"Directly at the outflow of the tailings pile leachate from the Hammerberg rinsing pile, the main settling basin of the Freiberg mining industry, we will be constructing an innovative pilot plant for efficient and cost-effective water treatment in the coming months. This will enable us to release even cleaner water into the Freiberg Mulde in the future," explains project manager Jun.-Prof. Sabrina Hedrich. "With the new process, which we are developing and testing in the pilot plant, we are preventing the carryover of toxic heavy metals such as cadmium, nickel and zinc into the river system of the Freiberg Mulde. We are thus making a contribution to improving the waters of mining regions and to safeguarding the quality of water, one of our most valuable and vital resources."

The Hammerberg slurry dump in Freiberg, a site owned by SAXONIA Standortentwicklungs- und -verwaltungsgesellschaft mbH has been undergoing remediation since 2012 and serves as a model site for the development and upscaling of the water treatment technology. The technology is to be flexibly designed for use at other sites to offer economic potential and regional connectivity through internationalization.

The water treatment plant consists of several chemical and biological stages, allowing selective separation of various dissolved substances by precipitation and accumulation. Such passive treatment systems have been in place in the U.S. and Canada since the 1990s, focusing primarily on neutralizing acid mine drainage and retaining various metals and other elements. The UK has made the most progress in Europe in using these innovative, technological approaches. The Freiberg researchers' project is intended to create the scientific and planning conditions needed to achieve wider application of these processes, which are largely based on natural purification mechanisms, and thus also to strengthen the innovative strength and competitiveness of the Central Saxony region.

Mobile plant for the treatment of mining water

The plant is being planned for modular construction, which means that it could also be used in other former mining regions after the successful pilot phase at Freiberg. The water treatment plant will operate without external energy, instead using the natural slope of the land to achieve a flow of water. Photovoltaic modules provide energy for technologically necessary process steps. The PV modules used are Made in Central Saxony, produced and made available for research purposes by Meyer Burger Technology AG, which operates Europe's largest solar module production facility in Freiberg. Local authorities, such as the Saxon State Office for the Environment, Agriculture and Geology, the Saxon State Directorate and the district of Central Saxony, are supporting the project. In the long term, the new technology is intended to help former mining regions achieve the goals set by the EU Water Framework Directive and develop measures to implement them.

The results of the project are to be presented in an active exchange with citizens and the general public. An inspection of the Hammerberg complex is planned for spring 2024 with the specialist mining history group of the Historische Freiberger Berg- und Hüttenknappschaft e.V.

About the MindMontan research project

The aim of the MindMontan project is to use innovative technologies to reduce the impact of mining on the environment, both regionally and globally, to expand regional structures, to minimize social conflicts and to strengthen social development by actively involving the public. The project "MindMontan - Reduction of Water Pollution in the Mining Region Erzgebirge/Krušnohoři using the example of the Hammerberg Flush Dump, Freiberg" is being carried out under the leadership of the TU Bergakademie Freiberg, Institute of Biosciences, with the partners G.E.O.S. Ingenieurgesellschaft mbH and the Förderverein Montanregion Erzgebirge e.V.. The project is supported by the associated partners:

• SAXONIA Standortentwicklungs- und -verwaltungsgesellschaft mbH
• Sächsisches Landesamt für Umwelt, Landwirtschaft und Geologie
• Landesdirektion Sachsen
• Landkreis Mittelsachsen
• Meyer Burger Technology AG

The project duration is from May 2023 to December 2025. The project is funded in the program WIR! (Change through Innovation in the Region) program by the German Federal Ministry of Education and Research with funding of around 370,000 euros. The research project is located under the umbrella of the recomine research network at the Helmholtz Institute Freiberg for Resource Technology (HIF) of the Helmholtz Center Dresden-Rossendorf (HZDR).