Membrane Filters
Membrane filtration is a technique for the separation of suspended or dissolved materials by molecular weight and size. Filtration can be done using cross-flow or dead-end techniques.
The application of a pressure differential across the membrane causes a sieving process. Substances smaller than the pore size of the membrane pass with the solvent (permeate) while larger solutes or particles are retained (retentate or concentrate). Membrane filtration is a simple process to implement and requires little maintenance. It is commonly used in the chemical, food and beverage, water and textile industries.
| Process | Components Retained | Transmembrane Pressure | Process Applications |
| Reverse Osmosis | 99% of most ions, most organics over 150 MW | 200- 1000 psig (13.8-69.0 bar) | Brackish sea water, Desalting, boiler feed purification, blowdown reclamation, pretreatment to ion exchange, ultrapure water production. |
| Nano Filtration | 95% divalent ions, 40% monovalent ions, organics greater than 150-300 MW | 135-230 psig (9.3-15.9 bar) | Hardness removal, organic and microbiological removal, dye desalting, color removal |
| Ultra Filtration | Most organics over 1000 MW | 25-l00 psig (1.7-6.9 bar) | Pre- and post-treatment to ion exchange, beverage clarification, concentration of industrial organics and dilute suspended oils, removal of pyrogens, bacteria, viruses, and colloids. |
| Micro Filtration | Small suspended particles greater than 0.1 m | 25 - 50 psig (1.7-3.4 bar) | High volume removal of small suspended solids. |