Abstract
The expansion of seawater desalination has significantly increased global brine production, exceeding 140 million m³/day, with more than half generated in the Middle East and North Africa (MENA) region [1]. Brine disposal poses environmental and economic challenges, particularly in semi-enclosed marine systems. Zero Liquid Discharge (ZLD) and brine valorization strategies aim to eliminate liquid effluent while recovering water and valuable minerals. This study analyzes current ZLD configurations, mineral recovery pathways, and techno-economic constraints. Particular attention is given to the Saudi Arabian national strategy as a leading example of industrial-scale brine mining. The findings indicate that hybrid membrane–thermal systems combined with selective mineral recovery may enable desalination to evolve into a circular resource platform.
Context and Rationale
Seawater desalination has become a cornerstone of water security in arid regions. Reverse osmosis (RO) represents the dominant global technology [1]. However, desalination generates hypersaline brine streams containing 65–85 g/L TDS in SWRO reject streams [1].
Global brine production exceeds 51.7 billion m³ annually [1]. Disposal costs may represent up to one-third of operational expenditure depending on discharge strategy [2]. Environmental impacts include localized salinity elevation, benthic ecosystem disturbance, and accumulation of chemical residuals.
These pressures have accelerated research into Minimum Liquid Discharge (MLD) and Zero Liquid Discharge (ZLD) configurations [2,3]. Simultaneously, brine is increasingly recognized as a secondary resource for minerals and energy [3].
This study evaluates current technological pathways for brine valorization and examines their strategic implications for the MENA region.
Analytical Framework and Evaluation Approach
The present work is based on:
- A systematic review of peer-reviewed literature (2019–2025) on ZLD and brine valorization [2–5];
- Comparative techno-economic assessments of membrane and thermal systems [2];
- Global mineral recovery potential modeling derived from SWRO brine composition data [3];
- Assessment of national-scale brine mining strategies in Saudi Arabia [6].
The evaluation integrates four dimensions:
- Technology classification and maturity
- Energy consumption comparison
- Mineral recovery potential estimation
- Strategic and policy analysis
This multi-criteria approach enables a structured assessment of technological feasibility and regional applicability.
Technological Performance and Recovery Pathways
Water Recovery Enhancement through MLD and ZLD
MLD systems typically achieve 80–90% total water recovery using membrane-based concentration technologies [2].
ZLD systems reach 95–99% recovery by combining membrane pre-concentration with thermal crystallization stages [3]. However, thermal polishing may increase specific energy consumption by 10–20 kWh/m³ [2].
Hybrid membrane–thermal configurations appear to provide the most balanced compromise between recovery efficiency and energy demand [2,3].
Principal Valorization Technologies
Four major technological pathways emerge:
(a) Advanced Membrane Technologies
- High-Pressure Reverse Osmosis (HPRO) [2]
- Forward Osmosis (FO) [4]
- Membrane Distillation (MD) [4]
- Electrodialysis (ED/EDR) [5]
- Bipolar Membrane Electrodialysis (BMED) [4]
These technologies enhance selective ion recovery and reduce thermal dependency.
(b) Thermal Concentration and Crystallization
- Multi-Effect Distillation (MED)
- Mechanical Vapor Compression (MVC)
- Forced circulation crystallizers
Thermal systems remain technically mature but energy-intensive [2].
(c) Mineral Recovery (Brine Mining)
Recoverable products include:
- Sodium chloride (NaCl)
- Magnesium compounds
- Calcium salts
- Bromine
- Trace elements (Sr, Rb, Li)
A recent global assessment demonstrated that magnesium recovery potential from SWRO brine could theoretically exceed current global mining production [3].
(d) Salinity Gradient Energy
Reverse Electrodialysis (RED) and Pressure Retarded Osmosis (PRO) allow electricity generation from salinity gradients [4], offering complementary valorization potential.
National-Scale Implementation: The Saudi Arabian Model
Saudi Arabia accounts for over 30% of global SWRO capacity [1].
Under Vision 2030, national authorities have initiated brine mining strategies targeting:
- Bromine recovery
- Industrial NaCl production
- Magnesium valorization
- Integration with petrochemical industries [6]
Preliminary assessments indicate that mineral recovery could significantly offset desalination production costs [6], positioning desalination as a strategic industrial platform rather than a pure utility service.
Interpretation and Strategic Implications
Technical Viability
ZLD is technically feasible but remains highly energy-dependent. Hybrid membrane–thermal integration represents the most promising route toward scalability [2,3].
Economic Considerations
NaCl and Mg recovery show near-term industrial potential, whereas trace element extraction remains constrained by concentration levels and purification costs [3].
Environmental Alignment
ZLD reduces marine discharge impacts and supports circular economy principles [4]. Renewable energy integration is critical to reduce carbon footprint.
Regional Strategy for MENA
Desalination-intensive countries in MENA may reposition brine as a strategic mineral resource. Saudi Arabia provides the most advanced example of national-scale integration [6], illustrating how desalination can contribute to economic diversification.
Conclusions and Future Outlook
Zero Liquid Discharge and brine valorization represent a transformative pathway for desalination-intensive regions. Although energy intensity remains a major constraint, hybrid technologies and selective mineral recovery demonstrate strong potential. Strategic policies, such as those implemented in Saudi Arabia, illustrate how desalination may evolve from a water production industry into a mineral resource platform.
Future research priorities include:
- Energy optimization
- Selective extraction technologies
- Advanced thermodynamic modeling
- Renewable coupling strategies
Desalination is no longer solely a water security instrument; it may become a cornerstone of resource security in arid regions.
References
[1] Jones, E.; Qadir, M.; van Vliet, M.; Smakhtin, V.; Kang, S.M. The state of desalination and brine production: A global outlook. Science of the Total Environment, 2019, 657, 1343–1356.
[2] Panagopoulos, A. Techno-economic assessment of minimal and zero liquid discharge desalination systems. Journal of Environmental Management, 2022, 301, 113859.
[3] Morgante, C.; Herrero-Gonzalez, M.; Lopez, J.; Imholze, J.; Boffa, V.; Ibañez, R.; Cortina, J.L. Seawater reverse osmosis brine valorization: Global mineral recovery potential. Desalination, 2025, 580, 119718.
[4] Ihsanullah. Potential of membrane and thermal technologies for brine management and resource recovery. Desalination, 2022, 530, 115682.
[5] Mavukkandy, M.; Choi, J.; Lee, S.; Kim, I.S. Brine management in desalination industry: A comprehensive review. Desalination, 2019, 463, 123–137.
[6] Alt, S.; Fellows, C. Seawater desalination brine mining: National strategy and economic assessment. Water Policy, 2024, 26, 1123–1142.
