Prevention of the Generation of Acid Mine Drainage in a Dump Rich-In Pyrite Uranium Ore

Abstract

The uranium deposit Curilo, Bulgaria for a long period of time was a site of intensive industrial-scale leaching of uranium and recovery of primary uranium-bearing concentrates. These activities were ceased twenty five years ago and since that time and until recently the deposit was, especially after rainfall, a huge site of spontaneous generation of acid mine drainage containing uranium, its radioactive disintegration products and several toxic heavy metals. This process was mainly due to the activity of the indigenous acidophilic chemolithotrophic bacteria which oxidized the pyrite, other sulphides and uranium - bearing minerals present in the deposit. Different methods to prevent the generation of such polluted waters were applied but the best results were achieved by construction of a specific rich-in-organics and crushed limestone soil cover on the surface of one of the waste dumps in the deposit.