Researchers help bring clean water to households in developing nations
Selon une étude menée dans l'Etat mexicain de Guerrero, l'utilisation d'un purificateur d'eau aux rayons ultra-violets permet de fournir dix litres d'eau potable par jour et par habitant pour moins de 2 dollars par an.



By Sarah Yang, Media Relations

Go to Berkeley - University of Califormia

Researchers help bring clean water to households in developing nations

BERKELEY – 02 June 2003 -
Throughout some regions of Mexico, the distribution of clean water is so variable that highly chlorinated water may reach some homes while others receive water contaminated with disease-causing pathogens.

Florentino Mota, a community outreach worker in Mexico, installs a UV Tube developed by UC Berkeley researchers... (Laura McLaughlin photo) L'eau à décontaminer est pompée et passe sous une lampe dont les rayons dénaturent l'ADN des pathogènes nocifs pour la santé. "La lampe est la pièce avec la plus courte durée de vie, et elle peut fonctionner 10 000 heures d'affilée"... Les coûts de 1,50 dollars américains par an sont essentiellement liés à l'énergie nécessaire pour pomper l'eau. D'après une information du site canadien Cybersciences (18/02/2004)

Researchers at the University of California, Berkeley, are offering a solution with a water disinfection system affordable enough for an individual household in a developing nation. Starting in July, researchers from the Mexican Institute of Water Technology will start a six-month pilot project using the UC Berkeley-designed UV Tube, a treatment system that uses ultraviolet light to disinfect the water.

"One big issue for rural areas in Mexico has to do with a lack of a reliable infrastructure for delivering drinking water," said Arturo González Herrera, the project coordinator at the Mexican Institute of Water Technology. "We want to know if the people find the UV Tube easy to use and prefer it to buying bottled water. If so, the UV Tube could save them money."

According to the World Health Organization, as many as 5 million people die every year from ingesting water contaminated with bacterial and viral pathogens. Most of the victims come from developing countries, and a majority are young children.

The UV Tube will be tested in five to 10 households in Jiutepac, about 50 miles south of Mexico. The UC Berkeley researchers have refined the UV Tube based upon previous tests in homes in Mexico, where they compared the levels of bacteria before and after treatment. Laboratory tests have already confirmed that the design is effective in disinfecting water flowing at a rate of five liters per minute. This year's pilot project will focus on whether the UV Tube continues to operate effectively in real-use conditions and whether residents find the UV Tube easy to use.

"We use materials that are readily available in local hardware stores to keep the costs down," said Alicia Cohn, who recently received her master's degree from UC Berkeley in civil and environmental engineering and is one of the lead researchers on the project. "PVC (polyvinyl chloride) is carried by stores in even small cities, and UV bulbs and stainless steel liners are available in mid-sized cities."

Cohn, who also earned her master's degree in energy and resources at UC Berkeley, said that once the materials are assembled, it takes only a few hours to put the UV Tube together.

The low-cost, point-of-use device consists of a PVC tube lined with stainless steel. Water passes through a tube that is 65 centimeters long and four inches in diameter. Inside the tube, the wavelength emitted by the UV bulb damages the DNA of bacteria, viruses and protozoa, inactivating the pathogens by preventing them from replicating. The average dose of 956 joules per square meter is more than twice as strong as required by the U.S. National Sanitation Foundation for microbiological treatment systems, capable of inactivating the polio virus, hepatitis A virus and rotavirus, as well as disease-causing bacteria such as Vibrio cholera and Salmonella.

"The problem of intermittent contamination of drinking water is pervasive throughout Mexico and many developing countries, even in urban areas" said Kara Nelson, assistant professor of civil and environmental engineering at UC Berkeley and the main technical advisor for the project. "There is no single technology that will meet the needs of the more than one billion people without access to safe water. Rather, we need a wide range of technologies that are appropriate for each situation. We believe the UV Tube will make sense for many people. Our plan is to eventually make the design specifications available free for anyone who wants to build it."

The UV Tube design was developed at the Renewable and Appropriate Energy Laboratory run by Daniel Kammen, professor at UC Berkeley's Energy and Resources Group, Goldman School of Public Policy and Department of Nuclear Engineering.

Other tube designs, such as those built from pottery or concrete, are also being considered. However, more testing needs to be completed in the lab before the UC Berkeley researchers are ready to start field trials.

The UC Berkeley researchers were inspired by a similar water disinfection system designed by Ashok Gadgil, a senior scientist at the Lawrence Berkeley National Laboratory. Gadgil, an Indian-born scientist who was troubled by outbreaks of cholera in southeastern India, developed a system called UV Waterworks, now sold by Water Health International.

"The general idea of using UV light in a tube to kill pathogens has been around since the 1970s, but Ashok really pioneered the use of the technology for low-cost applications in developing countries," said Kammen.

Lloyd Connelly, a scientist who worked with Gadgil on the UV Waterworks project, saw the need for a cheaper alternative. Connelly, now a medical student at UC Davis, came up with the idea of developing the UV Tube while he was a post-doctoral researcher in Kammen's lab.

The researchers say the UV Waterworks and UV Tube systems meet different needs. UV Waterworks is a manufactured unit to be purchased, with a price tag ranging from $300 to $1,500. While the system is ideal for small communities or disaster-relief encampments, the cost puts the unit out of reach for individual families in developing nations, according to the UC Berkeley researchers.

The UV Tube, in contrast, is designed to be built by local people from local materials, the researchers say. "This is an example of how simpler technology can be more appropriate," said Kammen. "It involves electricity and a light bulb, but it's not a snazzy gizmo overall."

The UC Berkeley researchers estimate that the final cost of the unit will be between $30 to $50. In addition, the understanding of how the system works is local, making maintenance and repair of the UV Tube more practical.

"We're looking to provide a range of tubes that can be used depending upon what is more convenient and appropriate for the local community," said Kammen. "Although individual families could build their own, what will probably end up happening is a local entrepreneur will develop a small business by selling units to families in the area."

Other UC Berkeley researchers on this project include Sarah Brownell, a PhD student in civil and environmental engineering, and Rachel Peletz, an undergraduate in environmental engineering science.

The research is partly supported by grants from the World Bank, the National Collegiate Inventors and Innovators Alliance and the San Francisco-based Energy Foundation.

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