Chlorine's importance in water treatment set to grow

Author: Charles Shaw


With global demand for clean water set to grow enormously, chlorine and other types of water treatment will become even more important

AS THE world becomes more populous, water is becoming more scarce. There is strong growth potential for all types of water treatment technologies, but some could do better as countries bid to quench their thirst in a cheap and environmentally friendly way.


 Rex Features

The UN's estimates (see map below, which shows projected global water withdrawal as a percentage of total water available) are based on its medium-population projections made in 1998. According to these, more than 2.8bn people in 48 countries will face water stress, or scarce conditions, by 2025. Of these, 40 are in West Asia (also known as the Middle East), North Africa or sub-Saharan Africa.

Over the next two decades, population increases and growing demands are projected to push all the West Asian countries into water scarcity conditions.

By 2050, the number of countries facing water stress or scarcity could rise to 54, with a combined population of 4bn - about 40% of the projected global population of 9.4bn. It is striking to note that even some developed nations, such as the US and many European countries will see more serious water scarcity by 2025. This could be one reason that some are already calling water the "new oil."

In order to arrive at the different qualities of water required for its various applications, and for the world to meet its goals, it must be treated. There are several different ways to do this, which are either combined or taken in isolation, according to each instance. Essentially, the aim is to remove, or in some cases reduce, the contaminants present in the water to bring it to an acceptable level for its required end use.

Chlorine is the first step that springs to mind for water treatment, as it is a well-established, cheap and effective method. As the World Chlorine Council, a global network representing the chlorine and chlorinated products industries says:

"Chlorine is used to destroy disease-causing organisms in water, an essential step in delivering safe drinking water and protecting public health. Chlorine is by far the most commonly used disinfectant in all regions of the world."

Chlorine's use has seen it help to virtually eliminate waterborne diseases, such as cholera, typhoid and dysentery in developed countries. It also eliminates slime bacteria, molds and algae that commonly grow in water supply areas, on the walls of water mains and in storage tanks. Chlorine is a versatile and low-cost disinfectant appropriate for any size of water system.

Specially packaged chlorine bleach can disinfect household water for less than $4/year (€3.20/year) per family. In addition, chlorine is critically needed for emergency relief efforts. In responding to the 2004 tsunami disaster in South Asia, the World Health Organisation reported:

"Chlorine quantities used for drinking water treatment have been decreasing"
Veronique Garny, regulatory affairs director, Euro Chlor 

"Chlorine is most widely and easily used, and the most affordable of the drinking water disinfectants. It is also highly effective against nearly all waterborne pathogens."

However, water treatment represents only a tiny proportion of global chlorine demand.

"Our data indicate that a maximum 5% of chlorine is used for water treatment, including drinking water," says Veronique Garny, regulatory affairs director at European trade group Euro Chlor.

Bob Beaumont, managing director of Biachem, a distributor of specialty chemicals based in London, gives a similar figure.

"As far as chlorine is concerned, I have seen a figure of 6% of chlorine production used in water treatment, which could include adding it directly to drinking water or for sanitation uses as sodium hypochlorite or addition to swimming pools," he says.

Garny also clarifies that, despite growing demand for clean water, it is unlikely that much more than this percentage of chlorine will be used to treat water. This is because growth projections for other applications of chlorine are also strong.

"Growing needs were never analyzed [in our data]. I suspect this would, anyway, still represent a small fraction of the total used. Other needs are growing as well and so we don't expect a very different figure in the coming years," she says.

While chlorine growth projections are strong, Euro Chlor notes that there is less demand for it in drinking water.

"Chlorine treatment is more and more used as a final treatment after filtration, ozonation and flocculation. In other words, the chlorine quantities used for drinking water treatment have been decreasing [at least in Europe] for the same treated water volumes."

One company that is investing a lot in non-chlorine water treatment technologies is German specialty chemicals group LANXESS. At its Bitterfeld site, the company has so far put €30m ($37m) into a project that aims to develop and produce a technology known as membrane filtration. In this ­process, a membrane is used as a specialized filter that allows water to pass through, but catches dissolved and suspended solids.

One of the advantages of this method is that it avoids the need for chemicals. It is also effective for the desalination of water.

Another process adopted by LANXESS and others in its field is a method known as ion exchange. In this case, ion exchange resins are used to remove unwanted ions from water, such as copper or lead, replacing them with innocuous ions like sodium. Its applications are many, as the process can be used to purify water, to obtain very high-quality water - such as is required in the electronics industry or for use in laboratories - or to soften water, an application that many households make use of.

A champion of these two methods, LANXESS' head of ion exchange resins ­business unit, Michael Zobel, stresses their environmental advantage: "Increasingly, we need a solution that doesn't involve too [many] chemicals," says Zobel. "We are strongly committed to this as we consider this as a strong growth business."

 "Chlorine is good for swimming pools…, though not so good for taste"
Michael Zobel, head of ion exchange resins, LANXESS

With ion exchange, in particular, Zobel says its advantage is that it is a selective approach, meaning one can target the harmful elements of the water without filtering everything. "You can take out selectively to decontaminate," he says.

Ion exchange resins are not new; the process has been around for a while. Membrane filtration, on the other hand, is a relatively emergent field. But people like Zobel see its growth potential, particularly when it comes to water treatment in drier regions. The Middle East is a region where they use the evaporation technique fairly widely, but it is costly to operate. Enthusiasm for this method is likely to wane in a more energy-conscious world. This is where membrane technology could step in.

He adds: "In other regions, the salt ­content of the available water sources becomes higher and higher, so that membrane technology is the most favorable ­solution to this issue."

This fast-growing segment of the global water treatment industry will not require the services of chlorine in the first place.

He concludes: "Chlorine is good for swimming pools [and] drinking water, though not so good for taste. It is not the technology [we need] to make additional water sources available to mankind."

If water is set to become an even more precious commodity, it is clear that all types of treatment will be in stronger demand, chlorine included. In a world increasingly framed by less energy-intensive, greener concerns, investments in chemical-free, cheaper alternatives could prove savvy.

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  • Total global chlorine production = 55,551,000 tonnes
  • Total US chlorine production = 11,956,000 tonnes
  • Total US consumption for water treatment = 615,000 tonnes
  • Total European Community chlorine production = 10,870 tonnes
  • Total European Community consumption for water treatment = 270,000 tonnes



Most fresh water is used for irrigation. In the developed world, agriculture accounts for around 30% of fresh water consumption, although this figure is higher in many first world countries. In poorer or warmer parts of the world, this figure can be more like 90%. This need not be water that is of a high enough quality to drink, but it is still a vast quantity that needs to be drawn and usually processed in some way before use.

Another major segment is industrial water treatment. Huge amounts of water are used in industry. When it comes to drinking water, the nearly 7bn of us on this planet need to pass at least 2 liters of it through our bodies each day. This should obviously be clean, although people in some areas do not necessarily have access to water that is of an acceptable drinking standard. The World Health Organisation says that 1.8m people die every year from diarrheal diseases (including cholera), of which 90% are children under five, mostly in developing countries. It adds that 88% of diarrheal disease is attributed to unsafe water supply, inadequate sanitation and hygiene.

"By 2025, the world's population will have moved from 6bn to 8bn, but with the same amount of drinking water available," the WHO says.

One of the UN's Millennium Development Goals is to reduce by half the proportion of people without sustainable access to safe drinking water by 2015. 1bn people lack access to safe drinking water, 2.4bn to adequate sanitation. To achieve this target, an additional 1.5bn people will require access to some form of improved water supply by 2015. That is an additional 100m people each year (or 274,000 a day) until 2015.