Brine Valorization — The Future Of Desalination

By Nikolay Voutchkov

Brine valorization plants are the next step in the evolution of desalination technology which opens a new horizon for wider use of desalination as a baseline source of drought-proof and environmentally and fiscally sustainable water supply. Over the past decade, the desalination industry has developed a number of brine concentration and mineral extraction technologies which enable the generation of commercially valuable products from brine. Valorizing minerals from seawater is more environmentally friendly enterprise than terrestrial mining. Moreover, brine mining does not require fresh water for mineral extraction, nor does it create contaminated water or waste materials for disposal, thereby combining both environmental and fiscal sustainability of mineral recovery. 

Figure 1 illustrates the typical configuration of brine valorization plants — it includes membrane nanofiltration (NF) system for the separation of the brine from the desalination plant into two streams — (1) NF permeate brine containing predominantly monovalent salts (NaCl, LiCl, KCl, RbCl) and (2) NF reject brine rich in plyvalent minerals (mainly Mg and Ca salts).

Figure 1. Process schematic of brine valorization plant

The recent breakthrough in viability of brine valorization (BV) technology is triggered by four core innovations: (1) integration of desalination and brine valorization technologies; (2) mineral-selective reverse osmosis (SWRO) membranes, (3) membrane crystallization, and (4) green chemicals. These advancements allow for the extraction of commercially valuable commodities such as sodium chloride, magnesium hydroxide, and calcium carbonate, as well as strategic metals like lithium and rubidium. Economically, the BV system can generate revenue from mineral sales that is over 16 times higher than revenue from water sales, potentially subsidizing water production to the point of "zero cost." Environmentally, it significantly reduces marine impact through lower intake requirements and moves toward zero liquid discharge (ZLD).

1. Integrated Desalination And Brine Mining

Unlike conventional desalination plants that produce only drinking water, BV plants are designed for multi-commodity output. System Design: The process uses NF to separate monovalent (NaCl, LiCl, KCl, RbCl) and multivalent (magnesium and calcium) salts. Concentration Stages: Monovalent streams are concentrated via followed by osmotically assisted reverse osmosis (OARO), reaching concentrations of 200,000 to 250,000 mg/L before crystallization. Recovery Rates: The system recovers nearly all minerals, returning only 14% of the volume and 8% of the mineral mass back to the sea. Figure 2 illustrates the key differences between a conventional desalination system and integrated desalination and brine valorization plant.

Figure 2. Paradigm Shift 1: Integrating desalination and brine valorization systems

2. Selective SWRO Membrane System

Recently developed multifunctional mineral-selective SWRO elements combine water production with the separation of specific target minerals. Mechanism: These membranes use “ionophores” — specialized molecule structures — to streamline water transport and selectively concentrate specific ions (e.g., K, Li, Mg, or Rb) in the permeate. Efficiency: These membranes operate at feed pressures 7 to 10 bars lower than conventional membranes, reducing energy demand by 10% to 15%. Flexibility: Different racks within a single SWRO system can be equipped with different selective membranes to adjust mineral production based on market demand. Figure 3 illustrates SWRO configuration with selective membranes.

Figure 3. Paradigm Shift 2: RO system for selective separation and recovery of minerals from seawater

After processing of the source seawater through a SWRO system equipped with selective membranes, the majority of the mineral which the membrane is designed to extract, is contained in the SWRO permeate, mixed with the desalinated water. A subsequent two-stage processing through a brackish RO (BWRO) membrane system separates the selected mineral from the SWRO membrane permeate into fresh water (BWRO permeate). The first stage of the BWRO System fully separates the mineral from the fresh water permeate and transfers over 90% of the selective mineral into the first-stage BWRO brine — see Figure 2. The second stage of the BWRO system concentrates the brine to a mineral content of 99 % or more — over 20 times its concentration in seawater. The selective mineral that is now contained in the second stage BWRO brine is further concentrated by osmotically — assisted reverse osmosis (OARO) membrane system. Then, the concentrated mineral is crystalized into a high-purity commercial product with a membrane crystallizer.  

The mineral-selective membranes open up the opportunity to harvest multiple valuable minerals from the source seawater by installing several different selective membranes in the different racks of the same SWRO system. For example, a SWRO system can have a number of RO racks (A) equipped with lithium chloride (LiCl) selective membranes; a different number of RO racks with potassium chloride (KCl)-selective membranes (B), and another set of RO racks equipped with magnesium chloride (MgCl₂)-selective membranes (C), producing these brine salts simultaneously (see Figure 4). 

Figure 4. Combining selective RO membranes for specific minerals in one SWRO system

3. Membrane Mineral Crystallization System (MBC)

The MBC system serves as a low-energy alternative to traditional thermal crystallizers, which typically account for 75% to 80% of a brine mining plant's total energy use. Energy Savings: MBC uses only 10% to 20% of the electrical energy required by thermal systems (less than 10 kWh/m³ vs. 75 kWh/m³). Process: It leverages forward osmosis (FO) using a highly soluble draw solution, such as magnesium chloride (MgCl₂), to extract water from the brine and form high-purity crystals on the membrane surface. Capital and Footprint: The MBC system is estimated to cost one-third of traditional crystallizers and occupies 5 times less space. Its low-pressure operation allows for the use of non-corrosive plastic materials rather than expensive alloys. Figure 5 illustrates an existing MBC system and Figure 5 summarizes the key differences between thermal and membrane crystallizers.

Figure 5. Membrane crystallizer for NaCl

Figure 6. Paradigm Shift 3: Membrane-based crystallization replaces thermal crystallization of seawater minerals

4. Green Chemicals Production

The BV system enables "circular" desalination by producing necessary process chemicals onsite from the brine itself. Coagulants and Post-treatment: Magnesium hydroxide [Mg(OH)₂] and calcium carbonate [CaCO₃] produced from the brine can replace commercial chemicals used for pretreatment and water stabilization. Disinfection: Sodium chloride manufactured on-site is used to generate chlorine dioxide for final disinfection, replacing externally sourced sodium chlorite. Scale Control: Scaling is managed by balancing magnesium and calcium content in the source water rather than using costly commercial antiscalants. Figure 7 illustrates the circularity in generating desalination plant process chemicals from brine.

Figure 7. Paradigm Shift 4: Generation of desalination plant chemicals from brine

Economic And Strategic Value Of Brine Valorization

The integration of brine valorization fundamentally alters the financial profile of desalination projects. (see Figure 8). BV allows for the production of high-purity sodium chloride at a cost of 25 to 35 US$/dry ton of NaCl while the current market price of this salt is 65 to 120 US$/dry ton of NaCl. It should be noted that NaCl is usually 86% of the total amount of minerals in typical seawater brine, while in brackish brines the predominant minerals could be calcium and magnesium salts. High purity NaCl is widely used by the chlor-alkali industry. This industry ultimately produces liquid PVC, which is the second most important product of the petro-chemical industry besides oil. The two source materials needed to produce liquid PVC are oil and NaCl salt. 

Figure 8. Integration of desalination and BV plants (Paradigm Shift 1) offers path to lowest cost of water

As seen from Figure 8, the annual revenue from drinking desalinated water sales at typical unit cost of water of US$0.65/m³ is US$22 million/year. Such revenue is approximately 3 times smaller than the revenue from selling NaCl contained in the brine from the desalination plant at low end of the market price for high purity (99.6%) NaCl — US$65 million/year.

Considering a very conservative production cost of NaCl from the brine of US$35/ton vs. market price of US$65/ton, the revenue from NaCl sales can not only cover the salt production costs but also can compensate for the costs for production of fresh water and even make sizable profit. 

Figure 8 reveals that as long as markets are available for the mineral products extracted from seawater brine in a reasonably close vicinity, brine valorization opens the opportunity for subsidizing drinking water production and thereby, making desalinated water the lowest cost freshwater resource in the world with the highest sustainability and long-term availability.

Despite the fact that the capital investment needed to construct the BV plant is approximately 4 times higher than that of conventional desalination plant of the same freshwater production capacity, the total annual revenue from sales of minerals is over 16 times higher that of drinking water sales. As a result, even if the entire amount of minerals contained in the seawater brine is not sold, the profit from mineral sales can completely offset/subsidize the expenditures for production of desalinated water and therefore, to elevate desalination to the status of widely affordable and sustainable source of drinking water.

Strategic Mineral Security

The ocean contains mineral reserves that often exceed terrestrial sources by orders of magnitude. BV technology allows countries with sea access to secure strategic materials like lithium, cobalt, and rubidium, reducing dependence on geopolitical rivals that currently control terrestrial mining (see Figure 9). As shown in this figure, the ocean brine contains valuable minerals at amounts that typically exceed the available terrestrial sources of the same minerals by one or more an order of magnitude.

Figure 9. Terrestrial vs seawater sources of minerals (Source: USGS National Minerals Information Center)

Summary And Conclusions

Continuous advances in membrane brine concentration and mineral crystallization technologies over the past five years are shifting the paradigm of desalination from being the costliest fresh water supply technology that has the potential to offset its production costs by extraction of commercially viable minerals and metals from the desalination brine. The desalination industry is entering a new era of sustainable water production propelled by the beneficial use of brine produced by the salt separation processes. Ultimately, brine valorization could render desalinated

BV technology addresses the three main environmental challenges of desalination: energy use, marine impact, and brine disposal. Reduced Marine Impact: By operating at 86% recovery, the BV system requires half the intake water of a conventional plant, thereby reducing the impingement and entrainment of marine organisms by 50%. Lower Carbon Footprint: The reduction in crystallization energy (10x lower than thermal) and the elimination of chemical transportation via "green" onsite production significantly lower Greenhouse Gas (GHG) emissions. Lifecycle Longevity: The system relies primarily on membrane-based, non-corrosive plastic components, offering a longer lifecycle and lower maintenance requirements compared to high-pressure, high-temperature thermal systems.

Nikolay Voutchkov, PE, BCEE, is the Executive Director and Founder of Water Globe Consultants, LLC (WGC), a U.S. company specialized in engineering and consulting services in the field of desalination, brine valorization, and water reuse worldwide. For 11 years prior to establishing WGC, Mr. Voutchkov was a Chief Technology Officer of Poseidon Resources, a private U.S. project development company which implemented a large number of desalination and water reuse projects in the U.S. and Mexico. Between 2019 and 2025, Mr. Voutchkov worked in Saudi Arabia as an Executive Director of NEOM Water Innovation Center and as a Senior Expert of the Saudi Water Authority. Mr. Voutchkov has published over dozen technical books and 120 peer-reviewed articles on advanced water treatment and reuse, and holds 8 patents. He is a professional engineer, Diplomate of the American Academy of Environmental Engineers, and a Fellow of the Water & Energy Nexus Center of the University of California, Irvine.