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Originally Posted by metarinka
yah but what about a few hours of direct sunlight if say a windowed case or resevoir was right in the sun, I feel that would be more than enough to kill most common bacteria. I'm just not convinced that by taking OUT the uv radiation and light would kill the bacteria, it could be something else like the property of the tubes or water but this just seems really ancedotal to me
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The type of UV radiation affects how well it kills bacteria. To kill bacteria you need UVC radiaton, with 264nm being the most effective frequency. The sun emits plenty of this, but it's all absorbed by ozone and oxygen in the upper atmosphere. Putting a windowed case in direct sunlight won't kill anything, it'll merely give it lots of light to grow with.
Also, CCFLs are generally "blacklight" or UVA frequencies and thus don't harm bacteria (or people).
As for why taking out the light kills bacteria - light is the energy source for it. Without light it has no source of energy and dies.