"Café des Sciences" on March 4th 2010 - Franck Roy

"Café des Sciences" March 4th 2010
Speaker : Franck Roy
Title : "Treating water with ultraviolets (UVs)
Subject : non chemical water disinfection / drinking water

The second edition of the "Café des Sciences" took place on Thursday March 4th at the Consulate General of France in Los Angeles. The speaker was Franck Roy, Chief Operating Officer of the Los Angeles-based Delta-UV firm. Delta-UV devises and commercializes solutions for water treatment based on UV rays. Delta-UV is part of the French group Bio-UV, #1 in France for UV lamps for water treatment and European leader in the field of private and collective swimming pools and spas.

During this conference, Franck Roy introduced the major issues for water treatment in private and collective swimming pools and pools. These are caracterised by large volumes in which water remains for long lenghts of time. This volume of water interacts with a complex environment : airborne particles, leaves falling from nearby trees, swimming humans and animals. Water is an excellent growing medium for many microorganisms, some of which can be pathogens such as bacterias, protozoans or algae, hence the necessity of a disinfectant treatment. Other physico-chemical parameters such as water turbidity (clearness) or pH (acidity) must also be taken into account. Altogether, these parameters make water treatment in a pool a complex problem.

Franck Roy presented the different regulations and solutions concerning water treatment, which divide in two broad categories : chemical treatments and physical treatments. The use of active compounds such as hydrogen peroxyde, chlorine, bromine or salt fall into the former category while UV treatment falls into the latter. Chlorine-based water treatment is used most often but has some drawbacks, in particular the fact that chlorinated organic compounds are formed when it is used - such as trichloramines or chloroalcanes - which are responsible for the chlorine "taste" and smell in many swimming pools. These molecules are noxious for eyes, skin and the respiratory system. In addition, some pathogens have developed a resistance to chlorine and are therefore not eliminated by this treatment.

Franck Roy then described the use of special lamps (containing mercury in gas form) to generate UV light in order to treat water. It was shown, more than a century ago, that UV rays emitted with a wavelenght of 253.7 nanometers can break the DNA of living organisms, thus provoking their destruction. This is the theoretical basis of the technology that Delta UV uses to inactivate microorganisms in water. By varying the wavelenght of the emitted radiation, it is also possible to break down molecules such as trichloroamines and chloroalcanes. It is therefore possible to couple a UV treatment to a chemical treatment and reduce the noxious secondary effects of the latter.

This presentation was followed by discussions on the scientific, regulatory and economic aspects of this sector such as the tremendous importance of the US market -60% of all swimming pools are located in the USA- the regulatory differences between countries and the environmental impacts of the different types of treatment. UV lamps are already broadly used to disinfect biological sciences laboratories and are more and more used to produce drinking water.

Last modified on 28/05/2010

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