Disinfecting water

Latest update: - Authors: Mieke Croughs, Ula Maniewski-Kelner

Bottled water is usually safe.

It can be useful to disinfect drinking water yourself during long trips (for example a prolonged stay in a foreign country) or when travelling to very remote areas or spending time in nature. This can be achieved by the following measures: 

Boiling

Bringing the water to boiling point and then covering it is sufficient. It is best to filter visibly murky water before boiling.

Technology is being developed to purify water by heating it below boiling point for a long period using solar energy. This method can be useful in areas with few resources, but is not very practical for travellers.   

Disinfection products

If the water is murky, then it should be filtered first, e.g. by pouring the water through a coffee filter or a clean handkerchief.

Various disinfection products are available from the pharmacy or outdoor sports store. It is important to allow the product enough time to work (1 to 2 hours for the standard dose at room temperature, less time for the higher dose). Follow the instructions for use.  

Chloramine tablets  

For drinking water: one 250 mg tablet per 10 litres of contaminated water or per 50 litres of relatively clean water.

For water for rinsing vegetables: five tablets per litre of water, the vegetables must be submerged in this disinfected water for ten minutes.

Bleach solution (5% sodium hypochlorite):

For drinking water, use two to four drops of bleach solution per litre of contaminated water and five to ten drops per 20 litres of clean water, which will result in a slight chlorine taste (drop counter for 20 drops per mL).

Leave the chlorine to work for 30 to 60 minutes. The colder the water, the longer the exposure time.

You can then remove the chlorine taste by:

  • Filtering the water over a filter containing activated charcoal.
  • Or by adding special anti-chlorine drops (containing the non-toxic sodium thiosulphate).

Use 5 mL per litre of water when preparing water to rinse vegetables. The vegetables must be submerged in this disinfected water for ten minutes.

Follow the instructions on commercial sodium hypochlorite solutions.

Iodine solution (2%):

Use 0.4 mL or eight drops per litre of water to prepare drinking water. Iodine may be more effective against amoebic cysts and will have less of an effect on the taste than chlorine.

You can then remove the iodine taste by filtering the water over a filter containing activated charcoal or by adding vitamin C.

Use iodine for a maximum of three months. Do not use iodine if you have thyroid problems or are pregnant.

Silver salts

Silver salts are not effective against viruses and are not suitable for disinfecting water. They can be used for germ-free storage of water that has already been disinfected. This water can then be stored in a suitable container for several months.

Chlorine with silver

For drinking water: tablets for 1 litre, liquid or powder for 100 litres of water or more.

Filtration

Various types of portable water filtration systems are commercially available. It is best to seek advice about this from specialised outdoor sports stores. If you are going to live in the tropics, it is best to purchase a larger, not portable filtration system. It is important that such systems are properly maintained.

Ultraviolet (UV) radiation

Portable devices that can purify water by means of UV radiation are available. The water is instantly purified and the taste is not altered. This technique is also effective against viruses. The disadvantages are that these are expensive products and you will always need to have access to electricity. This technique only works on clear water.

Water purification by means of UV- radiation from sunlight is also possible, but mainly useful in very primitive emergency situations and not applicable to travellers. It takes several hours before the water is purified and this technique only works on clear water.   

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