Modelling the Water Network of a PGM Mining and Beneficiation Value Chain: A System Dynamics Approach

The mining industry is faced with a double challenge of diminishing water availability and deteriorating water quality, with high mine effluent discharges exacerbating the latter. Mining companies must adopt effective ways to make their water service networks sustainable, simultaneously addressing problems of high water consumption and high pollution load, while ensuring that enough water is provided at the right quality for various processes. This papers aims to examine the water network for a PGM mining and beneficiation operation, in order to identify major drivers of poor water quality and high water usage, as well as to give direction for process optimisation. The study first considers the mining and beneficiation process steps, establishing the value-chains for both mineral and water. It then takes an LCA methodological approach to define each process step, identifying the variables that influence pollution load. Relevant process factors are extracted from literature and incorporated into a causal loop diagram. A stock and flow dynamic model is developed, with source, sink and flow rates of water clearly defined. The resulting system is simulated using modelling software and optimised for the following objectives: maximised mineral yield, maximised reused water, minimised freshwater extraction, discharged wastewater and treated water for reuse. Based on results, biggest factors influencing pollution load are identified and strategies for improving water efficiency are discussed. The extent to which water recycling offsets demand for freshwater extraction is determined, together with its impact on effluent discharge. Finally, challenges to be addressed in future research work are discussed. Unlike previous studies that mostly focussed on optimising water use for a single process, usually floatation, this study took a holistic approach and considered the entire value chain of mining and beneficiation.