The water is what they've evolved to use:
Since we're talking alien biology, the sky is the limit. If your planet has an atmosphere and there's a food supply (like photosynthetic or in this case maybe even chemosynthetic bacteria), then modest temperatures and water give you a mix for life.
Plenty of terrestrial organisms already live in geysers, so even finicky Terran life can use this water. There are even halophilic eukaryotes like fungi and algae, so salt isn't even an absolute barrier to mare advanced life. While typical Earth life forms won't always do well in such a metallic sludge of radioisotopes and arsenic (mostly extremophiles), these life forms have evolved in these conditions. This is the water evolution has given them, and they would be well evolved to use it. It might be a bit of a stretch for advanced life to have independently evolved in such cramped and limiting environments, but a bacterial soup, with imported organisms resistant to the toxins, or a massive network of interconnected geysers? Sure, why not?
As for geysers in the desert, water can cycle deep in the Earth. Aquifers can supply water for geysers, since by definition geysers are rather deep underground structures. And several moons are known to have subsurface oceans and even geysers associated with them, so a desert is not a hard barrier to geysers in the desert. Geysers from a subsurface ocean wouldn't even necessarily need vulcanism associated with them, but could be driven by simple pressure and might connect up life from multiple areas on the planet.