The history of filtration …
“Water is the principle of all things. Everything is made out of water and to water everything returns.” Thales of Miletus, around 600 BC.
The history of filtration goes back almost to the beginning of humankind: In the Stone Age, cave dwellers used twigs to drill holes in pieces of tree bark to separate water from dirt and coarse material. Later on, moss or other permeable tissue with much smaller apertures was used. Filtration techniques developed in parallel with the evolution of humankind.
Just a few centuries ago, water consumption was not an issue. The supply of water seemed to be inexhaustible. As a consequence of industrialization, water was also used in industrial manufacturing processes. The demand rose exponentially. As the population grew, the supposedly unlimited water resources had to be used more economically or water had to be treated for re-use.
Water: Clear does not always mean healthy
Since Louis Pasteur discovered microorganisms around 1865, we know that clear water does not necessarily mean clean and healthy water.
Most microorganisms, such as bacteria, viruses, fungi, protozoa, are useful and essential for the survival of humans.
However, some of them are harmful, even life threatening, and have to be reliably eliminated.
For a long time, microorganisms could only be eliminated by using environmentally harmful chemicals or high amounts of energy. That is, clean water was obtained at the expense of the environment.
This has changed: In recent years, filtration has become such an essential part of environmental engineering that water treatment is unimaginable without it. There are two main reasons for this: The first is that today it is possible to reliably remove microorganisms, turbidities and almost all pollutants through the use of filtration. The second is that filtration is a purely physical technique, which is applicable anywhere without using chemicals and requires relatively little energy, that is, it is environmentally friendly.
Cross-flow filtration: Rotating discs filter liquids
Comparable to a roundabout at a fun fair, filter discs rotate around their axis through the polluted water.
The centrifugal and shear forces occurring in this process can fling pollutants away from the surface of the filter. Therefore filters will only get clogged very slowly and the flow of the purified liquid will not be obstructed. In German too, this technique is sometimes referred to as “Cross-Flow-Filtration”.
There is an immense variety of possible applications. The method is used for water treatment in the production of fruit juice, in the pharmaceutical and semiconductor industries as well as in the vibratory finishing industry (in the final treatment of fittings), but also in the production of natural medicines or in biotechnology.
High-tech filters of tomorrow
In 1995, a tiny sieve was developed which had a large number of very fine pores. This sieve was made from a very thin, smooth and extremely hard material. That was the birth of what is known as wafer membrane. By today, these membranes can be manufactured with diameters of up to eight inches.
The filtration performance of wafer membranes is between ten and 100 times higher than before because the water that is to be purified only needs to pass through one single layer. With currently used filters, the liquid permeates slowly through several layers and through narrow, twisted channels.
Due to the very high performance, the separated material accumulates on the surface in a short time and blocks the pores of the membrane.
With the technology patented by Novoflow GmbH, wafer membranes were used to build filter discs, which were integrated into rotating cross-flow systems in such a way as to prevent separated material from accumulating on the membrane surface and blocking the pores. The combined technology was awarded the Bavarian State Prize in 2008.
This new technology enables the construction of significantly smaller plants operating at pressures that are only a fraction of those used so far, which saves both resources and energy – a real contribution to protecting the environment.
The author has been a partner in Novoflow GmbH since 2005. Prior to that, he worked in the hygiene and disinfection industry for more than 15 years, ten of which as managing director of medium-sized enterprises such as IGEFA-Südwestdeutschland, Henkel Hygiene GmbH and Steinfels AG in Switzerland. He studied economics at the University of St. Gallen (CH) and then spent three years in the financial industry in the USA.