Eww... snot
Personally I would just take off the nozzles and flush the lines with bleach water. Letting the bleach water drain to the floor or into another bucket.
Being me, I'd probably do it a few times bleach, then fresh water a couple more times.
Even better if you can hook up and blow high pressure through the lines
Scrub the bucket good with bleach water, then refill.
I cover our water buckets with a lid to keep dust out.