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What is Membrane Filtration?
Membrane filtration is a separation process used across industries to remove particles, microorganisms, and solutes from liquids. Relying on semi-permeable membranes, it allows selected substances to pass while rejecting others based on size or chemical properties. It’s a core technology in both water treatment and product purification, offering consistent performance with minimal chemical input.
How is Membrane Separation and Filtration Used?
Membrane separation is widely used across industries—from municipal water and wastewater treatment to chemical manufacturing and pharmaceuticals—because it offers reliable, high-precision purification. By acting as a selective barrier, the membrane filters out everything from suspended solids to dissolved salts, depending on its design. In more advanced applications, Veolia's membrane technologies can also concentrate brine streams up to 14%, improving waste handling efficiency and making it possible to recover valuable byproducts in the process.
How Does Membrane Separation Work?
Membrane filtration works by forcing liquid through a membrane that acts as a selective barrier. Only specific molecules or ions pass through, depending on the membrane's pore size and design.
Membrane Filters as a Barrier for Contaminants
Each membrane serves as a physical barrier—microscopically porous yet effective at rejecting targeted contaminants. Whether blocking suspended solids or separating ions, the membrane structure determines what stays and what passes through. For example, Veolia’s AK H Series ultra-low energy membranes are designed to remove a wide range of contaminants—delivering 97% rejection for nitrate, 95.8% for 1,4-dioxane, and more than 99% for pharmaceuticals such as carbamazepine and diclofenac.
The Role of Pressure in Driving Filtration
Pressure is essential. Applied pressure forces the feedwater across the membrane surface, enabling selective passage. The required pressure varies with the membrane type: microfiltration may operate under 1 bar, while reverse osmosis can require over 40 bar.
What Are Permeate and Retentate?
In membrane filtration, feedwater is split into permeate—the purified water that passes through—and retentate, which holds back the concentrated contaminants. Veolia's AK H Series ultra-low energy membranes deliver high-quality permeate with strong rejection of salts, organics, and micropollutants. Detailed performance specs help engineers select the right membrane for their treatment targets.
Components of Membrane Filtration Systems
Membrane filtration systems rely on several integrated components to perform efficiently. At the core are the membranes themselves—Veolia offers a wide range of spiral wound options tailored for different needs, including the AG H and AK H Series for brackish water, as well as membranes for seawater desalination and nanofiltration. Supporting elements like feed pumps, pressure vessels, and control systems are essential to maintaining consistent operation. Veolia also supplies complementary technologies—such as depth and pleated filters, hollow fiber ultrafiltration, electrodeionization, and UV or ozone disinfection—enabling complete, end-to-end solutions from a single provider.
Spiral Wound Membranes
Spiral wound membranes are the most common configuration. Flat sheets are layered with spacers and wound around a central tube. This compact design offers high surface area and efficient flow paths, particularly in reverse osmosis and nanofiltration systems. To learn more about how Veolia's spiral wound membranes can optimize your brine concentration processes, be sure to check out our dedicated "Spiral Wound Membrane" page for in-depth information.
Other Membrane Configurations
While spiral wound membranes are a core component of Veolia’s RO systems, alternative configurations are available to meet different performance demands. These options allow systems to be tailored for water source conditions, fouling potential, and treatment goals.
Veolia’s membrane configurations include:
Spiral wound membranes – high surface area, compact design; ideal for RO and NF
Hollow fiber ultrafiltration membranes – excellent for pretreatment and low-pressure applications
Fouling-resistant designs – such as the AG FR H Series membranes, offering high rejection and improved durability in challenging waters
Plate-and-frame and tubular membranes – suitable for high-solids or viscous feed streams
Selecting the right configuration ensures optimal system performance—whether you're aiming to improve energy efficiency, reduce fouling, or remove specific contaminants.
Types of Membrane Filtration
What is Cartridge Filtration?
Cartridge filtration is a pre-treatment method using replaceable filter elements. Though not a membrane process in the strictest sense, it protects downstream membranes by removing coarse particulates.
What is Microfiltration?
Microfiltration (MF) is a low-pressure process that uses microfilter membrane technology to remove particles between 0.1 and 10 microns. It effectively targets bacteria, some viruses, and suspended solids. Often used as a pretreatment for reverse osmosis or as a standalone solution, MF supports the production of high-quality drinking water.
What is Ultrafiltration?
Ultrafiltration (UF) uses finer membranes than microfiltration, removing particles from 0.001 to 0.1 microns. This ultrafiltration membrane filter technology effectively removes bacteria, viruses, proteins, and other large organics. It’s widely used in water treatment and the food and beverage industry for producing clean, high-quality water.
What is Nanofiltration?
Nanofiltration (NF) sits between ultrafiltration and reverse osmosis in selectivity. Using nano filter membrane technology, it removes particles around 0.001 microns, including dissolved organics and certain salts. It’s especially effective at filtering out divalent ions—ideal for water softening—and can also target pesticides, herbicides, and other organics. Its flexibility makes it useful across water treatment, industrial processes, and pharmaceutical applications.
What is Reverse Osmosis?
Reverse osmosis (RO) is a high-pressure membrane process that removes dissolved salts, ions, and impurities by forcing water through a semi-permeable membrane. Veolia's Industrial RO series is engineered to operate at pressures up to 120 bar, enabling brine concentrations of up to 14% total dissolved solids—among the highest in the industry. This reverse osmosis membrane filtration technology is precise enough to separate even monovalent ions like sodium and chloride. To learn more, visit our Reverse Osmosis and Nanofiltration Equipment page.
What is Electrodialysis?
Electrodialysis is a membrane process that removes ions from water using an electric field instead of pressure. It relies on ion-exchange membranes to selectively separate charged particles. Veolia's electrodialysis technology goes a step further—recovering valuable byproducts like 7% acid and 7% caustic from brine streams. This makes it an efficient option for brine management and supports circular resource use by turning waste into usable chemicals.
Cross-Flow Filtration vs. Dead-End Filtration
Membrane systems use either cross-flow or dead-end filtration. In cross-flow, the feed flows parallel to the membrane surface, reducing fouling and supporting longer run times— Veolia's ROTOWER system applies this method to reach up to 95% recovery in brine applications. Dead-end filtration directs flow straight into the membrane, which can lead to faster fouling but may suit low-solids applications. Veolia offers membrane elements for both modes, including fouling-resistant options like the AG FR H Series for demanding conditions.
Applications of Cross-Flow Filtration
In cross-flow mode, the feedwater flows tangentially across the membrane surface. This keeps particles in motion, reducing fouling and extending membrane life. Cross-flow is standard for RO, NF, and UF systems.
Why It Matters for Your Filtration System
Choosing the right flow mode affects operational stability. Dead-end filtration may offer higher recovery in low-fouling applications, but cross-flow systems provide better performance where water quality fluctuates or fouling risk is high.
Applications of Membrane Filtration
What is Membrane Filtration Used for Removal Of?
Veolia’s membrane filtration systems are tailored to remove a wide range of contaminants:
Particulate matter
Microorganisms
Organic compounds
Emerging contaminants (e.g., PFAS with RO)
Does Membrane Filtration Remove Bacteria?
Yes, membrane filtration is highly effective at removing bacteria. Microfiltration and ultrafiltration are specifically designed to eliminate microorganisms, while nanofiltration and reverse osmosis provide an added layer of protection. Veolia's AK H Series ultra-low energy membranes, for example, offer high rejection of micropollutants and small organics—enhancing microbiological safety even though they target finer contaminants.
Advantages of Choosing Membrane Filtration
Cost Efficiency
Membrane filtration reduces energy use and maintenance costs. Veolia's AG LE H Series delivers quality results at lower pressure, while its hydrophilic surface limits fouling and cleaning needs. The AG LE H Series offers a mid-range energy option, giving plants flexibility to manage costs without sacrificing performance.
Versatility Across Applications
Veolia's advanced membrane systems are built to handle diverse feedwaters—from pharmaceutical streams to mining effluents—with TDS levels up to 50 g/L. Their flexible configurations and specialized elements ensure consistent performance in water treatment, brine concentration, and byproduct recovery
High End Product
Quality membrane filters deliver consistently high-purity results that meet strict regulatory standards and evolving consumer expectations. Veolia's advanced reverse osmosis (RO) elements, like the AG H and AK H Series, offer salt rejections up to 99.8% and reliably remove challenging contaminants such as PFAS, nitrates, and pharmaceuticals—with rejection rates between 90.4% and 99.6%. This level of precision helps utilities meet safety targets while addressing growing concerns around emerging contaminants.
Membrane Filtration or Alternatives? Discover the Best Option with Veolia
When comparing membrane filtration with other treatment methods, Veolia provides the expertise to guide you toward the most effective solution. With a comprehensive range of membrane filtration options—including RO, NF, and low-energy systems—we support everything from drinking water to specialized industrial applications. Our global team of engineers helps assess technology choices based on removal efficiency, energy use, and cost. Backed by tools like Winflows design software and in-house water testing, Veolia offers data-driven recommendations to ensure your system performs reliably and sustainably.
To determine what’s best for your operation, contact a Veolia expert for guidance tailored to your water quality goals and system requirements.
