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Widely publicized reports of contamination and pollution of municipal and private drinking water sources have motivated many people to consider buying a home water treatment system. Others buy home water treatment systems to improve the smell or taste of the water. Regardless, the demand for home water treatment systems is on the rise.

Currently, about a 100 companies sell water filter systems that they claim can remove a whole host of contaminants and improve the taste and smell of your water. These systems can cost as little as $20 and as much as $1,000. Which one is right for you? The answer depends on your specific water problem. Despite claims to the contrary, no single home water treatment system available on the market today can remove all the contaminants that may affect the quality of your water. There are four broad classes of water contaminants -- heavy metals, organics, inorganic compounds and bacteria. Identifying which one(s) are affecting the quality of your drinking water is the first step in deciding which type of home water treatment system is best for your situation. Having your water tested will help in confirming the contaminants. Contact your local health department for information about water testing facilities. Private consultants and water testing laboratories can also be of assistance.

Two types of water treatment systems are currently available. Point-of-Use (POU) devices are installed under the sink, on the faucet or sit on the counter-top as a separate unit. Many commercially available home water treatment units are POU devices. Point-of-Entry (POE) devices are connected to the main water pipe(s) in the system. Examples of POE devices are water softeners and "reverse osmosis" systems. POE devices tend to be more expensive than POU devices.

Currently, home water treatment systems employ at least one or a combination of six different methods for removing contaminants: reverse osmosis, distillation, activated carbon, ion exchange, chemical oxidation or UV radiation. Each water treatment method has a comparative advantage in removing some but not all contaminants. Also, some problems have been found to occur with their use. To help you better understand what a home water treatment system that uses, for example "activated carbon filters with an ion exchange resin" actually does, we briefly describe how each method removes contaminants, the contaminants it removes and what problems have been detected with its use.

Method
Process
Contaminants Removed
Associated Concerns

Reverse Osmosis
Water passes through a carbon filter and then is forced through a semi-permeable membrane separating clean water from the contaminants.
· bacteria and viruses

· arsenic, chloride, fluoride, nitrate, sulfate

· lead, mercury, other heavy metals

· some organics
The semi-permeable membrane clogs easily and needs replacing every five years. The carbon filter must be replaced more often.

This system wastes a lot of water – 25-60 gallons per day depending upon the level of water use.

Distillation
Water is boiled and steam is collected and condenses into clean water in a storage tank. Contaminants that do not evaporate are left behind.
· bacteria and viruses

· arsenic, chloride, fluoride, nitrate, sulfate

· lead, mercury, other heavy metals

· some organics
Some beneficial minerals along with the contaminants are removed. Also, this system is slow and requires alot of electricity.

Activated Carbon
Activated carbon particles trap contaminants as water flows through the filter.
· bacteria

· chlorine, lead, mercury, radon

· hydrocarbons, pesticides, PCBs

· volatile organics like benzene
Care must be taken to replace the carbon cartridges when needed; otherwise contaminants in the cartridge may be flushed into the clean water reservoir.

Ion Exchange
Charged compounds are exchanged with compounds on a filter resin as water passes through.
· iron, nitrate

· calcium, magnesium
Water softeners that use sodium ion resins may pose a health risk to people with high blood pressure and heart disease.

Chemical Oxidation
Strong oxidants chemically transform contaminants to more benign forms and can kill bacteria and viruses.
· bacteria and viruses

· some organics
Chlorine is a commonly used oxidant. Chlorine may react with naturally occurring organics in the water to form a class of carcinogens known as trihalomines.

UV Radiation
UV radiation at appropriate levels kills bacteria and viruses.
· bacteria and viruses
If not applied at sufficient levels, this method only retards the growth of bacteria and viruses.


Consumer’s Report tested 27 widely used home water filter treatment systems and published the results in its August 1997 issue. Each system was tested in terms of its efficacy in removing chloroform, an organic compound, and lead, a heavy metal. The article also gave estimates of annual operating costs for each system. Many of the most popular home water treatment systems use some form of carbon filter which must be replaced when needed. Not doing so may introduce high concentrations of contaminants to your drinking water since these may be flushed from a full filter. Thus, when deciding among systems, consider the cost and capacity of replacement cartridges. A relatively inexpensive system may actually be quite costly over time.

Other Information Sources
MSU-Extension Water Quality Bulletins are available at the MSU Bulletin Office, 10-B Agriculture Hall, Michigan State University, East Lansing, MI 48824-1039.

You may also FAX this order to (517) 353-7168. You can also download the documents from the MSUE Water Quality website at http://www.msue.msu.edu/waterqual/

WQ-02 Testing of private water wells

WQ-19 Nitrate -- A drinking water concern

WQ-21 A guide to home water treatment

WQ-22 Distillation for home water treatment

WQ-23 Home water treatment using activated carbon

WQ-24 Reverse osmosis for home treatment of drinking water