Water footprint for mining process : a proposed method to improve water management in mining operations

The water footprint assessment for many products or processes has gained relevance; however, there are only a few aimed at the mining and metallurgy sector. The present study seeks to contribute a methodology to improve water footprint (WF) assessment in mining. The water footprint for the mining process (WFMP) method incorporates aspects that strengthen the Green WF (GreenWF), Blue WF (BWF) and Gray WF (GWF) quantification. The WFMP was applied in two study cases: 1) silver-gold heap leaching (SGHL) and 2) copper sulfide froth flotation (CSFF). The method proposed separating the main infrastructure and activities of the mine sites into modules, which can be assessed individually to obtain the water inventory by water type (green, blue or gray). The adaptation of this water classification in conjunction with a full flow set up module definition helps identifying the critical spots of the mining processes which enables taking actions aimed at minimizing water consumption and hence a better water management. A feature of mining processes is the vulnerability to the effect of the climate factors and the potential water gain/loss to process that can be monitored more precisely using daily data aimed to improve the use of water. The total WF for the SGHL process was 0.18 m3/t, where 0.13 m3/t corresponds to GreenWF and 0.04 m3/t to BWF. For the CSFF process, the WF was 0.26 m3/t, the GreenWF was 0.14 m3/t, and the BWF was 0.12 m3/t. Calculations of the GWF were not included as the processes studied were designed as zero liquid discharge. It was found that enabling changes in parameters that are dynamic contributes to obtain a more precise WF indicator.