Zero Liquid Discharge (ZLD) is an advanced treatment process in which almost all wastewater from various industrial processes is treated and reused, therefore leaving behind zero effluent or liquid discharge. Because of increasingly stringent environmental regulations regarding industrial waste, ZLD is becoming a popular method to minimize industry’s environmental impact, providing the opportunity to recover valuable products from waste streams and reduce costs through the reuse of purified wastewater.
Figure 1 provides a general process flow overview of a ZLD system. ZLD processing typically involves the following phases: pretreatment, membrane filtration, evaporation, crystallization and solids recovery.