PURIFYING WATER: FILTRATION FACT & FICTION
Water filters are devices that can improve the overall taste, smell and appearance of drinking water and can remove some chemical substances. Used mainly for drinking and cooking purposes, filters are the most inexpensive and easily available method of water purification. However, purifica- tion using filters is not 100 per cent. In general, water filters remove only the specific types of substances listed on their labels, like chlorine or lead. They do not remove micro-organisms and are intended for use with water that is known to be microbiologically safe. No single filter can be used to remove all types of substances from water. LEAD FROM PIPES CAN LEACH INTO WATER There are many water filter models on the market. Each drinking water treatment system has its own advantages and disadvantages. You must investigate which unit or combination of units is best suited for your household. While municipally treated water leaves the plant meeting all health and aesthetic standards, note that if your home has lead pipes or solder or if your water utility has lead pipes, you may have lead in your drinking water. If you aren’t sure and you live in an older neighbourhood or older home, you can have your water tested for lead. If your water does contain lead, remove water that’s sat in your pipes overnight by running the cold water until it feels cold, or use a water filter that’s been certified to remove lead.
THREE PRINCIPAL TYPES OF FILTERS
1. Particle filters operate on one basic principle: they use a membrane to screen out or trap particles based on their size. These filters are rated according to the pore size of the membrane, which is measured in microns – the lower the number of microns (i.e., the smaller the pore size), the more effective the filter.
2. Activated carbon (AC) filters are most effective in removing organic contaminants from water. Because organic chemicals are often responsible for taste, odour and colour problems, activated carbon filtration can generally be used to improve aesthetically objectionable water.
3. Resin filters consist of a module that contains resins able to remove contaminants such as lead and other heavy metals, as well as minerals that cause deposits in kettles and coffee makers. Basic water filters can be found in hardware, department or grocery stores. Water equipment dealers sell some of the more sophisticated activated carbon filters. These dealers are listed under Water or Water Companies in the Yellow Pages™. Water filter systems can be divided into two main groups: point-of-use devices and point-of-entry devices. Point-of-use devices are usually small units intended to treat water used for drinking and cooking. These can either be units installed on single or multiple taps or pitchers that filter water poured in the top. Point-of-entry devices are installed on the main water supply and treat all the water entering the home. The prices of water filters vary greatly, mostly depending on the size of the filter. Activated carbon filters range in cost from a few dollars to several hundred dollars. Faucet-mounted filters usually range in price from $20 to $60. Pitcher filters are usually the least expensive, retailing for under $25. Will water filters completely clean and purify your drinking water? Water filters cannot microbiologically disinfect drinking water. Water filters can remove certain chemicals and improve the taste, odour and appearance of water.
CAUTION: OLD FILTERS BECOME TOXIC
One of the drawbacks of filters is that if not used according to the manufacturer’s specifications, they will allow previously filtered contaminants to be released into the water. Moreover, the buildup of organic matter on the filter can promote bacterial growth in very short periods of time, even overnight. Studies have shown that levels of bacteria present in water that has passed through an improperly maintained home filtration device may be up to 2,000 times higher than levels in unfiltered water.
WANT MORE INFORMATION?
More information about water filters can be found at Health Canada’s web site, www.hc-sc.gc.ca/waterquality, which describes many activities related to drinking water quality. You can also check the web site of NSF International, www.nsf.org, for information about health-based performance standards related to drinking water treatment units. The NSF also provides a listing of systems that it has certified at www.nsf.com. The Canadian Water Quality Association site, www.cwqa.com, is also an industry source of information for drinking water treatment units. Your local water utility may also be of assistance.
This article was supplied by CMHC (the Canada Mortgage & Housing Corporation). Go to www.cmhc-schl.gc.ca for other articles.
FILTERS RELEASE THEIR TOXINS INTO THE WATER IF NOT CHANGED REGULARLY.