Zero liquid discharge systems have become a necessity for all the industries generating liquid effluents. Common effluent treatment plants in most areas have a limited capacity. The zero liquid discharge systems are normally incorporated to treat the R.O. reject streams.

Process
Zero liquid discharge plants consist of a combination of different types of evaporators depending upon the nature of liquid and it's contents. The waste liquid is concentrated to the maximum level in the evaporators which may be either falling film or forced circulation or a combination of both. The number of stages depends upon the quantity of liquid to be handled. The water evaporated from the evaporators is condensed in the condenser and can be reused in the process.

The concentrated liquid is then dried in either a spray dryer or a agitated thin film dryer. The dry product obtained in powder form can either be used as a by-product or can be sent for land filling.