4/10/2008 

Sand filtration has been a staple technology in the world of water treatment for more than a hundred years. It is now set to be replaced by a ground-breaking ultrafiltration technology, which employs membranes that look similar to macaroni arranged in a honeycomb structure

Greifenberg - Modelled on natural processes, the technique of cleaning drinking water by means of sand filtration was introduced in Europe as early as 1870. Similar to the natural water cycle, in which water flows through layers of rock and sand, this technique involved trickling the water through basins of sand in order to clean it. It was a revolution of its time in newly developing cities and continues to be the principal method used in many communities. The truly revolutionary technologies of today, however, have now moved a stage further, though they continue to be inspired by nature, this time taking their cue from honeycombs.

The new, "modern" method of treating drinking water is called ultrafiltration with multibore membranes. Engineers refer to the long, white, thin plastic capillaries simply as "spaghetti", though "macaroni" would perhaps be a more accurate term in terms of the pasta comparison! This is because each capillary has a hole that you could theoretically blow through, just like macaroni. The delicate tubes consist of a membrane that only lets through water molecules, but not viruses, germs or bacteria. These undesirable elements are larger than the water molecules and are simply unable to fit through the ultra-fine pores. The filter pores measure approximately 20 nanometres, which makes them 3000 times smaller than the diameter of a human hair.

And that is how you get clean drinking water: by forcing dirty water into the "macaroni" under pressure. The fact that the other end of the tube is sealed with a layer of resin means that the water can only escape through the walls of the pasta (read: membrane), where it emerges free from germs or particles of dirt. Once too much "dirt" has built up inside the pasta, it is washed out with a powerful surge of pressure in the reverse direction.

Borrowing from Bees
The strain on the membrane when the water is forced through under pressure is tremendous, however, and there is a real risk of the fibres breaking and letting through viruses and germs. To provide the membranes with greater stability, the developers from the German ultrafiltration specialists inge AG arranged seven macaroni tubes in a similar fashion to a honeycomb and combined them into a single "multibore capillary". However dirty the water is that they have to clean, the fibres of this honeycomb macaroni do not break, which means that the water they filter maintains the same degree of top-quality cleanliness.

Sand filtration simply cannot match this process. Heavy rainfall, floods or contamination in the water supply can cause the sand to clot together and go lumpy, which ultimately means it is no longer capable of retaining all the dirt particles.

SOURCE: Inge AG