The use of hollow fiber membrane for filtration can be traced back to 1830. However, the most accurate representation of the technology we have today was developed around 1960. The uses were for the reclamation of waste-water desalination gas separation and blood diffusion.
How do hollow fiber membranes work?
Hollow fiber membranes are small hollow tubes that look like straws. These fibers have a porous membrane that allows clean water into the fiber and prohibits contaminants from passing through the membrane. Hollow fiber membrane filters water by size exclusion. Size exclusion works by having a pore size smaller than the size of the contaminates. Try pushing a basketball down a golf ball hole. Not going to happen right? Same thing with contaminants in water. Clean water is allowed to go through the membrane while the large contaminates cannot fit through the pores.This is illustrated below:
What about pore size?
The industry standard pore size is 0.2 microns. At this size the hollow fiber membrane will exclude bacteria, protozoa and cysts from entering the membrane. However we recommend choosing a filter with a pore size of 0.1 microns. This is will give you a greater level of protection against bacteria protozoa and cysts. If you are looking to filter out viruses then you need a pore size of 0.01 microns. At this pore size rating the hollow fiber membrane is no longer considered a filter but a purifier.
Why not always get 0.01 micron rating hollow fiber membrane?
With the smaller pore size comes diminished flow rate. Like sucking a golf ball through a garden hose, it will take some effort to get water through the membrane. Most of the times a purifier using hollow fiber will be pump assisted rather than a straw type or using gravity.
More interesting facts
The hollow fiber membrane can be reclaimed by a process called back flushing where clean water travels through the filter in the opposite direction. This process cleans the pores of the membrane. Hollow fiber membranes can work in a variety of temperatures and climates though if left to freeze it can be damaged. Hollow fiber membrane technology has come along way and will continue to be used in various applications.