Since remediation of uranium mining legacies started, water treatment was and still is a key issue for Wismut GmbH. Contaminated water from remediation operations has to be collected and treated in water treatment plants to protect ground and surface waters against pollution.

Such waters are primarily:

Flood water:
Groundwater that rises during mine flooding or that overflows at the surface when mine flooding is completed

Pond and pore waters:
Water contained in uranium mill tailings ponds

Heap seepage:
Surface water infiltrated into waste rock piles and seeping from the toe of the dump

Contaminated water typically contains uranium, radium, arsenic, iron, and a series of other heavy metals. Depending on feed water quality and volume as well as on targets to be met, contaminant removal imposes different treatment methods. The range of methods in use includes ion exchange as well as precipitation techniques, and passive treatment technologies.

3 basic treatment technologies in use at Wismut GmbH are:

1. Precipitation techniques
Following the addition of specific chemicals, contaminants are precipitated as very slightly soluble compounds.

2. Ion exchange
Removal of water contaminants uses ion exchange resins. Contaminants are removed from the resin to where they are attached, and the resin is regenerated for multiple reuse. Wismut uses this technology at the Aue and Königstein sites to separate uranium from flood water.

3. Biological water treatment technique
This technique uses the capability of certain plants to accumulate contaminants in their roots and/or foliage mass, respectively. The process is implemented in what is known as constructed wetlands, whereby the water to be treated passes through a single or a number of basins which hold the respective biomass for contaminant removal. As large areas are required for the basins, this technique is particularly suited to treat small amounts of water.

Wismut GmbH currently operates six water treatment plants which remove relevant contaminants by chemical/physical processes. A passive biological treatment unit is undergoing trial runs.

Water treatment will continue to be a requirement for many years to come.