Microfiltration is the process of physically removing suspended solids from water, usually through a membrane. Unlike nanofiltration and reverse osmosis, microfiltration only utilizes physical filtration to remove particles in the 0.1 to 10 micron range, including bacteria but it doesn’t remove dissolved contaminants that nanofiltration and RO do.
Usually, water microfiltration is performed by cross-flow separation, which involves a feed stream being introduced into the membrane under pressure and passed over a membrane surface in a controlled flow path. The portion of the feed stream that passes through the membrane is called permeate.
The materials that do not pass through the membrane are flushed away and are referred to as concentrate. Cross-flow membrane filtration utilizes high cross flow rate to improve permeate passage and help prevent the fouling of the membrane. This process operates at a lower pressure than nanofiltration and reverse osmosis, typically less than 100 psig.
Microfiltration systems are typically used for:
- Clarification of fruit juices, wines and beer.
- Cold disinfection of pharmaceuticals and beverages.
- Pretreatment upstream of RO to remove suspended solids which can foul membranes.
- Separation of bacteria from water (water microfiltration is the preferred method for many community and municipal water treatment systems due to its ability to reliably remove spores such as Cryptosporidium and Giardia).
- Certain types of effluent treatment.
- Certain oil and water separation applications.
Microfiltration, like other membrane processes, requires precisely applied pretreatment in order to prevent frequent and/or irreversible membrane fouling. The WaterProfessionals® have extensive experience applying this and other water treatment technologies to assure economical, effective long-term operation.