NUKLEONIKA 2004, 49(Supplement 1):s17-s20
Veneta I. Groudeva1, Stoyan N. Groudev2, Anna D. Stoyanova1
1 Faculty of Biology, University of Sofia,
8 Dragan Tzankov Boul, 1421, Sofia, Bulgaria
2 Department of Engineering Geoecology, University of Mining and Geology,
Studentski grad-Durvenitza, Sofia 1700, Bulgaria
Acid drainage waters generated in the uranium deposit G-1, Western Bulgaria, were treated by means of
a natural wetland located in the deposit. The waters had a pH in the range of about 2.4-3.9 and contained
uranium and radium radionu-clides, heavy metals (copper, zinc, cadmium, iron, manganese), arsenic and
sulphates in concentrations usually much higher than the relevant permissible levels for waters intended
for use in the agriculture and/or industry. The wetland was characterized by abundant and emergent
vegetation and a diverse microflora. Typha latifolia, Typha angustifolia and Phragmites australis
were the main plant species in the wetland but representatives of the genera Scirpus, Juncus,
Eleocharis, Potamogeton, Carex and Poa as well as different algae were also
present. The water flow through the wetland varied in the range at about 0.2-1.2 l/s reflecting water
residence times in the wetland of about 10-50 hours. An efficient water cleanup took place in the
wetland, even during the cold winter months at ambient temperatures close to 0°C. The removal of
pollutants was due to different processes but the microbial dissimilatory sulphate reduction and the
sorption of pollutants on organic matter (living and dead plant and microbial biomass) and clays
present in the wetland played the main role.