Pressure retarded osmosis (PRO) for integrating seawater desalination and wastewater reclamation: Energy consumption and fouling

• A PRO–RO was proposed for integrating wastewater reuse and seawater desalination.
• Its application was however compromised by membrane fouling in PRO.
• Fouling within PRO support layer was hardly reversible by hydrodynamic cleaning.
• Anti-scaling alleviated fouling in PRO and improved its economic feasibility.

A hybrid process of pressure retarded osmosis (PRO) and reverse osmosis (RO) has a great potential for successfully integrating wastewater reclamation with seawater desalination, which can achieve several operational goals simultaneously including augmenting water resources, providing multiple barriers for wastewater purification, seawater dilution for lowering energy use as well as capital cost, osmotic power generation, and less environmental impact. The low energy use of a PRO–RO process was demonstrated by assessing specific energy consumption (SEC). However, a substantial flux decline was observed owing to the susceptibility of PRO to membrane fouling. Particularly, inorganic fouling was pronounced within the support layer, which was hardly reversible by hydrodynamic methods such as physical flushing and osmotic backwashing. Lastly, the anti-scaling pretreatment was shown to be very effective for lessening inorganic scaling within the support layer, suggesting that a PRO–RO hybrid process could be successfully applied with optimized fouling control strategies in PRO.

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