That would be a good question. Most CD's are a closed cell unit and not subject to serviceing, some have a replaceable chip.
In short, whether it is CD or UV both have limited life expectancies.
The UV bulb, yo can always clean dust residuals from the bulb, but it will eventually expire. Best recommendation at that time, buy a new one don't replace the bulb.
The CD is the equivilent of a supercharged "spark plug" which eventuall carbons up making it less effective. Best solution, contact the dealer or manufacturer of the CD to determine serviceability of the particular unit.
Keep in mind, what you pay to repair or replace amounts to the money you didn't spend on chemicals. IMHO, ozone is well worth the cost of replacement.
