Membrane-based separation technologies for zero liquid discharge

Zero liquid discharge (ZLD) is proof of various wastewater treatments and is applied in multiple industries across the globe. Additionally, ZLD limits the wastewater discharge at the end of an industrial process by converting wastewater to recycled water and solids. However, it is constrained due to high cost and energy consumption processes. In this context, membrane-based wastewater treatment attracted considerable attention in the last few decades due to its cost-effectiveness and pilot-scale processing. ZLD-membrane-based treatment is considered a significant part of liquid waste management, especially in industrial effluent treatment due to their ability to retrieve by-products from wastewater. Meanwhile, a dry solid cake is produced at the end of the treatment, which helps concentrate any compounds/waste. Here, we attempted to bring details of the membrane techniques (ultrafiltration/microfiltration/nanofiltration, reverse osmosis, forward osmosis, electrodialysis) applied for ZLD and their designs. Membrane-applied ZLD treatment, their key drivers, incentives, technologies, and environmental impacts of the coupled process are explained. This chapter also discusses the ecological consequences of such a strategy and the future scope for the techniques and research requirements.