What would you do if you were travelling in a foreign country and you needed water but were not able to buy clean water and you did not have any water purification tablets with you? Or maybe the public water supply has been damaged due to a severe storm, earthquake or other event so you are not sure whether the water really is fit to drink. How could you make it drinkable without having to spend a fortune?
Making A Water Steriliser
Firstly, let's hope you are never in this situation but if you are and if you have access to a clear plastic water bottle, you can make a fairly effective water steriliser. Here's how. Fill the bottle with the cleanest water you can find. If the water is murky, you may have to filter it through some clean cloth to remove the sediment and some suspended solids. Even better would be to pass it through a coffee filter paper optionally filled with clean sand.
Once the bottle has been filled, screw the cap on. Now place it where it will receive full sun for around 6 hours. Put it on a dark background, if possible.
Does it really sterilise the water?
Yes - to a degree. With sufficient good sunlight it will kill pathogens such as bacteria and cysts which can cause disease; however, it will not remove toxic chemicals if these are present in the water. Mind you, if it comes to a choice of dying from thirst or drinking chemically contaminated water you would drink the water and worry about the chemicals later.
How Does It Work?
There are two mechanisms at work here. The first is the UV which acts to kill bacteria. While there has been some discussion in various forums as to whether sufficient amounts of the right sort of UV actually penetrate the plastic, it is probably safe to say that some UV will definitely enter the water. It's effectiveness will be reduced if the water is turbid or murky - hence the requirement to run it through some sort of filter.
The second mechanism does not rely on UV but heat. Leaving a bottle in the sun will raise the water temperature to over 65°C. Maintaining this temperature for at least 1 hour will kill bacteria and cysts.
In summary, in an emergency situation, a plastic water bottle and sunlight will provide a temporary method for sterilising water or at least making it drinkable. Obviously it is better to have a proper water purifier for this situation. There are portable water purifiers which are light enough to be taken on trips. Some will purify the water without requiring chemicals or electricity, while others require water purification tablets to ensure water safety.
Portable water purifiers should be light enough to take anywhere, simple to operate, and easy to maintain in the field. Water purifiers meeting these requirements can be found at http://www.crystalclearwater.com.au/waterpurifiers/camping
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