Is was wondering if that is a widespread practice especially in cheeses like Parms?
Depends on the size of the plant, but most old school parm makers will keep the brine saturated and will leave it alone. Parms take such a long time to brine that the tanks are usually occupied as the cheeses are rotated through. For those thermo style cheeses, it's actually beneficial to leave the brine alone because it develops halophilic lactobacilli and other flora that may help in some cases with flavor development.
I wonder if there is any UV light treatment being used in it's place?
Same as Francois, I've seen them in newer plants because it's not economical for small shops to do a filter+UV when they can just mix up a new batch or boil. Salt is cheap. Typically, there's a macro filter for large particles, then membrane filter, then in-line UV system. End result is sanitized, clear brine. It came out of the water UV treatment industry, nearly identical equipment.