DIY Water Purification

More than 70 percent of the earth's surface is covered in water, yet 1.1 billion people still lack access to safe drinking water. Consequently, water purification methods are becoming increasingly popular. A technology called Solar Radiation Disinfection, or SODIS, simply uses sunlight to purify water. The World Health Organization recommends this system, which is used in developing countries to improve water quality and reduce water-borne illnesses. To understand how this technology works, set up a simple experiment.

Things You'll Need

• 5 2-liter plastic PET bottles (with caps)
• 1 sheet corrugated iron
• 10 liters dirty water

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Instructions

• 1

  Remove the labels and wash the bottles with tap water. Try to use bottles with few scratches or marks. Make sure the bottles are made with PET (polyethylene terephthalatebottle) by checking the label. Do not use glass, PVC or polycarbonate bottles because these block some, or all, of the light.

• 2

  Fill the bottles up with dirty water. If the water is very turbid (has lots of suspended solids in it), filter the water before purifying it. Without filtering, the water will not be safe to drink.

  For best results, fill up three-quarters of the bottle with water, put the cap on and shake vigorously for 20 seconds. Then remove the cap and fill to the top with water. This improves oxygen saturation.

• 3

  Take your corrugated iron outside and put it on the ground where sun exposure is greatest. Lay the water bottles horizontally on their sides on the metal, following the sheet's ridges.

• 4

  Leave the bottles for six hours on a sunny day, or for two days if more than 50 percent of the sky is covered in clouds, to produce drinking water.