How to Purify Water with Natural Sunlight

The water we drink everyday should be free from all impurities and there are several methods available for purification of water. However, not all methods are equally effective, given the different kinds of impurities present in water obtained from different sources. Some common methods for purification of drinking water include use of substances such as chlorine, iodine and activated charcoal, filtration, exposure to ultraviolet radiation (UV), boiling, etc. Filtration removes only the suspended particles present in water and is ineffective in removing germs and microbes. Boiling followed by filtration is an effective method as heating the water to its boiling point i.e. 100⁰C kills all kinds of harmful microscopic organisms present in water, including Cryptosporidium parvum and Giardia lamblia, which cause infections of the digestive tract.

Sunlight is a rich source of UV radiation which is effective in destroying germs and bacteria present in water. To purify water with sunlight, you need to expose the water to sunlight for the UV rays to destroy the harmful microbes present in the water. Although it is a very simple process, you need to follow certain steps in order to obtain the desired results.

How to Purify Water with Sunlight

You can purify water with sunlight in a few simple steps. This method can be used to purify water collected from fresh water bodies such as streams and lakes.

• Collect the water you wish to purify, in a transparent plastic or glass bottle. Note that the bottle should not be too big. This is because the strength of UV radiation decreases with the increase in depth of water.
• Find a place that receives adequate sunlight and keep the bottle(s) of water there. However, if you are using glass bottles, make sure you do not place them on a surface made of wood or any other inflammable substance. This is because the rays of the sun passing through the bottle can cause such a surface to catch fire.
• After you have placed your bottles in the sun, wait for 10 to 12 hours. Remember that this is a relatively slow process and you need to have a little patience!
• Once the wait is over, just open the lid and you have clear water that is free of harmful disease causing organisms.

Useful Tips to Purify Water with Sunlight

What we have learnt so far was simple, isn't it? To make things even simpler and hassle free, just go through a few tips given below.

• When choosing a bottle, remember to use one that is colorless. This will facilitate optimum exposure of the water to sunlight.
• The time span of 10-12 hours is optimum provided the day is bright and sunny. On a gloomy day, you might need to wait a little longer, may be even upto 24 hours or more.
• If using a plastic bottle, prefer one that is made from Polyethylene Terephthalate (PET). PET bottles are preferred because of their higher thermostability i.e. these bottles are more stable at higher temperatures as compared to ordinary plastic bottles.

It is important to note that this method is effective in destroying the microorganisms and bacteria present in water but if the water is slightly turbid or if dissolved salts are present in the water, it is recommended that you filter the water before subjecting it to purification with sunlight. Also, this method is for emergency situations when you don't have the required means to boil the water, like when you are out trekking on the mountains or when on a picnic you suddenly realize that you have no water left with you. In most other situations, however, boiling is always the best method to purify water.

So the next time you're in need of clear water, hope you know what to do! Just grab a bottle, fill it with the water and leave it out in the sun. After a few hours, you'll have water that you can safely drink.