I was Googling for something and I stumbled across this invention that is kind of similar in concept. I don't know much about it, but I just thought I'd throw the idea out there if anyone was interested in it.

It's called the Hydrosonic Pump, invented by a heating engineer out in Georgia. Basically, it heats water through turbulence or shock waves. Imagine a single car engine cylinder and piston head. Scale it up bigger and turn things on their side. Attach a motor to the piston head so that it spins in place (not travels back and forth). The sides of the piston head have a bunch of holes, and there's a bit of a gap between the piston (actually, I guess I should call it a rotor) and the cylinder wall. Fill the cylinder with water and start spinning the rotor. The caviation or turbulence generates heat, which then heats the water up. Even makes steam.

Here's the kicker, which makes the Hydrosonic Pump controversial--it apparently generates more energy than it uses. I know, I know, Law of Conservation of Energy and all, but I'm not sure if anyone has been able to discredit that claim. There are a few actual commercial installations running this thing, mostly for generating steam heat, and apparently their energy bills have all gone down.

Anyway, putting aside the energy issue, this thing really does heat up water without any combustion involved. OK, so out in the bush, you could carry one of those old manual egg beaters/mixers, with the hand crank, and crank that thing really, really fast, and then you'd be able to boil that river water and make it safe to drink...well, after you've recovered from all that faster-than-humanly-possible cranking.