Cleaning water with sunshine
It's raining in Beirut. Despite the miserable weather, the old man keeps his appointment on Museum Street. For the fist time in years, he is paying a visit to East Beirut, even though he lives only a few metres away, on the other side of the Green Line, the imaginary border that has divided the city since the beginning of the war. It is dangerous to cross over to the east, but he insists on meeting with us to report on the results of his research, partly funded by IDRC.
The man is Aftim Acra, a researcher and professor in the department of environmental sciences at the American University in Beirut. His work could have a significant impact on the health of more than a billion inhabitants of this planet, people affected by waterborne diseases such as cholera, typhoid, viral hepatitis, salmonellosis, and dysentery. Together with his assistant, Yester Ramhagopian, and a team of Lebanese university researchers, Dr Acra has developed a simple and inexpensive system for disinfecting water. It uses the most abundant natural resource in developing countries: sunshine.
His research, which began in June 1979, demonstrated that solar radiation, especially ultraviolet rays, can destroy microorganisms in water very efficiently. When exposed to the sun, water in small plastic or glass receptacles becomes free of pathogenic bacteria in a few hours, and is then safe for human consumption. "It's so simple and obvious that many people refuse to believe us, until they do the experiment themselves!" says Dr Acra.
Tests to date indicate that the effectiveness of the technique depends on several factors. The water must be irradiated in transparent containers of small volume, one to three litres. These must be exposed directly to the sun, when it is at its brightest, for periods varying from 95 to 300 minutes. The best results are obtained using clear water with few suspended particles and low bacterial density.
Dr Acra admits that his solar disinfection procedure has certain limitations. First, it isn't an efficient way to treat waste water. Secondly, the rainy season presents a major obstacle to its use in tropical countries. And thirdly, some bacteria can develop a resistance to the destructive effects of the ultraviolet rays.
However, Dr Acra believes the method has enormous advantages over current techniques. Chlorine and iodine, for example, are expensive and difficult to handle, must be imported, and give water a disagreeable taste. Boiling water is often an almost impossible task in regions where wood is scarce, and where much time and labour are needed to gather it. Compared with these methods, solar energy is free, plentiful, renewable, and can do the job without human intervention.
Treatment plants bombed
It is not surprising that research in this area has been carried out in Lebanon. Since the beginning of the war, many people have been regularly admitted to hospitals with illnesses stemming from contaminated water. The country's 120 water treatment plants have been seriously damaged or de stroyed by bombs. The employees have abandoned them, and the equipment has been stolen or destroyed by rust. In Beirut, where water is rationed, a single treatment plant serves over one million inhabitants. It is not maintained, the measuring equipment is out of order, and the water which comes from it smells strongly of chlorine. Last August, at the invitation of IDRC and McGill University's Brace Institute, a dozen researchers from Algeria, Colombia, Egypt, India, Peru, and Thailand met at Ste-Anne-de-Bellevue in Quebec to compare the results of their research, inspired to a large extent by the work of Dr Acra. His water purification technique has already been tested successfully in Poona, India, to prevent the transmission of cholera in particular. The International Red Cross has obtained the same positive results in tests carried out in the Arab Republic of Yemen.
Dr Salah Arafa, principal researcher in charge of a solar disinfection project in Egypt, has worked in close cooperation with Aftim Acra. Water drawn straight from the wells (most of which are contaminated) of a small village in northeast Cairo was tested in a lab. A period of three hours was sufficient to eliminate most of the bacteria that it contained.
Like Dr Acra, Dr Arafa is working to develop a permanent system for continuous water treatment. Such a system must be easy to install and must use simple and affordable materials. Some 75 percent of rural people in developing countries have no access to sources of clean drinking water. In these countries, 80 percent of all illnesses are waterborne, according to the World Health Organization. It is easy to see the enormous impact that the tests in Lebanon might have on the struggle to eliminate major diseases. Revolutionary or not, the prospect of using solar energy to purify water is of fundamental importance in developing countries.
|Accueil | Presse écrite | Radio | Photo | Formations | Perso | Liens | Email | English | Deutsch | Español | © 2003|