[chris__butters]

If the data is anonymised when collected you can't follow through with the right to erasure as they're should be nothing uniquely identifiable for that user.

Otherwise you have to do it on request, either by email or form submission or link; automated or manually as you will have 24 hours to follow through with the request. I'd keep track of these requests just in case you need to restore a backup where their data still exists, to notify them and delete their data again from the backup.