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Module-scale analysis of low-salt-rejection reverse osmosis: Design guidelines and system performance
Yuhao Du1, Zhangxin Wang2, Nathanial J Cooper1
1Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, United States.
Water Research
|December 18, 2021
Summary
Low-salt-rejection reverse osmosis (LSRRO) technology concentrates brine efficiently at moderate pressures. This study shows LSRRO significantly advances minimal/zero liquid discharge by reducing thermal brine concentrator use.
Area of Science:
- Membrane Science and Technology
- Water Treatment Technologies
- Chemical Engineering
Background:
- Conventional reverse osmosis (RO) faces limitations in high brine concentration.
- Minimal/zero liquid discharge (MLD/ZLD) strategies require efficient brine management.
- Novel technologies are needed to reduce reliance on energy-intensive thermal processes.
Purpose of the Study:
- To investigate the performance of low-salt-rejection reverse osmosis (LSRRO) membrane modules and systems.
- To correlate LSRRO membrane properties with performance metrics.
- To provide design guidelines and evaluate LSRRO for MLD/ZLD applications.
Main Methods:
- Module-scale analysis of LSRRO performance.
- Correlation of salt rejection with water and salt permeabilities.
- Evaluation of multi-stage LSRRO systems (2-stage and 3-stage) under varying feed salinities.
Main Results:
- LSRRO modules achieve high brine concentration at moderate pressures.
- 3-stage LSRRO effectively concentrates low-salinity feed to >4 M NaCl with low specific energy consumption (SEC) of ~3 kWh m-3.
- For high-salinity feed, 3-stage LSRRO achieves ~80% higher concentration than conventional RO with SEC not exceeding 6 kWh m-3.
Conclusions:
- LSRRO technology significantly enhances MLD/ZLD by minimizing the need for thermal brine concentrators.
- System design, including the number of stages, impacts energy consumption.
- LSRRO shows practical viability for advanced wastewater treatment and resource recovery.
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