Nanotechnology: The next great leap in water-filtration is already at work in AQUAPHOR filters.

Since its founding, AQUAPHOR's products have incorporated the latest developments in water purification. Applications that were, until recently, only available in large-scale industrial systems, are now realized in AQUAPHOR brand small-volume household filters. One of the latest revolutionary developments is the hollow-fiber membrane.

Hollow-fiber membranes are micro-thin tubules with porous walls. The tubules (fibers) are about 1mm thick. The pores that allow water to flow through the fibers are approx. .1 micrometer wide, which is about 600-800 times thinner than a human hair, too small for even the tiniest impurities to pass through.

Hollow-fiber

These are the advantages of hollow-fiber membrane filters:

  • Filtration of all mechanical impurities (clay, sand, rust) larger than .1 micrometer.
    Removal of these impurities, including colloidal iron particles, produces perfectly clear water. Water that has gone through a hollow-fiber membrane tastes and smells better, but most importantly, is significantly safer for human consumption. Certain small-particle pollutants, for example iron hydroxides, can irritate the epithelial wall of the intestines and bring about a range of digestive dysfunctions.
  • Filtration of microorganisms and bacteria.
    It's practically impossible to reduce the pore size in conventional filters (polypropylene or carbon-block cartridges) below .7-.8 micrometers. This is not sufficient to reliably filter out harmful bacteria. E. coli, for example, is between .3 x 1 and 1 x 6 micrometers in size, while Staph. aureus has a diameter of .5-1 micrometers.
  • Filtration of Giardia cysts.
    • The "cyst" form of Giardia is something like a cocoon, resistant to external factors, including most bactericides. Most household filters have no reliable anti-Giardia capability. The most effective method of removing Giardia cysts from drinking water is mechanical filtration through a hollow-fiber membrane.

Hollow-fiber membranes in AQUAPHOR filters

AQUAPHOR is the only brand of water filters in Russia to use hollow-fiber membranes.

This technology is used for end-stage filtration in the Crystal family of filters, as well as the reverse-osmosis AQUAPHOR Morion system. Module K1-07B uses a hollow-fiber membrane (made by Mitsubishi, Japan) in combination with an AQUAPHOR-made carbon block to provide optimal filtration capability.

Micro-crystalline activated silver in the carbon block does not allow bacteria captured by the filter to reproduce, which increases the effective life of the replaceable module.

 

Other useful properties of hollow-fiber membranes

Hollow-fiber membranes combine the useful properties of both "sieve"-type filters (flat-surface filtration) and bulk filters (large-volume filtration). The former enjoy a uniform pore size, while the latter have a large absorbent capacity.

  • Environmentally sound production
    Unlike rolled membranes, such as ones used in reverse-osmosis devices, hollow-fiber membranes are made out of pure polyethylene without the use of solvents.
  • Non-reactive materials
    Made of pure polyethylene - one of the most inert materials known - hollow-fiber membranes have a long service life and can hold up well under unfavorable conditions.
  • A huge filtering surface in a small volume of space
    The effective surface area of the membrane used in AQUAPHOR filters is 7,500 cm2 - over 8 sq. ft.
  • Large absorbent capacity
    A hollow-fiber membrane is capable of filtering a considerably larger amount of "dirt" (large-particle impurities) than bulk filters such as polypropylene cartridges or carbon blocks.
Cross-section
of Module K1-07B

How it's Manufactured

Molten polymer is pulled through a specialized apparatus (an extruder) so that a very thin "tube" forms. The tubule material is of variable consistency - some areas are elastic (capable of stretching) and some are crystalline (not capable of stretching).

As soon as the polymer tubule cools and sets, it is stretched precisely to the point where the crystalline areas "tear" and allow micro-pores of a specific uniform diameter to form in the walls of the tubule.

These micro-pores are what allows water filtration to happen.

Changing the parameters of extrusion and stretch makes for hollow-fiber of different sizes and porosity.

The next step is for the fibers, now cut to length, to be gathered into bundles and folded in half (exact 180 degree bend) into a loop shape, so that the "entrances" and "exits" (the openings on either end of each tubule) end up next to each other on one end of the loop.

After this, polymer glue is poured into the tubule openings. After it sets, it's cut off, so as to widen the tubule ends.

The loops of polymer fibers, now in their finished stage, are then gathered together into a final unit and fit inside the filter housing. The hollow-fiber membrane filter is now complete.

Water will enter on the closed end of the looped bundles, seep in through the micro-pores, and come out clean through the tubule openings on the other side.

Membranes in the body