Ultrafiltration is a physical separation process using membrane pore size comprised between 0.01 to 0.1μm.
For steady flux and effective removal of particles, bacteria and virus.
What is Ultrafiltration?
Ultrafiltration (UF) is a low-pressure filtration membrane process for water treatment that allows for the physical separation and retention of particles. It is designed to remove turbidity causing particles including those comprised of suspended solids, bacteria, viruses, colloidal matter and proteins.
Ultrafiltration membranes have a pore size range of 0.01-0.1μm, and a molecular weight cut-off range of 5k-200k Da. Regarding solute rejection, UF can be measured by passing molecules with a known molecular weight through the membrane (i.e. using markers such as polyethylene glycol or dextran). Ultrafiltration can be operated either in direct (dead-end) or cross-flow filtration.
When direct filtration is applied, the feed liquid is pushed through the membrane surface, resulting in a rather rapid build-up of particle matters on the membrane’s surface referred as cake layer formation. After some time, the flux will decrease to such an extent, that it requires cleaning operation.
Direct principle is applied because the energy loss is less when compared to cross-flow filtration.
When cross-flow filtration is applied, the feed liquid is recycled. All the feed liquid is pushed tangentially across the membrane, allowing a large quantity of feed liquid produced as permeate, the remaining feed liquid will leave the module and be recirculated.
Cross-flow principle is applied because it creates turbulence on the surface of the membrane, therefore controlling cake formation, while allowing a more constant flow and ultimately limiting the use of extensive chemical cleaning.