(694c) Mathematical Simulation of Acid Rock Drainage

Acid rock drainage (ARD) occurs in rock piles and tailings from mining operations when sulfide minerals oxidize in the presence of water and air to produce sulfuric acid. The rock piles and tailings are generally unsaturated and water (acid) flow is dictated by annual rainfall and snowfall patterns. The resulting acid leaches through the rock material, reacts with other minerals and can contaminate nearby streams and lakes. There have been numerous mathematical models of weathering and (ARD) over the last few decades, starting with rather simple models to very complicated coupled transport models. The problem is that ARD is a very complex process involving not only mineralogical and geochemical changes but physical and biological changes as well. We have developed a mathematical model of ARD using a modified version of TOUGHREACT that includes all the major mechanisms involved and that can be adapted to any particular mining site and environment. The multi-component, multi-phase, non-isothermal model has been calibrated with laboratory data collected from experiments using a modified standard operating procedure over a 52 week duration with actual mining rock material.