Paste and thickened tailings — friend against acid and metalliferous drainage?

Authors: Mudd, GM Download Paper

DOI https://doi.org/10.36487/ACG_rep/1104_18_Mudd

Cite As:
Mudd, GM 2011, 'Paste and thickened tailings — friend against acid and metalliferous drainage?', in R Jewell & AB Fourie (eds), Paste 2011: Proceedings of the 14th International Seminar on Paste and Thickened Tailings, Australian Centre for Geomechanics, Perth, pp. 187-201, https://doi.org/10.36487/ACG_rep/1104_18_Mudd



Abstract:
Tailings management has been a rapidly growing and demanding challenge across the global mining industry over the past century, primarily due to growing metals demand (and consequently production), declining ore grades (including refractory mineralogy issues), and increasingly stringent environmental and technical requirements. The typical approach historically has been to build engineered storage structures, involving valley fill walls or ring dykes, with the tailings delivered to the tailings storage facility (TSF) via a slurry pipeline. Conventional embankments, however, can fail under a variety of mechanisms and cause catastrophic environmental and public health impacts — the most recent event being the red mud dam failure in Hungary. Another major environmental issue associated with tailings (and waste rock) is the generation of acid and metalliferous drainage or AMD (also commonly known as acid mine drainage). The cause of AMD is the exposure of sulphidic minerals, such as pyrite and pyrrhotite, in mine wastes to water and oxygen, leading to oxidation and the release of sulphuric acid. This in turn dissolves a strong cocktail of heavy metals and if allowed to reach the environment, AMD can cause extreme impacts on biodiversity, water quality, ecosystem health and public amenity. If left unaddressed, AMD pollution can continue for hundreds or potentially even thousands of years. Over recent decades, major advances in thickening technology have enabled the development of paste and thickened tailings (P&TT) to be adopted as a realistic and economic alternative to conventional tailings dams. The primary driver of P&TT technology is the non-Newtonian fluid behaviour of the solid suspension of water and tailings. Given that one of the primary drivers of AMD is excess water flowing through the mine waste — can the relatively low moisture content and rheological characteristics of P&TT provide a natural defence against AMD generation? This is a fundamentally critical question and deserves thorough assessment and consideration. At present there appears to have been virtually no research on linking AMD issues to P&TT management, although it is understood that there appears to be no indications of AMD problems at existing P&TT operations. This paper will therefore review the basics and the scale of AMD problems around the world, present the essential rheological characteristics of paste and thickened tailings and then critically examine the potential for AMD associated with P&TT management. It then attempts to answer that critical question: can the P&TT provide a natural defence against AMD problems? The paper is therefore a timely and perhaps unique view of another potential advantage in P&TT which is yet to be well understood and receive due recognition.

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