After pretreatment, the high-salinity wastewater enters an evaporation system.
Multi-Effect Evaporation
A multi-effect evaporator reuses vapor generated in one evaporation stage as the heating source for the next stage. It is suitable for high-salt wastewater concentration and crystallization where a stable steam supply is available.
MVR Evaporation
Mechanical Vapor Recompression compresses and reuses secondary vapor as a heat source. It can reduce dependence on continuous fresh steam and is suitable for continuous wastewater concentration projects with relatively stable feed conditions.
The choice between MVR and multi-effect evaporation should be based on treatment capacity, energy conditions, wastewater boiling-point rise, corrosiveness, scaling tendency, and investment requirements.
As water is removed, dissolved salts become increasingly concentrated. When the solution reaches supersaturation, salts begin to crystallize.
Forced-circulation evaporation crystallization can be used for concentrated brines and wastewater with scaling or crystallization tendencies. Continuous circulation helps reduce salt deposition on heat-transfer surfaces.
The generated crystals are separated from the mother liquor using centrifuges, filters, or other solid-liquid separation equipment.
Recovered salts must be tested before reuse. Mixed salts or salts contaminated by heavy metals and organics may need to be managed as regulated solid waste rather than recycled.
