Patent ID: 7879243

Claim:
A process for removing water from a first solution, said process comprising: i) providing a first solution comprising seawater or brackish water, ii) forming a second solution having a higher osmotic potential than the first solution by dissolving a solute selected from the group consisting of MgSO 4 .6H 2 O, MgSO 4 .7H 2 O, MgCl 2 .6H 2 O, Na 2 SO 4 .10H 2 O, CaCl 2 .2H 2 O, CaCl 2 .6H 2 O, potassium alum.24H 2 O, potassium chloride, sodium chloride, and Na 2 HPO 4 .12H 2 O in water, wherein the second solution formed is substantially free of components that cause membrane fouling, iii) directly adding into the second solution an additive selected from the group consisting of anti-scaling agents and anti-fouling agents; a) positioning a first selective membrane between the first solution and the second solution, such that water from the first solution passes across the first membrane to dilute the second solution by direct osmosis, and b) passing the diluted second solution through a nano-filtration membrane, wherein the second solution contains solute species too large to pass through the pores of the first selective membrane and the nanofiltration membrane.