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Brackish water desalination system and seawater desalination system
Industry details
A comprehensive overview of the unconventional water resource utilization industry (data up to 2025).
This article provides a systematic overview of two unconventional water resource utilization industries: brackish water desalination and seawater desalination. It covers their definitions, technological routes, market size, industry chain structure, policy environment, application scenarios, development trends, and challenges. Data is primarily based on the Ministry of Natural Resources' "2024 National Seawater Utilization Report," research reports from QYResearch/Global Info Research, and publicly available industry information, up to 2025.
Both are essentially about desalination and removing salt, turning high-salinity raw water into drinkable or industrially usable freshwater. The fundamental difference lies in the raw water salinity (TDS) and operating conditions—this determines all the subsequent differences in technology, cost, materials, and energy consumption.
Dimension | Seawater desalination system | Brackish water desalination system |
Raw water source | Ocean, coastal water intake, offshore/island | Inland underground saline water, well water, drainage from saline-alkali land, and slightly saline water from some rivers |
Typical salinity (TDS) | Approximately 35,000–45,000 mg/L | Approximately 1,000–10,000 mg/L (some up to 15,000 mg/L) |
RO operating pressure | 55–80 bar (high pressure) | 15–25 bar (medium to low pressure) |
Typical recovery rate | 33%–45% | 50%–75% |
Unit energy consumption | Approximately 3.5–4 kWh/m³ (with energy recovery) | Approximately 0.5–2.5 kWh/m³ |
Corrosion protection requirements | High-performance (duplex/super duplex stainless steel, chlorine-resistant materials) | Medium to low (standard corrosion protection is sufficient) |
concentrated brine discharge | It can be discharged into the sea (diffuser and compliance permit required). | Inland emissions are difficult to manage, requiring solutions such as evaporation ponds/zero emissions. |
Typical applications | Coastal cities, islands, offshore platforms, and coastal industries | Northwest/North China water-scarce areas, agricultural irrigation, inland industry |
In short, salinity is the dividing line between the two technological approaches. The higher the salinity, the greater the osmotic pressure, and the higher the required pressure, energy consumption, and material grade. Therefore, seawater desalination is a tough battle with "heavy equipment and high energy consumption," while brackish water desalination is a lighter approach with "low energy consumption and easy distribution."
Membrane technology (dominant)
• Reverse osmosis (RO): Currently the absolute mainstream technology globally and in China. SWRO membranes (desalination rate >99.5%) are used for seawater desalination, while BWRO membranes (desalination rate 97–98%) are used for brackish water. Brackish water can also be treated with nanofiltration (NF) to achieve selective desalination while retaining some beneficial ions.
• Electrodialysis (ED/EDR): mostly used for small and medium-sized brackish water, especially suitable for water with high hardness/high sulfate content.
thermal method
• Low-temperature multi-effect distillation (MED): the main thermal method for seawater desalination in China, accounting for the vast majority of thermal engineering projects.
• Multi-stage flash (MSF): a traditional approach for large-scale projects in the Middle East, with only one project in China, accounting for 0.21%.
• Multi-effect distillation + combined hydropower: often coupled with power plant/nuclear power steam generation, driven by waste heat.
Modern large-scale SWROs are generally equipped with isobaric energy recovery devices (ERDs, such as pressure exchangers), which can recover about 60% of the high-pressure energy in the concentrate, reducing the energy consumption per ton of water produced from 5–6 kWh in the early days to about 3 kWh. Brackish water, due to its low pressure, generally does not require energy recovery devices.
technology | Seawater desalination applicability | Applicability of brackish water desalination | Remark |
Reverse osmosis (RO) | ★★★★★ (68% of the total scale) | ★★★★★ (Absolutely mainstream) | Membrane common chassis |
Nanofiltration NF | ★ (Use sparingly) | ★★★★ (Selective desalination) | Brackish water specialty route |
Low Temperature Multi-Effect MED | ★★★★ (31.5% of the total scale) | ★ (Rarely used) | Suitable for coupling with waste heat |
Multi-stage flash MSF | ★★ (Mainly Middle East) | — | Only 1 case in China |
Electrodialysis ED | ★ (Use sparingly) | ★★★★ | Small and medium-sized brackish water |
• China's engineering scale: As of the end of 2024, there were 158 seawater desalination projects nationwide, with a total capacity of 2.856 million tons/day, an increase of 333,000 tons/day compared to 2023; as of the end of August 2025, it had exceeded 2.9 million tons/day, achieving the "14th Five-Year Plan" target ahead of schedule.
• Regional concentration: Shandong (867,000 tons/day), Zhejiang (805,000 tons/day), and Tianjin (456,000 tons/day) lead the way; the scale of island regions reaches 877,000 tons/day.
• Technology breakdown: Reverse osmosis 141 projects, 1.94 million tons/day (68.25%); Low-temperature multi-effect evaporation 18 projects, 900,000 tons/day (31.54%); Multi-stage flash evaporation 1 project (0.21%).
• Water consumption: In 2024, the national utilization of desalinated seawater was 400 million cubic meters, of which Zhejiang alone accounted for 180 million cubic meters (45% of the national total).
• Industrial added value: In 2024, the added value of the seawater desalination and comprehensive utilization industry reached 33.7 billion yuan.
• Water production cost: In China, RO seawater desalination costs 4.2–5.0 yuan/m³ (energy accounts for 46%, depreciation 24%, and operation and maintenance 14%); abroad it is lower, about 2.5–3.5 yuan/m³.
• Global Equipment Market: According to Global Info Research, the global desalination system market is approximately US$614 million (2024), with the Middle East and Africa accounting for about 55% and the Asia-Pacific region about 23%.
• Global brackish water RO systems: approximately US$823 million in 2024, projected to reach US$1.263 billion in 2031, CAGR 6.4% (QYResearch).
• China's low-pressure brackish water membrane industry: approximately RMB 4.8 billion in 2024, and is projected to exceed RMB 8.5 billion by 2030, with a CAGR of 12.3%; the localization rate of membrane materials has increased from less than 50% in 2020 to nearly 70% in 2024.
• China's brackish water projects: In 2024, the total scale was approximately 1.56 million m³/day, an increase of 31.2% year-on-year, covering 15 provinces and regions including Xinjiang, Inner Mongolia, Gansu, and Qinghai, with approximately 234 projects.
• Equipment Market (Broad Definition): Dataintelo forecasts brackish water desalination equipment revenue to be approximately $15.9 billion by 2034, with a CAGR of 8.4%.
index | Seawater desalination | Brackish water desalination |
Unit investment (per million gallons/day production capacity) | $2,500–$4,000 | $1,200–$2,000 |
Operating cost ($/m³) | 0.80–1.20 | 0.35–0.65 |
Membrane replacement cycle | 3–5 years | 5–7 years |
Comprehensive cost per ton of water (China) | 4.2–5.0 yuan | Significantly lower than seawater (approximately 1–2 yuan). |
Upstream: Membrane materials / High-pressure pumps / Energy recovery devices / Pressure vessels / Pharmaceuticals / Duplex stainless steel
↓
Midstream: System Integrator (EPC + O&M) – Pretreatment + RO/thermal + Posttreatment + Concentrate Management
↓
Downstream: Municipal water supply / Power, petrochemical, and steel industries / Island and offshore water supply / Agricultural irrigation / Rural water improvement
International leader
• Suez, Veolia, IDE (Israel), Doosan (Korea), Fisia Italimpianti, Xylem, BWT, Toshiba, MHI, Toray, Hyflux, etc.; the top three manufacturers account for approximately 63% of the global market share.
China's strength
• Membrane materials: Beijing OriginWater Technology Co., Ltd., Times Water Technology Co., Ltd., and Tianjin Membrane Technology Co., Ltd. (the main domestic manufacturers of low-pressure RO/NF membranes);
• System Integration and Engineering: Beijing OriginWater Technology, Hangzhou Water Treatment (China Shipbuilding Industry Corporation), Tianjin Membrane Technology, Guangzhou Kangyang, etc.
• Key weakness: The localization rate of core equipment for membrane-based seawater desalination with a capacity of 10,000 tons or more (high-pressure pumps, energy recovery devices, SWRO membranes) is still relatively low, which is a key area for improvement.
• Brackish water RO heads: Advanced Watertek, AMPAC, AqSep, AWC, Beijing Originwater, etc.
• The Action Plan for the Development of Seawater Desalination Utilization (2021-2025) clarifies industry goals and promotes large-scale application.
• Water Conservation Regulations (2024.3): A landmark regulation that requires new, renovated, and expanded industrial projects in coastal/island areas with scarce freshwater resources to give priority to the use of desalinated seawater and encourages its use as a new municipal water source and emergency backup.
• The "Guiding Opinions on Strengthening the Allocation and Utilization of Unconventional Water Sources" states that desalinated seawater should be incorporated into the rigid constraints and allocation system of water resources.
• During the 14th Five-Year Plan period, unconventional water source utilization will be promoted in conjunction with brackish water desalination as a key pathway for water-scarce inland areas, along with rural water improvement and saline-alkali land management.
• Dual carbon constraints: Low-pressure membrane and new energy coupling (photovoltaics + desalination) have become the technology directions encouraged by policies, while energy consumption has become an important threshold for project approval and subsidies.
• Coastal industries (main focus): power, petrochemical, and steel industries with high water consumption, such as Tianjin Nangang Xianda (150,000 tons/day), Yantai Longkou Yulong Island (80,000 tons/day), and Lianyungang Tianwan Nuclear Power (36,500 tons/day).
• Islands and Offshore: 877,000 tons/day of island production capacity; self-developed polar equipment for Qinling Station in Antarctica; offshore platforms and ships.
• Municipal administration in water-scarce coastal cities: As a strategic reserve/new source of water, it still accounts for a small proportion but is strongly promoted by policies.
• Direct utilization of seawater (with supporting facilities): In 2024, the seawater cooling water consumption will be 188.3 billion tons, and circulating cooling will gradually replace direct current cooling (24 circulating cooling projects have been built).
• Inland industries (approximately 55%): coal chemical industry, power generation, and metallurgy, mainly in Northwest/North China.
• Municipal and rural water supply (approximately 30%): Water improvement projects in 15 provinces and regions, releasing incremental growth for rural revitalization.
• Agricultural irrigation and emergency water supply: solar-coupled irrigation in the Middle East (Israel, Saudi Arabia, UAE); agricultural water replenishment in the High Plains of the United States relying on the Ogallala aquifer.
• Saline-alkali land management: A demonstration project in Weifang, Shandong Province, explores a new approach to "improving saline-alkali land through seawater/brackish water desalination".
• Membrane technology dominates, while thermal technology is coupled with waste heat: RO's share continues to increase, and MED is used in power plants/nuclear power plants for combined heat and power generation to reduce costs.
• Breakthrough in the localization of core equipment: High-performance SWRO membranes, large high-pressure pumps, and energy recovery devices are the main battlegrounds for domestic substitution.
• Low-carbonization: Photovoltaic/wind power + desalination, low-pressure membrane (reducing energy consumption by 20-30%), and waste heat utilization are becoming new engines for green development.
• Modular and distributed: Containerized and miniaturized systems are being deployed to islands, rural areas, and emergency scenarios.
• Intelligent operation and maintenance: online monitoring, predictive maintenance, and digital twins improve reliability and reduce total lifecycle costs.
• Resource utilization of concentrated brine: bromine extraction, magnesium extraction, lithium extraction, and salt production, building a circular economy downstream.
• Energy consumption and costs: Desalination costs nearly half of the electricity bill, making it sensitive to electricity prices; while brackish water inland is cheap, its scale is limited.
• Treatment of concentrated brine: Inland brackish water has no way to be discharged into the sea, and evaporation ponds/zero discharge are costly and require a large area, which is the key to the success or failure of the project.
• System and mechanism: The laws, regulations, standards, water pricing mechanisms, and support policies are still imperfect, which restricts large-scale allocation.
• Membrane fouling and lifespan: Seawater is more prone to organic/biofouling, requiring more frequent membrane replacements and higher maintenance thresholds.
• Homogeneous competition: Price wars for low- and mid-range equipment, while high-end membranes and core components still rely on imports.
