NATO/CCMS Pilot Study Evaluation of Demonstrated and ... - CLU-IN

NATO/CCMS Pilot Project on Contaminated Land and Groundwater (Phase III) January 2001
2. SITES
The research is of a generic nature and the results applicable to a wide number of cases. The sites
examined as case studies are given below:
Site Description Material tested
Lavrion, GR
Redundant polymetallic sulphide mine
(argentiferous, galena, sphalerite, pyrite)
Active polymetallic sulphide mines (galena-
Sulphidic and oxidic
tailings, soils
Stratoni, GR sphalerite-pyrite) with a mining history of
more than 2.500 years.
Waste rock
Montevecchio,
Monteponi, Sardinia, IT
Extensive Pb-Zn historic mining area.
Currently, there is one operating and many
redundant mines.
Chemical industrial site. Production of
Sulphidic tailings,
calamina red mud,
soils
Estarreja, PT sulphuric acid by roasting of pyrites in the
period 1952-1991.
Pyrite cinders
3. DESCRIPTION OF THE PROCESSES-RESEARCH ACTIVITY
3.1 PREVENTIVE TECHNOLOGIES TO INHIBIT THE SPREAD OF POLLUTION FROM
THE ACTIVE SOURCES
Processes for the prevention of pollutant migration, which were investigated in laboratory scale and are
being evaluated in field scale, include:
a) Limestone or fly ash addition to prevent acid generation from sulphidic wastes
The technical objective is the development of a process for the inhibition of acid generation from
sulphidic wastes by making beneficial use of the oxidation-dissolution-neutralisation-precipitation
reactions so as to achieve: on the microscale, precipitation of reaction products around the pyrite grains,
inhibiting further oxidation and/or on the macroscale, formation of a hard pan that will drastically reduce
the permeability of wastes to water and oxygen. By achieving these goals, the required limestone or other
alkaline additive will be only a fraction of the stoichiometric requirements, therefore the cost of
application will be significantly lower compared to the current practice of adding near-stoichiometric
quantities.
An extensive laboratory kinetic test work was carried out using limestone, a low cost and commonly
found at mine sites alkaline material, and fly ash, a by product of Greek-lignite powered electricity plants
with significant neutralization potential and cementitious properties. Kinetic tests using columns or
humidity cells were carried out for a period of 270-600 days. After 270 days of operation a selected
number of columns as well the humidity cells were dismantled and a detailed geotechnical and
geochemical characterisation of the solid residues was performed.
b) Formation of surface barriers for the pyrite cinders and calamina residues
The technical objective is to develop an innovative, cost-effective process for the inhibition of the toxic
leachate generation from these wastes by modification of the top surface layer with bentonite or
bentonite-zeolite additives. The aim is to achieve very low permeability of the surface layer in order to
inhibit water infiltration and subsequent leaching of contaminants.
The laboratory work performed includes: a) selection of the stabilising agents (bentonites and/or zeolites
and/or other materials) having certain properties (proper sediment volume, swelling index, yield, filtrate
loss, and high cation exchange capacity), b) short term leaching tests to preliminarily determine
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