Water quality and human health have been closely linked throughout history. However, it was not until the last quarter of the 19th century that pioneering work by Robert Koch and Louis Pasteur established the germ theory of infectious disease. With the understanding that fecal-borne bacteria, viruses, and protozoans were responsible for most water-borne diseases, it was possible to develop sanitation and water treatment practices which provided people with a safe water supply. In industrial countries safe water is now taken for granted.
In developing countries however, the burden of disease caused by contaminated water and a lack of sanitation continues to be staggering, particularly among young children. UNICEF estimates that 60% of rural families and 23% of urban families in developing countries are without safe water. In some areas all water supplies may be contaminated. If a water source is suspected of being unsafe, the most common recommendation is to boil the water. This recommendation is seldom followed for several understandable reasons, the most important being the time and the amount of scarce fuel it would require.
Contrary to what many people believe, it is not necessary to boil water to make it safe to drink. Heating water to 65 C (149 F) for 6 minutes, or to a higher temperature for a shorter time, will kill all germs, viruses, and parasites. This process is called pasteurization and its use for milk is well known though milk requires slightly different time temperature combinations. One obvious problem that arises with pasteurization is the question of how to tell when and if the water has reached the right temperature
Chlorination, ultra-violet disinfection, and the use of a properly constructed, properly maintained well are other ways of providing clean water that may be more appropriate, particularly if a large amount of water is needed. Conversely, if a relatively small amount of water is needed, pasteurization systems have the advantage of being able to be scaled down with a corresponding decrease in cost. In other words, if you have only a little money, you can use pasteurization to get a little clean water, perhaps enough for a family but not a village. As always, the selection of the right system should be based on local conditions.
Source: RECENT ADVANCES IN DEVICES FOR THE HEAT PASTEURIZATION OF DRINKING WATER IN THE DEVELOPING WORLD by Dale Andreatta, Derek T. Yegian, Lloyd Connelly, and Robert H. Metcalf, from the proceedings of the 29th Intersociety Energy Conversion Engineering Conference, American Institute of Aeronautics and Astronautics, Inc., 1994.
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