| Summary: | A literature review conducted in 1992 revealed that an organic layer on sulphide tailings could be beneficial in the suppression of tailings oxidation and acidic mine drainage, in the following five ways: 1) creation of a physical oxygen barrier, 2) maintenance of an oxygen-consuming barrier, 3) chemical inhibition, 4) chemical amelioration, and 5) reduction of water infiltration due to compaction through decomposition. Organic cover materials were also believed to be potentially beneficial in the provision of a top cover for the introduction and maintenance of a vegetative cover. The natural cycling of vegetative growth and decay would assist in the replenishment of the organic carbon content of the cover layer.
Three different organic materials (peat, lime stabilized sewage sludge (LSSS) and municipal solid waste compost) were evaluated in a combination of bench and pilot scale laboratory test programs. A fourth nonorganic material, desulphurized tailings, was also tested to provide comparative data. The organic cover materials tested demonstrate that there are significant differences in the ability of each material to provide a beneficial tailings cover.
The results to date from the one year pilot scale test cells show that, of all the materials tested, the LSSS performed best at meeting the objectives of a good tailings cover. The data to date show no evidence of the dissolution of metals caused by the migration of organic acids into the underlying tailings, or the effect of reductive dissolution. The following paper summarizes the results of bench scale tests and a one year pilot scale test program designed to evaluate the effectiveness of organic cover materials at reducing acid generation.
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