Ultraviolet Disinfection
Ultraviolet Disinfection is using a special kind of light to kill germs in water.
Sunlight streaming through a kitchen window hits a glass of water on the counter. The light passes through the water and damages tiny germs floating inside. Those germs can no longer grow or spread. A UV lamp works the same way, shining a special light through water to kill the germs.
Explaining ultraviolet disinfection by grade level
Some light you can not see. This light is called UV light. When UV light shines on dirty water, it hurts the tiny germs inside. The germs can not grow or make you sick after that.
Projects that explore ultraviolet disinfection
A UV lamp can disinfect creek water, but its strength determines how well it works. With a low-wattage lamp, bacteria decreased at first — then rose above the original count. Switch to a higher-intensity lamp, and the decline is steady throughout the full 24 hours.
Sunlight can disinfect water inside a plastic bottle, but scratches on the bottle change the result. After six hours in direct sunlight, the clear unscratched bottle shows zero bacteria. As scratches increase, more bacteria survive.
The sun produces ultraviolet light that can kill germs in water. Those UV rays damage bacteria cells directly. When water bottles sit in sunlight for two days, the colonies in sun-exposed water are much smaller than in water kept in the dark.