Practically all (85 %) of industrially produced drinking water is prepared today by multistage distillation. This technology requires big investment into industrial plants able of supplying large amounts of water of satisfactory quality. The major water supply is sea water and also brackish water. The majority of such installations is placed close to sea shore. Some plants use also dirty water from rivers, lakes and other sources.
The remaining amount of drinking water in dry regions is prepared by membrane processes such as reverse osmosis, electrodialysis and recently by nanofiltration.
All these technologies require large investments and use huge amounts of energy.
After production of industrial amounts of clean water, the later must be distributed into the place of final use. It is known that about ninety percent of expenses are invested not into purification but into the water distributing system. Such an expense can be tolerated when clean water is provided into large agglomerations. However, it is too expensive to transport water to small cities, villages and individual homes. The water distribution nets suffer from considerable losses of water when pipes are not tight or are even ruptured. The water in the distribution system can be also easily contaminated before it is delivered to end user.
Some good thinking people or organizations in developed countries propose “clever ideas and simple solutions” for getting clean water to small communities or individuals living in isolated places. Decontamination of dirty water by exposing water in PET bottles to the heat of solar radiation is such an example. Construction of simple devices for purification of small volumes of drinking water by so called “water cones” is another one. The heated bottles can be mixed up with not heated ones by mistake and the issue may be fatal for the user and his children. Brackish water under the water cone is kept the whole day at temperature optimal for multiplication of pathogenic bacteria. Bacteria are well protected by the cone against the sterilizing UV radiation of sun and oxidizing effect of ozone, oxygen super oxide and other active forms of oxygen. These naturally decrease the population of bacteria if water is on free air and sun. When the supposedly drinking water is contaminated by such a bacterial broth, which must once happen, the issue may be dangerous when not fatal to the person whom we originally wanted to help.
2011-02-18 P. L.