Flood Water Treatment at the Former Uranium Mine Site Konigstein - a Field Report

Due to the rather high uranium concentration of about 10 to 60 mg/l (maximum of 250 mg/l in 2002) in the acidic flood water from the former in-situ leach mine Konigstein, a first treatment stage for uranium removal and processing has been implemented, followed by the further water treatment in a HDS (high density sludge) plant for neutralization and removal of various metals (Fe, Al, Zn, etc.), sulphate and naturally occurring radio-nuclides. In the late nineties, the former uranium plant was converted to a state-of-the-art processing unit meeting the specific requirements with regard to controlled flooding and recycling criteria for uranium. Uranium processing includes ion exchange for uranium removal from the flood water, multi-stage elution, precipitation of uranium oxide (UOX), and UOX washing and de-watering for removal of dissolved impurities. HDS treatment efficiency and sludge de-watering properties were considerably improved by applying a staged neutralization technology to limit super-saturation of mineral phases as well as the formation of amorphous solids and to increase the precipitation rate of crystalline phases in significantly larger particles. Adsorption on Fe phases is important to remove various metals and radio-nuclides efficiently. Centrifuges are used for sludge de-watering to levels 48 M% solids (average), thus, enabling disposal of the de-watered sludge to a dump at the site directly. This field report presents typical operational data and discharge water quality parameters meeting regulatory limits in all years of operation.