Integrated membrane system without adding chemicals for produced water desalination towards zero liquid discharge

Abstract

Treatment and management of produced water are of great significance but critical challenges remain due to the huge quantity and complexity of the liquid waste. Here we propose and demonstrate an integrated membrane based system combining electrodialysis, nanofiltration and membrane distillation (ED-NF-MD) for highly efficient treatment of oilfield produced water. Our new system enables zero liquid discharge (ZLD) by concentrating the produced water to an extremely high concentration (up to 373,000 mg/L) at a high water recovery of 99.8% without chemical (e.g. soda or anti-scalants) adding. To the best of our knowledge, such performance is the highest in terms of the final concentration and water recovery among various ZLD technologies. ZLD of our membrane system mainly comes from the metathesis by ED that separates the scaling ions into different streams, thereby creating a scaling-free environment. Basic economic evaluation shows that the total specific energy consumption for ZLD in the whole ED-NF-MD system includes a minimal electrical energy requirement (33 kW·h/m3) and a large thermal energy requirement for MD (154 kW·h/m3). The novel membrane based system shows great potential in realizing real ZLD in produced water treatment by minimizing scaling and thus highly concentrating the feed solution.