It is estimated that more than 30 million homes have point-of-use systems installed

Many people today have become concerned about the quality of their drinking water. A growing number of contaminants are regulated by the government's safe drinking water standards. These contaminants enter water supplies through landfills, deteriorating underground storage tanks, industrial waste, agricultural fertilizers and pesticides, sewer discharges reaching other sources of water supply, and leaching from pipes, solder and connector joints.

Individuals contaminate, too. Some believe storm sewers, septic tanks or empty lots are safe dumping grounds for home chemicals such as used car oil and cleaning solvents. Disposed this way, these contaminants can find their way into the water supply. In addition, in both rural and suburban areas, pesticides and fertilizers are posing water quality problems. In some regions, the contamination is widespread.

By the time it flows from your customers' taps, water has already been treated with a variety of chemicals and by a variety of processes to clarify it, alter it and disinfect it. Even though some of the more difficult questions are unresolved, the fact remains that many individuals find their water too hard, too cloudy, odorous, funny tasting, or they have health concerns for themselves, their children, and especially during pregnancy or illness.

Tap water is, thus, properly viewed as raw material for further improvement by the commercial, industrial and domestic user.

Both private-well users, estimated at more than 15 million across North America, and an increasing number of consumers on public water systems have decided to install a final barrier of protection or to simply improve the water in their homes or businesses. It is estimated that more than 30 million homes have point-of-use (POU) systems installed, and that number is growing by more than a million a year. Add to this the bottled water industry, and you have an important, publicly acceptable augmentation to central drinking water treatment, or in many cases an alternative to it.

Water quality can be improved at the time the water is to be used, in the appropriate amount and to the desired level. On average, the typical municipal water treatment plant yields 183 gallons per capita per day - but less than 1 gallon per person per day is used for drinking and cooking. The other 182 gallons per capita are used for other purposes, such as sprinkling lawns, flushing toilets, washing laundry, bathing, cleaning streets, fighting fires and industrial uses.

Single problems, such as simple hardness or one contaminant, may be effectively resolved with a single water quality improvement technique. For several problems, the answer might be found in a combination of POU equipment. For example, chlorination may be used for disinfection and the precipitation of iron or hydrogen sulfide, which is then removed by filtration. Or activated carbon may be used in combination with reverse osmosis treatment to remove low molecular weight organic compounds that pass through the RO membranes.

POU Applications: The point-of-use water treatment industry has developed a wide variety of methods for improving water at the point of consumers' use:

  • Filtration is used in homes and the food and beverage industries and whenever an improved water quality is desired for drinking, cooking, ice making, etc. Filtration removes turbidity, particulate matter and certain types of color. It removes dirt particles down to any desired micron size. Special microfiltration devices can also remove bacteria and other microorganisms.

  • Adsorption removes chlorine taste, certain organics, and musty and fishy odors. The process employs an adsorbent material, usually a solid, capable of adhering gases, liquids and/or suspended matter on its surface and in its exposed pores. Activated carbon is a common adsorbent used in water treatment. Activated alumina is a special application of the process, used in fluoride removal. New iron-based adsorbents are proving excellent for removing arsenic in hundreds of private and public drinking water systems to well below the U.S. EPA's revised limit of 10 micrograms per liter.

  • Deionization produces water virtually free of minerals as is required in high-pressure boilers, metal plating, electronics manufacturing, jet engine operation, ice making, etc. Deionization is often used as part of a purification system that prepares water for pharmaceuticals, computer chip manufacturing, injection into the body, hemodialysis, and wherever water of exceptionally high quality is difficult or impossible to achieve by other processes. Deionization also removes nitrates and sulfates.

  • Distillation removes solids and other impurities from water. In this familiar process that mimics the hydrologic cycle, water is converted into vapor by heating, then cooled, condensed to liquid and collected.

  • Reverse osmosis (RO) removes 90-98 percent of all suspended and dissolved matter from water. In the process, pressure is used to force water through a semi-permeable membrane. The membrane permits passage of the water, but rejects things that are suspended and even dissolved in it. RO may be used alone or as part of a system to prepare water of very high quality.

  • Electrodialysis uses direct current and special semi-permeable membranes rather than heat or high pressure to remove dissolved salts and minerals from water. The electric current used and the membrane surface design regulate the amount of salts removed. Therefore, only unwanted salts are removed to specified levels of purity, retaining desirable mineral flavors in drinking water without the need for post-treatment modification. Electrodialysis plants require relatively clear influent water, therefore pretreatment of the water supply may be necessary. Electrodialysis may be used in conjunction with ion exchange to produce ultra high purity waters for industry.

  • Disinfection destroys bacteria in water to make it “safe” to drink. Methods for disinfecting water at the point of use include chlorination, ultraviolet light, ozonation, iodination and bromination.

  • Silver bacteriostasis inhibits bacteriological growth by means of silver compounds.

  • Oxidation causes precipitates and allows water impurities, such as iron, manganese and hydrogen sulfide, to be removed by filtration.

  • Neutralization produces a water of neutral pH by the addition of bicarbonates, alkalinity, acid or a base.

  • Ion exchange softening removes calcium and magnesium, two minerals that seriously impair water's cleaning capabilities and which can deposit a damaging scale in boilers, heaters, plumbing pipes, fixtures and water-using appliances. Besides its use in homes where it is desirable for water used for bathing, personal grooming and cleaning, softened water is required by commercial laundries, car washes, restaurants, hotels, beauty salons and in manufacturing processes, such as textile making and those involving steam production.

  • Cation exchange water softening reduces hardness to less than 17 mg/L and may remove iron, manganese and other cationic heavy metals, depending on their concentration, to levels meeting and below drinking water standards. Ion exchange water softening also removes all radioactive radium and barium from a water supply.

  • Chemical treatment controls corrosion and the destructive disintegration of metal by electrochemical action. This usually involves the feeding of polyphosphates and/or silicates with a chemical feed pump.

    All the preceding technologies and processes may be applied at the point-of-use in a variety of ways. Likewise, the range of cost varies and most products are available for outright sale or for rental from one of thousands of water treatment professionals throughout the United States and the world.

    Finally, the degree of treatment can be customized to match an individual's specific needs and desires. For example, filtration at a single faucet may remove dirt particles from a rated micron size of 300 microns to below 1 micron, and full household filtration from 50 microns to 1 micron. Asbestos can be removed to undetectable levels with reverse osmosis or fine filtration. Lead, cadmium and similar heavy metals can be reduced by activated carbon and also removed to extremely low levels by ion exchange softening, reverse osmosis, deionization, distillation and electrodialysis. Properly designed activated carbon units and reverse osmosis plus activated carbon units can remove trihalomethanes and other disinfection by product chemicals, to a level below the maximum contaminant level.

    In short, the point-of-use water treatment industry offers treatment technologies for which there is widespread and popular need.