As an administrator with sufficient rights, you can use iRODS' irmtrash command to clear the trash that piles up over time.
When you are going to remove a lot files, that command may take a while, and it may get stuck without notifying you why. Our suggestion is that you tackle this exercise by removing trash as admin (-M) one user at a time (-u), using maximum verbosity (-V), like this:
irmtrash -V -r -M -u <username>