Method for removing dissolved solids from aqueous waste streams

A method for removing dissolved solids from a waste stream comprising:

• evaporating water from the waste stream in a first evaporator under pressure substantially lower than atmospheric pressure to form a first vapor stream and concentrating the waste stream causing dissolved solids to precipitate therefrom to form a first slurry stream having crystallized solids;
• mechanically compressing at least a portion the first vapor stream;
• condensing at least a portion of the mechanically compressed first vapor stream;
• heating at least a portion of the first slurry stream with at least a portion of the mechanically compressed first vapor stream;
• removing at least a portion of remaining dissolved solids in the first slurry stream by evaporating water from the first slurry stream in a second evaporator under pressure substantially lower than the pressure in the first evaporator to form a second vapor stream and concentrating the first slurry stream causing dissolved solids to precipitate therefrom to form a second slurry stream having crystallized solids;
• condensing at least a portion of the second vapor stream;
• heating at least a portion of the second slurry stream with a refrigerant;
• and
• separating at least a portion of the crystallized solids from the second slurry stream.

A method for removing dissolved solids from a waste stream, comprising:

• directing the waste stream to an evaporator;
• removing dissolved solids from the waste stream by heating the waste stream in the evaporator to a temperature below 60° C. and at a pressure substantially below atmospheric pressure causing water to be evaporated from the waste stream and concentrating the waste stream causing dissolved solids therein to precipitate therefrom which results in the formation of a slurry stream;
• directing the slurry stream to a solids separator;
• and
• separating the solids from the slurry stream.

A method for removing dissolved solids from a waste stream, comprising:

• evaporating water from the waste stream in a first evaporator at a temperature of less than 60° C. and under pressure substantially lower than atmospheric pressure to form a first vapor stream and a first slurry stream;
• compressing at least a portion of the first vapor stream;
• heating at least a portion of the first slurry stream with at least a portion of the compressed first vapor stream;
• evaporating water in the first slurry stream in a second evaporator at a temperature of less than 60° C. and under pressure substantially lower than the pressure in the first evaporator to form a second vapor stream and a second slurry stream;
• and
• heating the second slurry in the second evaporator and condensing the second vapor stream with a closed cycle heat pump.

A method for removing dissolved solids from a waste stream comprising:

• directing the waste stream to a crystallizer operated below atmospheric pressure;
• evaporating water from the waste stream in the crystallizer and forming a slurry stream having crystallized solids;
• directing the slurry stream to a separator;
• and
• separating at least a portion of the crystallized solids from the slurry stream and forming a mother liquor and a solid cake.