Ultraviolet (UV) irradiation has been around for more than a century, but only began to gain popularity in the water treatment sector during the past 20 years.

Today, UV is a growth area, with global estimates at £250M across all water sectors: municipal wastewater (£60M), municipal drinking water (£60M), industrial (£50M), commercial (£40M) and consumer/residential (£40M).

The market is forecast to grow to more than £440M by 2010, with a combined predicted growth rate of 10% for the industrial, commercial and consumer/residential markets, and 15% to 20% for the municipal water and wastewater markets.

In the past five years, the UV industry has undergone significant consolidation, with ITT acquiring Wedeco; Danaher, Trojan Technologies and Aquafine; Siemens Water Technologies, Sunlight Systems; and Severn Trent Services, Quay Technologies. This trend is expected to continue in the coming years, as small niche players represent excellent growth opportunities for large corporations wishing to get a piece of the UV pie.

In Europe and the US, regulatory drivers are already effecting UV market growth. The European Bathing Water Directive, the Water Framework Directive, and Integrated Pollution Prevention Control are just some of the many statutes driving the market in Europe.

While chemical disinfectants can treat bacteria and viruses, they are not very effective against such protozoa as giardia, and are almost useless against cryptosporidium.

The late-1990s discovery that UV inactivates cryptosporidium created a huge opportunity in the drinking water market. Compared with ozonation and membrane separation, also effective at removing cryptosporidium, UV is significantly less capital- and operations-intensive.

In most installations, UV will be one of many combined technologies that complement each other and add a degree of safety to water treatment.

The concern over cryptosporidium is not limited to the drinking-water market, however. Outbreaks have also been documented in swimming pools, creating yet another opportunity for UV.

Adenovirus, the most UV-resistant waterborne pathogen, has hindered use of UV for disinfecting groundwater supplies. While 40mJ/cm2 is considered sufficient for 4-log inactivation of most waterborne pathogens, 100mJ/cm2 is required for adenovirus. But this data came from experiments with low-pressure UV lamps. Recent research shows a dose less than 60mJ/cm2 is required with medium-pressure lamps.

UV also reduces chloramine levels in swimming pools, which create the chlorine smell, and contribute to dry skin, eye burn and potential respiratory ailments.

Demand for residential UV products is also expected to increase due to to public concern about tap water quality and the environmental impact of bottled water. UV is also expected to become more prevalent in industries such as food, beverages and biopharmaceuticals.

Recent technological developments have increased the mercury-based lamps’ power and lifetime, and decreased the impact of water temperature. Today, commercially available UV systems use either low-pressure (low-output, high-output or amalgam) or medium-pressure lamps.

Future developments, including microwave UV, broadband xenon-pulsed lamps, narrow-band dielectric barrier discharge excimer lamps, and LEDs will need to overcome hurdles such as high cost and poor UV conversion efficiency.

The cost-effectiveness of UV systems will also improve through continuous hydr-

aulics enhancements that will lead to better dose distribution within both closed-vessel and open-channel UV systems. The latter are used primarily for wastewater applications.

Bertrand W Dussert PhD is global product manager for UV technologies at Siemens Water Technologies in Vineland, US.

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