Membrane Processes for Efficient Brine Concentration and Recovery

Desalination removes salt and other minerals from water, producing two primary streams: freshwater and brine. As desalination capacity grows, effective brine management is becoming essential to reduce environmental impact and improve overall water recovery. 

Effective treatment of brine can result in higher water recovery and utilization of salts as a resource. Several membrane processes can be used for brine treatment and management; this includes Reverse Osmosis (RO), Osmosis Assisted Reverse Osmosis (OARO), Forward Osmosis (FO), and Membrane Distillation (MD). 

Reverse Osmosis (RO)

Reverse osmosis is the most mature and widely used membrane process for desalination applications. As osmotic pressure increases, conventional seawater RO (operating under 80 bar) cannot concentrate saline water with TDS higher than ~45 g/l  [1]. The introduction of High-Pressure Reverse Osmosis membranes extend this capability, designed to withstand pressures up to 120 bar, which can concentrate brines up to a maximum of 135 g/l TDS [2].  

An advantage is high water recovery at relatively low specific energy compared with thermal evaporation, especially when salinity is moderate. However, as brine salinity rises, osmotic pressure and required operating pressure climb sharply, which sets practical limits on achievable concentration and recovery.

Evaluating the pressure efficiency and tendency to fouling can be done using Sterlitech’s high pressure testing cells HP4750X, and Sepa CFX. These cells are designed to resist high pressure up to 2500 psi and are available in 316L, Dursan coated 316L and C276 options. High pressure fully assembled skid systems are available with similar pressure values and material.

Osmosis Assisted Reverse Osmosis (OARO)

OARO uses a high salinity feed and a lower salinity draw solution on the permeate side to reduce the osmotic pressure drop across the RO membrane. This sustains flux at lower applied pressure than pushing against full brine osmotic pressure in conventional RO.

OARO advantages include higher attainable recovery and reduced mechanical stress on membranes. However, the need to continuously regenerate the draw, added process complexity, and sensitivity to internal/external concentration polarization that reduces effective driving force.

Sterlitech’s four port (Forward Osmosis) cell can be utilized for OARO testing, including CF016, CF042, and SEPA cells. These cells must be used with a set of shims and spacer on the draw side to provide support for the membrane against the high pressure applied from the feed side.

Membrane Distillation (MD)

MD is suited for brine treatment, especially for RO concentrate and high‑TDS industrial brines, because it can recover water even when salinity exceeds the pressure limits of RO. In brine treatment, MD is typically applied as a post‑RO or near zero liquid discharge step to further concentrate the brine while producing high‑quality distillate, helping reduce liquid discharge volumes.

Key advantages are tolerance to extremely high salinity, near‑complete salt rejection, and operation at low hydraulic pressure, often using waste or low‑grade heat available in industrial plants. However, challenges in brine applications include severe scaling due to salt supersaturation, membrane wetting, declining flux at high concentrations, and thermal efficiency losses, all of which require careful pretreatment, temperature control, and membrane selection.

Sterlitech offers a wide variety of systems and cells suitable for MD testing applications.  

Forward Osmosis (FO) 

FO uses a highly concentrated draw solution to osmotically extract water from RO concentrate or high‑salinity brines, thereby reducing brine volume and increasing overall water recovery. In brine management applications, FO is often used as a pre‑concentration or hybrid step before thermal processes or crystallization, helping move systems toward low‑liquid‑discharge or zero liquid discharge.

The main advantages of FO for brine treatment are its ability to operate at low hydraulic pressure, lower fouling propensity compared to RO, and its effectiveness with high‑salinity streams that are difficult to treat by pressure‑driven membranes. However, key challenges include draw solution regeneration energy demand, internal concentration polarization limiting flux, reverse salt flux increasing brine salinity, and the need for process integration to make FO economically viable at high brine concentrations.

Sterlitech offers a wide variety of systems and cells suitable for FO testing applications. 

Conclusion 

Effective brine management requires a combination of membrane technologies to balance recovery, energy use, and operational limits. Conventional and high‑pressure RO are effective at moderate salinities, while OARO extends concentration capability by reducing the effective osmotic pressure and mechanical stress. FO and MD complement RO‑based systems by enabling further water recovery from high‑salinity brines, supporting zero liquid discharge. Each process has inherent trade‑offs related to energy demand, fouling, scaling, and system complexity, making pilot testing and careful process integration essential for developing efficient and sustainable brine treatment solutions

Selecting the right membrane configuration for your specific membrane stream is critical to maximizing recovery while managing cost and complexity. Ask an Expert to learn more about our membrane testing options for Brine treatment and management using membrane processes.  

References  
[1] Z. Zhang, A. A. Atia, J. A. Andrés-Mañas, G. Zaragoza, and V. Fthenakis, “Comparative techno-economic assessment of osmotically-assisted reverse osmosis and batch-operated vacuum-air-gap membrane distillation for high-salinity water desalination,” Desalination, vol. 532, p. 115737, Mar. 2022, doi: 10.1016/j.desal.2022.115737. 
[2] J. Zoshi, “Applying Ultra-High Pressure reverse osmosis in brine management,” Saltworks Technologies, Jan. 20, 2026. https://www.saltworkstech.com/articles/applying-ultra-high-pressure-reverse-osmosis-in-brine-management/