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Thanks to the epithermal polimetallic ore
formation processes, Gyöngyösoroszi was an important mining center in Hungary
from the middle ages until 1985. As a result of the mining activity, deposits
of refuse ores made of mainly sulfide minerals were piled up. On the surface the
oxidation of the sulfides generated sulfur which then mixed with rainwater,
forming sulfuric acid. This decreased the ph of the groundwater that helped the
toxic heavy metals to go into solution, thus transporting these toxic elements
in natural waters and in the soil.
To prevent the pollution to spread to municipal
areas our company was assigned by the former Ministry of Environmental
Protection and Regional Development (KTM) to make an environmental survey in
the area of the mine owned by the Országos Érc- és Ásványbányák (National Ore
and Mineral Mines) company, to examine the objects used for waste-material
storages, and to make a feasibility study for the remediation plan.
During the survey, heavy metal contamination in
excess of the background concentration typical of the area was found in several
areas. In the remediation process the 2000 m3 heavy metal
contaminated water from the mines surfacing at the adit was led in a concrete
ditch to a water treatment plant. In the plant lime hydrate was added which
increased the ph of the water, and the soluted heavy metals precipitated. The
generated sludge was placed in a settling storage. After the settling, the
treated water was led through an overflow back to the Toka-stream, and the
residual waste sludge was yielded in to a hazardous waste storage.
This water-treatment method proved to be
effective, but several storage structures were found to be leaking. As a result
of the survey at the engineering structures, the aim of the further operations
was to fortify and repair the walls and dams, so the leakages, i. e. the
sources of pollution could be eliminated.