UF is a purely physical treatment able to treat any kind of water with the same purifying efficiency.
Ultrafiltration is a process where the driving force is the pressure of the liquid to be treated (0.5 to 1.5 bars). Pressurized water enters the module and treated water (called filtrate or permeate) passes through the membrane barrier.
The retained substances are captured on the membrane surface and continuously or periodically removed from the module, depending on the filtration mode (cross flow or dead end), in the concentrate or in the backwash effluent.
The pore size is about one hundredth of a micron, allowing the retention of very small particles, providing a permeate turbidity of the less than 0.1 NTU, but also of micro-organisms and viruses (disinfection), of pyrogens…
The porous structure of membranes presents a very thin layer called “skin” on the filtration surface, with the smallest pores, while the rest of the thickness (more than 100 μ) has pore diameters of about a micron. The “skin” ensures the retention capacity while the internal structure of the fiber allows an easy passage of the filtrate.
Ultrafiltration is thus a filtration “on the membrane surface”, unlike microfiltration which is a “depth filtration” (MF pore size is the same over the entire thickness of the fiber).