SOLAR WATER DISTILLATION
SOLAR WATER DISTILLATION
There is almost no water left on Earth that is safe to drink without purification.
This is a seemingly bold statement, but it is unfortunately true. Only 1% of Earth's water is in a fresh, liquid state, and nearly all of this is polluted by both diseases and toxic chemicals. For this reason, purification of water supplies is extremely important.
The statistics are quite shocking. According to the World Health Organization, 1.5 billion people lack access to adequately purified drinking water. About 10,000 children die from drinking contaminated water every day, and 80% of all illnesses in the developing world result from waterborne diseases.
In the developed world, we take for granted water treatment processes that keep us safe from most diseases. However, these processes are far from perfect and can cause their own problems. For instance, it is now known that the use of chlorine for purification - standard in most municipal water treatment plants - results in the contamination of drinking water with carcinogenic chemicals.
Because of the challenges of dealing with the vast number of pollutants now loose in the environment, most city water systems are not even designed to remove most of them. In low levels, these chemicals are not thought to pose a high risk on an individual basis. The traditional thinking is that the added cost of purifying water of all these pollutants is not worth the public health benefits, since virtually every contaminant targeted requires another step in the purification process. However, the long-term consequence of ingesting a cocktail of many known toxic and carcinogenic substances has not been adequately studied. No one really knows how making these compromises impacts our health, but only that these compromises are economically necessary with the types of purification in widespread use.
Moreover, typical purification systems are easily damaged or compromised by disasters, natural or otherwise. This results in a very challenging situation for individuals trying to prepare for such situations, and keep themselves and their families safe from the myriad diseases and toxic chemicals present in untreated water.
Fortunately there is a solution to these problems. It is a technology that is not only capable of removing a very wide variety of contaminants in just one step, but is simple, cost-effective, and environmentally friendly.
This solution is solar water distillation. It is not a new process, but it has not received the attention that it deserves. Perhaps this is because it is such a low-tech and flexible solution to water problems. Nearly anyone is capable of building a still and providing themselves with completely pure water from very questionable sources.
In fact, the concept is nearly as old as the Earth itself. Solar distillation is nature's way of recycling water through the ecosystem. Many know it as "nature's water cycle". The sun's energy evaporates water from the ocean, and it condenses as clouds of pure water vapor which eventually fall as fresh rain.
Solar stills use a similar process on a much smaller scale, capturing it in a closed system. A simple but typical configuration is a sealed box with an angled glass top. Sunlight shining into the box heats contaminated water, causing it to evaporate. The moisture condenses on the relatively cool glass cover and runs down the sloped surface for collection.
Because the water is purified by evaporation, the water is separated from contaminants one molecule at a time, and the purified water is then collected drop by drop. This simple one-step process actually extracts pure water from the contaminants. This method is the exact opposite of traditional, expensive approaches, which attempt remove each contaminant from the water in turn. In this way, solar distillation automatically separates virtually any pollutants from the water, no matter what they are - and this means peace of mind, since you don't always know what water might be contaminated with.
In addition to being a great solution for dealing with a complex mix of pollutants, solar water distillation is also the most cost-effective and environmentally friendly means of converting sea water to fresh water. The majority of the world's population lives within 100 miles of the ocean, which could be a great source of drinking water. Unfortunately, technologies such as reverse osmosis are expensive and require a great deal of power. In contrast, solar distillation is inexpensive and utilizes clean, solar energy.
Solar stills come in a great variety of sizes and types. The most basic type can be made by any handy person with simple tools in their back yard. A web search will yield a variety of different plans. Other systems are more carefully engineered for greater efficiency and automation, and can be purchased as complete systems. Another class of collapsible, floating stills were designed around the end of World War II specifically for use in the ocean, to help those forced into a life raft survive at sea.
Today, solar stills are helping people all over the world solve their most challenging water quality problems. The inherent simplicity, ability to accept water polluted with many different contaminants, and environmental friendliness of solar water distillation make it a technology that is ripe for much wider use.
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