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A process and an apparatus are described for treating seven types of saline waters each having a concentration of total dissolved solids exceeding 1 g/L, wherein the concentration of total dissolved solids, the ratio of the chloride ion concentration to the bicarbonate ion concentration and the rati

A process and an apparatus are described for treating seven types of saline waters each having a concentration of total dissolved solids exceeding 1 g/L, wherein the concentration of total dissolved solids, the ratio of the chloride ion concentration to the bicarbonate ion concentration and the ratio of the chloride ion concentration to the sulphate ion concentration of each of the water types are as indicated in Table 1. The process includes the steps of contacting the water with a first reagent comprising a source of calcium ions selected from calcium oxide and calcium hydroxide to form a first solid product which is recovered. The process includes a further step of subjecting at least a portion of the partially processed water to at least partial evaporation so as to promote the formation of a precipitate and a mother liquor. The precipitate is recovered as a second product.

대표청구항 ▼

The invention claimed is: 1. A process for treatment of water containing dissolved solids, said process being usable for each of the following types of water: Type 1 water comprising total dissolved solids of 1 to 60 g/L, a Cl-/HCO3- ratio of <2 and a Cl-/2SO42- ratio of >1, Type 2 water comp

The invention claimed is: 1. A process for treatment of water containing dissolved solids, said process being usable for each of the following types of water: Type 1 water comprising total dissolved solids of 1 to 60 g/L, a Cl-/HCO3- ratio of <2 and a Cl-/2SO42- ratio of >1, Type 2 water comprising total dissolved solids of 1 to 15 g/L, a Cl-/HCO3- ratio of ≧2 and a Cl-/2SO42- ratio of >1, Type 3 water comprising total dissolved solids of 1 to 15 g/L, a Cl-/HCO3- ratio of >2 and a Cl-/2SO42- ratio of <1, Type 4 water comprising total dissolved solids of >15 and ≦60 g/L, a Cl-/HCO3- ratio of >5 and a Cl-/2SO42- ratio of >7, Type 5 water comprising total dissolved solids of >15 and ≦60 g/L, a Cl-/HCO3- ratio of >5 and a Cl-/2SO42- ratio of <7, Type 6 water comprising total dissolved solids of >60 g/L, a Cl-/HCO3- ratio of >5 and a Cl-/2SO42- ratio of >9, and Type 7 water comprising total dissolved solids of >60 g/L, a Cl-/HCO3- ratio of >5 and a Cl-/2SO42- ratio of <9, said process comprising the steps of: (a) contacting the said water with a first reagent comprising a source of calcium ions selected from the group consisting of calcium oxide, calcium hydroxide, and a combination thereof as a sole agent to cause at least some solids dissolved in the water to react with the first reagent and to form a first solid product and a partially processed water, wherein the water containing dissolved solids is a Type 1 water and the first solid product is precipitated calcium carbonate (PCC) or the water containing dissolved solids is a water of any of Types 2 to 7 and the first solid product is gypsum-magnesium hydroxide mixture (GMH) and wherein the said GMH is further treated by the addition of sulphuric acid to react with 5-50% of the stoichiometric amount of magnesium hydroxide present in the GMH; (b) recovering the first solid product from the partially processed water; (c) at least partially concentrating the partially processed water or a portion thereof, so as to promote the formation of a precipitate and a mother liquor; and (d) recovering the precipitate from the mother liquor as a second product, wherein the water is a water of type 1 and the second product is sodium hydroxide, sodium sulphate, sodium chloride or sodium carbonate; wherein the water is a water of any one of types 2, 4, 5, 6 and 7, and the second product is sodium chloride; or wherein the water is a water of type 3, and the second product is sodium sulphate. 2. A process as claimed in claim 1, wherein the water is a type 1 water having a salinity of from 1 to 60 g/L total dissolved solids (TDS). 3. A process as claimed in claim 1, wherein the water is contacted with a pre-determined amount of the first reagent. 4. A process as claimed in claim 1, wherein the water is a water of type 1 and the first product is precipitated calcium carbonate (PCC). 5. A process as claimed in claim 4, wherein, in step (a), only a portion of the bicarbonate ions in the water are converted to PCC and, wherein, in a secondary reaction step, the first solid product and the partially processed water of step (a) are contacted with a solution of calcium chloride to convert substantially all of the carbonate ions in the partially processed water to PCC. 6. A process as claimed in claim 4, wherein, in step (a), only a portion of the bicarbonate ions in the water are converted to PCC and, wherein, in a secondary reaction step after the recovery of the said PCC in step (b), the partially processed water of step (b) is contacted with a solution of calcium chloride to convert substantially all of the remainder of the carbonate ions in the partially processed water to supplementary PCC. 7. A process as claimed in claim 1, wherein the water is a water of type 1 and the second product is sodium hydroxide. 8. A process as claimed in claim 1, wherein the water is a water of any one of types 2, 4, 5, 6 and 7, and the second product is sodium chloride. 9. A process as claimed in claim 8, wherein, after step (b), the partially processed water is contacted, in a step (e), with a second reagent also comprising a source of calcium ions selected from the group consisting of calcium oxide, calcium hydroxide, and a combination thereof, so as to cause at least some of the solids dissolved in the partially processed water to react with the second reagent and to form magnesium hydroxide, and wherein the magnesium hydroxide is recovered from the partially processed water before the recovery of said sodium chloride therefrom. 10. A process as claimed in claim 1, wherein the water is a water of type 3, and the second product is sodium sulphate. 11. A process as claimed in claim 1, wherein the water is a water of type 1 and the pH of the partially processed water is reduced, in a step (b)(i), to a pH falling within the range of from 7 to 10. 12. A process as claimed in claim 11, wherein the pH of the partially processed water is reduced by adding to the partially processed water a pH reducing agent selected from the group consisting of hydrochloric acid, sulphuric acid, saline impaired feed water, a reverse osmosis (RO) concentrate of type 1 water, and a combination of any two or more thereof. 13. A process as claimed in claim 11, wherein the water is a type 1 water, the pH of the partially processed water is reduced to between 8 and 9 by adding sulphuric acid to the partially processed water and wherein the second product is sodium sulphate. 14. A process as claimed in claim 11, wherein the water is a type 1 water, the pH of the partially processed water is reduced to between 8 and 9 by adding hydrochloric acid to the partially processed water and wherein the second product is sodium chloride. 15. A process as claimed in claim 11, wherein the water is a type 1 water, the pH of the partially processed water is reduced to between 8 and 9 by adding type 1 water to the partially processed water and wherein the second product is sodium carbonate. 16. A process as claimed in claim 1, wherein the first reagent is hydrated lime slurry and the weighted average sulphate ion concentration of the water and the hydrated lime slurry is controlled below 3 g/L by controlling the volume of hydrated lime slurry contacted with the water or by controlling the concentration of solids in the hydrated lime slurry, or by both. 17. A process as claimed in claim 1, wherein the reacted GMH product is dried at a temperature between 120° C. and 300° C. 18. A process as claimed in claim 1, wherein the water to the process is a type 4 or a type 6 water, wherein, after step (b), sodium carbonate is added to the partially processed water, and wherein magnesium carbonate light (MCL) is recovered therefrom to produce a treated water which is low in magnesium content. 19. A process as claimed in claim 1, wherein the water is or comprises a concentrate from a reverse osmosis (RO) desalination plant. 20. A process as claimed in claim 1, wherein a portion of the mother liquor of step (d) is combined with the partially processed water from step (b) before it is subjected to evaporation in step (c). 21. A process as claimed in claim 1, wherein a portion of the mother liquor of step (d) is evaporated to total dryness. 22. The process of claim 1, wherein the process is carried out on water of Types 1-3 or 5-7.