Sorry, no. It is too dangerous to run a VFD that close to a river. I'll come by and pick up the sander, take it off your hands and solve that problem for you! . Seriously, nice finds! Suggest you just run a VFD off of a 220V (aka. 230V, 240V) circuit. A 15A, 240V circuit would likely do fine. Your rotary phase converter should work fine too. I think it would be nice to be able to control the speed of the sander using a VFD. Can't help you with the gas question.
Damn, that's good info, I would have just fired it up not knowing and caused the end of the earth as we know it...
110V would allow me to plug it in anywhere in the shop, 220 requires wiring in a circuit for it, I have thought about running a 220 circuit around the shop just for this kind of situation but haven't done it. The RPC would require a 50' run to get to that side of the shop but still doable. With the cost of the 110V VFD, that's off the table, the price on the 220V VFD (thanks Ulma Doctor) I think that's the way to go unless that 1hp motor on my shelf shows it's self.