What would you do with the fish?

Assuming you’re serious; It would be nearly financially impossible to do this just from the sheer amount of water we’re talking about. Have you seen how big the lakes are in person? I’ve only been on lake Huron, but you can get to a point where the horizon is just water. These lakes can also have deadly storms, since they are massive bodies of water. You would need the find a power source that would have to nearly be infinite. You would need a cooling system that suits it. You would need a LOT of maintenance. You’d spend a lot on materials, too. That’s all assuming that it would even work. That money would have to come from somewhere, and it would probably be one of if not the most expensive machines to exist. The scale of the filter would have to be miniscule to catch those chemicals.

We just don’t have the capacity for that yet. We would have to split things on such a small scale that it wouldn’t be a reasonable solution. It would be as difficult as trying to find a grain of sugar in a pound of sand.

We would have done this if we were at that point, at least somewhere. Who wouldn’t want credit for solving the world’s water problems? A filter of that size would make sea water drinkable. It would have to be on a molecular scale.