Conceptual model for estimating water recovery in tailings impoundments

In most semi-arid and arid regions water is a scarce commodity and “reclaim water” from the tailings impoundment is commonly used in the milling process to minimize water consumption. A comprehensive study has been initiated to study the influence of tailings management on water losses and water recovery for a very large tailings impoundment (52 km 2 ) in the Atacama Desert in northern Chile. This paper develops the theoretical background and presents a novel approach for estimating water recovery. Water recovery is controlled by a complex interplay of various physical processes including tailings deposition and consolidation, evaporation, rewetting and seepage. The use of a deterministic water balance model, which accounts for all of these transient processes, was not feasible for this large tailings impoundment. Instead, a water recovery model was developed, which focuses only on water losses from the active tailings stream to estimate water recovery. The model assumes that only process water liberated during the initial settlement is available for water recovery. The major water losses in this model include (i) entrainment losses during initial settlement of the tailings, (ii) evaporation losses from flooded areas of the tailings beach and (iii) rewetting losses during discharge of fresh tailings onto older, desiccated tailings beaches. This water recovery model was applied to the Tranque de Talabre tailings impoundment to explain existing water losses and to predict water losses and recovery for alternative tailings discharge plans.