Ultra filtration and Hollow Fiber Membranes explained

In this article we'll try to explain what ultra filtration is and how it is applied through special hollow fiber membranes to clean and process water.

Water filters are housings into which we put cartridges made of compact and solid material (such as activated carbon block). Water is trying to penetrate this block which has tiny holes. The tinier the holes, the more substances stay out of the filter and your water. Apart from carbon block a cartridge can be made from polypropylene, wound and other materials.

The diameter of the holes is called "permeability" and is measured in microns symbolised with "μm". The smaller the permeability, the tighter the cartridge.

Water treatment technologies are separated in 5 main categories:

Particle filtration (1000μm - 10μm).

Whole house water filters belong to this category. We usually install these water filters in house's main water supply to filter out particles, rust and dirt. Their usual permeability is from 1000μm to 10μm. They are mostly made from polypropylene, wound and even plastic or inox net.

Microfiltration 10μm - 0.1μm

Most domestic water filters belong to this category. Activated carbon block is the most usual medium to reduce chlorine and most of the standard impurites we come across city's water. You can use a single carbon block cartridge or add more depending on your water's quality.

Ultra-filtration 0.1μm - 0.01μm .

Ultra Filtration technology, using Hollow Fiber membranes, changes the way we clean and process water all over the world. Large water treatment companies and water recycling plants are now using this method, mainly because in relation to reverse osmosis technology, Hollow Fiber membranes do not have to drain water to function. A few years ago, this technology was so expensive that we only encountered it at very large water recycling plants. But as technology progresses, it is getting cheaper, so that water filters, known water filters, can now be introduced into domestic water treatment systems. It can be used in a wide range of applications, where water is quite "problematic", such as camps, lakes, motor homes, etc. Of course, it can also be used for more "simple" uses such as water cleaning of cities. It removes chlorine, bacteria, viruses, colloids, Giardia, Crypto (commonly found in tanks and non-city water sources), suspended solids, turbidity, micro-organisms, TOC's etc.ς, τα κολλοειδή κ.α..

Nano-filtration (0.01μm - 0.001μm).

This technology is still very expensive for domestic users.

Reverse Osmosis (0.0001μm).

Reverse osmosis systems are the most advanced water purification systems available in the world. They offer you 100% Safe and Clean Water by allowing only water molecules to pass through their semi-permeable membrane. RO can filter our limescale, pharmaceuticals, heavy metals (including lead), nitrates, bacteria, cysts, chlorine, arsenic, industrial chemicals, sulfates and a wide list of chemicals. RO is placed under your kitchen sink, so you'll need to drill a hole on your kitchen counter (diameter 1cm) to install a tap which you'll use just for the filtered water.