A Lesson in UV

Although many people think that treating water with ultraviolet light is a new idea, the ability of ultraviolet light to disinfect microbes was discovered at the turn of the 20^th century.

The first installation using ultraviolet (UV) light to disinfect public drinking water was in Marseille, France in 1910. While the science was right, the system was not robust, the technology was not quite advanced enough at the time, and it wasn’t until several decades later that other systems were installed.

Today the UV (UVC) light used is more energetic than sunlight and it destroys the ability of microbes in water to be pathogenic. All kinds of waters are treated with UV, from the nastiest of wastewaters, to cleaner waters used for irrigation, aquaculture, drinking water, and ultrapure waters used in the pharmaceutical, food and beverage, and microelectronics industries. UV disinfection can also be used as part of the treatment train allowing waste waters to be recycled to very high water standards for beneficial reuse in agriculture or for aquafer recharge. UV disinfection produces no identified byproducts. It can also be implemented at any scale—from the smallest faucet designed to fill one glass of water, to the full-scale treatment of the New York City water supply, currently under construction.

UV oxidation
When high doses of UV are applied to water with the addition of hydrogen peroxide, advanced oxidation occurs: the process is called UV oxidation. This combination allows for the destruction of micropollutants like pesticides and pharmaceuticals. UV oxidation is usually part of a complete treatment train which includes other technologies, and it has allowed contaminated well sites to be recovered, ground waters to be remediated and contaminated surface waters to be rendered safe for human consumption. UV oxidation is also used to treat algae in water—especially those like geosmin and MIB. These compounds are not toxic but are highly unpalatable as they cause waters to smell musty and unappealing.

To date, no pathogens have been identified that do not respond to UV light. There are chemicals that do not respond to direct UV destruction but together with hydrogen peroxide, the suite of compounds treated is vast.

Energy concerns
Because UV water treatment processes rely on electricity, electrical energy consumption for the technology is sometimes deemed to be a concern. However, studies of total life cycle energy consumption and carbon footprint show that UV is superior to chlorine and chlorinated compounds.

The UV industry continues to innovate on matters of efficiency, longevity of equipment, advanced oxidation, and the opening of new market sectors and new geographies. Those in the UV industry truly believe that this technology is exactly right for our time—a time of diminishing natural resources, increasing water stress, an increasing focus on environmental stewardship, and a social and economic need to bring clean water to all people.

IUVA
The International Ultraviolet Association (IUVA) is an organization that seeks to bring excellence and education to the robust use of UV in environmental and public health matters. IUVA is a collection of the leading academics, industrial scientists, consulting engineers, utility engineers, regulators, manufacturers and end users representing more than twenty countries.

The IUVA just celebrated its tenth anniversary at its International Congress in Amsterdam, September 21-24, 2009. More than two hundred participants, predominantly experts from more than twenty countries, participated in three days of scientific/engineering presentations and dialogue, tours of full-scale Dutch water treatment facilities in Rotterdam and Heemskerk, and a workshop on European regulatory standards for the use of UV in water treatment.

The association continues to promote the use of UV in treating air and water for the benefit of the environment and public health through education and dialogue, with the belief that the best outcome for all consumers will come with the best exchange of robust scientific information, leading to the best possible products and the best possible practical installations. Visit the organization’s website for more information.

Linda Gowman, Ph.D., P.Eng. is the past-president of the International UV Assocation (IUVA) and the chief technology officer for Trojan Technologies.