Well, water is bipolar either way, that's why it is able to work as a more or less universal solvent.

true, so it should do ok at grabbing both positive and negative ions. leaving only neutrally charged particles to deal with.

As far as I know "water filters" are acceptable for a lot of applications. There were vacuum cleaners around bubbling dust in a water tank and they work pretty well in my opinion. I didn't know this was used even on large scale, thank you Shippou!

Here is a diagram showing more detail

Yes, for a live demonstration go see your local Rainbow Vacuum salesman!