Jumat, 22 April 2011

Select Effective Water-treatment Methods



Taste. Odor. Hardness. Contamination. These are four of the most common reasons why people install water-treatment systems in their home. If you have a well and you identify excessive contaminant levels in it, first pinpoint the source and try to correct the problem. If correcting well deficiencies isn’t the answer, consider a water-treatment method.
Make sure you know exactly which contaminants you want to get rid of, as well as your financial limits. Consult with local officials and water-treatment specialists at state agencies or universities. And remember, each system does not work with equal efficiency on all the contaminants it removes.
An activated carbon filter removes many volatile organic chemicals, some pesticides, radon gas, hydrogen sulfide, and mercury. It also reduces odor, color, and taste problems (such as residual chlorine).
Water is filtered through carbon granules that trap contaminants. But infrequently maintained filters can result in higher concentrations of contaminants and can serve as a breeding ground for bacteria.
Distillation removes radium, odor, off-tastes, heavy metals, some pesticides, nitrate, fluoride, and salt. Units with volatile gas vents can remove some volatile organic chemicals as well.
With distillation, water is evaporated, leaving impurities behind. The steam is then cooled and becomes distilled water. But the distillation process is slow and consumes a lot of energy, making it expensive. It also consumes large amounts of water if the coolant used in the distillation process is water. Distilled water can corrode materials such as iron and copper in plumbing systems.
Reverse osmosis removes inorganic minerals such as radium, sulfate, calcium, magnesium, potassium, nitrate, fluoride, boron, and phosphorous. It also helps to remove salts, certain detergents, volatile organic contaminants, some pesticides, and taste- and odor-producing chemicals.
Water is filtered through a membrane that has passages smaller than the contaminant molecules. Under-the-sink installations are costly and take up a lot of space. In addition, reverse osmosis is slow and wasteful of water, and filter replacement is costly. Some microorganisms may be small enough to pass through the reverse osmosis membrane and colonize the holding tank.
Cation or anion exchange (water softening) removes barium; radium; and taste-, color-, and odor-producing chemicals. It will remove dissolved iron and manganese when they are present in low concentrations. Also, anion exchange units will remove nitrate and fluoride, but cation exchange units will not.
The water softening process works by passing hard water through resin beads. Magnesium and calcium ions in the water exchange places with sodium ions on the beads, softening the water. People with hypertension or high blood pressure should consult their doctor about personal health risks associated with drinking softened water because of the added sodium.
Mechanical filtration removes dirt, sediment, loose scale, and insoluble iron and manganese (flakes that have not dissolved). The water is cleared by sand, filter paper, compressed glass wool, or other straining material. Mechanical filtration does not do much to remove harmful, dissolved chemicals.
Chlorination removes bacteria; other microbiological contaminants; and some taste-, odor-, and color-producing chemicals. Also, it removes hydrogen sulfide and dissolved iron and manganese when followed by mechanical filtration or an activated carbon filter.
During chlorination, a pump feeds chlorine into the water. Chlorine has a residual effect, which means it works for a while after being added to the water. But if the system is not operated properly, it is expensive and possibly toxic. Also, chlorination byproducts may be harmful.
Ultraviolet radiation removes bacteria and other microbiological contaminants. Water passes a special light bulb where ultraviolet radiation kills contaminants. However, this system may not work effectively in cloudy water or when the water flow is too fast. Also, unless the unit is equipped with a special meter, it is hard to know whether the system is doing the job. UV units do not have a residual effect, as chlorination does.
Ozonation removes bacteria; other microbiological contaminants; some pesticides; and some taste-, odor-, and color-producing chemicals. It also removes hydrogen sulfide and dissolved iron and manganese when followed by mechanical filtration or an activated carbon filter. With ozonation, water is exposed to ozone gas, which destroys microorganisms. Equipment to generate ozone is expensive, and ozonation does not have a residual effect, as chlorination does.
An oxidizing filter (greensand filter or zeolite filter) removes iron, manganese, and hydrogen sulfide. In addition, it removes some taste-, odor-, and color-producing chemicals. Contaminants are removed through filtering and chemical reactions. But the system needs to be regenerated by pouring potassium permanganate into it. Potassium permanganate can pose a hazard to eyes and skin during handling, so always wear gloves.

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