A boy clean a lake?

This guy used a PhD to clean a lake that was heavily polluted, although he does not say exactly what and if an analysis was done to find out what was affecting the lake, it is not mentioned if they identified the source of said contamination, since I suppose that before making such an investment to clean it, the sources of contamination should be removed, since it will be in the same situation again in the short term otherwise 

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Beyond that, the truth is that I had never heard from PhD, I don't know if throwing a ton of this product into a lake can have side effects, as he says it is nanotechnology... The truth is that I would need to know more about this product before affirming that It is a good solution, but the change observed in the water is great! 

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If someone wants to help me looking for information on the subject, we will gladly discuss the subject!