I've salvaged a couple of treadmill motors, used one on a drill press. They're permanent magnet DC motors. Challenges include very non-standard mountings and unusual (threaded) motor shafts. The motors are all designed to turn a flywheel/fan/flat belt pulley. So you'll need to do some creative machining to use one.
Treadmill controllers come in two different "flavors": There's the classic MC-60, which uses a variable resistor to set speed. The other type (I forget the number, something like 2100?) requires a pulse train to set the speed - so you'd need something like an Arduino to drive it.
I've only used the MC-60. It has two quirks which you should be aware of. First off, almost the entire circuit,
including the leads to the speed control pot, floats at something like line voltage ... so be careful with your wiring. Secondly, the circuit includes a "safety" slowdown feature. Think of somebody on the treadmill. They might stumble and fall if the belt stopped too suddenly. So no matter how quickly you turn the speed to zero, the controller will slow the motor down in a controlled fashion. Oh yes ... startup can also be a pain. The way the circuit is designed, if the speed pot is not at zero when you apply power, you have to turn it all the way down before you can get the motor to run. The way to get around that is to put a switch between the center lead of the pot and the wire to the control board. Turning the switch off and back on fools the controller into "starting up" at the set speed.
Alternatively, you can get a standalone DC motor controller. If you search ebay for "90v dc motor controller" you'll find a bunch. Just be sure to get one with enough current capacity.
As for 220 volt ... I recall seeing a post recently from an offshore member about a 220 volt treadmill controller. I doubt you'd easily find one of those here in the US. And a final PS -
@itsme_Bernie has recently posted about having a number of DC motors and controllers. You might want to get in touch with him via PM, and see what advice he might have.