Water Distillers are performing not only as one of the most effective forms of treatment, but they're one of the easiest to understand: untreated water is converted into water vapor, which is then condensed back into liquid form.
Most of the contaminants are left behind in the boiling chamber, with the condensed water being virtually contaminant-free.
Anyone who has accidentally let a pot of water boil completely out on the stove is familiar with this process, and familiar with the crust of contaminants typically left behind after the water is gone.
In nature, this basic process is responsible for the hydrologic cycle. The sun causes water to evaporate from surface sources such as lakes, oceans, and streams. The water vapor eventually comes in contact with cooler air, where it re-condenses to form dew or rain. This process can be imitated artificially, and more rapidly than in nature, using alternative sources of heating and cooling.
Most distillation units use either electricity, or, to a lesser extent, gas to generate the heat necessary. While it is difficult to get past the initial heating of the water, efficiency can be gained in keeping the process going by reusing the heated steam to preheat the incoming water.
In a single-effect distiller, a heating element heats the water until it boils and eventually becomes steam. The steam is then drawn away from the boiling chamber, where it cools, condensing into highly treated distilled water. The contaminants in the original water are left behind in the boiling chamber.
The condensing process is accomplished by using air or water to cool the steam. With some designs, the steam passes through coiled tubing which is either immersed in cool water, or cooled by a fan. In others, the roof of the boiling chamber is cone-shaped, with the cone being cooled by the non-heated water stored above it. Water droplets condense on the inside of the cone-shaped dome, and run down for collection in a drip pan. With some water-cooled systems, a portion of the heat lost as the steam is cooled and condensed can be reclaimed by channeling the heated cooling water into the boiling chamber. It is then replaced with fresh, cool water. The pre-heated water requires less new energy to convert it into steam.
While the distillation process alone is very effective, certain pesticides and contaminants like volatile organic compounds (VOCs) and radon convert into vapor readily, and can travel with the steam our of the boiling chamber. Almost all household distillers use special vents and carbon pre- and post-filters to effectively deal with these contaminants.
Distillation units do require some maintenance, which usually involves draining off the concentrated sediment and other contaminants that accumulate at the bottom of the boiling chamber. The walls of the chamber may also need to be cleaned of hard-water scale and other sediment that can accumulate. The required amount of cleaning depends greatly upon the initial quality of water used. Very hard water can produce heavy scaling in a relatively short period of time. If soft water is used, cleaning difficulties should be minimal. The carbon pre- and post-filters must be changed periodically as well.
Typical household distillers cost between $300 and $1,000 and produce water for as low as $.25 a gallon, energy and filter costs included. A variation of the multiple-effect distiller concept is the vapor-compression distiller, which is typically used in commercial applications requiring between 25 and 5000 gallons per day. Vapor-compression water distillers also use high-pressure, superheated steam to boil water; however, they only use a single chamber. The water in the boiling chamber is initially converted to steam at normal pressures and temperatures by an electric or gas heating element. The steam then passes through an electric compressor; the compression causes it to become superheated. The superheated steam is then directed through tubes back into the boiling chamber, where it eventually takes over the boiling process, condensing into distilled water as the heat transfer occurs. These systems are typically more efficient than multi-stage units, since the energy required to operate the compressor is less than that required to heat water using a heating element. The greater efficiency usually brings with it a greater cost, as compared to multistage units.
Both multi-stage and vapor-compression distillers can incorporate various forms of filtration to make a broadly effective treatment system. These systems can provide water for such uses as commercial water bottling. Both systems also require water that is softened to be practical, to prevent debilitating scaling with resultant heat transfer losses and maintenance costs.
At the municipal level, both multi-stage and vapor-compression distillation can provide large quantities of distilled water for drinking use, and are especially used in distilling seawater for use in arid areas adjacent to the oceans. A distillation system with activated carbon filtration can also be quite effective for treating aesthetic drinking water contaminants like chlorine or iron bacteria, which lead to unpleasant tastes, odors, or colors.
Distillation is an effective water treatment technology for household and commercial use. It provides water with a distinct clarity, up to 98% free of impurities. Distillation units are continually being improved to increase efficiency and water output, making them increasingly popular and cost-effective for residential and commercial users alike.
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