Travel Health Service Water purification methods
Travel health advice

Water Purification Methods

Risks from drink

Contamination of drinking water with living organisms is a major cause of illness amongst travellers. Water pollution is usually caused by human and animal excrement. The likelihood of this must be considered especially in developing countries. Most package tours are arranged to hotels where tap water is reliable or filtered boiled water is provided for drinking and cleaning teeth, but special care should still be taken when drinking out. Among the more common infections that travellers may acquire from contaminated water are Escherichia Coli infections, Shigellosis or Amoebic Dysentery, Giardiasis, Cryptosporidiosis, and Hepatitis A. Other common infectious disease risks for travellers include Typhoid Fever and other Salmonelloses, Cholera, infections caused by rotavirus and Norwalk-like viruses, and a variety of protozoan and helminthic parasites (other than those that cause Giardiasis and Cryptosporidiosis).

How do you prevent water-borne diseases?

If you are travelling through areas with less-than-adequate sanitation, or with water sources of unknown purity, you can reduce your chances of illness by following these precautions.

  • Drink beverages made only with boiled water (such as coffee or tea) whenever possible.

  • Drink canned or commercially bottled carbonated water or other drinks that are fully sealed, well-known international brands whenever possible. It's not unusual for bottles to be refilled with local water and sold to tourists.

  • Beer and wine are regarded to be safe to drink.

  • Ice should also be considered contaminated and should not be used in beverages. If ice has been in contact with containers used for drinking, the containers should be thoroughly cleaned, preferably with soap and hot water, after the ice has been discarded.

  • Don't drink tap water or anything mixed with such water (e.g. lemonade).

  • Don't assume that water is safe because it is chlorinated. Chlorine treatment alone may not kill some enteric viruses and the parasitic organisms that cause Giardiasis, Amoebiasis, and Cryptosporidiosis.

  • Decide which method you will be using for water purification and bring the appropriate equipment with you. Urban travellers may choose an immersion coil for boiling (a plug adapter and current converter might be necessary).

What are the methods used to purify water ?

Boiling is by far the most reliable method to make water of uncertain purity safe for drinking. Water should be boiled vigorously for 1 minute and allowed to cool to room temperature — don' t add ice which could be contaminated. At altitudes higher than 2000 meters(6,000 feet), for an extra margin of safety, boil for 3 minutes.

Those without access to electricity or adequate fuel for boiling can use chemical purifiers such as iodine to treat water. Iodine, available in liquid, crystals or tablets, will destroy most organisms that cause illness. To disinfect water using tincture of iodine (2% solution):

  • Add 5 drops to 1 liter of clear water and wait for 30 minutes before using.

  • For very cold or cloudy water, add 10 drops to 1 liter of water and wait for several hours before using.

  • To remove the iodine taste and odor, add 50 mg of vitamin C, then wait 30 minutes after adding the iodine.

However, this method cannot be relied on to kill Cryptosporidium unless the water is allowed to sit for 15 hours before drinking it. Pregnant women may use iodine-based water purification for short trips, but alternate techniques are recommended for prolonged stays in areas of risk. Those with thyroid problems or iodine allergies should not use iodine for water purification.

Chlorine, in various forms, has also been used for chemical disinfection. However, its germicidal activity varies greatly with the pH, temperature, and organic content of the water to be purified, and it is less reliable than iodine.

There are many types of portable water filters available, with varying degrees of effectiveness. If you plan to use a water filter, do some research to find the best one for your needs. Filtered water must also be treated chemically to ensure its purity, as they do not remove viruses.