Effect of boron rejection and recovery rate on a single-pass design of SWRO using hybrid membrane inter-stage design (HID) concept

Seawater reverse osmosis (SWRO) has been applied as a desalination method to provide potable water to regions under the stress of water shortages and is more effective than other desalination processes. However, specific energy consumption (SEC) must be considered in SWRO process design because of its energy intensive features. Hybrid membrane inter-stage design (HID) was examined to enhance the SEC efficiency of the reverse osmosis process. The additional removal of boron may improve the water quality by adding a second pass. However, this additional factor may increase costs. This study investigated a potential HID that satisfies water quality standards with single pass SWRO only. The element configuration for the HID was evaluated by changes in SEC, salt rejection, and boron rejection under general seawater quality conditions. Case studies were also conducted to estimate the energy efficiency of the HID under three feed conditions: high concentration and high temperature (Case 1); low concentration and high temperature (Case 2); and low concentration and low temperature (Case 3). The results showed HID application can save up to 0.41 kWh/m3 of SEC. Temperature is a more important design factor than recovery rate for HID application.