Evaporate the reject stream, recover distilled water and leave only dry salt — no liquid effluent leaves the plant.
Pollution control boards increasingly require industries — especially those with high-TDS or coloured effluent — to discharge no liquid at all. A ZLD scheme concentrates the treated reject and evaporates it.
The condensed vapour returns as high-purity distilled water for reuse, and the residue leaves as dry salt or sludge cake. The right evaporator depends on your reject volume and available utilities — steam, electricity or both.
Steam heats the effluent in a single calandria; the vapour is condensed and recovered as distilled water while the concentrate thickens for salt separation. Simple, robust and economical for low to medium reject volumes.
Where no boiler or steam line exists, electrically heated evaporators do the same job in a compact skid. Ideal for laboratories, small process units and sites with intermittent reject generation.
Vapour from the first effect becomes the heating medium of the next, so each kilogram of steam evaporates several kilograms of water. For large, continuous reject volumes an MEE — often with a thermo-vapour compressor — cuts energy cost dramatically.
The concentrate goes to salt separation — ATFD / centrifuge — so no liquid leaves the plant.
Evaporation systems recovering water from reject.