Ultrafiltration membrane filtration is a pressure-driven membrane separation process that uses a semi-permeable membrane with pore sizes of 0.01-0.1 microns to remove suspended solids, bacteria, viruses, colloids, and macromolecular organic compounds from water. Operating at low pressure (0.1-0.3 MPa / 15-45 psi), ultrafiltration membrane filtration provides an effective barrier against microorganisms while allowing dissolved minerals to pass through, making it ideal for both drinking water purification and industrial process applications. Xi’an CHIWATEC manufactures high-quality ultrafiltration membrane systems for residential, commercial, and industrial water treatment worldwide.
The global ultrafiltration membrane market was valued at approximately USD 5.6 billion in 2025 and is projected to reach USD 10.2 billion by 2035, growing at a CAGR of 6.1% (Grand View Research, 2025). UF membrane technology has become the preferred filtration method for removing pathogens without chemical disinfection, with applications spanning municipal drinking water treatment, wastewater reuse, food and beverage processing, pharmaceutical manufacturing, and industrial process water. Unlike reverse osmosis, ultrafiltration membrane filtration retains beneficial minerals while achieving 99.99% removal of bacteria and viruses. Understanding the filtration principle, membrane configurations, operational parameters, and maintenance requirements of UF membrane systems is essential for water treatment professionals and facility managers.
*Last Updated: August 2026 | Industry-Verified Technical Data
Ultrafiltration Membrane Filtration: Definition and Separation Mechanism
Ultrafiltration is a screening process that uses membrane separation technology. The pressure difference between the two sides of the membrane is the driving force, and the ultrafiltration membrane serves as the filter medium. Under a certain pressure, when the feed water flows across the membrane surface, the numerous tiny pores on the membrane surface (0.01-0.1 microns) allow only water molecules and small solutes to pass through as permeate, while particles larger than the membrane pore size are retained on the feed side as concentrate. This achieves purification, separation, and concentration in a single operation.
Position in the Membrane Filtration Spectrum
Ultrafiltration membrane filtration occupies the middle range of the pressure-driven membrane filtration spectrum:
| Process | Pore Size | What It Removes |
| Microfiltration (MF) | 0.1-10 microns | Suspended particles, bacteria |
| Ultrafiltration (UF) | 0.01-0.1 microns | Bacteria, viruses, colloids, macromolecules |
| Nanofiltration (NF) | 0.001-0.01 microns | Divalent ions, small organic molecules |
| Reverse osmosis (RO) | Below 0.001 microns | All dissolved salts |
UF provides the best balance of pathogen removal and flow rate for most water purification applications. The complete membrane separation principle is explained in our companion guide, and the RO membrane separation technology guide covers the salt-removal end of the spectrum.
How Ultrafiltration Membrane Filtration Works: The Screening Process
Approximately 6 billion micropores with diameters of 0.01 microns exist on the wall of each meter-long hollow fiber UF membrane. These pores allow water molecules, beneficial minerals, and trace elements to pass through while rejecting particles larger than 0.01 microns. The smallest bacteria have sizes above 0.02 microns, meaning they are effectively intercepted by the UF membrane. Suspended solids, rust particles, colloidal matter, silt, and macromolecular organic compounds — all much larger than bacteria — are also retained, achieving comprehensive purification.
Water Production Process
Feed water enters the ultrafiltration membrane module under operating pressure. Inside the hollow fibers, the densely packed pores on the membrane surface allow only water molecules, beneficial minerals, and trace elements to penetrate as purified water. Bacteria, rust, colloids, silt, suspended matter, and macromolecular organic substances are trapped inside the hollow fiber lumens and are periodically flushed out during backwash cycles. This continuous cross-flow or dead-end ultrafiltration membrane filtration process produces consistent-quality permeate. The factors that control how well a UF system performs are detailed in our ultrafiltration membrane performance factors guide.
Ultrafiltration Membrane Types: Hollow Fiber Configurations
Hollow fiber membranes are the most common UF configuration, consisting of hundreds to thousands of tiny hollow fiber filaments bundled together. Each fiber has an inner diameter of 0.6-6 mm, classifying them as capillary ultrafiltration membranes. The larger inner diameter of capillary membranes makes them less prone to clogging by large particles compared to finer hollow fibers. The membranes can operate in either inside-out (internal pressure) or outside-in (external pressure) flow configuration. See our dedicated hollow fiber ultrafiltration membrane guide for a deeper look at this configuration.
Internal Pressure vs. External Pressure Configuration
In internal pressure (inside-out) configuration, feed water flows through the lumen (inside) of the hollow fibers, and permeate is collected from the outside. This configuration is more common for drinking water applications as it allows easy flushing of accumulated particles from the fiber lumens. In external pressure (outside-in) configuration, feed water flows around the outside of the fibers, and permeate is collected from the inside. This configuration handles higher suspended solids loads and is preferred for wastewater and industrial applications. CHIWATEC supplies both ultrafiltration membrane filtration configurations based on application requirements.
Structure of a UF Membrane Filter Element
A bundled UF membrane filter element consists of: an ABS or PVC outer shell that provides mechanical protection and contains the feed water, epoxy resin potting at both ends of the shell that seals the gap between individual membrane filaments and separates feed water from permeate, and the bundle of hollow fiber UF membrane filaments that performs the actual filtration. The epoxy heads create a leak-tight separation — feed water must pass through the membrane pores to become permeate, preventing any direct bypass of unfiltered water.
Membrane Area Calculation
Under conditions where water production per unit membrane area remains constant, the total water production of an ultrafiltration membrane filtration element is directly proportional to the effective membrane area packed into the module. The total surface area is calculated as: S(inner) = pi × d × L × n (internal surface area, where d = inner diameter, L = fiber length, n = number of fibers) and S(outer) = pi × D × L × n (external surface area, where D = outer diameter). UF modules are designed with the maximum practical fiber packing density to achieve the highest flow rate within the given module dimensions.
UF Membrane Flushing and Chemical Cleaning Process
After a period of operation, trapped bacteria, rust, colloids, suspended solids, and macromolecular organic substances accumulate on the inner surface of UF membrane fibers, causing ultrafiltration membrane filtration productivity to gradually decline. This is especially pronounced when feed water quality is poor. Regular forward flushing or backwashing effectively removes accumulated particles and restores ultrafiltration membrane filtration capacity. Automatic backwash systems initiate flushes at preset intervals (typically every 30-60 minutes of operation) or based on transmembrane pressure (TMP) increase.
Chemical Cleaning (CIP)
Periodic chemical cleaning is required to remove fouling that cannot be eliminated by hydraulic flushing alone. Standard cleaning agents include: citric acid (1-2% solution, pH 2-3) for inorganic scale and metal oxide fouling, sodium hydroxide (0.1-0.5% solution, pH 11-12) for organic and biological fouling, and sodium hypochlorite (50-200 ppm free chlorine) for disinfection and biofilm control. Chemical cleaning-in-place (CIP) is typically performed every 3-12 months, depending on feed water quality and operating conditions.
Key Operational Parameters of UF Membranes
Ultrafiltration membrane filtration performance is defined by a set of operational parameters that must be monitored and controlled:
| Parameter | Typical Range |
| Pore size | 0.01-0.1 microns |
| Operating pressure (TMP) | 0.05-0.3 MPa (7-45 psi) |
| Permeate flux | 30-150 L/m2-h |
| Maximum feed turbidity | 50-100 NTU (with pretreatment) |
| Operating temperature | 5-40 degrees C (41-104 degrees F) |
| Operating pH range | 2-11 (standard), 1-13 (cleaning) |
| Backwash frequency | Every 30-60 minutes |
| Recovery rate | 90-99% (depends on feed quality) |
Factors Affecting UF Performance
Key factors that influence ultrafiltration membrane filtration performance include: feed water turbidity and suspended solids concentration (higher loads require more frequent backwashing and shorter chemical cleaning intervals), temperature (flux increases approximately 2-3% per degree C temperature rise), transmembrane pressure (higher TMP increases flux but accelerates fouling), cross-flow velocity (higher velocity reduces concentration polarization but increases energy consumption), and membrane material properties (hydrophilicity, surface charge, and pore size distribution). The full parameter set is covered in our ultrafiltration membrane operating parameters guide.
Contaminants Removed by UF Membranes
Microorganisms
Ultrafiltration membrane filtration achieves 4-6 log removal (99.99-99.9999%) of bacteria including Escherichia coli, Salmonella, and Legionella, and 3-4 log removal (99.9-99.99%) of viruses including enterovirus and rotavirus. This makes UF an effective physical disinfection barrier without chemical addition, unlike chlorine or ozone disinfection which can form disinfection byproducts. For regulatory compliance, UF systems used for pathogen removal must include continuous integrity monitoring.
Particles and Colloids
UF completely removes suspended solids, silt, rust particles, and colloidal matter. Effluent turbidity consistently falls below 0.1 NTU regardless of influent turbidity (up to the design limit of 50-100 NTU). The silt density index (SDI) of UF permeate is typically below 1-2, making it excellent feed water for downstream RO systems.
Macromolecular Organics
UF effectively removes natural organic matter (NOM), proteins, polysaccharides, and humic/fulvic acids with molecular weights above 10,000-100,000 Daltons. However, UF does not remove dissolved salts, low-molecular-weight organic compounds, pesticides, or emerging contaminants such as PFAS — these require NF or RO membranes for effective removal.
Main Applications of UF Membranes
Drinking Water Purification
Ultrafiltration membrane filtration systems are widely used for municipal and household drinking water treatment, providing reliable removal of pathogens and particles without removing beneficial minerals. In municipal water treatment, UF has largely replaced conventional coagulation, sedimentation, and sand filtration for new plant designs due to its smaller footprint, automated operation, and superior effluent quality.
Industrial Process Water and Wastewater Reuse
UF is used as pretreatment for RO systems in industrial applications, protecting RO membranes from particulate and colloidal fouling and extending RO membrane life by 2-3 times. UF is also the core technology in membrane bioreactors (MBRs) for wastewater treatment, combining biological treatment with membrane filtration for high-quality effluent suitable for reuse. Our ultrafiltration membrane application guide covers these use cases in depth.
Food and Beverage Processing
Ultrafiltration membrane filtration is used for juice clarification (removing pectin and suspended solids while preserving flavor and nutrients), wine and beer processing (sterile filtration without heat treatment), dairy processing (protein concentration and fractionation), and edible oil processing.
Pharmaceutical and Biotechnology
UF is used for protein concentration and buffer exchange, virus removal in biopharmaceutical manufacturing, fermentation broth clarification, and production of water for injection (WFI) as an alternative to distillation.
UF Membrane System Maintenance
Daily and Weekly Maintenance
Daily tasks: monitor permeate flow rate, transmembrane pressure, feed water turbidity, and effluent turbidity. Log operating parameters and compare with baseline values. Weekly tasks: perform manual integrity test (pressure hold test) if automatic integrity monitoring is not installed, inspect chemical dosing levels for cleaning agents, and check valve and pump operation.
Periodic Maintenance
Chemical cleaning (CIP) should be performed when TMP increases by 30-50% above the initial clean value, or when permeate flux decreases by 20-30% at constant pressure. Typical CIP frequency is every 3-12 months — the standard trigger points for ultrafiltration membrane filtration maintenance. Membrane replacement is typically required every 5-10 years for well-maintained systems, depending on feed water quality and cleaning practices. Fiber breakage or irreversible fouling are the primary reasons for module replacement. Proper storage between uses is covered in our hollow ultrafiltration membrane storage and maintenance guide.
How to Select the Right UF Membrane System
Feed Water Quality Assessment
Analyze feed water for: turbidity, TSS (total suspended solids), TOC (total organic carbon), bacteria count, iron and manganese concentration, and hardness. High turbidity or organic content requires adequate pretreatment (strainers, media filtration, or coagulation) before the UF system. Iron and manganese may cause scaling on membrane surfaces and require removal or chelation.
System Configuration and Sizing
Select the UF membrane configuration based on feed water quality and application: internal pressure hollow fiber for drinking water and low-turbidity applications, external pressure hollow fiber for higher solids loads and wastewater applications, and submerged UF for MBR applications. Size the system based on peak flow plus 20-30% safety margin, considering temperature variations (flux decreases in cold water) and periodic backwash downtime. CHIWATEC provides complete ultrafiltration membrane filtration system design, from point-of-use units to industrial-scale installations handling flow rates up to 500 m3/h. See also our ultrafiltration membrane technology overview for the broader technology landscape.
Conclusion
Ultrafiltration membrane filtration delivers reliable pathogen removal at low operating pressure while retaining beneficial minerals, making it the most versatile filtration technology in the pressure-driven membrane spectrum. Its 0.01-0.1 micron pores remove bacteria, viruses, colloids, and macromolecular organics with 99.99%+ efficiency, its configurations range from point-of-use cartridges to 500 m3/h industrial plants, and its automatic backwash plus periodic CIP keeps maintenance simple and predictable.
Xi’an CHIWATEC manufactures high-quality ultrafiltration membrane systems for residential, commercial, and industrial water treatment worldwide. Every ultrafiltration membrane filtration project is delivered with complete system design from feed water analysis to installation and commissioning.
Contact us for UF membrane system design and supply: [email protected] | [email protected] | [email protected]
FAQ: UF Membrane Filtration Systems
What is the difference between ultrafiltration and reverse osmosis?
Ultrafiltration membrane filtration uses 0.01-0.1 micron pores to remove suspended solids, bacteria, viruses, and macromolecules while allowing dissolved minerals to pass through. Reverse osmosis uses a dense membrane (below 0.001 microns) that removes nearly all dissolved salts. UF retains beneficial minerals; RO removes them.
What contaminants can a UF membrane remove?
Ultrafiltration membrane filtration removes 4-6 log (99.99-99.9999%) of bacteria, 3-4 log (99.9-99.99%) of viruses, all suspended solids and colloids (effluent below 0.1 NTU), and macromolecular organics above 10,000-100,000 Daltons. It does not remove dissolved salts, pesticides, or PFAS — those need NF or RO.
How often should UF membranes be backwashed?
Automatic backwash systems typically initiate flushes every 30-60 minutes of operation, or when transmembrane pressure rises to a preset threshold. The exact interval depends on feed water turbidity and suspended solids load.
When should chemical cleaning (CIP) be performed on UF membranes?
Chemical cleaning is needed when TMP increases by 30-50% above the initial clean value, or when permeate flux drops 20-30% at constant pressure — typically every 3-12 months. Citric acid (pH 2-3) removes inorganic scale, sodium hydroxide (pH 11-12) removes organic fouling, and sodium hypochlorite (50-200 ppm) controls biofilm.
How long do UF membrane modules last?
Well-maintained ultrafiltration membrane filtration modules typically last 5-10 years, depending on feed water quality and cleaning practices. Fiber breakage and irreversible fouling are the primary reasons for earlier replacement.
Related Resources
- Ultrafiltration Membrane Performance Factors: Key Parameters and Optimization 2026
- Optimizing Ultrafiltration Membrane Process in Water Treatment: Operating Parameters Guide 2026
- What Is a Hollow Fiber Ultrafiltration Membrane? Complete Guide 2026
- Application of Ultrafiltration Membrane in Water Treatment
- Dupont RO Membrane Elements
Xi’an CHIWATEC Water Treatment Technology provides RO membranes to clients both inland and overseas with more than 10 years of experience. We manufacture our own Daltonen RO membrane brand and are the official distributor of Dupont, Toray, CSM, Nitto, LG and Vontron RO membranes. Whatever product you need, we can meet your requirement.
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