I’m not so sure. “A cheap and easy way to clean water” is probably the easiest Kickstarter scheme you can pull off. So naturally you will hear a lot of ideas, and none of them will work.

But lets say that your right on your first point, and a general solution exists. Then your second point is most definitely false. It is not the problem that nobody wants to pay for it. It is a problem that the people who need it can’t pay for it, and that nobody is willing to give it to them. See it’s a problem of distribution, not of demand.