WATER DECONTAMINATION

Microbiological contamination of drinking water presents a significant risk.

The traveller should neither consume ice nor trust drinking water, even in the finest hotels. Brushing teeth should never be done uring tap water.

The traveller should consume only safe drinks:

• drinks made with boiling water (bouillon, tea, coffee);
• bottled and sealed drinks (water, juice or aerated beverages of a known mark, beer, wine);
• water treated beforehand by means of a reliable method: Boiling, chemical disinfection, fine filtration, purification.

1. Boiling:

Bring to a boil (with large bubbles) for two (2) minutes, five (5) minutes if at more than 3000 meters of altitude. To improve the taste, add a salt pinch of salt per liter or to repeatedly pour the water from one clean container to another (oxygenation of water).

Advantages: The most reliable method. No toxicity.

Disadvantages: Not always practical, requires cauldron and heater.

2. Chemical disinfection:

Iodine: For better results, it is preferable to filter before. Five (5) drops of tincture of 2% iodine or a tablet of hydroperiodic tetraglycine per liter of water. Product sold in in pharmacies and sporting goods stores as well as stores specializing in travel products. Let rest according to the temperature: cold water (between 5 and 15 C), 120 minutes; tepid water (between 15 and 20 C), 60 minutes; water at more than 20 C, should be left 30 minutes. Stir the solution frequently.

Advantages: Easy.

Disadvantages: Contraindicated in pregnant women because it can affect the fetus. Not recommended for children, people who are afflicted with a thyroid disorder or allergic to iodine, not for regular use over more than 3 weeks, because of potential harm to the thyroid gland. Iodine taste. Time of 30 minutes contact at more than 20 C.

Chlorination : For better results, it is preferable to filter before. Two (2) drops of bleach (to 4 to 6 %) per liter of water. Chlorine tablets lose their effectiveness in a few months and are not recommended. Let rest 30 minutes at more than 20 C. Stir the solution frequently. To mask the chlorine or iodine taste which one can find in treated water, it is sufficient to add vitamin C tablets or fruit juice powder or to pour the water several times from one suitable container to another.

Advantages: Ease.

Disadvantages: Chlorine less effective than iodine, especially against the Giardia cysts. Chlorine taste. Effectiveness varies according to pH, temperature, water turbidity and organic contaminants. 30 minutes contact time at over 20 C; fine filtration necessary beforehand.

With one of these two methods of chemical disinfection, water cleanliness is preserved several days without refrigeration.

3. Fine filtration:

As a preliminary adjunct to disinfection, never alone. According to the size of the pores of the filter, elimination of bacteria and cysts, but not viruses, is possible. Filters with pores of less than 1 micron eliminate bacteria and the parasites. Several types are available to travellers.

Advantages: Rapid, practical, easy to transport. Effective against Giardia cysts.

Disadvantages: Cost, ineffective against viruses, regular maintenance (change of an element or cleaning), possible obstruction. Lifespan varies according to the quantity of contaminants in water. Sometimes difficult to determine when a filter is no longer effective.

4. Purification Devices:

Impregnated iodine resin, with or without filter. Any device with a membrane having pores of less than 1 micron and an impregnated iodine resin can be used for one-step purification.

Advantages: Chemical disinfection with iodine with or without filtration. Practical

Disadvantages: Cost, regular maintenance. Sometimes difficult to determine at what point a filter is no longer effective. Absence of independent studies of effectiveness.

© Centre santé-voyage de Québec, 1997