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Water Treatment

Innovative Water Treatment with RO and IX Separation Technology

| Author / Editor: DR JENS LIPNIZKI, BERYN ADAMS; DR MOTOHIRO OKAZAKI; KEDAR OKE / Dominik Stephan

For quality assurance purposes each individual Lewabrane module is checked in an element tester at the Lanxess site in Bitterfeld Germany
For quality assurance purposes each individual Lewabrane module is checked in an element tester at the Lanxess site in Bitterfeld Germany (Picture: Lanxess)

Clean water is more than just nice to have - it's a necessity. Especially in developing countries, huge efforts are undertaken to supply water for population and industry alike.Lanxess has developed a new water treatment technology that involves the stateof-the-art plant as well as advanced software to complete the solution...

Water treatment in today’s modern world requires highly technical, high performance separation products to achieve increasingly stringent treated water qualities, or to provide the lowest cost of water production. To achieve the demanded quality, often, more than one separation technology is applied. This development was a main consideration for Lanxess to start production of Lewabrane reverse osmosis (RO) membrane and elements at a new production site in Bitterfeld, Germany.

Innovative Water Treatment with RO Technology

The dominant RO membrane structure is based on a thin film composite membrane. The barrier (or rejection) layer is a 0.1μm thick polyamide layer, which is supported by a polysulfone substructure. The polyamide layer is formed by a polymerization process. Although thin film composite membranes based on this process have been used for more than thirty years, the newest technology offers the possibility to control the polymerization process more precisely.

Accordingly, a strong focus of the company‘s membrane development was the enhanced polymerization degree of the polyamide layer. A higher polymerization degree improves the mechanical and chemical stability of the thin barrier layer offering greater durability. Additionally, the negative charge on the membrane surface is reduced, which leads to a lower cationic adsorption (fouling) on the membrane surface.

Cationic Fouling of Water Treatment Membranes

Due to its chemistry, the surface of a polyamide membrane is usually negatively charged, and often results in cationic fouling that is extremely difficult to remove. A typical example for cationic fouling is the fouling with iron. Iron chloride (FeCl3) is a very common flocculation chemical used in pretreatment systems. If the dosing is too high, even just for a short period, the cationic fouling can irreversibly foul the RO membrane surface. Apart from a well adjusted iron chloride dosing system, a lower negative surface charge is the best option to reduce the fouling potential of this event.

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