Purification techniques can beat the nasties – filtering your water

Purification techniques can beat the nasties

By Dora Boersma

IT’S A WONDERFUL LIFE.

You’ve hiked for hours and the hammock is rocking in the gentle breeze. Can things get better than this? Let’s see…a drink of water would be nice after that long trek. You set out with the recommended two litres per person, but you drank that long ago. The lake water is as clear as a bell with no visible signs of pollution, so you can just dip your cup in and drink, right? Besides, we’re not talking the Rideau Canal here — you’re out in the middle of nowhere.

You just might wish to heed Health Canada’s no-nonsense directive instead: “No surface water can be considered safe for human consumption without treatment.”

Unfortunately, water from lakes, rivers, mountain streams and ponds may contain invisible but harmful microorganisms called pathogens. They include bacteria, viruses and cysts that can transform the sweet dreams in that hammock into a nightmare. You could display a range of symptoms from mild nausea and fever to severe diarrhea and hepatitis.

So where do these little beasts come from? The most common parasitic cysts in Canada are Cryptosporidium parvum and Giardia lamblia (sometimes called “beaver fever”). Both are caused by animal fecal matter washing into water by heavy rainfall or spring run-off. At three to 12 microns (a millionth of a metre), these cysts are too small to see. They reproduce in your body, building up their numbers until they make you sick.

The symptoms of both of these cysts include cramps, diarrhea, gas, fever and fatigue. One to two days after drinking water infected with Cryptosporidium,

you can begin to experience symptoms that can last from one to two weeks. The symptoms of Giardia usually appear five to 10 days after infection and can be hard to diagnose by then, because you’ve had time to forget drinking that unpurified water. Once Giardia is diagnosed, it usually lasts a week or two with proper medical treatment. The sickness can occasionally become chronic, however, and last months or even years.

When unpurified water gives a free ride to bacteria and viruses, they can cause symptoms similar to stomach flu, food poisoning and hepatitis. Bacteria range in size from 0.3-0.9 microns. The good news is, some filters are effective against them.

Toxic chemicals may also be present in lakes, rivers and streams. Runoff from agricultural and forestry operations are a common source, as rainfall washes pesticides and fertilizers into nearby bodies of water. Contaminants may include heavy metals like cadmium, mercury and lead.

Still thirsty? Let’s see how ancient science and modern technology can help turn on the tap.

Get rid of the pathogens

Prevention is always better than the cure. Everyone should practice good hygiene around water so we don’t pass pathogens on to others. Indeed, there are many options for ensuring that our drinking water is clean and safe. The most popular include boiling, chemicals and filtration.

Boiling: This method has been used for hundreds of years and is very effective against Cryptosporidium, Giardia and most bacteria and viruses if the water is boiled for between three and five minutes (there is no agreement on the exact time required). Don’t forget to add one minute for every 300 metres that you are above sea level. All you need is time and fuel to make this method work.

Chemicals: Chlorine and iodine are frequently used chemicals for disinfecting water. They can leave an unpleasant taste in the water that can be masked by adding juice crystals, tea, soup, or other flavours (but remember most additives accelerate dehydration). Chemical reactions slow down in cold environments, and chemicals may not be effective in the presence of contaminants, such as organic matter. Check to ensure that the expiry date of your tablets/solution hasn’t passed. Chlorine dioxide, a third option, is easier to keep and very effective. Keep all of these away from children because they can be toxic when not used properly.

Filtration: Filtering systems physically remove dirt, dust and other dangerous material by pumping water through a canister containing a screen. People have used cheesecloth for centuries to filter out floating particles in water. More recently, manufactured filters are relatively easy to obtain, and they provide a nice alternative for those who enjoy the backcountry.

If you are going to be using your filter in North America, get one with a maximum pore size of 0.3 microns. If you are going to other countries, beware that filters do not stop viruses and you should therefore use a chemical purifier in addition to a filter.

Filter pores are generally made from polypropylene, ceramics or charcoal. Muddy water or other impurities can quickly clog the filter. It is a good idea to take the directions for cleaning the filter into the field with you. For some filter systems, you can use an old toothbrush to clean the filter, some can be backwashed, and others can be wiped clean.

Before you buy a filtration system, look for a product that addresses these elements: • Where do you plan to use it? • How easy is the filter to use? • How long does it take to filter a litre of water?

• How easy is it to clean and maintain in the field? • How available and expensive are replacement filters, membranes, cartridges and pumping mechanisms?

No filtration method will absolutely guarantee pure water, but by keeping your water bottles and pumps clean and in proper working condition, you will be well protected.

For more information, check out the Health Canada Web site at http://www.hc-sc.gc.ca/hecs-sesc/water/factsheets/away_home.htm

—Dora Boersma is a biologist with Environment Canada, and an avid canoeist.

Did you know…?

An average adult human loses approximately three litres of water a day through perspiration, respiration, urination and defecation — even more when active.

By the time your mouth feels dry, you have waited too long to drink water; your body is already more dehydrated than it should be.

Fatigue, lethargy and whining are all symptoms of dehydration. Drink regularly.

Many additives, such as tea, coffee and drink crystals, contain enough dehydrating substances and salts that your body will need both the water in the drink and reserves held in the body to dilute and eliminate it.

Canadians use about 1,650 cm 3 of freshwater per capita each year, which is more than double the average European rate.