Inclined forward osmosis module system for fouling control in sustainable produced water treatment using seawater as draw solution

Produced water (PW) generated from oil and gas production is a threat to the environment if not treated properly. Conventional methods for PW treatment are often accompanied by a series of treatments to fulfill the discharge standard. Forward osmosis (FO) is a promising option due to its high solute retention, less irreversible fouling, low energy footprint and potentially used as a standalone unit. However, FO still suffers from the low flux and fouling when treating highly contaminated feeds. This study investigated fouling control in the FO system for concentrating PW by using seawater as a draw solution (DS). A multi-stage filtration system (via via replenishments of the DS) with an aeration and module inclination for fouling mitigation was proposed to improve concentration factor (CF) and flux. Results showed that the multi-stage concentration offered higher fluxes range of 1.72–15.48−1.72 L/(m2h) (LMH) and four times of CF than the single-stage one with fluxes range of 0.39–9.49 LMH corresponding to CF of 1.75. The aeration was effective to enhance the water flux and suppress the fouling, and showed a significant impact at the rate of 0.4 L/min, reaching flux increment by 11 times at a rate of 1 L/min. The impact of aeration was enhanced by inclining the filtration cell up to 5 times at the inclination angle (θ) of 90° due to the improved contacts of air bubbles with the membrane surface. The contribution of the aeration and cell inclination on the water flux can be explained through the forces acting on moving air bubbles