Membranfiltration

Membranfiltration is a separation process that uses a semi-permeable membrane to remove unwanted constituents from a liquid. The driving force is usually hydraulic pressure, which pushes the solvent through the membrane while retaining suspended solids, macromolecules, salts, or other solutes on the retentate side. Filtration by membranes is typically continuous and scalable, enabling processing of large volumes with relatively stable energy use.

The main families of membrane filtration are microfiltration, ultrafiltration, nanofiltration, and reverse osmosis. Microfiltration typically removes suspended solids and microorganisms with pore sizes around 0.1 to 10 micrometers. Ultrafiltration targets larger biomolecules and colloids, roughly 1 to 100 nanometers in effective pore size. Nanofiltration handles smaller ions and multivalent species, about 0.5 to 2 nanometers, while reverse osmosis relies on very dense barriers to reject virtually all ions, enabling high-purity water production. The process is driven by pressure in all cases except some osmotic or diffusion-driven variants.

Membranes are made from polymeric materials such as polysulfone, polyethersulfone, polyvinylidene fluoride, and cellulose derivatives, or from inorganic ceramics. Common module types include hollow-fiber, tubular, spiral-wound, and flat-sheet configurations, each with distinct fouling and cleaning profiles. Fouling from organic matter, biofilms, or inorganic scale is a central operational concern and is mitigated by pretreatment, crossflow operation, air scouring, backwashing, and chemical cleaning.

Applications cover drinking water and wastewater treatment, food and beverage processing, pharmaceutical and biotech purification, and industrial process streams, as well as desalination in the case of reverse osmosis. Membranfiltration offers precise separation, moderate energy use, and modular scalability, balanced against membrane lifetime and fouling management.