Patent ID: 7595001

Claim:
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 − /HCO 3 − ratio of <2 and a Cl − /2SO 4 2− ratio of >1, Type 2 water comprising total dissolved solids of 1 to 15 g/L, a Cl − /HCO 3 − ratio of ≧2 and a Cl − /2SO 4 2− ratio of >1, Type 3 water comprising total dissolved solids of 1 to 15 g/L, a Cl − /HCO 3 − ratio of >2 and a Cl − /2SO 4 2− ratio of <1, Type 4 water comprising total dissolved solids of >15 and ≦60 g/L, a Cl − /HCO 3 − ratio of >5 and a Cl − /2SO 4 2− ratio of >7, Type 5 water comprising total dissolved solids of >15 and ≦60 g/L, a Cl − /HCO 3 − ratio of >5 and a Cl − /2SO 4 2− ratio of <7, Type 6 water comprising total dissolved solids of >60 g/L, a Cl − /HCO 3 − ratio of >5 and a Cl − /2SO 4 2− ratio of >9, and Type 7 water comprising total dissolved solids of >60 g/L, a Cl − /HCO 3 − ratio of >5 and a Cl − /2SO 4 2− 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.