Sorry if this is too basic of a question but for places close enough to the sea, would sea water for cooling and cleaning be an option? Too much salt residue?
Seriously: Maybe residue wouldn't be an issue if it was never allowed to dry, but the corrosion-proof construction, drainage system, and pumping costs would be considerable. Then there's the 100 problems we're not aware of yet...
I think this will not be a problem, as the salt would be continuously washed away with new water. But the corrosion would be a problem indeed.
Maybe some plastic/epoxy/glass casing would help, but it might also hinder recyclability.