Process for pre-treating and desalinating sea water

A process for treating sea water to reduce the concentration of salts therein comprising

• (A) adding to said sea water about 0.04 to about 40 g/L of a compound selected from the group consisting of calcium hydroxide, calcium oxide, and mixtures thereof, whereby a first precipitate that comprises calcium hydroxide is formed;
• (B) separating said first precipitate from said water;
• (C) adding to said water about 0.01 to about 60 g/L sodium carbonate and about 0.04 to about 40 g/L sodium hydroxide, whereby a second precipitate that comprises magnesium hydroxide is formed;
• (D) separating said second precipitate from said water;
• and
• (E) desalinating said water using reverse osmosis to produce a first stream that has a lower concentration of dissolved solids and a second stream that has a higher concentration of dissolved solids, and
• (1) a mixture is formed of said second stream and said sea water;
• (2) a sufficient amount of said compound is added to said mixture to bring its concentration within a range of about 0.4 to about 40 g/L;
• and
• (3) said mixture is recycled to step (C).

A process for treating sea water to reduce the concentration of dissolved salts therein comprising

• (A) adding to said sea water about 0.4 to about 40 g/L of a compound selected from the group consisting of calcium hydroxide, calcium oxide, and mixtures thereof, whereby a first precipitate that comprises calcium hydroxide is formed;
• (B) separating said first precipitate from said water;
• (C) adding to said water about 0.1 to about 60 g/L sodium carbonate and about 0.04 to about 40 g/L sodium hydroxide , whereby a second precipitate that comprises magnesium hydroxide is formed;
• (D) separating said second precipitate from said water;
• and
• (E) desalinating said water using flash evaporation to produce a first stream that has a lower concentration of dissolved solids and a second stream that has a higher concentration of dissolved solids, and
• (1) a mixture is formed of said second stream and said sea water;
• (2) a sufficient amount of said compound is added to said mixture to bring its concentration within a range of about 0.4 to about 40 g/L;
• and
• (3) said mixture is recycled to step (C).