Generation of acid drainage in an uranium ore deposit” Paper presented at

ABSTRACT: The mining operations in the uranium deposit Curilo were ended in 1990 but since that time the deposit is a permanent source of acid drainage waters. These waters have a low pH (usually in the range of 2-3) and contain uranium, radium, some toxic heavy metals, arsenic and sulphates as main pollutants. The concentrations of these pollutants are usually 2-5 times higher than the relevant permissible levels. The waters are generated as a result of bacterial oxidation of the residual amounts of pyrite, other sulphides and uranium minerals present in the abandoned open-pit and underground mining works as well as in some dumps consisting of rock mass and low-grade ores. Some data about the generation of acid drainage waters after rainfall in such a dump are shown in this paper. It was found that the dump was inhabited by a varied microflora in which different chemolithotrophic bacteria were the prevalent microorganisms. The influence of some essential environmental factors such as pH, temperature, and water, oxygen and nutrient contents of the dump on the microbial activity was established. Key words: bacterial leaching, chemolithotrophic bacteria, radioactive elements, toxic heavy metal