Helmsdorf - Since 1991, regions in Saxony and Thuringia damaged by uranium ore mining have been comprehensively rehabilitated at great financial expense. At the Helmsdorf site near Oberrothenbach, north of Zwickau, WISMUT GmbH has been commissioned with the remediation of the industrial tailings pond and the contaminated areas. The resulting waters of the tailings pond have a slightly basic character and are characterized by relatively high contents of arsenic and uranium. They are purified in the Helmsdorf water treatment plant (WBA).
However, when the remediation measures are completed in mid-2021, the treatment plant used to date will become uneconomical due to its dimensions and is to be dismantled in the long term. For the necessary treatment of the leachate still accumulating on the landfill site, a new water treatment plant including a new operating building with transformer station, sanitary and social facilities was built.
For this purpose, WISMUT GmbH commissioned SCHACHTBAU NORDHAUSEN GmbH in mid-2019 as part of a consortium with BAUER Resources GmbH with the planning and implementation of the complete multi-stage water treatment plant, the necessary ancillary facilities, and the complete electrotechnical equipment and control system for the treatment process.
In March 2021, project manager Dominik Koch and his colleagues completed the one-year construction phase and started the three-month trial operation. The water treatment plant now houses a combination of ion exchangers and adsorber columns that purify the mine water in three stages using a special combination of processes.
In the first treatment stage, the leachate is pre-cleaned. This involves the separation of particles larger than 0.5 mm, using two sand filter columns. These are automatically cleaned by a backwash function so that the filter material can be reused.
In the second cleaning stage, ion exchangers with a special resin are used to recover the uranium from the leachate. The six installed orange columns are divided into two streets, each with three filter columns, which are run in series. The contaminated resin is then regenerated and reused in another filter column.
Subsequently, in the third treatment stage, the arsenic is recovered from the leachate by means of iron hydroxide material in adsorber columns. The structure of the adsorber columns corresponds to that of the ion exchangers.
After purification, the contaminated material is finally recycled. For this purpose, the uranium sludge and adsorber material are collected in the immobilization section of the plant and mixed with cement. Among other things, the cement binds the uranium radiation and enables safe final disposal.
For the water treatment and immobilization sections of the plant, ARGE SCHACHTBAU NORDHAUSEN GmbH and BAUER Resources GmbH supplied the complete tanks, the steel structure and the piping; for the cleaning section, they also supplied the accessories and filter material as well as the special resin.

The new treatment plant will ensure active aftercare, monitoring of the rehabilitated former mining and processing sites, and above all water management, for decades to come. The project, estimated at 5.5 million euros, is scheduled for completion by October 2021.