Precipitation-membrane distillation hybrid system for the treatment of aqueous streams

A method of treating an aqueous stream having inorganic material dissolved therein, said method comprising the steps of:

• (a) adding organic solvent to said aqueous stream in an amount effective to form a precipitate comprising at least a portion of said inorganic material, said organic solvent having an increased relative volatility in said aqueous stream in the presence of said inorganic material;
• (b) removing at least most of said organic solvent from said aqueous stream by vacuum membrane distillation;
• (c) after step (b), removing at least most of said precipitate from said aqueous stream to produce an intermediate aqueous product;
• and
• (d) distilling said intermediate aqueous product by membrane distillation to produce an aqueous permeate product.

A method of treating an aqueous stream having inorganic material dissolved therein at a concentration sufficiently low for direct treatment of said aqueous stream by membrane distillation, said method comprising the steps of:

• (a) distilling said aqueous stream by membrane distillation to produce an aqueous permeate product and an intermediate concentrate comprising at least most of said inorganic material;
• (b) adding organic solvent to said intermediate concentrate in an amount effective to form a precipitate comprising at least a portion of said inorganic material, said organic solvent having an increased relative volatility in said intermediate concentrate in the presence of said inorganic material;
• (c) removing at least most of said organic solvent from said intermediate concentrate by vacuum membrane distillation;
• and
• (d) after step (c), removing at least most of said precipitate from said intermediate concentrate to produce a concentrate product and an at least partially purified aqueous product.

A method of treating an aqueous stream having inorganic material dissolved therein and said aqueous stream also having an volatile organic material therein, said method comprising the steps of:

• (a) removing said volatile organic material from said aqueous stream by vacuum membrane distillation;
• (b) then adding organic solvent to said aqueous stream in an amount effective to form a precipitate comprising at least a portion of said inorganic material, said organic solvent having an increased relative volatility in said aqueous stream in the presence of said inorganic material;
• (c) removing at least most of said organic solvent from said aqueous stream by vacuum membrane distillation;
• and
• (d) after step (c), removing at least most of said precipitate from said aqueous stream.

A method of treating an aqueous stream having inorganic material dissolved therein and said aqueous stream also having a volatile organic material therein, said inorganic material being present at a concentration sufficiently low for direct treatment of said aqueous stream by vacuum membrane distillation but for the presence of said volatile organic material, said method comprising the steps of:

• (a) removing said volatile organic material from said aqueous stream by vacuum membrane distillation;
• (b) distilling said aqueous stream by membrane distillation to produce an aqueous permeate product and a concentrate comprising at least most of said inorganic material;
• (c) adding organic solvent to said concentrate in an amount effective to form a precipitate comprising at least a portion of said inorganic material, said organic solvent having an increased relative volatility in said intermediate concentrate in the presence of said inorganic material;
• (d) removing at least most of said organic solvent from said intermediate concentrate by vacuum membrane distillation;
• and
• (e) after step (d), removing at least most of said precipitate from said intermediate concentrate to produce a concentrate product and an at least partially purified aqueous product.