The small Mite Away pads have 35 ml of 65% formic in them x 6 or 7 applications 4 to 7 days apart to give the same result as the larger pads. The large pads which I used are left in the hive for a full brood cycle - between 24 to 26 days.
The pads work by fumigating the hive to a point where it doesn't kill the bees but makes the mites let go of the bees. The heaviest concentration of acid fumes are on the floor of the hive where it kills the mites.
Regular garbage is fine for disposal of the pads after treatment. Most of the acid will have evaporated and formic is a natural acid.