Water Purification
Introduction
Contaminated water can contain visible particles, invisible organisms (living creatures including bacteria and viruses), toxins (poisonous substances) or chemical pollutants which can be harmful if ingested. Even if water is clear and colourless, both tap and bottled water may not be safe if it has not been produced under proper conditions.
Water should only be used for drinking if is known to be pure and safe. This also applies to water used for making ice cubes and cleaning teeth.
In areas of the world where it is difficult to maintain good hygiene and sanitation, you are advised to take safe food and water precautions to avoid becoming unwell, and this may include taking measures to purify drinking water.
Water should only be drunk if it comes from a bottle with an intact seal; or if it has been boiled or chemically disinfected or passed through a reliable water filter.
Even where bottled water is readily available, it is a good idea to have a backup system for purifying water should you run out of bottled water. In addition, water purification is generally agreed to be more 'environmentally friendly' than using bottled water since the same plastic bottle can be reused and refilled with purified water.
Water Purification
Water purification is the removal of contaminants from water to make it safe to drink. There are several different methods of purifying water. Some are more effective than others.
The method of water purification which you decide to use should consider how contaminated the water is likely to be at your destination, and also which method is going to be most practical and easy for you to use. We will discuss the main methods of water purification here.
Boiling
Bringing water to a rolling boil is the simplest and most effective way to kill all types of disease-causing organisms, even in cloudy water and at high altitudes.
If water is cloudy, allow it to settle and filter through a clean cloth or coffee filter before boiling.
Boiling water for one minute is sufficient to kill most harmful organisms.
You will need to boil water for longer (around three minutes) if you are at an altitude over 6500 feet (2000m) to compensate for lower boiling temperatures.
After water has been boiled, it should be removed from the heat and allowed to cool naturally (without adding ice) and stored in a clean container to prevent it becoming re-contaminated.
Remember that boiling won't improve the taste, smell or appearance of the water.
It might not be convenient for you to carry a stoves, kettle or heating coil whilst travelling. But boiling may be the easiest method of water purification if you are self-catering or visiting friends and relatives where equipment is readily available.
If water cannot be boiled, then you should use a combination of techniques to safely disinfect water. This can include the use of special filters, chemical disinfectants, or UV radiation.
Water Filtration
Water filtration devices remove contamination by physically blocking particles (such as debris and other microorganisms) while letting the water pass through the filter. Unfortunately, filtration is not 100% effective at removing all organisms that can make you unwell, so you will also need to use chemicals or boil filtered water to make sure it is safe to drink.
There are a wide variety of filters to buy which vary in how much they cost and how effective they are on removing different types of organisms. We recommend you should always read the information provided by the manufacturers and follow their instructions carefully.
Remember that filters collect germs from water, so you should wear gloves whenever possible and wash your hands carefully after using a filter. If you have a condition affecting your immune system, you should avoid changing filters if possible.
For more information read our Guide to Water Filters
Chemical Disinfection
Chemical disinfectants are commonly available to buy in liquid and tablet form to treat drinking water. The temperature and cloudiness of the water and time the chemical is left in the water will determine how effective the chemical is in disinfecting the water. You should follow manufacturers’ instructions carefully.
The most common chemical disinfectants are chlorine based formulas such as sodium hypochlorite (the active ingredient in household bleach), calcium hypochlorite and sodium dichloroisocyanurate. These are non-toxic and effective at killing most bacteria and viruses, but not all organisms therefore you should use chemicals in combination with another method such as boiling or filtration.
Chlorine Dioxide (chemical symbol ClO2) is a gas used for its powerful oxidising properties which kills organisms in water. It is simple to use and is available in liquid or tablet form (and converts into a gas on activation). Chlorine Dioxide kills most but not all water borne organisms. You should read and closely follow the manufacturer's instructions.
Iodine is no longer recommended within the EU or available to buy for the purpose of water purification because there are concerns it may be toxic.
Ultraviolet (UV) light
UV light kills organisms in water by radiation and can be used as an alternative to chemical disinfection. A portable, battery operated device can be purchased that delivers a metered, timed dose of UV light. This method can be effective in distilling small quantities of clear water. The manufacturer's instructions must be followed to confirm the length of time needed for activation. Unfortunately, these won't work in cloudy water.
Salt (Sodium Chloride) Electrolysis
Salt electrolysis works by using a hand-held battery powered product which passes an electrical current through a solution of salt and water (brine) to create mixed oxidants (including hypochlorite, as in bleach). When the oxidant solution is added to untreated water it will inactivate organisms and purify the water. The manufacturers advise most organisms are killed when using this method, but it is unlikely to be effective against cyclospora.
Purchasing Equipment
Equipment for sterilizing water and water filters can usually be purchased at outdoor sports, camping and adventure shops, or online.
MSR Thru-Link In-Line Microfilter
Katadyn Water Filter's Hiker Pro Transparent
Chlorine preparations can often be obtained from local pharmacies.
Filters for sterilizing water must not be confused with cheaper versions (available in supermarkets) designed only to remove odour and chlorine from domestic water.
The manufacturers leaflet should always be checked before purchase to make sure the product will eliminate all of the organisms that you may be at risk from.