Use of forward osmosis in treatment of hyper-saline water

Produced water is the largest waste stream in the oil and gas industry. The quality of produced water varies greatly, from near drinkable to highly contaminated (large amounts of inorganics and organics). Some of the most challenging produced waters in the world today are found in Iraq, where concentrations of dissolved solids can exceed 200,000 ppm and oil content can be near 100 ppm. In this work, forward osmosis is investigated as a suitable treatment method for hyper-saline produced water. Two draw solutions, ammonia-carbon dioxide (NH3-CO2) and magnesium chloride (MgCl2), were evaluated for dewatering these brines. The NH3-CO2 draw solution, though easily recycled, demonstrated low flux and substantial scaling issues caused by pH changes and carbonate fluxes. MgCl2 showed substantially higher fluxes due to higher osmotic efficiency and lower scaling propensity.