Bacteria neutralize uranium in mine waters — scientists have revealed the mechanism for the first time

In just 130 days, the uranium content in mine water was reduced by 95%. The discovery is published in the journal Nature Communications, reports the publication NIA "Ecology", and opens the way for biological remediation of contaminated uranium mine sites. For Kazakhstan — the world leader in uranium production — this is a potentially significant reclamation technology.

In Brief

• Scientists from the Helmholtz Center (Dresden-Rossendorf), the University of Granada, and Wismut GmbH conducted an experiment with water from a flooded uranium mine in the Ore Mountains of Germany.
• Natural bacteria, with glycerin added as a nutrient, reduced the concentration of dissolved uranium in the water by 95% over 130 days.
• Key discovery: the bacteria convert uranium into an unusual pentavalent state (U(V)), previously considered unstable. This results in the formation of the compound FeU(V)O₄, which remains stable even when exposed to atmospheric oxygen.
• Previously, a similar compound had only been found once — in soils in Croatia contaminated by uranium munitions.
• Practical application is still far off: the authors emphasize the need for detailed study of the biochemical mechanisms and assessment of the possibilities for field application.

The Problem Being Addressed

Uranium mining leaves behind a specific legacy: flooded mines, tailings ponds, and open pits — all sources of slow but persistent contamination of groundwater and surface water with dissolved uranium compounds. Classical treatment methods — chemical precipitation, ion exchange, reverse osmosis — work, but are expensive and require constant maintenance. Biological methods could be significantly cheaper and more applicable in hard-to-reach locations.

This is precisely why the research was conducted in collaboration with Wismut GmbH, a company engaged in the reclamation of former uranium mines in Germany — among the largest in Europe, developed during the Soviet era.

Pentavalent Uranium: Why It Matters

Uranium exists primarily in two soluble forms: tetravalent (U(IV), insoluble, stable) and hexavalent (U(VI), soluble and mobile — this is the form that contaminates water). Converting from the hexavalent to the tetravalent form is the goal of treatment, but this process is unstable in the presence of oxygen: U(IV) re-oxidizes and returns to solution.

The discovery by the German-Spanish group breaks this logic. The bacteria create not U(IV), but an intermediate pentavalent state U(V) — previously considered short-lived and unstable. However, in combination with iron, it forms FeU(V)O₄, which remains stable even when exposed to oxygen. This is a fundamental difference from previous biological methods, where treated water became re-contaminated upon aeration.

Kazakhstan Context

Kazakhstan produces about 43% of the world's uranium — primarily using the in-situ leaching (ISL) method, where an acidic or alkaline solution is injected into the formation, dissolves the uranium, and is pumped to the surface. This method is less damaging to the landscape than open-pit mining, but creates specific problems of subsurface contamination and requires subsequent reclamation of aquifers.

In addition to active sites, Kazakhstan has a significant legacy from the Soviet uranium industry: old mines, tailings ponds, and contaminated areas in the Aktobe, Kyzylorda, and South Kazakhstan regions. Their reclamation is a long-term environmental challenge, partially funded by the state.

Biological treatment methods based on the discovered mechanism could potentially reduce the cost of reclamation and expand the possibilities for restoring contaminated aquifers. Kazakhstan's environmental regulators and Kazatomprom should monitor the development of this field — especially as the technology approaches field trials.

Author's Conclusion

Nature has been using bacteria for millennia to transform heavy metals — scientists are only just beginning to understand how. The discovery of the mechanism for forming FeU(V)O₄ is not a practical solution for today, but fundamental knowledge that, after a few more years of research, could become a working tool for cleaning uranium mines. For the country with the world's largest uranium sector, this is a development worth keeping an eye on.