Ways Out of Water Stress; Responsibility, Expertise and Contributions of a Global Corporation

The current coronavirus pandemic is highlighting the importance of hygiene. However, hygiene without water is almost inconceivable. Clean drinking water is vital, but is not available in adequate quantities everywhere. Agriculture and industry also depend on water to produce their products. Even today, water shortages are by no means restricted to developing countries or desert regions. Increasing competition for this scarce resource means that new and better solutions are constantly required to ensure that water is and remains available in adequate quantities and that it is of sufficient quality.

. Closely intertwined with the challenges of population growth and climate change, the battle against water shortages calls for responsible commitment and the willingness to change. Approaches to solving the problem need to be as varied as regional or local conditions. This must start with valuing water as a resource, in line with the central theme of this year’s World Water Day: “Valuing Water”.

Qualitative requirements for clean drinking water are so high that to this day, many people around the world have no access to it. Some production processes, such as for pharmaceuticals or electronic semiconductor components, require water that is even more pure. Such ultra-pure water can be obtained in particular from ion exchange with specialized resin systems and membrane techniques. These thus help to ensure a reliable supply of medicines in addition to playing a significant role in our information and communication technology, which is based on microelectronics.

. Measures to Combat Water Stress

There are different approaches to overcoming “water stress”, i.e. a local imbalance between availability and demand. These include:

Opening up additional water sources that were not previously usable or whose use was limited

Treatment of water containing anthropogenic contaminants before it is returned to ecosystems

Implementation of closed water circuits in production processes

A careful analysis of the status quo is a prerequisite for efficient water management and allows priority recommendations and measures to be determined. That applies to local authorities, regions and countries but also to companies with all their sites, production facilities and products. LANXESS is doing this as part of a water program which was launched in late 2020. The initiative encompasses Group-wide targets and voluntary commitments as well as local water stewardship measures and will initially focus on four sites where there is a particularly high risk to a stable water supply.

. A few examples relating to the Liquid Purification Technologies (LPT) business unit illustrate efficient water management by LANXESS and the underlying premises in practice.

. Removal of Natural Impurities

Opening up additional water sources means overcoming obstacles that until now have prevented their use. One such obstacle is dissolved pollutants. Natural contamination of drinking water with arsenic is the most significant natural cause of poisoning worldwide, particularly in India and Bangladesh. Water is also polluted with arsenic in parts of Argentina and Chile and in the west of the USA. As well as acute and chronic illnesses, this can result in an increase in tumors. To be able to adhere to the limit of 10 mg/l set by the World Health Organization (WHO), millions of people are dependent on their drinking water being treated. Special iron oxide adsorbers from our plant in Krefeld have proven very efficient at this and are used in filter systems around the world.

Impurities from surface water due to natural organic matter (NOM), such as humic and fulvic acids or polyphenols, which arise during the decomposition of plant matter and give water a brownish-yellow color, can be removed with strongly basic ion exchange resins with specially adjusted porosity. These ionically bind the impurities or adsorb them. This is how drinking water is treated in the Netherlands and the UK, for example. Regeneration of the resins requires only around one tenth of a percent of the volume of drinking water obtained, Moreover, the spent regenerant can be reused multiple times after the organic matter is removed by precipitation.

Heavy metals such as nickel, cadmium and lead can be leached out of minerals by acid rain or sulphuric acid generated by the oxidation of sulphide ores. Nitrate from natural or synthetic fertilizers can also release metals from sulfidic minerals through oxidation. Selective ion exchangers with chelating groups even bind traces of such impurities reliably. If metal ions are present in higher concentrations, for example in industrial wastewater, it may be worth recovering them. This technology has long been established for precious and platinum group metals.

. Treatment of Various Types of Wastewater

Anthropogenic pollutants in groundwater and surface water present major challenges for the production of drinking water and also for the treatment of wastewater. This applies to the discharge of heavy metals from mining and industry, for example, as well as for organic impurities. Zero liquid discharge, i.e. the complete avoidance of liquid waste and wastewater, is not always possible. Specific ion exchangers, as described above using the example of nickel, allow the wastewater to be cleaned in these cases. Even traces of chromate(VI), which is very toxic and carcinogenic, can be removed highly selectively from groundwater with a regenerable, strongly basic anion exchanger, for example. This technology can also be applied for other oxoanions such as chlorate or perchlorate, which are often detected in aquifiers of areas in which rocket fuels and explosives are or have been produced, tested or used.

Pollutants can also be introduced into groundwater in regions that are used for agricultural purposes. In Germany in particular, nitrate from fields that have been overfertilized is currently a problem. One solution may be to find an alternative use for the applied manure. But even if it is thickened and processed to form solid fertilizer, the liquid residual phase containing ammonia must not be discharged untreated as Ion exchange resins facilitate the efficient separation of nitrate and ammonium ions and ultimately enable them to be converted into solids that can either be disposed of or used as fertilizers.

There is also currently a focus on the widespread contamination of water around the world with per- and polyfluoroalkyl substances (PFAS), which are found in products such as fire-extinguishing foams, impregnation agents for textiles and paper and lubricants. Compounds of this class, which are almost completely non-biodegradable, accumulate in the body tissue of men and animals after ingestion. Their durability means that even traces must be removed from wastewater and that contaminated groundwater must be cleaned up. This can be achieved by a heterodisperse, gel-type, strongly basic anion exchange resin from the Lewatit ® product family, which will deplete even traces of PFAS right down to the ppt range. Because of this and its greater absorption capacity, this process is far superior over conventional filtration employing activated carbon. A mobile system that was in operation for several years at Australian airports led to a cost advantage of almost 60% compared with activated carbon filtration, even when the resin was used only once without regeneration. At higher PFAS concentrations, regeneration can enhance the viability of this technology further.

. Industrial Water Circuits

If water is circulated in industrial processes, the amount of feed water required is significantly reduced – in extreme cases to as low as zero. A classic example for these is water–steam circuits, in power plants or in the industrial use of steam. The use of cooling towers can prevent cooling water from heating the surface waters if the residual heat is also used in the process, this will open up additional potential for energy savings.

Improvements in the efficiency of ion exchange resins also pave the way for lower water consumption when they are used. Specialized, strongly basic anion exchangers like those mentioned above have about five times the higher capacity for complex oxoanions such as chromate than standard resins. That means they need to be regenerated less often, which reduces the overall volumes of chemicals and water required. At the same time, these resins exhibit a longer lifetime, which further reduces their water footprint.

Even the manufacture of ion exchange resins at LANXESS benefits from water circuits. The newly produced resin beads are classified by fluidization in rinsing towers, i.e. they are separated into grades based on their size in an upflow of water. Depending on the separation requirements, the volume of water needed is several times that of resin. The water from the overflow is filtered, collected, supplemented with fresh water if necessary and then used again in the same classification process.

. An Ongoing Challenge

In view of the natural and anthropogenic pollutants in groundwater and surface water, the constantly rising demand for drinking water for a growing global population as well as the equally fast-growing demand for agricultural produce and industrial goods are placing increasingly complex demands on water treatment technologies and products.

Economical use of water and minimization of anthropogenic contamination are essential for sustainable water management. Innovative water treatment and intelligent water circuits can play an important part in this.

Ways Out of Water Stress; Responsibility, Expertise and Contributions of a Global Corporation

Dr. Stefan Neufeind

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