EXECUTIVE SUMMARY

The present study was undertaken to evaluate the impact of flooding of the Solbec-Cupra oxidized mine tailings on the production of acid mine drainage (AMD). Representative oxidized and unoxidized mine tailings samples were collected on the site and used in experimental columns and reservoirs (large lysimeters) to simulate artificial flooding during a minimal period of nine months. The objectives of this research projet was to verify the efficiency of flooding on the viability and oxidative activity of microorganisms producing AMD and also to obtain data on the efficiency of the incorporation of lime into the tailings.

We obtained the following results:

1. Flooding of unoxidized tailings prevented their colonization by known iron-oxidizers such as Thiobacillus ferrooxidans and Leptospinllum ferrooxidans mainly because of the neutral pH water. We did not isolate any of the sulfide oxidizing bacterial strains from the already installed experimental large lysimeters on the Solbec-Cupra tailings site; however, the oxidized tailings yielded numerous and varied acidophilic and acidifying bacterial species.
2. Artificial flooding of unoxidized tailings mixed with neutralizing lime material caused the inhibition of inoculated bacteria as well as their oxidative properties towards pyrite in columns without eliminating them; their overall viability was presented during the entire experimentation period.
3. Lime application was estimated to be 118 tons/hectare to a depth of 15 cm, this rate of application was found to neutralize most of the accumulated acidity in the oxidized tailings, it also prevented the iron and calcium migration. A security factor, to be determined, could be used to maintain the pH at an acceptable level on a long term basis. liming material could be added directly to water if re-acidification was to occur after flooding.
4. The existing methods to asses lime dosage in soils are not adequate to predict neutralizing material needed in mine tailings, mainly because they do not have any buffering capacity.

Last Modified: 2003-11-26		Important Notices

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