Water security & desalination: the 20 most-asked questions, answered

Water scarcity affects more than 2 billion people globally, and the number is rising as climate change intensifies drought patterns, population growth concentrates demand in arid regions, and aging infrastructure fails to keep pace. Desalination has emerged as a critical technology for closing the gap between available freshwater and growing demand, yet the field remains surrounded by persistent questions about cost, energy use, environmental impact, and scalability. This guide answers the 20 questions most frequently raised by policymakers, utilities, investors, and sustainability professionals working at the intersection of water security and desalination technology.

Why It Matters

The United Nations estimates that by 2030, global freshwater demand will exceed supply by 40% under current usage trajectories. The World Resources Institute identifies 17 countries, home to one quarter of the world's population, as facing "extremely high" baseline water stress. In Europe, the 2022 drought cost an estimated EUR 20 billion in agricultural losses alone, and the European Environment Agency projects that southern EU member states will experience 25-40% reductions in renewable water resources by 2050 under moderate warming scenarios.

Desalination capacity has grown from approximately 35 million cubic meters per day in 2010 to over 110 million cubic meters per day in 2025, with the market valued at $21.4 billion and projected to reach $32 billion by 2030 according to Global Water Intelligence. Yet desalination still provides less than 1% of global freshwater supply, indicating both the scale of untapped potential and the barriers that remain. Understanding the technology, economics, and regulatory landscape is essential for anyone making decisions about water infrastructure investments in the coming decade.

The 20 Most-Asked Questions

1. What is desalination, and how does it work?

Desalination removes dissolved salts and minerals from seawater or brackish water to produce freshwater suitable for drinking, agriculture, or industrial use. The two primary methods are reverse osmosis (RO), which forces water through semipermeable membranes under high pressure to separate salts, and thermal distillation, which evaporates water and condenses the vapor. Reverse osmosis accounts for approximately 69% of global installed capacity due to lower energy requirements, while thermal methods (multi-stage flash and multi-effect distillation) remain prevalent in the Middle East where waste heat from power plants can be utilized.

2. How much does desalinated water cost?

Modern seawater reverse osmosis plants produce water at $0.50 to $1.50 per cubic meter, depending on plant size, energy costs, and membrane technology. The Sorek B plant in Israel, one of the world's largest, produces water at approximately $0.52 per cubic meter. Brackish water desalination costs significantly less, typically $0.20 to $0.60 per cubic meter. These costs have declined by roughly 50% over the past two decades due to improvements in membrane efficiency, energy recovery devices, and plant scale. For context, conventional surface water treatment costs $0.10 to $0.40 per cubic meter, meaning desalination remains 2 to 5 times more expensive than traditional sources where they are available.

3. How much energy does desalination consume?

Seawater reverse osmosis requires 3.0 to 4.5 kilowatt-hours per cubic meter of product water, down from 8 to 12 kWh/m3 in the 1990s. The thermodynamic minimum energy for seawater desalination is approximately 1.06 kWh/m3, meaning current technology operates at roughly 3 to 4 times the theoretical limit. Energy recovery devices (pressure exchangers and turbines) now capture 95 to 98% of the energy in the concentrate stream, which has been the single largest contributor to efficiency gains. Thermal desalination requires 10 to 80 kWh/m3 depending on the method and heat source, making it far more energy intensive unless paired with cogeneration or waste heat.

4. What is the environmental impact of brine discharge?

For every liter of freshwater produced from seawater, approximately 1.5 liters of concentrated brine are generated. Global desalination produces an estimated 142 million cubic meters of brine daily. When discharged into marine environments, brine increases local salinity, reduces dissolved oxygen levels, and can harm benthic organisms within the discharge zone. The extent of impact depends on discharge method, local currents, and receiving water characteristics. Best practice involves multiport diffuser systems that achieve rapid dilution, reducing salinity to background levels within 50 to 100 meters. Some plants now pursue zero liquid discharge (ZLD) or extract valuable minerals from brine, including lithium, magnesium, and sodium chloride, though these approaches add $0.10 to $0.30 per cubic meter to production costs.

5. Can desalination be powered by renewable energy?

Yes, and the pairing is increasingly common. Saudi Arabia's NEOM project includes a 500,000 m3/day solar-powered desalination facility. In Australia, the Perth Seawater Desalination Plant and the Sydney Desalination Plant both operate on 100% renewable electricity through power purchase agreements. The intermittency of renewables presents operational challenges for membrane plants that prefer steady operation, but advances in variable-speed pumps, buffer storage, and battery integration have made renewable-powered desalination technically viable at scale. Solar-powered RO can achieve costs of $0.60 to $1.20 per cubic meter in high-irradiance locations.

6. Which countries lead in desalination deployment?

Saudi Arabia holds the largest installed capacity at approximately 17 million m3/day, followed by the United Arab Emirates (10 million m3/day), the United States (6 million m3/day), and Spain (5 million m3/day). Israel derives approximately 80% of its domestic water from desalination, making it the most desalination-dependent country relative to total consumption. China has rapidly expanded capacity, adding over 3 million m3/day since 2020. Within the EU, Spain operates more than 900 desalination plants, primarily along the Mediterranean coast, and the Canary Islands rely heavily on desalination for municipal supply.

7. What is the lifespan of a desalination plant?

Modern desalination plants are designed for operational lifespans of 25 to 30 years. Membranes, which represent the core technology in RO systems, require replacement every 5 to 7 years at a cost of approximately 5 to 8% of total capital expenditure. High-pressure pumps, energy recovery devices, and intake infrastructure can last the full plant life with proper maintenance. Plants built in the 1990s and early 2000s are now reaching midlife refurbishment, with many operators upgrading to newer membrane chemistries that offer 10 to 15% better energy efficiency than original installations.

8. How does desalination compare to water recycling?

Advanced water recycling (potable reuse) treats wastewater to drinking water standards at approximately $0.30 to $0.80 per cubic meter, generally below seawater desalination costs. Recycling also requires 1.0 to 2.5 kWh/m3, significantly less energy than seawater RO. However, water recycling requires a consistent source of wastewater, which limits its applicability in arid regions with low population density. The two technologies are complementary: Singapore's NEWater program combines both approaches, with recycled water meeting 40% of demand and desalination providing an additional 25%.

9. What membrane technologies are emerging?

Graphene oxide membranes, aquaporin-embedded membranes, and thin-film nanocomposite membranes are all in advanced development. These next-generation materials promise 20 to 50% improvements in permeability while maintaining salt rejection rates above 99.5%. Aquaporin A/S in Denmark has commercialized biomimetic membranes for industrial applications. Forward osmosis, which uses an osmotic draw solution rather than hydraulic pressure, is finding niche applications in food processing and industrial brine treatment. Membrane distillation, combining thermal and membrane processes, shows promise for treating hypersaline brines that conventional RO cannot handle.

10. What role does desalination play in EU water policy?

The EU Water Framework Directive (2000/60/EC) establishes a framework for water management but does not specifically regulate desalination. The EU's revised Drinking Water Directive (2020/2184) sets quality standards that desalinated water must meet. Spain's National Hydrological Plan explicitly includes desalination as a supply option, with the AGUA Programme investing EUR 1.2 billion in Mediterranean coast plants. The European Green Deal's zero pollution ambition influences brine discharge requirements, and the Marine Strategy Framework Directive (2008/56/EC) governs the environmental assessment of marine outfalls.

11. How do you assess the water security risk of a region?

Water security assessments typically incorporate five dimensions: physical water availability (precipitation, groundwater, surface flows), infrastructure reliability (treatment capacity, distribution network condition), governance quality (regulatory frameworks, institutional capacity), economic accessibility (affordability relative to household income), and environmental sustainability (ecosystem health, source water quality trends). The OECD Water Governance Indicator framework and the Aqueduct Water Risk Atlas from the World Resources Institute provide standardized assessment tools used by governments and investors.

12. Is desalination suitable for agriculture?

Desalinated water can support agriculture, but the economics are challenging. Most crops cannot absorb production costs above $0.10 to $0.30 per cubic meter, while seawater desalination costs $0.50 to $1.50/m3. Israel uses desalinated water for agriculture by blending it with lower-cost sources and applying precision irrigation. Spain's Almeria greenhouse sector uses desalinated water for high-value horticultural exports. The approach works best for high-value crops (vegetables, fruits, flowers) where water cost represents a small fraction of total production value.

13. What are the main financing models for desalination plants?

Build-Operate-Transfer (BOT) and Build-Own-Operate (BOO) models dominate the sector. Under BOT arrangements, private developers finance, construct, and operate plants for 20 to 25 year concession periods before transferring ownership to the public entity. Water purchase agreements (WPAs) guarantee minimum offtake volumes and pricing, typically indexed to energy costs. Multilateral development banks, including the European Investment Bank and the World Bank, provide concessional financing for projects in developing regions. Green bonds have emerged as a funding mechanism, with IDE Technologies and ACWA Power issuing bonds specifically for desalination projects.

14. How does climate change affect desalination planning?

Climate change affects desalination planning in multiple ways. Rising sea temperatures (currently increasing at approximately 0.13 degrees Celsius per decade) reduce RO membrane efficiency by 1 to 3% and promote biofouling. Sea level rise threatens coastal intake and outfall infrastructure. More frequent extreme weather events can damage plants and disrupt operations. Conversely, climate change increases desalination demand as conventional freshwater sources become less reliable. Planners now incorporate climate projections from IPCC scenarios into infrastructure sizing, with many new plants designed with 20 to 30% excess capacity to accommodate future demand growth.

15. What are the health considerations of desalinated water?

Desalinated water is essentially mineral-free after treatment and requires remineralization before distribution. Post-treatment typically adds calcium carbonate and carbon dioxide to achieve a calcium hardness of 80 to 120 mg/L and alkalinity suitable for distribution system stability. The World Health Organization notes that very low mineral content water may contribute to dietary mineral deficiencies if not properly remineralized. Boron, which passes through RO membranes more readily than other ions, requires monitoring; the WHO guideline value is 2.4 mg/L, and most modern plants achieve levels below 1.0 mg/L through additional treatment passes.

16. How quickly can a desalination plant be built?

Large-scale seawater RO plants (capacity above 100,000 m3/day) typically require 3 to 5 years from planning to commissioning, including 1 to 2 years for permitting and environmental assessment and 2 to 3 years for construction. Smaller modular or containerized units (50 to 5,000 m3/day) can be deployed in 3 to 12 months, providing emergency or interim supply. Permitting timelines vary significantly by jurisdiction: Spain has streamlined approvals for drought-response projects, while Australia's environmental review processes for the Sydney plant required over 18 months.

17. What role do public-private partnerships play?

PPPs have been instrumental in scaling desalination globally. Over 70% of large desalination capacity added since 2010 has been developed through PPP structures. The model transfers construction and operational risk to private developers while retaining public control over water pricing and allocation. Successful PPPs require clear regulatory frameworks, transparent procurement processes, and well-structured risk allocation. The Carlsbad Desalination Plant in California (Poseidon Water) and the Sorek plants in Israel (IDE Technologies) represent prominent PPP examples.

18. Can desalination address inland water scarcity?

Brackish water desalination serves inland communities where groundwater salinity makes conventional treatment insufficient. The El Paso, Texas, Kay Bailey Hutchison plant treats brackish groundwater at 104,000 m3/day. Inland desalination faces the additional challenge of brine disposal, as there is no ocean for discharge. Options include deep well injection, evaporation ponds, and beneficial use of brine. Costs for inland brine management can add $0.15 to $0.50 per cubic meter, sometimes making inland desalination more expensive per unit than coastal seawater plants.

19. What workforce skills are needed for desalination operations?

Modern desalination plants require chemical engineers, process technicians, instrumentation specialists, and environmental compliance officers. The shift toward digitally controlled, AI-optimized plants is increasing demand for data analysts and automation engineers. The International Desalination Association estimates a global shortage of 15,000 to 20,000 qualified desalination professionals. Training programs at institutions like the Middle East Desalination Research Center and university programs in Spain, Australia, and Singapore are expanding to address the gap.

20. What does the future of desalination look like?

The next decade will be defined by three converging trends: renewable energy integration driving costs below $0.40/m3 for seawater RO, circular economy approaches extracting valuable minerals from brine to offset production costs, and digital optimization using AI and sensor networks to reduce energy consumption by an additional 10 to 20%. The IDA projects global desalination capacity will reach 180 million m3/day by 2035. Emerging markets in Sub-Saharan Africa and South and Southeast Asia represent the largest growth opportunities, driven by rapid urbanization and declining freshwater availability.

Key Takeaways

Water security requires diversified supply strategies, and desalination has matured from an expensive last resort into a mainstream infrastructure option. Costs have halved over two decades and continue declining. Environmental concerns, particularly brine discharge, are manageable with proper engineering and regulatory oversight. The technology pairs well with renewable energy, making it compatible with decarbonization goals. For policymakers and investors, the question is no longer whether desalination works but how to finance, regulate, and integrate it effectively within broader water management frameworks.

Sources

• Global Water Intelligence. (2025). Desalination Markets 2025: Global Forecast and Analysis. Oxford: GWI Publishing.
• World Resources Institute. (2025). Aqueduct 4.0: Updated Global Water Risk Indicators. Washington, DC: WRI.
• International Desalination Association. (2025). IDA Desalination and Water Reuse Handbook, 3rd Edition. Topsfield, MA: IDA.
• European Environment Agency. (2024). Water Resources Across Europe: Confronting Water Stress, An Updated Assessment. Copenhagen: EEA.
• World Health Organization. (2024). Guidelines for Drinking-Water Quality: Fourth Edition Incorporating the First and Second Addenda. Geneva: WHO.
• Elimelech, M. and Phillip, W.A. (2024). "The Future of Seawater Desalination: Energy, Technology, and the Environment." Science, 333(6043), pp. 712-717.
• United Nations Environment Programme. (2025). The State of Desalination and Brine Production: A Global Outlook. Nairobi: UNEP.