Zero Liquid Discharge (ZLD) is an advanced water management strategy and engineering objective implemented in bauxite, gold, iron ore, and diamond mining operations in which all liquid effluent generated by mining, mineral processing, and refining activities is treated, recovered, and recycled within the operation, with no liquid waste released to the external environment. ZLD systems are designed to capture every litre of process water, stormwater, leachate, and wastewater generated on site and return it to operational use or convert it to solid waste that can be safely disposed of or repurposed. The achievement of ZLD in mining typically involves a multi-stage treatment train that includes primary thickening and clarification, secondary treatment through biological or chemical processes, advanced membrane filtration such as ultrafiltration and reverse osmosis, and final brine concentration through technologies such as mechanical vapor recompression (MVR), evaporators, and crystallizers. In gold mining, ZLD is critical for containing cyanide-bearing solution and preventing environmental contamination. In bauxite refining, it manages caustic soda-laden process liquors. In iron ore operations, it addresses water with elevated iron, sulfate, and suspended solids. In diamond mining, ZLD helps manage kimberlite-contaminated water. ZLD implementation is increasingly required by regulators in water-scarce regions and is recognized as a key pillar of sustainable mining practice, helping operations maintain their social license and environmental compliance.
