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Pilot scale field performance
of a reclamation scheme for sulphidic waste rock
For the environmentally safe management of the sulphidic waste rock produced
from the Stratoni lead–zinc sulphide mine in Greece, the effectiveness of an
alternative scheme to conventional disposal methods management, involving
the segregation of the –4mm sulphide rich fraction of waste rock and its
amendment with the engineered application of limestone was examined.
Following successful laboratory test results, pilot field tests were carried
out in order to assess the performance of the above reclamation scheme and
compare it with the behaviour of the “as–it–is” waste rock, i.e. increased
drainage volume with acidic pH and elevated metals concentration. Based on
the results of a three–year (1,114 days) monitoring programme, it was
deduced that for the “as–it–is” waste rock, the amount of infiltration
corresponded to 20% of the precipitation received; the leachates collected
were acidic to alkaline, i.e. pH: 3.5–7.7 and mainly contaminated with Zn,
Mn and Cd. The separation of the –4mm waste rock fraction and its placement
above the coarse size material, reduced the overall infiltration and
improved the quality of drainage collected. Homogeneous mixing of the fine
waste rock fraction with limestone was recorded to further reduce the
infiltration rate and resulted in the production of alkaline drainage
throughout the test period. Complete inhibition of water percolation was
achieved by the successive layering of the homogeneous –4mm waste
rock/limestone mixture and coarse waste rock fraction, where no leachate was
collected after three years of testing. |
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