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“Clean water needs strong technologies”

Interview with Jean-Marc Vesselle

World Water Day has been celebrated annually on 22 March since 1993. It is a direct result of the UNConference on Environment and Development in Rio de Janeiro in 1992. The UNGeneral Assembly called for the establishment of World Water Day in a resolution on 22 December 1992. To mark World Water Day, LANXESS web magazine spoke with the Head of LANXESS Business Unit Liquid Purification Technologies, Jean-Marc Vesselle.

Jean-Marc Vesselle

Jean-Marc Vesselle

This year, World Water Day is being celebrated under the slogan Water and Sustainable Development. What contribution is LANXESS making to World Water Day?

Vesselle: Our products – ion exchange resins (IX) and reverse osmosis (RO) membrane elements – help desalinate water and other liquids and remove undesirable substances. They therefore play an essential role in conserving one of the most important prerequisites for life on our planet. Clean water needs strong technologies.

Water is in short supply in many parts of the world, although 72% of the earth’s surface is covered by it. 97% of this water, however, is seawater, 2.7% is fresh water and only 0.3% is drinking water. How do LANXESS products help solve the drinking water problem?

Vesselle: Let me give you an example: LANXESS supplies RO membrane elements specifically developed for seawater desalination. The new elements underwent thorough pre-marketing testing in desalination plants on the Red Sea in Egypt over a period of several months. They demonstrate high salt rejection, even under fluctuating temperatures, salt content and pH values, thereby ensuring that the purified water (permeate) is of a consistently high quality.

LANXESS produces ion exchange resins and RO membrane elements. Could you briefly explain what type of product they are and how they work?

Vesselle: Ions are minute electrically charged particles. Salts, acids and alkalis are made of ions and they more or less completely break down into ions when dissolved in water. Ion exchangers can unbind specific ions from solutions and replace them with others with the same charge sign. This is how water is softened, for example.
Membranes are used as barriers for suspended particles and even for dissolved substances. When a solution flows through a membrane under pressure, a distinction is drawn between micro-, ultra- and nano filtration and reverse osmosis in descending order of particle size. Reverse osmosis allows even individual molecules/ions to be removed from water. This is how the membranes achieve desalination in reverse osmosis. We have over 75 years of experience in this field with the brand Lewatit and can supply outstanding products with comprehensive technical expertise in their use and with global market access.

Lewatit__014Where are ion exchange resins used?

Vesselle: Possible applications include the softening of water in dishwashers or decarbonization in household water filters. In power plants, the tiny polymer beads are used to produce ultra pure water and steam. This prevents deposits and corrosion and increases efficiency, operational reliability and service life. In addition, ion exchange resins help to selectively remove heavy metals and organic pollutants from both groundwater and industrial waste water. Whereas ion exchangers tend to be used at low salt concentrations for fine cleaning down to trace levels, the membrane technology is applied in water with a high salt content.
Last year, we increased production capacity for weakly acidic cation exchange resins at our Leverkusen site by about a third. The demand for these products is growing year on year by three to five percent. Our investment in this area is a clear commitment to the responsible use of the precious resource of water.
Weakly acidic cation exchange resins are primarily used in household water filter cartridges and in an increasing number of domestic waterworks. They absorb water-hardening calcium and magnesium ions and, where applicable, also lead and copper ions from the mains water supply and replace them with harmless ions. This improves both the quality and taste of the water. More recently, drinking water has also been enriched with specific ions. In certain areas of Italy, for example, specific ion exchange resins charged with calcium or magnesium ions are used to treat water with a very low mineral content.

LXS_IAB_IonenaustauscherHow are membrane elements used in water treatment?

Vesselle: Globally, reverse osmosis is most widely used in the desalination of salt water to produce drinking water. In industry, reverse osmosis membrane elements are used, for example, in power plants to produce boiler feed water. They are also used in industry to produce the ultra-pure water needed for the manufacture of microchips. Reverse osmosis is often combined with an ion exchange process in these applications.
In co-generation plants such as in Chemnitz, for example, operated by the energy supplier eins energie in Sachsen GmbH & Co KG, LANXESS membrane filter elements significantly reduce fluctuations in water quality, filtering out organic substances in particular. The 60 Lewabrane filter elements treat 50 to 60 cubic meters of pretreated river water an hour for steam generation processes.
However, our reverse osmosis filter elements are also used to ensure clean drinking water – for example, in Ghana. The water treatment plant run by Mazareka Co. Ltd., Tamale/Kanshegu, and equipped with Lewabrane membrane elements has a capacity of 40 cubic meters an hour and supplies water for approximately 600,000 people. These comprise the 400,000 inhabitants of Tamale, the capital of the Northern Region, and of places within a 200- kilometer radius.
In general, in areas where water is in short supply or there is a population explosion, increasing use is being made of water recycling to produce drinking water – in cities such as Singapore. In Singapore, reverse osmosis is not used to desalinate all the water but the used water from the city is treated in water treatment plants or using other filtration technologies and only the water lost is replaced with desalinated seawater.

The chemical industry uses vast amounts of water. What solutions does it have to limit its use of water?

Vesselle: As a result of all the changes in industrial production processes and the continuing improvements in water treatment, water consumption has continued to fall over the years with the increased use of recycled water. Chemical industry products have played a crucial role in the recycling of water.
In the mid-1950s, for example, water was recycled 2.4 times in the manufacture of paper; it is now reused 12 times. In the chemical industry itself, water is recycled on average 28 times before it is fed into the downstream purification stage, cleaned and returned to the water circulation.
The overall trend is towards zero liquid discharge, i.e. that no waste water is generated in production. This is achieved by examining in each process what quality of water can be reused in a particular process stage and how heavily contaminated water can be treated and fed back into the process. We are ourselves working on just such a concept for our own production sites.