Treatment of a hypersaline brine, extracted from a potential CO₂ sequestration site, and an industrial wastewater by membrane distillation and forward osmosis

Industrial-scale CO₂ geological sequestration in deep saline aquifers may require extraction of large volumes of hypersaline brine. We investigated different strategies for treatment of Mt. Simon brine (a hypersaline brine with total dissolved solids of ∼225,000 ppm, extracted from a potential CO₂ sequestration site in Illinois) and an industrial wastewater. The extracted brine was first subjected to a coagulation/filtration pretreatment and then treated directly by membrane distillation (MD), or used as a draw solution to harvest purified water from an industrial wastewater by the forward osmosis (FO) process. Results indicated that the pretreated brine could be treated directly by MD with a water flux of 38 kg/m²·h and ∼40% water recovery. In simultaneous treatment of the wastewater and Mt. Simon brine using FO-MD, the Mt. Simon brine draw solution outperformed a 20% MgSO₄ draw solution by showing a higher osmotic pressure that resulted in a 60% higher water flux. However, the brine draw solution also showed a higher reverse salt flux. The treatment of wastewater by FO using the hypersaline brine as a draw solution, performed in multicycles by periodic flushing with deionized water, demonstrated a stable water flux and reduced the wastewater volume by ∼10 times. The treatment strategies investigated reduced the volume of industrial wastewater by ∼10 times and that of Mt. Simon brine by ∼2 times, and they generated a significant amount of usable water through direct and indirect treatment of the Mt. Simon brine by the MD process.