A Zero Liquid Discharge (ZLD) process diagram that highlights how wastewater from an industrial process is converted to solids and treated water for reuse via a ZLD plant.

Despite the variable sources of a wastewater stream, a ZLD system is generally comprised by two steps:

1. Pre-Concentration: Pre-concentrating a brine is usually achieved with membrane brine concentrators or electrodialysis. These technologies concentrate a stream to a high salinity and are able to recover up to 60–80% of the water.
2. Evaporation/Crystallization: The next step, using thermal processes or evaporation, evaporates all the leftover water, collects it, and sends it to reuse. The waste that is left behind then goes to a crystallizer that boils all the water until all its impurities crystallize and can be filtered out as solids.