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TREATMENT OF ACID MINE DRAINAGE BY MEANS OF A SYSTEM OF CONSTRUCTED WETLANDS
Authors: S. GROUDEV, I. SPASOVA, M. NICOLOVA
Number of views: 398
acid drainage waters generated in the
uranium deposit curilo, bulgaria, were treated by
means of a passive system consisting of two
constructed wetlands connected in a series. The
waters had a ph in the range of about 2 – 4 and were
heavily polluted by radionuclides, several heavy
metals, arsenic and sulphates. The first wetland was
characterized by a subsurface water flow, a very
dense water and emergent vegetation and a large
anaerobic zone in which different sulphate-reducing
bacteria and some metabolically interdependent
species were the prevalent microorganisms. The
second wetland was a predominantly aerobic system
due to the cascade-type construction of its bottom
and the surface water flow. The water flow through
the wetlands varied in the range of about 0.2 – 0.75
l/s, reflecting total residence times of about 90 to 25
hours. An efficient removal of pollutants was
achieved by this system during the different climatic
seasons, even during the cold winter months at water
temperatures close to the freezing point.