This should have surely helped you in clearing Trash. In case you are getting a Locked file error, then press and hold the Option key, go to Finder → Empty Trash. Force Empty Trash in Mac OS X When File is Locked or in Use. Now try to empty trash, if it still doesn’t clear the dump, keep reading.
Make sure you type it exactly as it appears above with no extra spaces or anything else. Open Terminal by going to Applications, Utilities and Terminal and type in the following command: rm -rf /.Trash/.
Note: The Empty Trash Securely option has been removed from OS X El Capitan and probably all future versions of OS X. Quitting Mail, emptying the Trash, and reopening Mail. Quit the last app that accessed that file (if you know what it is). Reboot your Mac, press and hold the Shift key, as you do so you will find Apple logo appear on the screen. Reboot the Mac in Safe Mode and clear Trash as shown below. The file that you are trying to delete might be in use by another application, making it difficult for you to empty Trash.