Friday, January 28, 2005
Thursday, January 13, 2005
The Need for Water Purification
The Need for Water Purification
The Environmental Protection Agency (EPA) has recently released information stating that, no matter where we live in the U.S., there is likely to be some toxic substance in our groundwater. Indeed, the agency estimates that one in five Americans, supplied by one-quarter of the nation's drinking water systems, consume tap water that violates EPA safety standards under the Clean Water Act. Even some of the substances that are added to our drinking water to protect us, such as chlorine, can form toxic compounds-such as trihalomethanes, or THMs-and have been linked to certain cancers. The EPA has established enforceable standards for more than 100 contaminants. However, credible studies have identified more than 2,110 contaminants in the nation's water supplies.
The most obvious solution to water pollution is a point-of-use water purification device. The tap is the end of the road for water consumed by our families, so this is the logical, and most efficient, place to focus water treatment. Different water purification technologies each have strengths and weaknesses, and are particularly effective against specific kinds of impurities or toxins. So the system you need depends first and foremost on the nature of the problem you have, which in turn requires testing and diagnosis. We will describe the options available with such systems in detail after we discuss the contaminants you might encounter. Most treatment systems are point-of-use and deal only with the drinking and cooking water, which is less than 5% of the typical home use. Full treatment of all household water is a very expensive undertaking, and is usually reserved for water sources with serious, health-threatening problems.
Contaminants in Water
Presumably your drinking water comes from a municipal system, a shallow dug well, or a deep, drilled well. If you drink bottled water, you've already taken steps to control what you consume. Bottled water drinkers should read on, too: most good purification systems provide tasty potable water for less money than the cost of regularly drinking bottled water. Each type of water supply is more or less vulnerable to different kinds of pollutants, because surface water (rivers, lakes, reservoirs), groundwater (underground aquifers), and treated water each are exposed to environmental contaminants in different ways. Obviously, the hydrogeological characteristics of the area you live in, and localized activities and sites that create pollution, such as factories, agricultural spraying, or a landfill, will potentially impact your water quality. And some impurities, such as lead and other metals, can be introduced by the piping that delivers the water to your tap.
Reliable and inexpensive tests are available to identify the biological and chemical contaminants that may be in your water. Here's what you may find.
Biological Impurities: Bacteria, Viruses, and Parasites.
Microorganisms originating from human and animal feces, or other sources, can cause waterborne diseases. Approximately 4,000 cases of waterborne illness are reported each year in the U.S. Additionally, many of the minor illnesses and gastrointestinal disorders that go unreported can be traced to organisms found in water supplies.
Biological impurities have largely been eliminated in municipal water systems with chlorine treatment. However, such treated water can still become biologically contaminated. Residual chlorine throughout the system may not be adequate, and therefore microorganisms can grow in stagnant water sitting in storage facilities or at the ends of pipes.
Water from private wells and small public systems is more vulnerable to biological contamination. These systems generally use untreated groundwater supplies, which could be polluted due to septic tank leakage or poor construction.
Organic Impurities: Tastes, and Odors
If water has a disagreeable taste or odor, the likely cause is one or more organic substances, ranging from decaying vegetation to algae to organic chemicals (organic chemicals are compounds containing carbon.)
Inorganic Impurities: Dirt and Sediment, or Turbidity
Most water contains suspended particles of fine sand, clay, silt, and precipitated salts. This cloudiness or muddiness is called turbidity. Turbidity is unsightly, and it can be a source of food and lodging for bacteria. Turbidity can also interfere with effective disinfection and purification of water.
Total Dissolved Solids (TDS)
Total dissolved solids consist of rock and numerous other compounds from the earth. The significance of TDS in water is a point of controversy among water purveyors, but here are some facts about the consequences of higher levels of TDS:
High TDS results in undesirable taste, which can be salty, bitter, or metallic.
Certain mineral salts may pose health hazards. The most problematic are nitrates, sodium, barium, copper sulfates, and fluoride.
High TDS interferes with the taste of foods and beverages.
High TDS makes ice cubes cloudy, softer, and faster melting.
High TDS causes scaling on showers, tubs, sinks, and inside pipes and water heaters.
Toxic Metals or Heavy Metals.
The presence of toxic metals in drinking water is one of the greatest threats to human health. The major culprits include lead, arsenic, cadmium, mercury, and silver. Maximum limits for each of these metals are established by the EPA's Drinking Water Regulations.
Toxic Organic Chemicals
The most pressing and widespread water contamination problem results from the organic chemicals (those containing carbon) created by industry. The American Chemical Society lists more than four million distinct chemical compounds, most of which are synthetic (man-made) organic chemicals, and industry creates new ones every week. Production of these chemicals exceeds a billion pounds per year. Synthetic organic chemicals have been detected in many water supplies throughout the country. They get into the groundwater from improper disposal of industrial waste (including discharge into waterways), poorly designed and sited industrial lagoons, wastewater discharge from sewage treatment plants, unlined landfills, and chemical spills.
Studies since the mid-1970s have linked organic chemicals in drinking water to specific adverse health effects. However, only a fraction of these compounds have been tested for such effects. Well over three-quarters of the substances identified by the EPA as priority pollutants are synthetic organic chemicals.
Volatile Organic Compounds (VOCs)
Volatile Organic Compounds are very lightweight organic chemicals that easily evaporate into the air. VOCs are the most prevalent chemicals found in drinking water, and they comprise a large proportion of the substances regulated as priority pollutants by the EPA.
Chlorine is part of the solution and part of the problem. In 1974 it was discovered that VOCs known as Trihalomethanes (THMs) are formed when the chlorine added to water to kill bacteria and viruses reacts with other organic substances in the water. Chlorinated water has been linked to cancer, high blood pressure, and anemia.
The scientific research linking various synthetic organic chemicals to specific adverse health effects is not conclusive, and remains the subject of considerable debate. However, given the ubiquity of these pollutants and their known presence in water supplies, and given some demonstrated toxicity associations, it would be reasonable to assume that chronic exposure to high levels of synthetic organic chemicals in water could be harmful. If they're in your water, you want to get them out.
Pesticides and Herbicides
The increased use of pesticides and herbicides-cide means a thing that kills-in American agriculture since World War II has had a profound effect on water quality. Rain and irrigation carry these deadly chemicals into groundwater, as well as into surface waters. These are poisonous, plain and simple.
Asbestos exists in water as microscopic suspended fibers. Its primary source is asbestos-cement pipe, which was commonly used after World War II for city water systems. It has been estimated that some 200,000 miles of this pipe are currently in use delivering drinking water. Because pipes wear as water courses through them, asbestos shows up with increasing frequency in municipal water supplies. It has been linked to gastrointestinal cancer.
The earth contains naturally occurring radioactive substances. Due to their geological characteristics, certain areas of the U.S. exhibit relatively high background levels of radioactivity. The three substances of concern to human health that show up in drinking water are uranium, radium, and radon (a gas). Various purification techniques can be effective at reducing the levels of radionuclides in water.
The first step in choosing a treatment method is to find out what contaminants are in your water. Different levels of testing are commercially available, including a comprehensive screening for nearly 100 substances. See the product section that follows.
Even before you test your water, a simple comparison can help you figure out what level of treatment your domestic water supply may need to make you happy. Find some bottled water that you like. Note the normal levels of total dissolved solids (TDS), hardness, and pH, and also how high these levels range. If you don't find this information on the label, call the bottler and ask. Then get the same information about your tap water, which can be obtained by calling your municipal supplier. If your tap water has lower levels of these things than the bottled water, a good filter should satisfy your needs. If your tap water has higher levels than the bottled water you prefer, you may need more extensive purification. If you're drinking water from a private well . . . well, you'll have to get it tested to know what's in it. Some common problems with well water, such as staining, sediment, hydrogen sulfide (rotten-egg smell), and excess iron or manganese, should be corrected before you purchase a point-of-use treatment system, because they will interfere with the effective operation of the system. These problems can easily be identified with a low-priced test; many state water quality agencies will perform such tests for a nominal fee, or we offer some tests in our product section.
If you have any reason to worry that your water may be polluted, we strongly advise you to conduct a more comprehensive test.
Water Choices: Bottled, Filtered, Purified
If you're not satisfied with your drinking water, you suspect it may be contaminated, or you've had it tested and you know it's unhealthful, you have two choices. You can buy bottled water, or you can install a point-of-use water treatment system in your home.
There are three kinds of bottled water: distilled, purified, and spring. Distillation evaporates the water, then recondenses it, thereby theoretically leaving all impurities behind (although some VOCs can pass right through this process with the water). Purified water is usually prepared by reverse osmosis, de-ionization, or a combination of both processes (see below for explanations). Spring water is usually acquired from a mountain spring or an artesian well, but it may be no more than processed tap water. Spring water will generally have higher total dissolved solids than purified water. Distilled water and purified water are better for batteries and steam irons because of their lower content of TDS.
But why pay for bottled water forever when treatment will be cheaper? Bottled water typically costs anywhere from 80 cents to $2.00 per gallon or more. Many manufacturers claim that their purifiers produce clean water for just pennies a gallon; certainly these systems will pay for themselves in cost savings within a few years.
There are two basic processes used to clean water: filtration and purification. The word "filter" usually refers to a mechanical filter which strains the water, and/or a carbon filter system, which reduces certain impurities by chemically bonding them -especially chlorine, lead and many organic molecules. Purification refers to a slower process, such as reverse osmosis, which greatly reduces dissolved solids, hardness, and certain other impurities, as well as many organics. Many systems combine both processes. Make sure that the claims of any filter or purifier you consider have been verified by independent testing.
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