area. We also highlight the practical experience of the design, construction and the first years of operation of the Pohla wetland, which represents a good example. Finally, we discuss some of the pitfalls and potential problems including some realistic cost estimates which are often hidden behind the general, over-optimistic statement of "maintenance-free, zero-cost" passive water treatment systems.