Today, there are water treatment systems available to solve most home water problems. Once you've identified the contaminants you want to reduce or eliminate, you can determine which technology - or combination of technologies - is best suited to your needs. Here is an overview of the most common home water treatment systems:
Activated Carbon Filters
A convenient and effective means of removing offensive tastes and odours, carbon filters also eliminate a wide range of organic materials and residual chlorine as well as many hazardous contaminants including certain pesticides. Carbon block filters also can reduce lead and treat for the biological contaminants Cryptosporidium and Giardia. Activated carbon comes in two forms - granulated and solid block; each has its own removal capabilities so it is important to choose the right form for your specific needs. Activated carbon is used in:
Tabletop Pitchers: Pour-through filter pitchers, the fastest growing segment of the water treatment industry, address aesthetic concerns such as taste and odour problems, although some are also effective against lead and synthetic chemicals.
Faucet-Mounted Filters: These small units attach to the end of your faucet. Turning the unit in one direction gives you filtered water while returning it to its original position gives you unfiltered water. Faucet-mounts provide unlimited water on demand and many models screen out more contaminants than pour-through filters.
Countertop Units: These units, which are small enough to fit on the countertop, direct water from the tap through the filter and then back to the tap via small hoses. Many countertop units can screen out more contaminants than faucet-mounts do, and their filters can last longer.
Undercounter Units: These systems contain more activated carbon than either the pour-through, faucet-mounted or countertop models. They are designed to be installed in-line, generally under the sink. They are installed on the cold water line and some units include a bypass to separate cooking and drinking water from other uses.
Whole-House: In some cases, all water in the house may need to be treated by activated carbon filtration. A high-volume unit may be installed at the point of entry in the house if this is the case.
Portable Filters: You can find activated carbon filters in portable units suitable for camping as well as in sports bottles perfect for using during a workout.
Reverse Osmosis (RO)
A highly-effective technology for reducing a wide range of both health-related and aesthetic contaminants, RO systems work by pressuring water up against a semi-permeable membrane that stops contaminants from passing but allows clean water to get through. Reverse osmosis systems offer a comprehensive means of eliminating more than 90 percent of potentially harmful contaminants in home drinking water including Cryptosporidium and Giardia.
Most RO systems are compact units installed under your sink. (In some cases, they can also be installed on the countertop). A typical system is comprised of one or more pre-filters, a reverse osmosis module, a post-filter and a pressurized holding tank.
"Hardness" in water is caused by the presence of calcium and magnesium, which lessen the effectiveness of soaps and detergents and can produce scale in pipes, hot water tanks and appliances. Hard water is most commonly treated with an ion exchange water softener. These softeners replace the calcium and magnesium in the water with sodium or potassium chloride, neither of which has the negative effects associated with hardness.
These point-of-entry systems consist of a brine tank which holds the sodium or potassium chloride and a softener tank that contains the resins that remove hardness.
The distillation process provides water that is up to 98 percent free of impurities and is effective in removing biological contaminants such as Cryptosporidium and Giardia. Distillation works by heating water until it turns into steam - leaving behing contaminants - and then condensing the vapor back into clean, clear water.
The most common type of household distiller is a basic single-effect distiller. Simple in design, most single-effect distillers are relatively compact countertop or stand-alone units for use in the kitchen.
These systems use ultraviolet lights to disinfect water. Water passes through a flow chamber where UV rays - which destroy bacteria and inactivate many viruses - are admitted and absorbed into the water stream. UV systems are often combined with other technologies to provide complete water solutions.
UV technology is available in point-of-entry systems treating all water entering the house as well as point-of-use units treating drinking water only.
Ozone generators produce small quantities of ozone gas, which is a very strong oxidizing agent and is effective in killing bacteria with even brief exposure times. Ozone is also effective in oxidizing organic matter, iron and manganese. Ozone generators are generally used in conjunction with other technologies for complete water treatment solutions.
In the past, ozonation was primarily used in point-of-entry systems to treat all water entering the house. Now, new countertop units are available to treat drinking water only.
Source: Water Quality Association, Fact Sheet, "An Overview of Home Water Treatment Technologies", 2000.