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Increased Support Layer Hydraulic Resistance Partially Explains Permeability Loss in High-Pressure Reverse Osmosis
Sima Zeinali Danalou1, Hongchen Wang2, Niher R Sarker1
1Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, OntarioM5S 3E5, Canada.
Environmental Science & Technology
|July 22, 2026
Summary
High-pressure reverse osmosis (HPRO) faces reduced water permeability due to membrane compaction. This study reveals that both support layer densification and interlayer resistance contribute to significant permeability loss in hypersaline brine treatment.
Area of Science:
- Membrane science and technology
- Water treatment and desalination
- Chemical engineering
Background:
- High-pressure reverse osmosis (HPRO) is crucial for energy-efficient minimal- and zero-liquid-discharge (MLD/ZLD) of hypersaline brines.
- Membrane compaction at high pressures significantly reduces water permeability, with underlying mechanisms not fully understood.
Purpose of the Study:
- To investigate compaction-induced transport and structural changes in a commercial thin-film composite (TFC) membrane under HPRO conditions (up to 150 bar).
- To elucidate the contributions of support layer densification and interlayer resistance to permeability decline.
Main Methods:
- Operated a commercial seawater TFC membrane up to 150 bar.
- Performed selective removal of the polyamide active layer for direct measurement of compacted support permeability.
- Utilized resistance-in-series analysis and uniaxial compression testing.
- Characterized support surface pore size changes.
Main Results:
- Water permeability decreased by 61% (from 2.44 to 0.96 L m-2 h-1 bar-1).
- Support permeability dropped by 90%, but bulk support densification accounted for only 32% of total TFC permeability loss.
- Elastic deformation (20-30%) did not fully explain the decline, indicating additional resistance.
- Mean surface pore diameter reduced by 41%, with potential interfacial resistance between layers contributing to residual loss.
Conclusions:
- Permeability loss in HPRO is a complex phenomenon involving both support hydraulic resistance and interlayer transport limitations.
- Membrane design must focus on maintaining bulk integrity and surface pore accessibility under high pressures for effective HPRO applications.
- Further research is needed to experimentally confirm the role of interfacial resistance in HPRO membrane performance.
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