If your water supply is part of the City of Ottawa’s main distribution system, then the quality of your drinking water falls well within both federal and provincial water quality standards set out by Health Canada and the Ontario Ministry of the Environment. In accordance with these standards, the City of Ottawa’s water supply is rated as being one of the safest in North America – in the last report put out by MOE’s Chief Drinking Water Inspector in 2008 (http://www.ontario.ca/drinkingwater/246898.pdf), the City received exceptional inspection ratings, with four of the six municipal water supply facilities receiving a rating of 100% and the two remaining facilities receiving ratings of slightly under 100%. Further in-home water treatment or filtration of municipal water is generally considered to be unnecessary.
If your home is not part of the City’s distribution system (for example, local well water distribution), or if you are concerned about the quality of the municipal supply, there are several in-home water filtration systems available to ensure the safest possible drinking water for your home. The following is a summary of the major types of filtration systems which can be installed in your home:
In-Home Water Treatment Systems
Activated Carbon Filters
Organic compounds are removed by absorption in the filter and residual disinfectants from municipal treatment processes are removed by catalytic reduction, a process in which negatively charged contaminants are attracted to the positively charged activated carbon particles.
Benefits: Effectively remove sediments, trace amounts of VOCs and chlorine; can significantly reduce bad tastes and odours.
Limitations: Minimal removal of fluoride, bacteria and viruses; regular replacement of filter is required to ensure proper functioning; potential for harmful bacterial growth in the filter if not maintained properly.
Reverse Osmosis Systems
A semi-permeable membrane, typically installed at the point of entry for a household’s water system, allows uncontaminated water to pass through the membrane, while water contaminated with particles too large to pass through the membrane pores is diverted away and becomes wastewater.
Benefits: Effectively remove nitrates, sulphate, most microbes, sediments and small amounts of some pesticides.
Limitations: Slow water flow; between 75-90% of water can be wasted in the process; can require pre-filtration and softening of hard water before membrane filtration; are costly due to replacement and maintenance requirements.
Distillation Systems
Heats the contaminated water to the boiling point, collects and condenses the steam, which is then passed through an additional filter to remove impurities in the water.
Benefits: Effectively kills microbes in the water; can remove heavy metals, salt and minerals.
Limitations: Can only remove chemicals with a boiling point higher than water but can increase concentration of chemicals with a boiling point lower than water; needs regular de-scaling and weekly disinfecting with bleach or heat; require large amounts of energy to operate and are thus costly over the long term.
Ultra-Violet Treatment Systems
Water is forced through a flow chamber in which it is exposed to UV-C rays from the UV lamp, which sterilizes any microbes present in the water thereby removing the threat of infection to anyone drinking the water.
Benefits: Effectively kills the majority of bacteria, viruses and other harmful microorganisms; is very energy-efficient (requires about the same amount of energy as a 60 watt bulb)
Limitations: Requires additional filtration to remove microbes embedded in dirt particles suspended in the water; slow water flow; requires regular cleaning and routine replacement of bulb.
Greensand Treatment Filters
Typically used for slightly more alkaline water (higher pH), these filtration systems force water through the oxygen-charged manganese greensand in the filter which leads to the oxidization of iron, manganese and sulfur into particles which are trapped in the filter bed.
Benefits: Effectively removes hydrogen sulfide, iron and manganese when present in moderate amounts.
Limitations: Unsuitable for removing microbes from water; difficult to operate and maintain; requires regular backwash and periodic reactivation with permanganate solution and/or bleach.
Water Softeners
Water is passed over a resin bed of softener salts (sodium and potassium), which essentially take the place of the calcium and magnesium ions found in the water.
Benefits: Effectively reduces ‘hardness’ of water; reduces scale build-up in pipes, fixtures and appliances; reduces odours derived from certain minerals.
Limitations: Are unsuitable for removing microbes and most chemicals; increases sodium concentration in water; requires frequent replacement of softener salts and frequent disposal of treated water.
There are currently no official guidelines regulating the sale and manufacture of filtration devices in Canada; however the National Sanitation Foundation (NSF) provides certification for these devices according to strict regulations set out by the Environmental Protection Agency in the United States. If you decide to purchase an in-home water filtration system, it is highly recommended to refer to the NSF’s website (www.nsf.org)) to find out which products have been NSF certified.
To find out more about water filtration devices, their uses and their limitations:
Health Canada – Water Treatment Devices for Disinfection of Drinking Water
http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/disinfect-disinfection-eng.php
City of Ottawa – In-Home Water Filtration Systems
http://www.ottawa.ca/residents/water/wq/facts/inhome_en.html
National Sanitation Foundation – Home Water Treatment Devices
http://www.nsf.org/consumer/drinking_water/dw_treatment.asp?program=WaterTre#devices
For a comparison of water filtration products available for purchase:
http://www.waterfiltercomparisons.com/water_filter_comparison.php
(Note: prices quoted on the above website are in US funds)