Metody ługowania zanieczyszczeń z odpadów mineralnych w ...

Metody ługowania zanieczyszczeń z odpadów mineralnych…
Methods of Leaching Contaminants from Mineral Waste
in the Aspect of its Potential Utilization
in Hydrotechnical Construction
Abstract
The research conducted in static and dynamic conditions was aimed at determining
the vulnerability of soluble compounds contained in ashes to leaching with the
objective to define the quantity and type of contaminants which may affect soil, ground
and surface waters in the case of ash utilization or disposal on land surface.
Silica, aluminum and iron oxides are the basic compounds of fly ashes while
calcium, magnesium, potassium as well as other oxides occur in significantly less
amounts. Taking into account the chemical composition recalculated into SiO2, CaO,
Al2O3, SO3, the following 3 categories of ashes have been recognized in Poland: silica,
aluminum and calcium ashes.
Solubility tests of the Polish fly-ashes showed that depending on the ash category,
0,5% (aluminium ashes) up to 10% and more (calcium ash) of their mass may
dissolve in water.
In different conditions of the leaching processes, the vulnerability of fly ashes
to the release water soluble compounds contained in them may vary. The main substances
leached from the analyzed ashes ( in descending order) were sulphates, calcium,
sodium and chloride ions, while the trace elements included chromium, cadmium and
lead. The leachability of other elements was insignificant.
Eluates from the investigated fly-ashes were characterised by an elevated reaction
and the content of some ions (SO4 -2 , Cr 3+ , Cd 2+ , Pb 2+ ) exceeding the permissible
concentrations compared to the standards for wastewater discharged to waters or soil,
which in consequence may lead to a negative impact on the water environment in the
vicinity of the disposal sites.
A comprehensive environmental impact analysis has been made based on the
effective legal regulations (including Geological and Mining Law, Waste Act and its
executive regulations). Doubts have been raised if determining the potential risk to the
environment based on the leachability test is sufficient as it does not reflect the volume
of the leached substances under natural conditions. Tests conducted in dynamic conditions
showed that the total load of the leached substances was significantly higher compared
to the leachability test data. The dynamic method (alternative I and II) simulates
the course of the leaching processes taking place in natural conditions and allows foreseeing
the concentration distribution the leached contaminants in a given time.
The conducted research proved the real-time dynamic leaching method more
reliable in conducting a preliminary environmental impact assessment.
Also as a result of the studies the thesis has been confirmed that fly ashes are
vulnerable to the release of soluble compounds contained in them and thus show some
negative tendencies in their impact on the environment. Disposal of fly ashes in landfills
or their underground storage in mines may cause degradation of surface and groundwaters
due to the penetration of the leachable compounds from waste in the areas of its disposal.
Tom 10. Rok 2008 219