TABLE OF CONTENTS The disposal of mill tailings is a major environmental problem, which is becoming more serious with the increasing exploration for metals and the working of lower-grade deposits. Apart from the visual effect on the landscape of tailings disposal, the major ecological effect is usually water pollution, arising from the discharge of water contaminated with solids, heavy metals, mill reagents, sulphur compounds, etc. (Chalkley et al., 1989). Waste must therefore be disposed of in both an environmentally acceptable and, if possible, economically viable manner (Sofr and Boger, 2002). Disposal is governed by legislation and may involve long-term rehabilitation of the site.
The nature of tailings varies widely; they are usually transported and disposed of as a slurry of high water content, but they may be composed of very coarse dry material, such as the float fraction from dense medium plants. Due to the lower costs of mining from open pits, ore from such locations is often of very low grade, resulting in the production of large amounts of very fine tailings.
The methods used to dispose of tailings have developed due to environmental pressures, changing milling practice, and realisation of profitable applications. Early methods included discharge of tailings into rivers and streams, which is still practised at some mines, and the dumping of coarse dewatered tailings on to land. The many nineteenthcentury tips seen in Cornwall and other parts of Britain are evidence of this method. Due to the damage caused by such methods, and...
