Microfiltration (MF) is used to separate suspended solids from dissolved substances in a process stream, or to concentrate fine colloidal suspensions.
Microfiltration membranes are the most open of the four membranes filtration categories:
Generally, Microfiltration membranes separate or reject particles from about 0.05-0.1 micron to about 1 micron. On a molecular weight basis, these membranes can separate or reject macromolecules generally less than 100,000 MW pass through. The separation mechanism of microfiltration is commonly attributed to geometry; i.e. passage through the membrane is a function of particle size relative to opening or pore dimensions of the membrane.
Cross-flow filtration devices using Microfiltration membranes usually operate at low transmembrane pressure (the pressure difference from one side of the membrane and the other), 0.7 to 3.4 bar (10 to 50 psig), to limit flow through the membrane. Increasing pressure initially increases flow through the membrane; however, because of mass transfer phenomena, higher pressures do not result in increasing permeate flow. It is possible to influence this plateau by intensifying the sweeping action by increasing the cross-flow velocity.
Benefits of Microfiltration
Microfiltration membranes have many advantages over conventional systems. In one important aspect, it is more cost effective as Microfiltration systems offer a comprehensive solution. Microfiltration systems do not require chemical pre-feed equipment, flash mixers, flocculators, nor complicated concrete work such as settling and filter basins. Furthermore, the systems are easy to operate as filtration, backwashing and cleaning are all performed automatically.