The management of brine generated by desalination plants has become one of the key determinants of the environmental and economic sustainability of this technology, which is now strategic for global water security. The production of desalinated water has increased significantly over the past two decades, particularly in arid regions of the Middle East, North Africa, Australia, and certain coastal areas of Europe and North America. This growth has inevitably been accompanied by a proportional increase in brine volumes. Globally, desalination facilities are estimated to produce more than 140 million cubic meters of brine per day, exceeding the volume of freshwater produced due to limited recovery rates, particularly in seawater reverse osmosis systems [1].
This brine typically exhibits salinity levels between 60 and 75 g/L, along with residual concentrations of chemical additives used during pretreatment and membrane cleaning. Without proper management, these discharges may cause localized density disturbances, increased water column stratification, impacts on benthic macrofauna, and shifts in biological communities [2].
Current best practices primarily rely on optimizing marine discharge systems. Modern approaches favor the use of submarine outfalls equipped with multiport diffusers to ensure rapid and controlled dilution of brine in the water column. Studies conducted in the western Mediterranean have shown that properly designed diffusers can reduce salinity anomalies to near-background levels within a few tens of meters from the discharge point, thereby limiting the spatial footprint of impacts [3].
The integration of three-dimensional hydrodynamic modeling during the design phase enables accurate prediction of saline plume dispersion based on currents, bathymetry, and seasonal thermal gradients. These tools are now considered essential requirements in environmental impact assessments associated with large-scale desalination projects [4].
At the same time, source reduction represents a crucial lever. Improvements in high-permeability reverse osmosis membranes and the widespread adoption of energy recovery devices have increased recovery rates while reducing specific energy consumption, which can now fall below 3 kWh/m³ in high-performance facilities [5]. Even a few percentage points increase in recovery directly translates into a significant reduction in brine volume. Pilot studies conducted in California have demonstrated that hybrid configurations combining reverse osmosis with secondary membrane stages can achieve high yields while controlling scaling phenomena through optimized antiscalant dosing and pH management [6].
Beyond discharge optimization, the most promising innovations concern liquid effluent minimization and brine component valorization. The concept of “zero liquid discharge” has been tested in several industrial contexts. In Australia, the Perth desalination plant has been the subject of exploratory studies on integrating advanced concentration processes and solar evaporation ponds to reduce discharge volumes, particularly in capacity expansion scenarios [7]. These approaches combine reverse osmosis with additional thermal or membrane processes such as membrane distillation or reverse electrodialysis to further concentrate salts and recover additional water.
In Europe, the collaborative project “ZERO BRINE,” funded under the Horizon 2020 program, demonstrated at pilot scale the feasibility of selectively recovering salts and minerals from industrial saline effluents and concentrated brines [8]. By combining nanofiltration, electrodialysis, and fractional crystallization, researchers successfully produced industrial-grade sodium chloride, magnesium, and other valuable compounds. These results confirm that brine can be regarded as a secondary resource within a circular economy framework, simultaneously reducing environmental burdens and generating potential revenue streams.
Research conducted in China within pilot projects on seawater desalination brine valorization has explored lithium, magnesium, and boron recovery through combined selective precipitation and membrane extraction processes [9]. Some experimental coastal facilities have demonstrated the technical feasibility of extracting strategically valuable elements from saline concentrates, particularly in the context of growing lithium demand for batteries. Although concentrations remain lower than in natural continental brines, these studies show that process optimization can enhance economic viability and contribute to mineral supply diversification.
Integrated aquaculture represents another innovative pathway. Pilot projects in Australia and Asia have investigated the controlled use of diluted brines for cultivating halotolerant microalgae, with prospects for producing biomass for animal feed or energy valorization [10]. While these systems require strict chemical parameter control to prevent residual toxicity, they illustrate the potential synergies between desalination and the marine bioeconomy.
Energy integration is a key success factor for advanced brine management strategies. Additional concentration processes can be energy-intensive unless coupled with renewable energy sources or waste heat recovery systems. Recent research has shown that combining membrane distillation with industrial waste heat or solar thermal sources can improve overall system efficiency while reducing carbon footprints [11]. Integrating desalination into multi-purpose industrial platforms also promotes shared discharge infrastructure and monitoring systems.
Environmental monitoring constitutes an essential component of best practices. Advances in continuous sensing technologies and predictive modeling now enable real-time tracking of physicochemical parameters around outfalls. Long-term studies in the Mediterranean have demonstrated that adaptive monitoring allows discharge rate adjustments and prevents localized salinity accumulation, thereby reducing risks to sensitive seagrass meadows [12]. The use of big data analytics and artificial intelligence algorithms opens new perspectives for dynamic operational optimization.
Despite these advances, several challenges remain. Valorization technologies must still demonstrate large-scale economic viability, particularly in contexts where mineral prices fluctuate. Initial investments for advanced concentration systems can be substantial, and their adoption strongly depends on regulatory frameworks and economic incentives. Nevertheless, global trends increasingly favor the integration of circular economy principles into the desalination sector. Recognizing brine as a valuable resource stream, combined with technological innovation and rigorous environmental planning, represents a major paradigm shift.
Conclusion
Sustainable brine management requires a comprehensive approach combining discharge optimization, source reduction, mineral recovery, energy integration, and advanced environmental monitoring. Pilot studies conducted in Europe, Australia, and North America demonstrate the technical feasibility of innovative solutions, even though their widespread deployment requires economic and institutional adjustments. As desalination becomes a structural pillar of global water security, brine management emerges as a key indicator of environmental performance and a strategic field of innovation for the decades ahead.
References
[1] Jones, E., Qadir, M., van Vliet, M.T.H., Smakhtin, V., Kang, S.M., 2019. The state of desalination and brine production: A global outlook. Sci. Total Environ. 657, 1343–1356.
[2] Roberts, D.A., Johnston, E.L., Knott, N.A., 2010. Impacts of desalination plant discharges on the marine environment: A critical review. Water Res. 44, 5117–5128.
[3] Fernández-Torquemada, Y., Sánchez-Lizaso, J.L., 2007. Effects of salinity on leaf growth and survival of the seagrass Posidonia oceanica. J. Exp. Mar. Biol. Ecol. 350, 120–129.
[4] Lattemann, S., Höpner, T., 2008. Environmental impact and impact assessment of seawater desalination. Desalination 220, 1–15.
[5] Elimelech, M., Phillip, W.A., 2011. The future of seawater desalination: Energy, technology, and the environment. Science 333, 712–717.
[6] Greenlee, L.F., Lawler, D.F., Freeman, B.D., Marrot, B., Moulin, P., 2009. Reverse osmosis desalination: Water sources, technology, and today’s challenges. Water Res. 43, 2317–2348.
[7] Barron, O.V., et al., 2015. Brine disposal from seawater desalination: Australian case studies and environmental implications. Desalin. Water Treat. 57, 1–12.
[8] ZERO BRINE Consortium, 2020. Circular economy solutions for saline wastewater streams. Desalination 479, 114313.
[9] Oren, Y., 2010. Capacitive deionization (CDI) for desalination and water treatment—past, present and future. Desalination 228, 10–29.
[10] Neori, A., 2008. Essential role of seaweed cultivation in integrated multi-trophic aquaculture farms for global expansion of mariculture. J. Appl. Phycol. 20, 567–570.
[11] Khayet, M., Matsuura, T., 2011. Membrane distillation: Principles and applications. Desalination 287, 2–18.
[12] Ruiz, J.M., Romero, J., Pérez, M., 2001. Effects of fish farm loadings on seagrass (Posidonia oceanica) distribution, growth and photosynthesis. Mar. Pollut. Bull. 42, 749–760.
