Zero liquid discharge

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A zero liquid discharge process diagram that highlights how wastewater from an industrial process is converted via a ZLD plant to solids and treated water for reuse.

Zero liquid discharge is a process that is beneficial to industrial and municipal organizations as well as the environment because it saves money and no effluent, or discharge, is left over. ZLD systems employ the most advanced wastewater treatment technologies to purify and recycle virtually all of the wastewater produced. Also Zero liquid discharge technologies help plants meet discharge and water reuse requirements, enabling businesses to:

A Zero liquid discharge facility (ZLD), is an industrial plant without discharge of wastewaters. Target ZLD is normally reached by

ZLD discharge system overview[edit]

ZLD technology includes pre-treatment and evaporation of the industrial effluent until the dissolved solids precipitate as crystals. These crystals are removed and dewatered. The water vapor from evaporation is condensed and returned to the process.

The state of Tamil Nadu in India has made zero liquid discharge mandatory for all its industries.[1]


Normally the evaporation-crystallizing section receives the reject from a reverse osmosis section that concentrates dissolved solids. To prevent fouling during the reverse osmosis process, ultrafiltration is often used to eliminate suspended solids.

See also[edit]