Abstract: A process of treating nano-filtration membrane retentate comprises introducing seawater comprising a sulfate ion concentration of greater than or equal to 3000 mg/l to the NF membrane to produce a retentate stream and a permeate stream, wherein the retentate stream has a sulfate ion concentration greater than or equal to 10,000 mg/l, and mixing barium additives comprising barium chloride dehydrate (BaCl2·2H2O), barium chloride (BaCl2), or both with the retentate stream to precipitate sulfate from the retentate stream to form barite (BaSO4) and reduce the sulfate ion concentration, wherein the barium additives are added into the retentate stream at a barium ion concentration of greater than 10,000 mg/l.

Abstract: A method of desulfating seawater includes adding a produced water to a sulfated seawater, forming a first precipitate, separating the first precipitate from the sulfated seawater, measuring the sulfate ion concentration of the desulfated seawater, adding a precipitating agent to the sulfated seawater, and separating a second precipitate from the sulfated seawater. Another method of desulfating seawater includes determining concentrations of sulfates in a sulfated seawater and a precipitating agent in a produced water, adding the produced water to the sulfated seawater based on the determined concentrations of sulfates in the sulfated seawater and the precipitating agent in the produced water, forming a first precipitate, separating the first precipitate from the sulfated seawater, measuring the sulfate ion concentration of the desulfated seawater, adding a precipitating agent to a sulfated seawater, and separating a second precipitate from the sulfated seawater.

Abstract: A process of treating nano-filtration membrane retentate comprises introducing seawater comprising a sulfate ion concentration of greater than or equal to 3000 mg/l to the NF membrane to produce a retentate stream and a permeate stream, wherein the retentate stream has a sulfate ion concentration greater than or equal to 10,000 mg/l, and mixing barium additives comprising barium chloride dehydrate (BaCl2.2H2O), barium chloride (BaCl2), or both with the retentate stream to precipitate sulfate from the retentate stream to form barite (BaSO4) and reduce the sulfate ion concentration, wherein the barium additives are added into the retentate stream at a barium ion concentration of greater than 10,000 mg/l.