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Public water supply

A major need in water treatment, especially in public supplies of drinking water, is the elimination of bacteria and viruses. This is becoming a vital component of the water treatment business with cases of microbial contamination still regrettably frequent. Methods of disinfection are changing away from direct chlorination (because of the problems of residual chlorine taste), partly towards UV-irradiation, but the removal of pathogens by micro- and ultrafiltration is going to provide a great deal of business for the filter industry.

The equipment needs for public service water treatment depend to a large extent on the source of the water to be processed - whether it be ground water or surface water. Ground water comes, by means of a well, from reservoirs in porous rock strata deep underground. These aquifers are stocked by rain water that permeates slowly through the higher strata. Surface water is that derived from rain that has run off the surface on to which it has fallen, into a lake or river system, from which it can easily be abstracted.

By virtue of its passage through many layers of rock above the aquifer, and through the aquifer itself, ground water is largely free of suspended solids material. However, it is loaded with dissolved material, some of which may be organic, but most will be inorganic, especially the salts that make the water hard. On the other hand, surface water will be quite heavily laden with suspended solids, and will have relatively little dissolved inorganic salts (and so will be soft), but a considerable amount of dissolved organic matter, as well as the colloidal solids.

Ground water has to be treated to reduce its hardness, adjust pH and remove pathogens, while surface water needs its suspended solid content to be reduced (after coagulation or flocculation, usually by deep bed filters, but also by sedimentation), and its bacteria and virus content lowered together with that of dissolved organics, which is increasingly becoming a task for ultrafiltration.

Treated water increasingly has to undergo a polishing stage for the removal of nitrates, pesticides, hormones and other contaminants. Water companies in England and Wales spend about 10% of the total cost of water treatment on this polishing process alone. A final stage will usually be disinfection, if only to protect the water in its sometimes long journey from treatment works to end-user.

Industrial end-users will still need to improve the quality of public supplies (although many will have their own bore-hole abstractions). Typical examples are boiler feed water in almost any industry (which must be free of dissolved material, including gases), semi-conductor fabricators (who need a lot of water for washing silicon and other components), the food processing sector and especially beverage production (where water is a major ingredient in their products), and pharmaceutical and medicinal chemical production (especially for injectable materials).

These special needs will normally involve a microfiltration stage, followed by ultrafiltration to remove ultrafine solids and large dissolved material - with reverse osmosis for the most critical needs of solute free water. "Ultrapure" is a term much in use nowadays to describe industrial needs.

The provision of fresh water for public consumption, and the supplementary quality improvement demands by industrial users, will continue to provide good business for the international filtration and sedimentation industry, at growth rates well above national economic averages, and for the foreseeable future. The key areas for development are finer filtration for fresh water provision, involving microfiltration and ultrafiltration, and their use in pathogen removal. The key membrane processes must become cheaper to enable their use at the capacity that the processes demand.

The sales of filtration and sedimentation equipment for the public service supply of fresh water in 2007 are expected to be in the region of $1770 million, and will grow over the next five years at an annual rate of about 7%. Sales to industrial end-users of public water supplies wishing to reduce the contamination level of that water are expected to be about $850 million, also growing at about 7% per annum.

Domestic uses

The clean water needs of humans at home or at work have created a huge demand for relatively simple filters. The applications covered here are the domestic dwelling (house or apartment), and the working office. Water supply companies, of course, claim that public water is perfectly satisfactory for domestic purposes - but for many customers the colour or taste or turbidity level may not be good enough.

Whilst the individual filter installation in any home or office may be a tiny part of the cost of the whole, the huge numerical volumes of their application creates a very large market, with a great degree of conformity across it. There are approximately 150 million households in Western Europe, over 100 million in the USA , and similar numbers in East Asia . The number of offices around the world is at least another 100 million. It takes very little by way of drinking water filters in each of these to create a large market from this number of end users - and that still leaves swimming pool filters to add to its size.

By contrast with the public water supply applications, the unit sizes in domestic, commercial and institutional filtration are much smaller, although some large hospitals or residential complexes will have filters of industrial scale. The smallest and simplest filter is the counter-top jug filter, intended to remove colour and taste from the as-received public service water. These units have become a regular feature of kitchen equipment, a segment growing almost as fast as the parallel market in bottled waters. The treatment is provided by a replaceable cassette in the jug, which is discarded when used (and at the user's discretion). The other point-of-use unit is the filter that is piped into the domestic water system just before the kitchen tap. This uses a replaceable cartridge.

The domestic, commercial and institutional market is a steadily growing one, as personal needs for high quality drinking water outstrip the ability of the water services to provide such quality, and as swimming pool usage increases. Sales into this sector for water quality improvement could reach $760 million in 2007. As with the other components of the whole fresh water sector, this one grow at about 7% per annum.

Contact:

ken.suth@ntlworld.com.

Ken Sutherland has managed his process engineering and market research consultancy, Northdoe Limited, for nearly 30 years, a business largely concerned with filtration and other such separation technologies. He was a co-author of Elsevier's Decanter Centrifuge Handbook, and has also written the second edition of Elsevier's Handbook of Filter Media. More recently he has written Elsevier's A to Z of Filtration.

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