Michael Pritchard, a British inventor, served it to me after running it through his Lifesaver ultra filtration water bottle.

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"The bacteria concentration after filtration depends on the initial concentration of bacteria in water, " said developer Dr Cui of Stanford University.

CNN: Nanotech and 'tea bag' to clean up drinking water

And maybe after only one filtration you will get 'safe' water.

CNN: Nanotech and 'tea bag' to clean up drinking water